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1 | \input texinfo |
2 | @setfilename stabs.info | |
3 | ||
6fe91f2c | 4 | @c @finalout |
a9ded3ac | 5 | |
e505224d PB |
6 | @ifinfo |
7 | @format | |
8 | START-INFO-DIR-ENTRY | |
8a6d5d4f | 9 | * Stabs:: The "stabs" debugging information format. |
e505224d PB |
10 | END-INFO-DIR-ENTRY |
11 | @end format | |
12 | @end ifinfo | |
13 | ||
14 | @ifinfo | |
8c59ee11 | 15 | This document describes the stabs debugging symbol tables. |
e505224d | 16 | |
6fe91f2c | 17 | Copyright 1992, 1993 Free Software Foundation, Inc. |
ee5e0932 JK |
18 | Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon, |
19 | and David MacKenzie. | |
e505224d PB |
20 | |
21 | Permission is granted to make and distribute verbatim copies of | |
22 | this manual provided the copyright notice and this permission notice | |
23 | are preserved on all copies. | |
24 | ||
25 | @ignore | |
26 | Permission is granted to process this file through Tex and print the | |
27 | results, provided the printed document carries copying permission | |
28 | notice identical to this one except for the removal of this paragraph | |
29 | (this paragraph not being relevant to the printed manual). | |
30 | ||
31 | @end ignore | |
32 | Permission is granted to copy or distribute modified versions of this | |
33 | manual under the terms of the GPL (for which purpose this text may be | |
34 | regarded as a program in the language TeX). | |
35 | @end ifinfo | |
36 | ||
139741da | 37 | @setchapternewpage odd |
e505224d PB |
38 | @settitle STABS |
39 | @titlepage | |
139741da | 40 | @title The ``stabs'' debug format |
f958d5cd | 41 | @author Julia Menapace, Jim Kingdon, David MacKenzie |
e505224d PB |
42 | @author Cygnus Support |
43 | @page | |
44 | @tex | |
45 | \def\$#1${{#1}} % Kluge: collect RCS revision info without $...$ | |
46 | \xdef\manvers{\$Revision$} % For use in headers, footers too | |
47 | {\parskip=0pt | |
48 | \hfill Cygnus Support\par | |
49 | \hfill \manvers\par | |
50 | \hfill \TeX{}info \texinfoversion\par | |
51 | } | |
52 | @end tex | |
53 | ||
54 | @vskip 0pt plus 1filll | |
6fe91f2c | 55 | Copyright @copyright{} 1992, 1993 Free Software Foundation, Inc. |
899bafeb | 56 | Contributed by Cygnus Support. |
e505224d PB |
57 | |
58 | Permission is granted to make and distribute verbatim copies of | |
59 | this manual provided the copyright notice and this permission notice | |
60 | are preserved on all copies. | |
61 | ||
62 | @end titlepage | |
63 | ||
899bafeb RP |
64 | @ifinfo |
65 | @node Top | |
66 | @top The "stabs" representation of debugging information | |
e505224d | 67 | |
6ae55c65 | 68 | This document describes the stabs debugging format. |
e505224d PB |
69 | |
70 | @menu | |
8eb5e289 | 71 | * Overview:: Overview of stabs |
bf9d2537 | 72 | * Program Structure:: Encoding of the structure of the program |
6897f9ec | 73 | * Constants:: Constants |
6fe91f2c | 74 | * Variables:: |
8c59ee11 | 75 | * Types:: Type definitions |
bf9d2537 | 76 | * Symbol Tables:: Symbol information in symbol tables |
8eb5e289 | 77 | * Cplusplus:: Appendixes: |
bf9d2537 DM |
78 | * Stab Types:: Symbol types in a.out files |
79 | * Symbol Descriptors:: Table of symbol descriptors | |
80 | * Type Descriptors:: Table of type descriptors | |
81 | * Expanded Reference:: Reference information by stab type | |
8eb5e289 | 82 | * Questions:: Questions and anomolies |
bf9d2537 | 83 | * XCOFF Differences:: Differences between GNU stabs in a.out |
f958d5cd | 84 | and GNU stabs in XCOFF |
bf9d2537 | 85 | * Sun Differences:: Differences between GNU stabs and Sun |
139741da | 86 | native stabs |
bf9d2537 DM |
87 | * Stabs In ELF:: Stabs in an ELF file. |
88 | * Symbol Types Index:: Index of symbolic stab symbol type names. | |
e505224d | 89 | @end menu |
899bafeb | 90 | @end ifinfo |
e505224d PB |
91 | |
92 | ||
899bafeb | 93 | @node Overview |
bf9d2537 | 94 | @chapter Overview of Stabs |
e505224d | 95 | |
139741da RP |
96 | @dfn{Stabs} refers to a format for information that describes a program |
97 | to a debugger. This format was apparently invented by | |
98 | @c FIXME! <<name of inventor>> at | |
99 | the University of California at Berkeley, for the @code{pdx} Pascal | |
100 | debugger; the format has spread widely since then. | |
101 | ||
8c59ee11 | 102 | This document is one of the few published sources of documentation on |
dd8126d9 | 103 | stabs. It is believed to be comprehensive for stabs used by C. The |
bf9d2537 DM |
104 | lists of symbol descriptors (@pxref{Symbol Descriptors}) and type |
105 | descriptors (@pxref{Type Descriptors}) are believed to be completely | |
dd8126d9 JK |
106 | comprehensive. Stabs for COBOL-specific features and for variant |
107 | records (used by Pascal and Modula-2) are poorly documented here. | |
108 | ||
109 | Other sources of information on stabs are @cite{Dbx and Dbxtool | |
110 | Interfaces}, 2nd edition, by Sun, 1988, and @cite{AIX Version 3.2 Files | |
111 | Reference}, Fourth Edition, September 1992, "dbx Stabstring Grammar" in | |
112 | the a.out section, page 2-31. This document is believed to incorporate | |
113 | the information from those two sources except where it explictly directs | |
114 | you to them for more information. | |
8c59ee11 | 115 | |
e505224d | 116 | @menu |
8eb5e289 | 117 | * Flow:: Overview of debugging information flow |
bf9d2537 DM |
118 | * Stabs Format:: Overview of stab format |
119 | * String Field:: The string field | |
120 | * C Example:: A simple example in C source | |
121 | * Assembly Code:: The simple example at the assembly level | |
e505224d PB |
122 | @end menu |
123 | ||
899bafeb | 124 | @node Flow |
bf9d2537 | 125 | @section Overview of Debugging Information Flow |
e505224d | 126 | |
139741da | 127 | The GNU C compiler compiles C source in a @file{.c} file into assembly |
6fe91f2c DM |
128 | language in a @file{.s} file, which the assembler translates into |
129 | a @file{.o} file, which the linker combines with other @file{.o} files and | |
139741da | 130 | libraries to produce an executable file. |
e505224d | 131 | |
6fe91f2c DM |
132 | With the @samp{-g} option, GCC puts in the @file{.s} file additional |
133 | debugging information, which is slightly transformed by the assembler | |
134 | and linker, and carried through into the final executable. This | |
135 | debugging information describes features of the source file like line | |
136 | numbers, the types and scopes of variables, and function names, | |
137 | parameters, and scopes. | |
e505224d | 138 | |
6fe91f2c DM |
139 | For some object file formats, the debugging information is encapsulated |
140 | in assembler directives known collectively as @dfn{stab} (symbol table) | |
141 | directives, which are interspersed with the generated code. Stabs are | |
f958d5cd DM |
142 | the native format for debugging information in the a.out and XCOFF |
143 | object file formats. The GNU tools can also emit stabs in the COFF and | |
144 | ECOFF object file formats. | |
e505224d | 145 | |
139741da RP |
146 | The assembler adds the information from stabs to the symbol information |
147 | it places by default in the symbol table and the string table of the | |
148 | @file{.o} file it is building. The linker consolidates the @file{.o} | |
149 | files into one executable file, with one symbol table and one string | |
150 | table. Debuggers use the symbol and string tables in the executable as | |
151 | a source of debugging information about the program. | |
e505224d | 152 | |
bf9d2537 DM |
153 | @node Stabs Format |
154 | @section Overview of Stab Format | |
e505224d | 155 | |
6fe91f2c | 156 | There are three overall formats for stab assembler directives, |
139741da | 157 | differentiated by the first word of the stab. The name of the directive |
6fe91f2c DM |
158 | describes which combination of four possible data fields follows. It is |
159 | either @code{.stabs} (string), @code{.stabn} (number), or @code{.stabd} | |
f958d5cd | 160 | (dot). IBM's XCOFF assembler uses @code{.stabx} (and some other |
63cef7d7 JK |
161 | directives such as @code{.file} and @code{.bi}) instead of |
162 | @code{.stabs}, @code{.stabn} or @code{.stabd}. | |
e505224d PB |
163 | |
164 | The overall format of each class of stab is: | |
165 | ||
166 | @example | |
0a95c18c JK |
167 | .stabs "@var{string}",@var{type},@var{other},@var{desc},@var{value} |
168 | .stabn @var{type},@var{other},@var{desc},@var{value} | |
169 | .stabd @var{type},@var{other},@var{desc} | |
6fe91f2c | 170 | .stabx "@var{string}",@var{value},@var{type},@var{sdb-type} |
e505224d PB |
171 | @end example |
172 | ||
63cef7d7 JK |
173 | @c what is the correct term for "current file location"? My AIX |
174 | @c assembler manual calls it "the value of the current location counter". | |
6fe91f2c | 175 | For @code{.stabn} and @code{.stabd}, there is no @var{string} (the |
bf9d2537 | 176 | @code{n_strx} field is zero; see @ref{Symbol Tables}). For |
6fe91f2c DM |
177 | @code{.stabd}, the @var{value} field is implicit and has the value of |
178 | the current file location. For @code{.stabx}, the @var{sdb-type} field | |
0a95c18c JK |
179 | is unused for stabs and can always be set to zero. The @var{other} |
180 | field is almost always unused and can be set to zero. | |
6fe91f2c DM |
181 | |
182 | The number in the @var{type} field gives some basic information about | |
183 | which type of stab this is (or whether it @emph{is} a stab, as opposed | |
184 | to an ordinary symbol). Each valid type number defines a different stab | |
685a5e86 | 185 | type; further, the stab type defines the exact interpretation of, and |
6fe91f2c | 186 | possible values for, any remaining @var{string}, @var{desc}, or |
bf9d2537 | 187 | @var{value} fields present in the stab. @xref{Stab Types}, for a list |
685a5e86 | 188 | in numeric order of the valid @var{type} field values for stab directives. |
6fe91f2c | 189 | |
bf9d2537 | 190 | @node String Field |
0a95c18c | 191 | @section The String Field |
e505224d | 192 | |
0a95c18c JK |
193 | For most stabs the string field holds the meat of the |
194 | debugging information. The flexible nature of this field | |
195 | is what makes stabs extensible. For some stab types the string field | |
139741da RP |
196 | contains only a name. For other stab types the contents can be a great |
197 | deal more complex. | |
e505224d | 198 | |
0a95c18c | 199 | The overall format of the string field for most stab types is: |
e505224d PB |
200 | |
201 | @example | |
46351197 | 202 | "@var{name}:@var{symbol-descriptor} @var{type-information}" |
e505224d PB |
203 | @end example |
204 | ||
139741da | 205 | @var{name} is the name of the symbol represented by the stab. |
6897f9ec | 206 | @var{name} can be omitted, which means the stab represents an unnamed |
8c59ee11 | 207 | object. For example, @samp{:t10=*2} defines type 10 as a pointer to |
6897f9ec | 208 | type 2, but does not give the type a name. Omitting the @var{name} |
dd8126d9 | 209 | field is supported by AIX dbx and GDB after about version 4.8, but not |
46351197 JK |
210 | other debuggers. GCC sometimes uses a single space as the name instead |
211 | of omitting the name altogether; apparently that is supported by most | |
6fe91f2c | 212 | debuggers. |
e505224d | 213 | |
685a5e86 | 214 | The @var{symbol-descriptor} following the @samp{:} is an alphabetic |
139741da | 215 | character that tells more specifically what kind of symbol the stab |
685a5e86 | 216 | represents. If the @var{symbol-descriptor} is omitted, but type |
139741da | 217 | information follows, then the stab represents a local variable. For a |
bf9d2537 | 218 | list of symbol descriptors, see @ref{Symbol Descriptors}. The @samp{c} |
6fe91f2c DM |
219 | symbol descriptor is an exception in that it is not followed by type |
220 | information. @xref{Constants}. | |
e505224d | 221 | |
685a5e86 DM |
222 | @var{type-information} is either a @var{type-number}, or |
223 | @samp{@var{type-number}=}. A @var{type-number} alone is a type | |
139741da | 224 | reference, referring directly to a type that has already been defined. |
e505224d | 225 | |
685a5e86 | 226 | The @samp{@var{type-number}=} form is a type definition, where the |
e7bb76cc JK |
227 | number represents a new type which is about to be defined. The type |
228 | definition may refer to other types by number, and those type numbers | |
229 | may be followed by @samp{=} and nested definitions. | |
e505224d PB |
230 | |
231 | In a type definition, if the character that follows the equals sign is | |
685a5e86 | 232 | non-numeric then it is a @var{type-descriptor}, and tells what kind of |
139741da | 233 | type is about to be defined. Any other values following the |
685a5e86 | 234 | @var{type-descriptor} vary, depending on the @var{type-descriptor}. |
bf9d2537 | 235 | @xref{Type Descriptors}, for a list of @var{type-descriptor} values. If |
685a5e86 DM |
236 | a number follows the @samp{=} then the number is a @var{type-reference}. |
237 | For a full description of types, @ref{Types}. | |
139741da | 238 | |
6897f9ec | 239 | There is an AIX extension for type attributes. Following the @samp{=} |
685a5e86 | 240 | are any number of type attributes. Each one starts with @samp{@@} and |
dd8126d9 JK |
241 | ends with @samp{;}. Debuggers, including AIX's dbx and GDB 4.10, skip |
242 | any type attributes they do not recognize. GDB 4.9 and other versions | |
243 | of dbx may not do this. Because of a conflict with C++ | |
8c59ee11 JK |
244 | (@pxref{Cplusplus}), new attributes should not be defined which begin |
245 | with a digit, @samp{(}, or @samp{-}; GDB may be unable to distinguish | |
246 | those from the C++ type descriptor @samp{@@}. The attributes are: | |
6897f9ec JK |
247 | |
248 | @table @code | |
249 | @item a@var{boundary} | |
8c59ee11 | 250 | @var{boundary} is an integer specifying the alignment. I assume it |
6897f9ec JK |
251 | applies to all variables of this type. |
252 | ||
253 | @item s@var{size} | |
ae701604 JK |
254 | Size in bits of a variable of this type. This is fully supported by GDB |
255 | 4.11 and later. | |
6897f9ec JK |
256 | |
257 | @item p@var{integer} | |
258 | Pointer class (for checking). Not sure what this means, or how | |
259 | @var{integer} is interpreted. | |
260 | ||
261 | @item P | |
262 | Indicate this is a packed type, meaning that structure fields or array | |
263 | elements are placed more closely in memory, to save memory at the | |
264 | expense of speed. | |
265 | @end table | |
266 | ||
ae701604 JK |
267 | All of this can make the string field quite long. All versions of GDB, |
268 | and some versions of dbx, can handle arbitrarily long strings. But many | |
269 | versions of dbx (or assemblers or linkers, I'm not sure which) | |
270 | cretinously limit the strings to about 80 characters, so compilers which | |
271 | must work with such systems need to split the @code{.stabs} directive | |
272 | into several @code{.stabs} directives. Each stab duplicates every field | |
273 | except the string field. The string field of every stab except the last | |
274 | is marked as continued with a backslash at the end (in the assembly code | |
275 | this may be written as a double backslash, depending on the assembler). | |
276 | Removing the backslashes and concatenating the string fields of each | |
277 | stab produces the original, long string. | |
e505224d | 278 | |
bf9d2537 DM |
279 | @node C Example |
280 | @section A Simple Example in C Source | |
e505224d PB |
281 | |
282 | To get the flavor of how stabs describe source information for a C | |
283 | program, let's look at the simple program: | |
284 | ||
285 | @example | |
6fe91f2c | 286 | main() |
e505224d | 287 | @{ |
139741da | 288 | printf("Hello world"); |
e505224d PB |
289 | @} |
290 | @end example | |
291 | ||
139741da RP |
292 | When compiled with @samp{-g}, the program above yields the following |
293 | @file{.s} file. Line numbers have been added to make it easier to refer | |
294 | to parts of the @file{.s} file in the description of the stabs that | |
295 | follows. | |
e505224d | 296 | |
bf9d2537 DM |
297 | @node Assembly Code |
298 | @section The Simple Example at the Assembly Level | |
e505224d | 299 | |
6fe91f2c DM |
300 | This simple ``hello world'' example demonstrates several of the stab |
301 | types used to describe C language source files. | |
302 | ||
e505224d PB |
303 | @example |
304 | 1 gcc2_compiled.: | |
305 | 2 .stabs "/cygint/s1/users/jcm/play/",100,0,0,Ltext0 | |
306 | 3 .stabs "hello.c",100,0,0,Ltext0 | |
307 | 4 .text | |
308 | 5 Ltext0: | |
309 | 6 .stabs "int:t1=r1;-2147483648;2147483647;",128,0,0,0 | |
310 | 7 .stabs "char:t2=r2;0;127;",128,0,0,0 | |
311 | 8 .stabs "long int:t3=r1;-2147483648;2147483647;",128,0,0,0 | |
312 | 9 .stabs "unsigned int:t4=r1;0;-1;",128,0,0,0 | |
313 | 10 .stabs "long unsigned int:t5=r1;0;-1;",128,0,0,0 | |
314 | 11 .stabs "short int:t6=r1;-32768;32767;",128,0,0,0 | |
315 | 12 .stabs "long long int:t7=r1;0;-1;",128,0,0,0 | |
316 | 13 .stabs "short unsigned int:t8=r1;0;65535;",128,0,0,0 | |
317 | 14 .stabs "long long unsigned int:t9=r1;0;-1;",128,0,0,0 | |
318 | 15 .stabs "signed char:t10=r1;-128;127;",128,0,0,0 | |
319 | 16 .stabs "unsigned char:t11=r1;0;255;",128,0,0,0 | |
320 | 17 .stabs "float:t12=r1;4;0;",128,0,0,0 | |
321 | 18 .stabs "double:t13=r1;8;0;",128,0,0,0 | |
322 | 19 .stabs "long double:t14=r1;8;0;",128,0,0,0 | |
323 | 20 .stabs "void:t15=15",128,0,0,0 | |
139741da | 324 | 21 .align 4 |
e505224d | 325 | 22 LC0: |
139741da RP |
326 | 23 .ascii "Hello, world!\12\0" |
327 | 24 .align 4 | |
328 | 25 .global _main | |
329 | 26 .proc 1 | |
e505224d PB |
330 | 27 _main: |
331 | 28 .stabn 68,0,4,LM1 | |
332 | 29 LM1: | |
139741da RP |
333 | 30 !#PROLOGUE# 0 |
334 | 31 save %sp,-136,%sp | |
335 | 32 !#PROLOGUE# 1 | |
336 | 33 call ___main,0 | |
337 | 34 nop | |
e505224d PB |
338 | 35 .stabn 68,0,5,LM2 |
339 | 36 LM2: | |
340 | 37 LBB2: | |
139741da RP |
341 | 38 sethi %hi(LC0),%o1 |
342 | 39 or %o1,%lo(LC0),%o0 | |
343 | 40 call _printf,0 | |
344 | 41 nop | |
e505224d PB |
345 | 42 .stabn 68,0,6,LM3 |
346 | 43 LM3: | |
347 | 44 LBE2: | |
348 | 45 .stabn 68,0,6,LM4 | |
349 | 46 LM4: | |
350 | 47 L1: | |
139741da RP |
351 | 48 ret |
352 | 49 restore | |
e505224d PB |
353 | 50 .stabs "main:F1",36,0,0,_main |
354 | 51 .stabn 192,0,0,LBB2 | |
355 | 52 .stabn 224,0,0,LBE2 | |
356 | @end example | |
357 | ||
bf9d2537 DM |
358 | @node Program Structure |
359 | @chapter Encoding the Structure of the Program | |
e505224d | 360 | |
685a5e86 DM |
361 | The elements of the program structure that stabs encode include the name |
362 | of the main function, the names of the source and include files, the | |
363 | line numbers, procedure names and types, and the beginnings and ends of | |
364 | blocks of code. | |
365 | ||
e505224d | 366 | @menu |
bf9d2537 DM |
367 | * Main Program:: Indicate what the main program is |
368 | * Source Files:: The path and name of the source file | |
369 | * Include Files:: Names of include files | |
370 | * Line Numbers:: | |
6fe91f2c | 371 | * Procedures:: |
bf9d2537 DM |
372 | * Nested Procedures:: |
373 | * Block Structure:: | |
e505224d PB |
374 | @end menu |
375 | ||
bf9d2537 DM |
376 | @node Main Program |
377 | @section Main Program | |
499a5faa | 378 | |
685a5e86 | 379 | @findex N_MAIN |
499a5faa | 380 | Most languages allow the main program to have any name. The |
685a5e86 | 381 | @code{N_MAIN} stab type tells the debugger the name that is used in this |
0a95c18c | 382 | program. Only the string field is significant; it is the name of |
685a5e86 DM |
383 | a function which is the main program. Most C compilers do not use this |
384 | stab (they expect the debugger to assume that the name is @code{main}), | |
385 | but some C compilers emit an @code{N_MAIN} stab for the @code{main} | |
386 | function. | |
499a5faa | 387 | |
bf9d2537 DM |
388 | @node Source Files |
389 | @section Paths and Names of the Source Files | |
e505224d | 390 | |
685a5e86 | 391 | @findex N_SO |
63cef7d7 JK |
392 | Before any other stabs occur, there must be a stab specifying the source |
393 | file. This information is contained in a symbol of stab type | |
0a95c18c JK |
394 | @code{N_SO}; the string field contains the name of the file. The |
395 | value of the symbol is the start address of the portion of the | |
685a5e86 | 396 | text section corresponding to that file. |
e505224d | 397 | |
0a95c18c | 398 | With the Sun Solaris2 compiler, the desc field contains a |
ded6bcab | 399 | source-language code. |
685a5e86 | 400 | @c Do the debuggers use it? What are the codes? -djm |
ded6bcab | 401 | |
6fe91f2c | 402 | Some compilers (for example, GCC2 and SunOS4 @file{/bin/cc}) also |
63cef7d7 JK |
403 | include the directory in which the source was compiled, in a second |
404 | @code{N_SO} symbol preceding the one containing the file name. This | |
ded6bcab | 405 | symbol can be distinguished by the fact that it ends in a slash. Code |
685a5e86 | 406 | from the @code{cfront} C++ compiler can have additional @code{N_SO} symbols for |
ded6bcab JK |
407 | nonexistent source files after the @code{N_SO} for the real source file; |
408 | these are believed to contain no useful information. | |
e505224d | 409 | |
63cef7d7 JK |
410 | For example: |
411 | ||
412 | @example | |
baf4ded0 | 413 | .stabs "/cygint/s1/users/jcm/play/",100,0,0,Ltext0 # @r{100 is N_SO} |
63cef7d7 JK |
414 | .stabs "hello.c",100,0,0,Ltext0 |
415 | .text | |
416 | Ltext0: | |
417 | @end example | |
418 | ||
419 | Instead of @code{N_SO} symbols, XCOFF uses a @code{.file} assembler | |
420 | directive which assembles to a standard COFF @code{.file} symbol; | |
421 | explaining this in detail is outside the scope of this document. | |
422 | ||
bf9d2537 DM |
423 | @node Include Files |
424 | @section Names of Include Files | |
6fe91f2c | 425 | |
685a5e86 | 426 | There are several schemes for dealing with include files: the |
6fe91f2c DM |
427 | traditional @code{N_SOL} approach, Sun's @code{N_BINCL} approach, and the |
428 | XCOFF @code{C_BINCL} approach (which despite the similar name has little in | |
63cef7d7 JK |
429 | common with @code{N_BINCL}). |
430 | ||
685a5e86 | 431 | @findex N_SOL |
63cef7d7 | 432 | An @code{N_SOL} symbol specifies which include file subsequent symbols |
f4548a46 JK |
433 | refer to. The string field is the name of the file and the value is the |
434 | text address corresponding to the end of the previous include file and | |
435 | the start of this one. To specify the main source file again, use an | |
436 | @code{N_SOL} symbol with the name of the main source file. | |
685a5e86 | 437 | |
685a5e86 DM |
438 | @findex N_BINCL |
439 | @findex N_EINCL | |
440 | @findex N_EXCL | |
43603088 JK |
441 | The @code{N_BINCL} approach works as follows. An @code{N_BINCL} symbol |
442 | specifies the start of an include file. In an object file, only the | |
0a95c18c | 443 | string is significant; the Sun linker puts data into some of the |
43603088 | 444 | other fields. The end of the include file is marked by an |
0a95c18c | 445 | @code{N_EINCL} symbol (which has no string field). In an object |
43603088 JK |
446 | file, there is no significant data in the @code{N_EINCL} symbol; the Sun |
447 | linker puts data into some of the fields. @code{N_BINCL} and | |
448 | @code{N_EINCL} can be nested. | |
449 | ||
450 | If the linker detects that two source files have identical stabs between | |
451 | an @code{N_BINCL} and @code{N_EINCL} pair (as will generally be the case | |
685a5e86 DM |
452 | for a header file), then it only puts out the stabs once. Each |
453 | additional occurance is replaced by an @code{N_EXCL} symbol. I believe | |
454 | the Sun (SunOS4, not sure about Solaris) linker is the only one which | |
455 | supports this feature. | |
456 | @c What do the fields of N_EXCL contain? -djm | |
685a5e86 | 457 | |
685a5e86 DM |
458 | @findex C_BINCL |
459 | @findex C_EINCL | |
63cef7d7 | 460 | For the start of an include file in XCOFF, use the @file{.bi} assembler |
6fe91f2c | 461 | directive, which generates a @code{C_BINCL} symbol. A @file{.ei} |
63cef7d7 JK |
462 | directive, which generates a @code{C_EINCL} symbol, denotes the end of |
463 | the include file. Both directives are followed by the name of the | |
0a95c18c JK |
464 | source file in quotes, which becomes the string for the symbol. |
465 | The value of each symbol, produced automatically by the assembler | |
685a5e86 DM |
466 | and linker, is the offset into the executable of the beginning |
467 | (inclusive, as you'd expect) or end (inclusive, as you would not expect) | |
468 | of the portion of the COFF line table that corresponds to this include | |
469 | file. @code{C_BINCL} and @code{C_EINCL} do not nest. | |
63cef7d7 | 470 | |
bf9d2537 DM |
471 | @node Line Numbers |
472 | @section Line Numbers | |
e505224d | 473 | |
685a5e86 DM |
474 | @findex N_SLINE |
475 | An @code{N_SLINE} symbol represents the start of a source line. The | |
ac31351a | 476 | desc field contains the line number and the value |
f0f4b04e | 477 | contains the code address for the start of that source line. On most |
6fe91f2c | 478 | machines the address is absolute; for Sun's stabs-in-ELF, it is relative |
f0f4b04e | 479 | to the function in which the @code{N_SLINE} symbol occurs. |
e505224d | 480 | |
685a5e86 DM |
481 | @findex N_DSLINE |
482 | @findex N_BSLINE | |
63cef7d7 JK |
483 | GNU documents @code{N_DSLINE} and @code{N_BSLINE} symbols for line |
484 | numbers in the data or bss segments, respectively. They are identical | |
485 | to @code{N_SLINE} but are relocated differently by the linker. They | |
486 | were intended to be used to describe the source location of a variable | |
6fe91f2c | 487 | declaration, but I believe that GCC2 actually puts the line number in |
0a95c18c JK |
488 | the desc field of the stab for the variable itself. GDB has been |
489 | ignoring these symbols (unless they contain a string field) since | |
685a5e86 | 490 | at least GDB 3.5. |
139741da | 491 | |
63cef7d7 JK |
492 | For single source lines that generate discontiguous code, such as flow |
493 | of control statements, there may be more than one line number entry for | |
494 | the same source line. In this case there is a line number entry at the | |
495 | start of each code range, each with the same line number. | |
e505224d | 496 | |
56bfba9c JK |
497 | XCOFF does not use stabs for line numbers. Instead, it uses COFF line |
498 | numbers (which are outside the scope of this document). Standard COFF | |
499 | line numbers cannot deal with include files, but in XCOFF this is fixed | |
f19027a6 | 500 | with the @code{C_BINCL} method of marking include files (@pxref{Include |
408f6c34 | 501 | Files}). |
685a5e86 | 502 | |
899bafeb | 503 | @node Procedures |
6897f9ec JK |
504 | @section Procedures |
505 | ||
f19027a6 | 506 | @findex N_FUN, for functions |
43603088 JK |
507 | @findex N_FNAME |
508 | @findex N_STSYM, for functions (Sun acc) | |
509 | @findex N_GSYM, for functions (Sun acc) | |
510 | All of the following stabs normally use the @code{N_FUN} symbol type. | |
511 | However, Sun's @code{acc} compiler on SunOS4 uses @code{N_GSYM} and | |
512 | @code{N_STSYM}, which means that the value of the stab for the function | |
513 | is useless and the debugger must get the address of the function from | |
514 | the non-stab symbols instead. BSD Fortran is said to use @code{N_FNAME} | |
515 | with the same restriction; the value of the symbol is not useful (I'm | |
516 | not sure it really does use this, because GDB doesn't handle this and no | |
517 | one has complained). | |
6897f9ec | 518 | |
dd8126d9 | 519 | A function is represented by an @samp{F} symbol descriptor for a global |
43603088 | 520 | (extern) function, and @samp{f} for a static (local) function. The |
f8cbe518 JK |
521 | value is the address of the start of the function. For @code{a.out}, it |
522 | is already relocated. For stabs in ELF, the SunPRO compiler version | |
523 | 2.0.1 and GCC put out an address which gets relocated by the linker. In | |
524 | a future release SunPRO is planning to put out zero, in which case the | |
525 | address can be found from the ELF (non-stab) symbol. Because looking | |
526 | things up in the ELF symbols would probably be slow, I'm not sure how to | |
527 | find which symbol of that name is the right one, and this doesn't | |
528 | provide any way to deal with nested functions, it would probably be | |
529 | better to make the value of the stab an address relative to the start of | |
530 | the file. See @ref{Stabs In ELF} for more information on linker | |
531 | relocation of stabs in ELF files. | |
532 | ||
533 | The type information of the stab represents the return type of the | |
534 | function; thus @samp{foo:f5} means that foo is a function returning type | |
535 | 5. There is no need to try to get the line number of the start of the | |
536 | function from the stab for the function; it is in the next | |
43603088 JK |
537 | @code{N_SLINE} symbol. |
538 | ||
539 | @c FIXME: verify whether the "I suspect" below is true or not. | |
540 | Some compilers (such as Sun's Solaris compiler) support an extension for | |
541 | specifying the types of the arguments. I suspect this extension is not | |
542 | used for old (non-prototyped) function definitions in C. If the | |
543 | extension is in use, the type information of the stab for the function | |
544 | is followed by type information for each argument, with each argument | |
545 | preceded by @samp{;}. An argument type of 0 means that additional | |
546 | arguments are being passed, whose types and number may vary (@samp{...} | |
547 | in ANSI C). GDB has tolerated this extension (parsed the syntax, if not | |
548 | necessarily used the information) since at least version 4.8; I don't | |
549 | know whether all versions of dbx tolerate it. The argument types given | |
550 | here are not redundant with the symbols for the formal parameters | |
551 | (@pxref{Parameters}); they are the types of the arguments as they are | |
552 | passed, before any conversions might take place. For example, if a C | |
553 | function which is declared without a prototype takes a @code{float} | |
554 | argument, the value is passed as a @code{double} but then converted to a | |
555 | @code{float}. Debuggers need to use the types given in the arguments | |
556 | when printing values, but when calling the function they need to use the | |
557 | types given in the symbol defining the function. | |
ded6bcab JK |
558 | |
559 | If the return type and types of arguments of a function which is defined | |
6fe91f2c | 560 | in another source file are specified (i.e., a function prototype in ANSI |
ded6bcab JK |
561 | C), traditionally compilers emit no stab; the only way for the debugger |
562 | to find the information is if the source file where the function is | |
563 | defined was also compiled with debugging symbols. As an extension the | |
564 | Solaris compiler uses symbol descriptor @samp{P} followed by the return | |
565 | type of the function, followed by the arguments, each preceded by | |
566 | @samp{;}, as in a stab with symbol descriptor @samp{f} or @samp{F}. | |
567 | This use of symbol descriptor @samp{P} can be distinguished from its use | |
bf9d2537 | 568 | for register parameters (@pxref{Register Parameters}) by the fact that it has |
ded6bcab JK |
569 | symbol type @code{N_FUN}. |
570 | ||
6897f9ec JK |
571 | The AIX documentation also defines symbol descriptor @samp{J} as an |
572 | internal function. I assume this means a function nested within another | |
6fe91f2c | 573 | function. It also says symbol descriptor @samp{m} is a module in |
6897f9ec JK |
574 | Modula-2 or extended Pascal. |
575 | ||
576 | Procedures (functions which do not return values) are represented as | |
6fe91f2c DM |
577 | functions returning the @code{void} type in C. I don't see why this couldn't |
578 | be used for all languages (inventing a @code{void} type for this purpose if | |
6897f9ec JK |
579 | necessary), but the AIX documentation defines @samp{I}, @samp{P}, and |
580 | @samp{Q} for internal, global, and static procedures, respectively. | |
581 | These symbol descriptors are unusual in that they are not followed by | |
582 | type information. | |
583 | ||
43603088 JK |
584 | The following example shows a stab for a function @code{main} which |
585 | returns type number @code{1}. The @code{_main} specified for the value | |
586 | is a reference to an assembler label which is used to fill in the start | |
587 | address of the function. | |
685a5e86 DM |
588 | |
589 | @example | |
43603088 | 590 | .stabs "main:F1",36,0,0,_main # @r{36 is N_FUN} |
685a5e86 DM |
591 | @end example |
592 | ||
593 | The stab representing a procedure is located immediately following the | |
594 | code of the procedure. This stab is in turn directly followed by a | |
595 | group of other stabs describing elements of the procedure. These other | |
596 | stabs describe the procedure's parameters, its block local variables, and | |
597 | its block structure. | |
685a5e86 | 598 | |
bf9d2537 DM |
599 | @node Nested Procedures |
600 | @section Nested Procedures | |
685a5e86 | 601 | |
43603088 JK |
602 | For any of the symbol descriptors representing procedures, after the |
603 | symbol descriptor and the type information is optionally a scope | |
604 | specifier. This consists of a comma, the name of the procedure, another | |
605 | comma, and the name of the enclosing procedure. The first name is local | |
606 | to the scope specified, and seems to be redundant with the name of the | |
607 | symbol (before the @samp{:}). This feature is used by GCC, and | |
608 | presumably Pascal, Modula-2, etc., compilers, for nested functions. | |
6ea34847 JK |
609 | |
610 | If procedures are nested more than one level deep, only the immediately | |
685a5e86 | 611 | containing scope is specified. For example, this code: |
6ea34847 JK |
612 | |
613 | @example | |
614 | int | |
615 | foo (int x) | |
616 | @{ | |
617 | int bar (int y) | |
618 | @{ | |
619 | int baz (int z) | |
6fe91f2c DM |
620 | @{ |
621 | return x + y + z; | |
622 | @} | |
6ea34847 JK |
623 | return baz (x + 2 * y); |
624 | @} | |
625 | return x + bar (3 * x); | |
626 | @} | |
627 | @end example | |
628 | ||
629 | @noindent | |
630 | produces the stabs: | |
631 | ||
632 | @example | |
baf4ded0 | 633 | .stabs "baz:f1,baz,bar",36,0,0,_baz.15 # @r{36 is N_FUN} |
6ea34847 JK |
634 | .stabs "bar:f1,bar,foo",36,0,0,_bar.12 |
635 | .stabs "foo:F1",36,0,0,_foo | |
636 | @end example | |
6897f9ec | 637 | |
bf9d2537 DM |
638 | @node Block Structure |
639 | @section Block Structure | |
e505224d | 640 | |
685a5e86 DM |
641 | @findex N_LBRAC |
642 | @findex N_RBRAC | |
139741da | 643 | The program's block structure is represented by the @code{N_LBRAC} (left |
f0f4b04e | 644 | brace) and the @code{N_RBRAC} (right brace) stab types. The variables |
dd8126d9 | 645 | defined inside a block precede the @code{N_LBRAC} symbol for most |
f0f4b04e | 646 | compilers, including GCC. Other compilers, such as the Convex, Acorn |
f958d5cd | 647 | RISC machine, and Sun @code{acc} compilers, put the variables after the |
0a95c18c | 648 | @code{N_LBRAC} symbol. The values of the @code{N_LBRAC} and |
f0f4b04e JK |
649 | @code{N_RBRAC} symbols are the start and end addresses of the code of |
650 | the block, respectively. For most machines, they are relative to the | |
651 | starting address of this source file. For the Gould NP1, they are | |
6fe91f2c | 652 | absolute. For Sun's stabs-in-ELF, they are relative to the function in |
f0f4b04e | 653 | which they occur. |
e505224d | 654 | |
139741da | 655 | The @code{N_LBRAC} and @code{N_RBRAC} stabs that describe the block |
f0f4b04e | 656 | scope of a procedure are located after the @code{N_FUN} stab that |
6fe91f2c | 657 | represents the procedure itself. |
e505224d | 658 | |
0a95c18c | 659 | Sun documents the desc field of @code{N_LBRAC} and |
f0f4b04e | 660 | @code{N_RBRAC} symbols as containing the nesting level of the block. |
0a95c18c | 661 | However, dbx seems to not care, and GCC always sets desc to |
f0f4b04e | 662 | zero. |
e505224d | 663 | |
6897f9ec JK |
664 | @node Constants |
665 | @chapter Constants | |
666 | ||
667 | The @samp{c} symbol descriptor indicates that this stab represents a | |
668 | constant. This symbol descriptor is an exception to the general rule | |
669 | that symbol descriptors are followed by type information. Instead, it | |
670 | is followed by @samp{=} and one of the following: | |
671 | ||
672 | @table @code | |
b273dc0f | 673 | @item b @var{value} |
6897f9ec JK |
674 | Boolean constant. @var{value} is a numeric value; I assume it is 0 for |
675 | false or 1 for true. | |
676 | ||
b273dc0f | 677 | @item c @var{value} |
6897f9ec JK |
678 | Character constant. @var{value} is the numeric value of the constant. |
679 | ||
b273dc0f JK |
680 | @item e @var{type-information} , @var{value} |
681 | Constant whose value can be represented as integral. | |
682 | @var{type-information} is the type of the constant, as it would appear | |
bf9d2537 | 683 | after a symbol descriptor (@pxref{String Field}). @var{value} is the |
b273dc0f JK |
684 | numeric value of the constant. GDB 4.9 does not actually get the right |
685 | value if @var{value} does not fit in a host @code{int}, but it does not | |
686 | do anything violent, and future debuggers could be extended to accept | |
687 | integers of any size (whether unsigned or not). This constant type is | |
688 | usually documented as being only for enumeration constants, but GDB has | |
689 | never imposed that restriction; I don't know about other debuggers. | |
690 | ||
691 | @item i @var{value} | |
692 | Integer constant. @var{value} is the numeric value. The type is some | |
693 | sort of generic integer type (for GDB, a host @code{int}); to specify | |
694 | the type explicitly, use @samp{e} instead. | |
695 | ||
696 | @item r @var{value} | |
6897f9ec JK |
697 | Real constant. @var{value} is the real value, which can be @samp{INF} |
698 | (optionally preceded by a sign) for infinity, @samp{QNAN} for a quiet | |
699 | NaN (not-a-number), or @samp{SNAN} for a signalling NaN. If it is a | |
700 | normal number the format is that accepted by the C library function | |
701 | @code{atof}. | |
702 | ||
b273dc0f | 703 | @item s @var{string} |
6897f9ec JK |
704 | String constant. @var{string} is a string enclosed in either @samp{'} |
705 | (in which case @samp{'} characters within the string are represented as | |
706 | @samp{\'} or @samp{"} (in which case @samp{"} characters within the | |
707 | string are represented as @samp{\"}). | |
708 | ||
b273dc0f | 709 | @item S @var{type-information} , @var{elements} , @var{bits} , @var{pattern} |
6897f9ec | 710 | Set constant. @var{type-information} is the type of the constant, as it |
bf9d2537 | 711 | would appear after a symbol descriptor (@pxref{String Field}). |
685a5e86 | 712 | @var{elements} is the number of elements in the set (does this means |
a03f27c3 JK |
713 | how many bits of @var{pattern} are actually used, which would be |
714 | redundant with the type, or perhaps the number of bits set in | |
715 | @var{pattern}? I don't get it), @var{bits} is the number of bits in the | |
716 | constant (meaning it specifies the length of @var{pattern}, I think), | |
717 | and @var{pattern} is a hexadecimal representation of the set. AIX | |
718 | documentation refers to a limit of 32 bytes, but I see no reason why | |
719 | this limit should exist. This form could probably be used for arbitrary | |
720 | constants, not just sets; the only catch is that @var{pattern} should be | |
721 | understood to be target, not host, byte order and format. | |
6897f9ec JK |
722 | @end table |
723 | ||
724 | The boolean, character, string, and set constants are not supported by | |
685a5e86 | 725 | GDB 4.9, but it ignores them. GDB 4.8 and earlier gave an error |
6897f9ec JK |
726 | message and refused to read symbols from the file containing the |
727 | constants. | |
728 | ||
685a5e86 | 729 | The above information is followed by @samp{;}. |
e505224d | 730 | |
899bafeb | 731 | @node Variables |
e505224d PB |
732 | @chapter Variables |
733 | ||
685a5e86 DM |
734 | Different types of stabs describe the various ways that variables can be |
735 | allocated: on the stack, globally, in registers, in common blocks, | |
736 | statically, or as arguments to a function. | |
737 | ||
e505224d | 738 | @menu |
bf9d2537 DM |
739 | * Stack Variables:: Variables allocated on the stack. |
740 | * Global Variables:: Variables used by more than one source file. | |
741 | * Register Variables:: Variables in registers. | |
742 | * Common Blocks:: Variables statically allocated together. | |
24dcc707 | 743 | * Statics:: Variables local to one source file. |
f19027a6 | 744 | * Based Variables:: Fortran pointer based variables. |
24dcc707 | 745 | * Parameters:: Variables for arguments to functions. |
e505224d PB |
746 | @end menu |
747 | ||
bf9d2537 DM |
748 | @node Stack Variables |
749 | @section Automatic Variables Allocated on the Stack | |
e505224d | 750 | |
685a5e86 DM |
751 | If a variable's scope is local to a function and its lifetime is only as |
752 | long as that function executes (C calls such variables | |
753 | @dfn{automatic}), it can be allocated in a register (@pxref{Register | |
bf9d2537 | 754 | Variables}) or on the stack. |
e505224d | 755 | |
685a5e86 | 756 | @findex N_LSYM |
43603088 JK |
757 | Each variable allocated on the stack has a stab with the symbol |
758 | descriptor omitted. Since type information should begin with a digit, | |
759 | @samp{-}, or @samp{(}, only those characters precluded from being used | |
760 | for symbol descriptors. However, the Acorn RISC machine (ARM) is said | |
761 | to get this wrong: it puts out a mere type definition here, without the | |
762 | preceding @samp{@var{type-number}=}. This is a bad idea; there is no | |
763 | guarantee that type descriptors are distinct from symbol descriptors. | |
764 | Stabs for stack variables use the @code{N_LSYM} stab type. | |
e505224d | 765 | |
0a95c18c | 766 | The value of the stab is the offset of the variable within the |
685a5e86 DM |
767 | local variables. On most machines this is an offset from the frame |
768 | pointer and is negative. The location of the stab specifies which block | |
bf9d2537 | 769 | it is defined in; see @ref{Block Structure}. |
e505224d | 770 | |
685a5e86 | 771 | For example, the following C code: |
e505224d | 772 | |
e7bb76cc JK |
773 | @example |
774 | int | |
775 | main () | |
776 | @{ | |
777 | int x; | |
778 | @} | |
779 | @end example | |
139741da | 780 | |
685a5e86 | 781 | produces the following stabs: |
e505224d | 782 | |
e7bb76cc | 783 | @example |
baf4ded0 JK |
784 | .stabs "main:F1",36,0,0,_main # @r{36 is N_FUN} |
785 | .stabs "x:1",128,0,0,-12 # @r{128 is N_LSYM} | |
786 | .stabn 192,0,0,LBB2 # @r{192 is N_LBRAC} | |
787 | .stabn 224,0,0,LBE2 # @r{224 is N_RBRAC} | |
e505224d PB |
788 | @end example |
789 | ||
685a5e86 | 790 | @xref{Procedures} for more information on the @code{N_FUN} stab, and |
bf9d2537 | 791 | @ref{Block Structure} for more information on the @code{N_LBRAC} and |
685a5e86 | 792 | @code{N_RBRAC} stabs. |
e505224d | 793 | |
bf9d2537 DM |
794 | @node Global Variables |
795 | @section Global Variables | |
e505224d | 796 | |
685a5e86 DM |
797 | @findex N_GSYM |
798 | A variable whose scope is not specific to just one source file is | |
baf4ded0 JK |
799 | represented by the @samp{G} symbol descriptor. These stabs use the |
800 | @code{N_GSYM} stab type. The type information for the stab | |
bf9d2537 | 801 | (@pxref{String Field}) gives the type of the variable. |
e505224d | 802 | |
baf4ded0 | 803 | For example, the following source code: |
6fe91f2c | 804 | |
e505224d | 805 | @example |
baf4ded0 | 806 | char g_foo = 'c'; |
e505224d PB |
807 | @end example |
808 | ||
139741da | 809 | @noindent |
baf4ded0 | 810 | yields the following assembly code: |
e505224d PB |
811 | |
812 | @example | |
baf4ded0 JK |
813 | .stabs "g_foo:G2",32,0,0,0 # @r{32 is N_GSYM} |
814 | .global _g_foo | |
815 | .data | |
816 | _g_foo: | |
817 | .byte 99 | |
e505224d PB |
818 | @end example |
819 | ||
baf4ded0 JK |
820 | The address of the variable represented by the @code{N_GSYM} is not |
821 | contained in the @code{N_GSYM} stab. The debugger gets this information | |
822 | from the external symbol for the global variable. In the example above, | |
823 | the @code{.global _g_foo} and @code{_g_foo:} lines tell the assembler to | |
824 | produce an external symbol. | |
e505224d | 825 | |
bf9d2537 DM |
826 | @node Register Variables |
827 | @section Register Variables | |
139741da | 828 | |
685a5e86 | 829 | @findex N_RSYM |
8c59ee11 JK |
830 | @c According to an old version of this manual, AIX uses C_RPSYM instead |
831 | @c of C_RSYM. I am skeptical; this should be verified. | |
6897f9ec | 832 | Register variables have their own stab type, @code{N_RSYM}, and their |
ac31351a | 833 | own symbol descriptor, @samp{r}. The stab's value is the |
6897f9ec | 834 | number of the register where the variable data will be stored. |
685a5e86 | 835 | @c .stabs "name:type",N_RSYM,0,RegSize,RegNumber (Sun doc) |
e505224d | 836 | |
6897f9ec | 837 | AIX defines a separate symbol descriptor @samp{d} for floating point |
935d305d | 838 | registers. This seems unnecessary; why not just just give floating |
807e8368 JK |
839 | point registers different register numbers? I have not verified whether |
840 | the compiler actually uses @samp{d}. | |
e505224d | 841 | |
6897f9ec | 842 | If the register is explicitly allocated to a global variable, but not |
685a5e86 | 843 | initialized, as in: |
e505224d PB |
844 | |
845 | @example | |
6897f9ec | 846 | register int g_bar asm ("%g5"); |
e505224d PB |
847 | @end example |
848 | ||
685a5e86 DM |
849 | @noindent |
850 | then the stab may be emitted at the end of the object file, with | |
6897f9ec | 851 | the other bss symbols. |
e505224d | 852 | |
bf9d2537 DM |
853 | @node Common Blocks |
854 | @section Common Blocks | |
807e8368 JK |
855 | |
856 | A common block is a statically allocated section of memory which can be | |
857 | referred to by several source files. It may contain several variables. | |
685a5e86 DM |
858 | I believe Fortran is the only language with this feature. |
859 | ||
685a5e86 DM |
860 | @findex N_BCOMM |
861 | @findex N_ECOMM | |
05238df4 JK |
862 | @findex C_BCOMM |
863 | @findex C_ECOMM | |
685a5e86 DM |
864 | A @code{N_BCOMM} stab begins a common block and an @code{N_ECOMM} stab |
865 | ends it. The only field that is significant in these two stabs is the | |
0a95c18c | 866 | string, which names a normal (non-debugging) symbol that gives the |
05238df4 JK |
867 | address of the common block. According to IBM documentation, only the |
868 | @code{N_BCOMM} has the name of the common block (even though their | |
869 | compiler actually puts it both places). | |
685a5e86 | 870 | |
685a5e86 | 871 | @findex N_ECOML |
05238df4 JK |
872 | @findex C_ECOML |
873 | The stabs for the members of the common block are between the | |
874 | @code{N_BCOMM} and the @code{N_ECOMM}; the value of each stab is the | |
875 | offset within the common block of that variable. IBM uses the | |
876 | @code{C_ECOML} stab type, and there is a corresponding @code{N_ECOML} | |
877 | stab type, but Sun's Fortran compiler uses @code{N_GSYM} instead. The | |
878 | variables within a common block use the @samp{V} symbol descriptor (I | |
879 | believe this is true of all Fortran variables). Other stabs (at least | |
880 | type declarations using @code{C_DECL}) can also be between the | |
881 | @code{N_BCOMM} and the @code{N_ECOMM}. | |
807e8368 | 882 | |
24dcc707 | 883 | @node Statics |
bf9d2537 | 884 | @section Static Variables |
e505224d | 885 | |
24dcc707 JK |
886 | Initialized static variables are represented by the @samp{S} and |
887 | @samp{V} symbol descriptors. @samp{S} means file scope static, and | |
888 | @samp{V} means procedure scope static. | |
e505224d | 889 | |
935d305d JK |
890 | @c This is probably not worth mentioning; it is only true on the sparc |
891 | @c for `double' variables which although declared const are actually in | |
892 | @c the data segment (the text segment can't guarantee 8 byte alignment). | |
6fe91f2c | 893 | @c (although GCC |
dd8126d9 | 894 | @c 2.4.5 has a bug in that it uses @code{N_FUN}, so neither dbx nor GDB can |
935d305d | 895 | @c find the variables) |
685a5e86 DM |
896 | @findex N_STSYM |
897 | @findex N_LCSYM | |
f19027a6 JK |
898 | @findex N_FUN, for variables |
899 | @findex N_ROSYM | |
31a932d8 JK |
900 | In a.out files, @code{N_STSYM} means the data section, @code{N_FUN} |
901 | means the text section, and @code{N_LCSYM} means the bss section. For | |
902 | those systems with a read-only data section separate from the text | |
903 | section (Solaris), @code{N_ROSYM} means the read-only data section. | |
e505224d | 904 | |
685a5e86 | 905 | For example, the source lines: |
e505224d PB |
906 | |
907 | @example | |
24dcc707 JK |
908 | static const int var_const = 5; |
909 | static int var_init = 2; | |
910 | static int var_noinit; | |
e505224d PB |
911 | @end example |
912 | ||
24dcc707 JK |
913 | @noindent |
914 | yield the following stabs: | |
e505224d PB |
915 | |
916 | @example | |
baf4ded0 | 917 | .stabs "var_const:S1",36,0,0,_var_const # @r{36 is N_FUN} |
685a5e86 | 918 | @dots{} |
baf4ded0 | 919 | .stabs "var_init:S1",38,0,0,_var_init # @r{38 is N_STSYM} |
685a5e86 | 920 | @dots{} |
baf4ded0 | 921 | .stabs "var_noinit:S1",40,0,0,_var_noinit # @r{40 is N_LCSYM} |
e505224d | 922 | @end example |
685a5e86 DM |
923 | |
924 | In XCOFF files, each symbol has a section number, so the stab type | |
31a932d8 | 925 | need not indicate the section. |
685a5e86 DM |
926 | |
927 | In ECOFF files, the storage class is used to specify the section, so the | |
31a932d8 | 928 | stab type need not indicate the section. |
685a5e86 | 929 | |
f8cbe518 JK |
930 | In ELF files, for the SunPRO compiler version 2.0.1, symbol descriptor |
931 | @samp{S} means that the address is absolute (the linker relocates it) | |
932 | and symbol descriptor @samp{V} means that the address is relative to the | |
933 | start of the relevant section for that compilation unit. SunPRO has | |
934 | plans to have the linker stop relocating stabs; I suspect that their the | |
935 | debugger gets the address from the corresponding ELF (not stab) symbol. | |
936 | I'm not sure how to find which symbol of that name is the right one. | |
937 | The clean way to do all this would be to have a the value of a symbol | |
938 | descriptor @samp{S} symbol be an offset relative to the start of the | |
939 | file, just like everything else, but that introduces obvious | |
940 | compatibility problems. For more information on linker stab relocation, | |
941 | @xref{Stabs In ELF}. | |
e505224d | 942 | |
f19027a6 JK |
943 | @node Based Variables |
944 | @section Fortran Based Variables | |
945 | ||
946 | Fortran (at least, the Sun and SGI dialects of FORTRAN-77) has a feature | |
947 | which allows allocating arrays with @code{malloc}, but which avoids | |
948 | blurring the line between arrays and pointers the way that C does. In | |
949 | stabs such a variable uses the @samp{b} symbol descriptor. | |
950 | ||
951 | For example, the Fortran declarations | |
952 | ||
953 | @example | |
954 | real foo, foo10(10), foo10_5(10,5) | |
955 | pointer (foop, foo) | |
956 | pointer (foo10p, foo10) | |
957 | pointer (foo105p, foo10_5) | |
958 | @end example | |
959 | ||
960 | produce the stabs | |
961 | ||
962 | @example | |
963 | foo:b6 | |
964 | foo10:bar3;1;10;6 | |
965 | foo10_5:bar3;1;5;ar3;1;10;6 | |
966 | @end example | |
967 | ||
968 | In this example, @code{real} is type 6 and type 3 is an integral type | |
969 | which is the type of the subscripts of the array (probably | |
970 | @code{integer}). | |
971 | ||
972 | The @samp{b} symbol descriptor is like @samp{V} in that it denotes a | |
973 | statically allocated symbol whose scope is local to a function; see | |
974 | @xref{Statics}. The value of the symbol, instead of being the address | |
975 | of the variable itself, is the address of a pointer to that variable. | |
976 | So in the above example, the value of the @code{foo} stab is the address | |
977 | of a pointer to a real, the value of the @code{foo10} stab is the | |
978 | address of a pointer to a 10-element array of reals, and the value of | |
979 | the @code{foo10_5} stab is the address of a pointer to a 5-element array | |
980 | of 10-element arrays of reals. | |
981 | ||
899bafeb | 982 | @node Parameters |
907a9cab JK |
983 | @section Parameters |
984 | ||
43603088 | 985 | Formal parameters to a function are represented by a stab (or sometimes |
685a5e86 DM |
986 | two; see below) for each parameter. The stabs are in the order in which |
987 | the debugger should print the parameters (i.e., the order in which the | |
dd8126d9 JK |
988 | parameters are declared in the source file). The exact form of the stab |
989 | depends on how the parameter is being passed. | |
e505224d | 990 | |
685a5e86 DM |
991 | @findex N_PSYM |
992 | Parameters passed on the stack use the symbol descriptor @samp{p} and | |
0a95c18c | 993 | the @code{N_PSYM} symbol type. The value of the symbol is an offset |
dd8126d9 | 994 | used to locate the parameter on the stack; its exact meaning is |
685a5e86 | 995 | machine-dependent, but on most machines it is an offset from the frame |
dd8126d9 | 996 | pointer. |
b82ea042 | 997 | |
685a5e86 DM |
998 | As a simple example, the code: |
999 | ||
1000 | @example | |
1001 | main (argc, argv) | |
1002 | int argc; | |
1003 | char **argv; | |
1004 | @end example | |
1005 | ||
1006 | produces the stabs: | |
1007 | ||
1008 | @example | |
1009 | .stabs "main:F1",36,0,0,_main # @r{36 is N_FUN} | |
1010 | .stabs "argc:p1",160,0,0,68 # @r{160 is N_PSYM} | |
1011 | .stabs "argv:p20=*21=*2",160,0,0,72 | |
1012 | @end example | |
1013 | ||
1014 | The type definition of @code{argv} is interesting because it contains | |
1015 | several type definitions. Type 21 is pointer to type 2 (char) and | |
1016 | @code{argv} (type 20) is pointer to type 21. | |
43603088 JK |
1017 | |
1018 | @c FIXME: figure out what these mean and describe them coherently. | |
408f6c34 JK |
1019 | The following symbol descriptors are also said to go with @code{N_PSYM}. |
1020 | The value of the symbol is said to be an offset from the argument | |
1021 | pointer (I'm not sure whether this is true or not). | |
43603088 JK |
1022 | |
1023 | @example | |
408f6c34 JK |
1024 | pP (<<??>>) |
1025 | pF Fortran function parameter | |
1026 | X (function result variable) | |
43603088 | 1027 | @end example |
685a5e86 DM |
1028 | |
1029 | @menu | |
bf9d2537 DM |
1030 | * Register Parameters:: |
1031 | * Local Variable Parameters:: | |
1032 | * Reference Parameters:: | |
1033 | * Conformant Arrays:: | |
685a5e86 DM |
1034 | @end menu |
1035 | ||
bf9d2537 DM |
1036 | @node Register Parameters |
1037 | @subsection Passing Parameters in Registers | |
685a5e86 DM |
1038 | |
1039 | If the parameter is passed in a register, then traditionally there are | |
1040 | two symbols for each argument: | |
e505224d PB |
1041 | |
1042 | @example | |
baf4ded0 JK |
1043 | .stabs "arg:p1" . . . ; N_PSYM |
1044 | .stabs "arg:r1" . . . ; N_RSYM | |
e505224d PB |
1045 | @end example |
1046 | ||
685a5e86 DM |
1047 | Debuggers use the second one to find the value, and the first one to |
1048 | know that it is an argument. | |
1049 | ||
685a5e86 | 1050 | @findex C_RPSYM |
43603088 | 1051 | @findex N_RSYM, for parameters |
685a5e86 DM |
1052 | Because that approach is kind of ugly, some compilers use symbol |
1053 | descriptor @samp{P} or @samp{R} to indicate an argument which is in a | |
1054 | register. Symbol type @code{C_RPSYM} is used with @samp{R} and | |
ac31351a | 1055 | @code{N_RSYM} is used with @samp{P}. The symbol's value is |
685a5e86 DM |
1056 | the register number. @samp{P} and @samp{R} mean the same thing; the |
1057 | difference is that @samp{P} is a GNU invention and @samp{R} is an IBM | |
1058 | (XCOFF) invention. As of version 4.9, GDB should handle either one. | |
e505224d | 1059 | |
685a5e86 DM |
1060 | There is at least one case where GCC uses a @samp{p} and @samp{r} pair |
1061 | rather than @samp{P}; this is where the argument is passed in the | |
1062 | argument list and then loaded into a register. | |
b82ea042 | 1063 | |
685a5e86 | 1064 | According to the AIX documentation, symbol descriptor @samp{D} is for a |
acf7d010 JK |
1065 | parameter passed in a floating point register. This seems |
1066 | unnecessary---why not just use @samp{R} with a register number which | |
23aed449 | 1067 | indicates that it's a floating point register? I haven't verified |
6897f9ec JK |
1068 | whether the system actually does what the documentation indicates. |
1069 | ||
43603088 JK |
1070 | @c FIXME: On the hppa this is for any type > 8 bytes, I think, and not |
1071 | @c for small structures (investigate). | |
c156f3c1 JK |
1072 | On the sparc and hppa, for a @samp{P} symbol whose type is a structure |
1073 | or union, the register contains the address of the structure. On the | |
685a5e86 DM |
1074 | sparc, this is also true of a @samp{p} and @samp{r} pair (using Sun |
1075 | @code{cc}) or a @samp{p} symbol. However, if a (small) structure is | |
1076 | really in a register, @samp{r} is used. And, to top it all off, on the | |
1077 | hppa it might be a structure which was passed on the stack and loaded | |
1078 | into a register and for which there is a @samp{p} and @samp{r} pair! I | |
1079 | believe that symbol descriptor @samp{i} is supposed to deal with this | |
1080 | case (it is said to mean "value parameter by reference, indirect | |
1081 | access"; I don't know the source for this information), but I don't know | |
1082 | details or what compilers or debuggers use it, if any (not GDB or GCC). | |
1083 | It is not clear to me whether this case needs to be dealt with | |
bf9d2537 | 1084 | differently than parameters passed by reference (@pxref{Reference Parameters}). |
685a5e86 | 1085 | |
bf9d2537 DM |
1086 | @node Local Variable Parameters |
1087 | @subsection Storing Parameters as Local Variables | |
685a5e86 DM |
1088 | |
1089 | There is a case similar to an argument in a register, which is an | |
1090 | argument that is actually stored as a local variable. Sometimes this | |
98ef6f31 JK |
1091 | happens when the argument was passed in a register and then the compiler |
1092 | stores it as a local variable. If possible, the compiler should claim | |
685a5e86 DM |
1093 | that it's in a register, but this isn't always done. |
1094 | ||
9ab86fa3 JK |
1095 | If a parameter is passed as one type and converted to a smaller type by |
1096 | the prologue (for example, the parameter is declared as a @code{float}, | |
1097 | but the calling conventions specify that it is passed as a | |
1098 | @code{double}), then GCC2 (sometimes) uses a pair of symbols. The first | |
1099 | symbol uses symbol descriptor @samp{p} and the type which is passed. | |
1100 | The second symbol has the type and location which the parameter actually | |
1101 | has after the prologue. For example, suppose the following C code | |
1102 | appears with no prototypes involved: | |
1103 | ||
1104 | @example | |
1105 | void | |
1106 | subr (f) | |
1107 | float f; | |
1108 | @{ | |
1109 | @end example | |
f3bb0be2 | 1110 | |
e2525986 JK |
1111 | if @code{f} is passed as a double at stack offset 8, and the prologue |
1112 | converts it to a float in register number 0, then the stabs look like: | |
9ab86fa3 | 1113 | |
9ab86fa3 | 1114 | @example |
e2525986 JK |
1115 | .stabs "f:p13",160,0,3,8 # @r{160 is @code{N_PSYM}, here 13 is @code{double}} |
1116 | .stabs "f:r12",64,0,3,0 # @r{64 is @code{N_RSYM}, here 12 is @code{float}} | |
9ab86fa3 JK |
1117 | @end example |
1118 | ||
e2525986 JK |
1119 | In both stabs 3 is the line number where @code{f} is declared |
1120 | (@pxref{Line Numbers}). | |
1121 | ||
9ab86fa3 | 1122 | @findex N_LSYM, for parameter |
f3bb0be2 JK |
1123 | GCC, at least on the 960, has another solution to the same problem. It |
1124 | uses a single @samp{p} symbol descriptor for an argument which is stored | |
1125 | as a local variable but uses @code{N_LSYM} instead of @code{N_PSYM}. In | |
1126 | this case, the value of the symbol is an offset relative to the local | |
1127 | variables for that function, not relative to the arguments; on some | |
1128 | machines those are the same thing, but not on all. | |
1129 | ||
1130 | @c This is mostly just background info; the part that logically belongs | |
1131 | @c here is the last sentence. | |
1132 | On the VAX or on other machines in which the calling convention includes | |
1133 | the number of words of arguments actually passed, the debugger (GDB at | |
1134 | least) uses the parameter symbols to keep track of whether it needs to | |
1135 | print nameless arguments in addition to the formal parameters which it | |
1136 | has printed because each one has a stab. For example, in | |
1137 | ||
1138 | @example | |
1139 | extern int fprintf (FILE *stream, char *format, @dots{}); | |
1140 | @dots{} | |
1141 | fprintf (stdout, "%d\n", x); | |
1142 | @end example | |
1143 | ||
1144 | there are stabs for @code{stream} and @code{format}. On most machines, | |
1145 | the debugger can only print those two arguments (because it has no way | |
1146 | of knowing that additional arguments were passed), but on the VAX or | |
1147 | other machines with a calling convention which indicates the number of | |
1148 | words of arguments, the debugger can print all three arguments. To do | |
1149 | so, the parameter symbol (symbol descriptor @samp{p}) (not necessarily | |
1150 | @samp{r} or symbol descriptor omitted symbols) needs to contain the | |
1151 | actual type as passed (for example, @code{double} not @code{float} if it | |
1152 | is passed as a double and converted to a float). | |
685a5e86 | 1153 | |
bf9d2537 DM |
1154 | @node Reference Parameters |
1155 | @subsection Passing Parameters by Reference | |
685a5e86 DM |
1156 | |
1157 | If the parameter is passed by reference (e.g., Pascal @code{VAR} | |
1158 | parameters), then the symbol descriptor is @samp{v} if it is in the | |
1159 | argument list, or @samp{a} if it in a register. Other than the fact | |
1160 | that these contain the address of the parameter rather than the | |
1161 | parameter itself, they are identical to @samp{p} and @samp{R}, | |
1162 | respectively. I believe @samp{a} is an AIX invention; @samp{v} is | |
1163 | supported by all stabs-using systems as far as I know. | |
1164 | ||
bf9d2537 DM |
1165 | @node Conformant Arrays |
1166 | @subsection Passing Conformant Array Parameters | |
6897f9ec JK |
1167 | |
1168 | @c Is this paragraph correct? It is based on piecing together patchy | |
1169 | @c information and some guesswork | |
685a5e86 | 1170 | Conformant arrays are a feature of Modula-2, and perhaps other |
6897f9ec | 1171 | languages, in which the size of an array parameter is not known to the |
685a5e86 | 1172 | called function until run-time. Such parameters have two stabs: a |
6897f9ec | 1173 | @samp{x} for the array itself, and a @samp{C}, which represents the size |
0a95c18c | 1174 | of the array. The value of the @samp{x} stab is the offset in the |
6897f9ec | 1175 | argument list where the address of the array is stored (it this right? |
0a95c18c | 1176 | it is a guess); the value of the @samp{C} stab is the offset in the |
6897f9ec JK |
1177 | argument list where the size of the array (in elements? in bytes?) is |
1178 | stored. | |
1179 | ||
8c59ee11 | 1180 | @node Types |
bf9d2537 | 1181 | @chapter Defining Types |
e505224d | 1182 | |
685a5e86 DM |
1183 | The examples so far have described types as references to previously |
1184 | defined types, or defined in terms of subranges of or pointers to | |
1185 | previously defined types. This chapter describes the other type | |
1186 | descriptors that may follow the @samp{=} in a type definition. | |
e505224d PB |
1187 | |
1188 | @menu | |
bf9d2537 DM |
1189 | * Builtin Types:: Integers, floating point, void, etc. |
1190 | * Miscellaneous Types:: Pointers, sets, files, etc. | |
1191 | * Cross-References:: Referring to a type not yet defined. | |
8c59ee11 JK |
1192 | * Subranges:: A type with a specific range. |
1193 | * Arrays:: An aggregate type of same-typed elements. | |
1194 | * Strings:: Like an array but also has a length. | |
1195 | * Enumerations:: Like an integer but the values have names. | |
1196 | * Structures:: An aggregate type of different-typed elements. | |
ded6bcab JK |
1197 | * Typedefs:: Giving a type a name. |
1198 | * Unions:: Different types sharing storage. | |
bf9d2537 | 1199 | * Function Types:: |
e505224d PB |
1200 | @end menu |
1201 | ||
bf9d2537 DM |
1202 | @node Builtin Types |
1203 | @section Builtin Types | |
e505224d | 1204 | |
8c59ee11 JK |
1205 | Certain types are built in (@code{int}, @code{short}, @code{void}, |
1206 | @code{float}, etc.); the debugger recognizes these types and knows how | |
685a5e86 | 1207 | to handle them. Thus, don't be surprised if some of the following ways |
8c59ee11 JK |
1208 | of specifying builtin types do not specify everything that a debugger |
1209 | would need to know about the type---in some cases they merely specify | |
1210 | enough information to distinguish the type from other types. | |
1211 | ||
1212 | The traditional way to define builtin types is convolunted, so new ways | |
dd8126d9 JK |
1213 | have been invented to describe them. Sun's @code{acc} uses special |
1214 | builtin type descriptors (@samp{b} and @samp{R}), and IBM uses negative | |
685a5e86 | 1215 | type numbers. GDB accepts all three ways, as of version 4.8; dbx just |
dd8126d9 JK |
1216 | accepts the traditional builtin types and perhaps one of the other two |
1217 | formats. The following sections describe each of these formats. | |
8c59ee11 JK |
1218 | |
1219 | @menu | |
bf9d2537 DM |
1220 | * Traditional Builtin Types:: Put on your seatbelts and prepare for kludgery |
1221 | * Builtin Type Descriptors:: Builtin types with special type descriptors | |
1222 | * Negative Type Numbers:: Builtin types using negative type numbers | |
8c59ee11 JK |
1223 | @end menu |
1224 | ||
bf9d2537 DM |
1225 | @node Traditional Builtin Types |
1226 | @subsection Traditional Builtin Types | |
8c59ee11 | 1227 | |
685a5e86 DM |
1228 | This is the traditional, convoluted method for defining builtin types. |
1229 | There are several classes of such type definitions: integer, floating | |
1230 | point, and @code{void}. | |
1231 | ||
1232 | @menu | |
bf9d2537 DM |
1233 | * Traditional Integer Types:: |
1234 | * Traditional Other Types:: | |
685a5e86 DM |
1235 | @end menu |
1236 | ||
bf9d2537 DM |
1237 | @node Traditional Integer Types |
1238 | @subsubsection Traditional Integer Types | |
685a5e86 DM |
1239 | |
1240 | Often types are defined as subranges of themselves. If the bounding values | |
1241 | fit within an @code{int}, then they are given normally. For example: | |
8c59ee11 JK |
1242 | |
1243 | @example | |
baf4ded0 | 1244 | .stabs "int:t1=r1;-2147483648;2147483647;",128,0,0,0 # @r{128 is N_LSYM} |
8c59ee11 JK |
1245 | .stabs "char:t2=r2;0;127;",128,0,0,0 |
1246 | @end example | |
1247 | ||
1248 | Builtin types can also be described as subranges of @code{int}: | |
1249 | ||
1250 | @example | |
1251 | .stabs "unsigned short:t6=r1;0;65535;",128,0,0,0 | |
1252 | @end example | |
1253 | ||
685a5e86 DM |
1254 | If the lower bound of a subrange is 0 and the upper bound is -1, |
1255 | the type is an unsigned integral type whose bounds are too | |
1256 | big to describe in an @code{int}. Traditionally this is only used for | |
1257 | @code{unsigned int} and @code{unsigned long}: | |
8c59ee11 JK |
1258 | |
1259 | @example | |
1260 | .stabs "unsigned int:t4=r1;0;-1;",128,0,0,0 | |
8c59ee11 JK |
1261 | @end example |
1262 | ||
f8cbe518 JK |
1263 | For larger types, GCC 2.4.5 puts out bounds in octal, with one or more |
1264 | leading zeroes. In this case a negative bound consists of a number | |
1265 | which is a 1 bit (for the sign bit) followed by a 0 bit for each bit in | |
1266 | the number (except the sign bit), and a positive bound is one which is a | |
1267 | 1 bit for each bit in the number (except possibly the sign bit). All | |
1268 | known versions of dbx and GDB version 4 accept this (at least in the | |
1269 | sense of not refusing to process the file), but GDB 3.5 refuses to read | |
1270 | the whole file containing such symbols. So GCC 2.3.3 did not output the | |
1271 | proper size for these types. As an example of octal bounds, the string | |
1272 | fields of the stabs for 64 bit integer types look like: | |
1273 | ||
1274 | @c .stabs directives, etc., omitted to make it fit on the page. | |
1275 | @example | |
1276 | long int:t3=r1;001000000000000000000000;000777777777777777777777; | |
1277 | long unsigned int:t5=r1;000000000000000000000000;001777777777777777777777; | |
1278 | @end example | |
685a5e86 | 1279 | |
b273dc0f | 1280 | If the lower bound of a subrange is 0 and the upper bound is negative, |
685a5e86 | 1281 | the type is an unsigned integral type whose size in bytes is the |
b273dc0f JK |
1282 | absolute value of the upper bound. I believe this is a Convex |
1283 | convention for @code{unsigned long long}. | |
1284 | ||
1285 | If the lower bound of a subrange is negative and the upper bound is 0, | |
685a5e86 | 1286 | the type is a signed integral type whose size in bytes is |
b273dc0f JK |
1287 | the absolute value of the lower bound. I believe this is a Convex |
1288 | convention for @code{long long}. To distinguish this from a legitimate | |
1289 | subrange, the type should be a subrange of itself. I'm not sure whether | |
1290 | this is the case for Convex. | |
1291 | ||
bf9d2537 DM |
1292 | @node Traditional Other Types |
1293 | @subsubsection Traditional Other Types | |
685a5e86 DM |
1294 | |
1295 | If the upper bound of a subrange is 0 and the lower bound is positive, | |
1296 | the type is a floating point type, and the lower bound of the subrange | |
1297 | indicates the number of bytes in the type: | |
8c59ee11 JK |
1298 | |
1299 | @example | |
1300 | .stabs "float:t12=r1;4;0;",128,0,0,0 | |
1301 | .stabs "double:t13=r1;8;0;",128,0,0,0 | |
1302 | @end example | |
1303 | ||
1304 | However, GCC writes @code{long double} the same way it writes | |
dd8126d9 | 1305 | @code{double}, so there is no way to distinguish. |
8c59ee11 JK |
1306 | |
1307 | @example | |
1308 | .stabs "long double:t14=r1;8;0;",128,0,0,0 | |
1309 | @end example | |
1310 | ||
dd8126d9 JK |
1311 | Complex types are defined the same way as floating-point types; there is |
1312 | no way to distinguish a single-precision complex from a double-precision | |
1313 | floating-point type. | |
8c59ee11 JK |
1314 | |
1315 | The C @code{void} type is defined as itself: | |
1316 | ||
1317 | @example | |
1318 | .stabs "void:t15=15",128,0,0,0 | |
1319 | @end example | |
1320 | ||
1321 | I'm not sure how a boolean type is represented. | |
1322 | ||
bf9d2537 DM |
1323 | @node Builtin Type Descriptors |
1324 | @subsection Defining Builtin Types Using Builtin Type Descriptors | |
8c59ee11 | 1325 | |
685a5e86 DM |
1326 | This is the method used by Sun's @code{acc} for defining builtin types. |
1327 | These are the type descriptors to define builtin types: | |
8c59ee11 JK |
1328 | |
1329 | @table @code | |
1a8b5668 JK |
1330 | @c FIXME: clean up description of width and offset, once we figure out |
1331 | @c what they mean | |
8c59ee11 JK |
1332 | @item b @var{signed} @var{char-flag} @var{width} ; @var{offset} ; @var{nbits} ; |
1333 | Define an integral type. @var{signed} is @samp{u} for unsigned or | |
1334 | @samp{s} for signed. @var{char-flag} is @samp{c} which indicates this | |
1335 | is a character type, or is omitted. I assume this is to distinguish an | |
1336 | integral type from a character type of the same size, for example it | |
1337 | might make sense to set it for the C type @code{wchar_t} so the debugger | |
1338 | can print such variables differently (Solaris does not do this). Sun | |
1339 | sets it on the C types @code{signed char} and @code{unsigned char} which | |
1340 | arguably is wrong. @var{width} and @var{offset} appear to be for small | |
1341 | objects stored in larger ones, for example a @code{short} in an | |
1342 | @code{int} register. @var{width} is normally the number of bytes in the | |
1343 | type. @var{offset} seems to always be zero. @var{nbits} is the number | |
1344 | of bits in the type. | |
1345 | ||
1346 | Note that type descriptor @samp{b} used for builtin types conflicts with | |
bf9d2537 | 1347 | its use for Pascal space types (@pxref{Miscellaneous Types}); they can |
8c59ee11 JK |
1348 | be distinguished because the character following the type descriptor |
1349 | will be a digit, @samp{(}, or @samp{-} for a Pascal space type, or | |
1350 | @samp{u} or @samp{s} for a builtin type. | |
1351 | ||
1352 | @item w | |
1353 | Documented by AIX to define a wide character type, but their compiler | |
bf9d2537 | 1354 | actually uses negative type numbers (@pxref{Negative Type Numbers}). |
8c59ee11 | 1355 | |
685a5e86 DM |
1356 | @item R @var{fp-type} ; @var{bytes} ; |
1357 | Define a floating point type. @var{fp-type} has one of the following values: | |
1a8b5668 JK |
1358 | |
1359 | @table @code | |
1360 | @item 1 (NF_SINGLE) | |
1361 | IEEE 32-bit (single precision) floating point format. | |
1362 | ||
1363 | @item 2 (NF_DOUBLE) | |
1364 | IEEE 64-bit (double precision) floating point format. | |
1365 | ||
1366 | @item 3 (NF_COMPLEX) | |
1367 | @item 4 (NF_COMPLEX16) | |
1368 | @item 5 (NF_COMPLEX32) | |
3d4cf720 JK |
1369 | @c "GDB source" really means @file{include/aout/stab_gnu.h}, but trying |
1370 | @c to put that here got an overfull hbox. | |
1371 | These are for complex numbers. A comment in the GDB source describes | |
685a5e86 DM |
1372 | them as Fortran @code{complex}, @code{double complex}, and |
1373 | @code{complex*16}, respectively, but what does that mean? (i.e., Single | |
1374 | precision? Double precison?). | |
1a8b5668 JK |
1375 | |
1376 | @item 6 (NF_LDOUBLE) | |
43603088 | 1377 | Long double. This should probably only be used for Sun format |
685a5e86 DM |
1378 | @code{long double}, and new codes should be used for other floating |
1379 | point formats (@code{NF_DOUBLE} can be used if a @code{long double} is | |
1380 | really just an IEEE double, of course). | |
1a8b5668 JK |
1381 | @end table |
1382 | ||
1383 | @var{bytes} is the number of bytes occupied by the type. This allows a | |
1384 | debugger to perform some operations with the type even if it doesn't | |
685a5e86 | 1385 | understand @var{fp-type}. |
8c59ee11 JK |
1386 | |
1387 | @item g @var{type-information} ; @var{nbits} | |
1388 | Documented by AIX to define a floating type, but their compiler actually | |
bf9d2537 | 1389 | uses negative type numbers (@pxref{Negative Type Numbers}). |
8c59ee11 JK |
1390 | |
1391 | @item c @var{type-information} ; @var{nbits} | |
1392 | Documented by AIX to define a complex type, but their compiler actually | |
bf9d2537 | 1393 | uses negative type numbers (@pxref{Negative Type Numbers}). |
8c59ee11 JK |
1394 | @end table |
1395 | ||
1396 | The C @code{void} type is defined as a signed integral type 0 bits long: | |
1397 | @example | |
1398 | .stabs "void:t19=bs0;0;0",128,0,0,0 | |
1399 | @end example | |
e9f687d5 JK |
1400 | The Solaris compiler seems to omit the trailing semicolon in this case. |
1401 | Getting sloppy in this way is not a swift move because if a type is | |
1402 | embedded in a more complex expression it is necessary to be able to tell | |
1403 | where it ends. | |
8c59ee11 JK |
1404 | |
1405 | I'm not sure how a boolean type is represented. | |
1406 | ||
bf9d2537 DM |
1407 | @node Negative Type Numbers |
1408 | @subsection Negative Type Numbers | |
8c59ee11 | 1409 | |
685a5e86 | 1410 | This is the method used in XCOFF for defining builtin types. |
8c59ee11 JK |
1411 | Since the debugger knows about the builtin types anyway, the idea of |
1412 | negative type numbers is simply to give a special type number which | |
685a5e86 | 1413 | indicates the builtin type. There is no stab defining these types. |
8c59ee11 | 1414 | |
23afb447 JK |
1415 | There are several subtle issues with negative type numbers. |
1416 | ||
1417 | One is the size of the type. A builtin type (for example the C types | |
1418 | @code{int} or @code{long}) might have different sizes depending on | |
1419 | compiler options, the target architecture, the ABI, etc. This issue | |
1420 | doesn't come up for IBM tools since (so far) they just target the | |
1421 | RS/6000; the sizes indicated below for each size are what the IBM | |
1422 | RS/6000 tools use. To deal with differing sizes, either define separate | |
1423 | negative type numbers for each size (which works but requires changing | |
1424 | the debugger, and, unless you get both AIX dbx and GDB to accept the | |
1425 | change, introduces an incompatibility), or use a type attribute | |
1426 | (@pxref{String Field}) to define a new type with the appropriate size | |
1427 | (which merely requires a debugger which understands type attributes, | |
1428 | like AIX dbx). For example, | |
1429 | ||
1430 | @example | |
1431 | .stabs "boolean:t10=@@s8;-16",128,0,0,0 | |
1432 | @end example | |
1433 | ||
1434 | defines an 8-bit boolean type, and | |
1435 | ||
1436 | @example | |
1437 | .stabs "boolean:t10=@@s64;-16",128,0,0,0 | |
1438 | @end example | |
1439 | ||
1440 | defines a 64-bit boolean type. | |
1441 | ||
1442 | A similar issue is the format of the type. This comes up most often for | |
1443 | floating-point types, which could have various formats (particularly | |
1444 | extended doubles, which vary quite a bit even among IEEE systems). | |
1445 | Again, it is best to define a new negative type number for each | |
1446 | different format; changing the format based on the target system has | |
1447 | various problems. One such problem is that the Alpha has both VAX and | |
1448 | IEEE floating types. One can easily imagine one library using the VAX | |
1449 | types and another library in the same executable using the IEEE types. | |
1450 | Another example is that the interpretation of whether a boolean is true | |
1451 | or false can be based on the least significant bit, most significant | |
1452 | bit, whether it is zero, etc., and different compilers (or different | |
1453 | options to the same compiler) might provide different kinds of boolean. | |
1454 | ||
1455 | The last major issue is the names of the types. The name of a given | |
1456 | type depends @emph{only} on the negative type number given; these do not | |
1457 | vary depending on the language, the target system, or anything else. | |
1458 | One can always define separate type numbers---in the following list you | |
1459 | will see for example separate @code{int} and @code{integer*4} types | |
1460 | which are identical except for the name. But compatibility can be | |
1461 | maintained by not inventing new negative type numbers and instead just | |
1462 | defining a new type with a new name. For example: | |
1463 | ||
1464 | @example | |
1465 | .stabs "CARDINAL:t10=-8",128,0,0,0 | |
1466 | @end example | |
1467 | ||
1468 | Here is the list of negative type numbers. The phrase @dfn{integral | |
1469 | type} is used to mean twos-complement (I strongly suspect that all | |
1470 | machines which use stabs use twos-complement; most machines use | |
1471 | twos-complement these days). | |
b273dc0f | 1472 | |
8c59ee11 JK |
1473 | @table @code |
1474 | @item -1 | |
1475 | @code{int}, 32 bit signed integral type. | |
1476 | ||
1477 | @item -2 | |
dd8126d9 | 1478 | @code{char}, 8 bit type holding a character. Both GDB and dbx on AIX |
8c59ee11 | 1479 | treat this as signed. GCC uses this type whether @code{char} is signed |
685a5e86 | 1480 | or not, which seems like a bad idea. The AIX compiler (@code{xlc}) seems to |
8c59ee11 JK |
1481 | avoid this type; it uses -5 instead for @code{char}. |
1482 | ||
1483 | @item -3 | |
1484 | @code{short}, 16 bit signed integral type. | |
1485 | ||
1486 | @item -4 | |
1487 | @code{long}, 32 bit signed integral type. | |
1488 | ||
1489 | @item -5 | |
1490 | @code{unsigned char}, 8 bit unsigned integral type. | |
1491 | ||
1492 | @item -6 | |
1493 | @code{signed char}, 8 bit signed integral type. | |
1494 | ||
1495 | @item -7 | |
1496 | @code{unsigned short}, 16 bit unsigned integral type. | |
1497 | ||
1498 | @item -8 | |
1499 | @code{unsigned int}, 32 bit unsigned integral type. | |
1500 | ||
1501 | @item -9 | |
1502 | @code{unsigned}, 32 bit unsigned integral type. | |
1503 | ||
1504 | @item -10 | |
1505 | @code{unsigned long}, 32 bit unsigned integral type. | |
1506 | ||
1507 | @item -11 | |
1508 | @code{void}, type indicating the lack of a value. | |
1509 | ||
1510 | @item -12 | |
1511 | @code{float}, IEEE single precision. | |
1512 | ||
1513 | @item -13 | |
1514 | @code{double}, IEEE double precision. | |
1515 | ||
1516 | @item -14 | |
b273dc0f JK |
1517 | @code{long double}, IEEE double precision. The compiler claims the size |
1518 | will increase in a future release, and for binary compatibility you have | |
1519 | to avoid using @code{long double}. I hope when they increase it they | |
1520 | use a new negative type number. | |
8c59ee11 JK |
1521 | |
1522 | @item -15 | |
b273dc0f | 1523 | @code{integer}. 32 bit signed integral type. |
8c59ee11 JK |
1524 | |
1525 | @item -16 | |
455c8603 JK |
1526 | @code{boolean}. 32 bit type. How is the truth value encoded? Is it |
1527 | the least significant bit or is it a question of whether the whole value | |
1528 | is zero or non-zero? | |
8c59ee11 JK |
1529 | |
1530 | @item -17 | |
b273dc0f | 1531 | @code{short real}. IEEE single precision. |
8c59ee11 JK |
1532 | |
1533 | @item -18 | |
b273dc0f | 1534 | @code{real}. IEEE double precision. |
8c59ee11 JK |
1535 | |
1536 | @item -19 | |
b273dc0f | 1537 | @code{stringptr}. @xref{Strings}. |
8c59ee11 JK |
1538 | |
1539 | @item -20 | |
dcb9e869 | 1540 | @code{character}, 8 bit unsigned character type. |
8c59ee11 JK |
1541 | |
1542 | @item -21 | |
6fe91f2c | 1543 | @code{logical*1}, 8 bit type. This Fortran type has a split |
01c4b039 | 1544 | personality in that it is used for boolean variables, but can also be |
03ffea63 JK |
1545 | used for unsigned integers. 0 is false, 1 is true, and other values are |
1546 | non-boolean. | |
8c59ee11 JK |
1547 | |
1548 | @item -22 | |
6fe91f2c | 1549 | @code{logical*2}, 16 bit type. This Fortran type has a split |
01c4b039 | 1550 | personality in that it is used for boolean variables, but can also be |
03ffea63 JK |
1551 | used for unsigned integers. 0 is false, 1 is true, and other values are |
1552 | non-boolean. | |
8c59ee11 JK |
1553 | |
1554 | @item -23 | |
6fe91f2c | 1555 | @code{logical*4}, 32 bit type. This Fortran type has a split |
01c4b039 | 1556 | personality in that it is used for boolean variables, but can also be |
03ffea63 JK |
1557 | used for unsigned integers. 0 is false, 1 is true, and other values are |
1558 | non-boolean. | |
8c59ee11 JK |
1559 | |
1560 | @item -24 | |
6fe91f2c | 1561 | @code{logical}, 32 bit type. This Fortran type has a split |
0e84d6ec | 1562 | personality in that it is used for boolean variables, but can also be |
03ffea63 JK |
1563 | used for unsigned integers. 0 is false, 1 is true, and other values are |
1564 | non-boolean. | |
8c59ee11 JK |
1565 | |
1566 | @item -25 | |
b273dc0f JK |
1567 | @code{complex}. A complex type consisting of two IEEE single-precision |
1568 | floating point values. | |
8c59ee11 JK |
1569 | |
1570 | @item -26 | |
b273dc0f JK |
1571 | @code{complex}. A complex type consisting of two IEEE double-precision |
1572 | floating point values. | |
8c59ee11 JK |
1573 | |
1574 | @item -27 | |
1575 | @code{integer*1}, 8 bit signed integral type. | |
1576 | ||
1577 | @item -28 | |
1578 | @code{integer*2}, 16 bit signed integral type. | |
1579 | ||
1580 | @item -29 | |
1581 | @code{integer*4}, 32 bit signed integral type. | |
1582 | ||
1583 | @item -30 | |
dcb9e869 JK |
1584 | @code{wchar}. Wide character, 16 bits wide, unsigned (what format? |
1585 | Unicode?). | |
8c59ee11 JK |
1586 | @end table |
1587 | ||
bf9d2537 DM |
1588 | @node Miscellaneous Types |
1589 | @section Miscellaneous Types | |
8c59ee11 JK |
1590 | |
1591 | @table @code | |
1592 | @item b @var{type-information} ; @var{bytes} | |
1593 | Pascal space type. This is documented by IBM; what does it mean? | |
1594 | ||
685a5e86 | 1595 | This use of the @samp{b} type descriptor can be distinguished |
bf9d2537 DM |
1596 | from its use for builtin integral types (@pxref{Builtin Type |
1597 | Descriptors}) because the character following the type descriptor is | |
8c59ee11 JK |
1598 | always a digit, @samp{(}, or @samp{-}. |
1599 | ||
1600 | @item B @var{type-information} | |
43603088 | 1601 | A volatile-qualified version of @var{type-information}. This is |
685a5e86 | 1602 | a Sun extension. References and stores to a variable with a |
43603088 | 1603 | volatile-qualified type must not be optimized or cached; they |
685a5e86 | 1604 | must occur as the user specifies them. |
8c59ee11 JK |
1605 | |
1606 | @item d @var{type-information} | |
1607 | File of type @var{type-information}. As far as I know this is only used | |
1608 | by Pascal. | |
1609 | ||
1610 | @item k @var{type-information} | |
43603088 JK |
1611 | A const-qualified version of @var{type-information}. This is a Sun |
1612 | extension. A variable with a const-qualified type cannot be modified. | |
8c59ee11 JK |
1613 | |
1614 | @item M @var{type-information} ; @var{length} | |
1615 | Multiple instance type. The type seems to composed of @var{length} | |
1616 | repetitions of @var{type-information}, for example @code{character*3} is | |
1617 | represented by @samp{M-2;3}, where @samp{-2} is a reference to a | |
bf9d2537 | 1618 | character type (@pxref{Negative Type Numbers}). I'm not sure how this |
6fe91f2c DM |
1619 | differs from an array. This appears to be a Fortran feature. |
1620 | @var{length} is a bound, like those in range types; see @ref{Subranges}. | |
8c59ee11 JK |
1621 | |
1622 | @item S @var{type-information} | |
1623 | Pascal set type. @var{type-information} must be a small type such as an | |
1624 | enumeration or a subrange, and the type is a bitmask whose length is | |
1625 | specified by the number of elements in @var{type-information}. | |
1626 | ||
1627 | @item * @var{type-information} | |
1628 | Pointer to @var{type-information}. | |
139741da | 1629 | @end table |
e505224d | 1630 | |
bf9d2537 DM |
1631 | @node Cross-References |
1632 | @section Cross-References to Other Types | |
8c59ee11 | 1633 | |
685a5e86 DM |
1634 | A type can be used before it is defined; one common way to deal with |
1635 | that situation is just to use a type reference to a type which has not | |
1636 | yet been defined. | |
8c59ee11 JK |
1637 | |
1638 | Another way is with the @samp{x} type descriptor, which is followed by | |
1639 | @samp{s} for a structure tag, @samp{u} for a union tag, or @samp{e} for | |
1640 | a enumerator tag, followed by the name of the tag, followed by @samp{:}. | |
685a5e86 | 1641 | For example, the following C declarations: |
e505224d PB |
1642 | |
1643 | @example | |
8c59ee11 JK |
1644 | struct foo; |
1645 | struct foo *bar; | |
e505224d PB |
1646 | @end example |
1647 | ||
685a5e86 DM |
1648 | @noindent |
1649 | produce: | |
8c59ee11 JK |
1650 | |
1651 | @example | |
1652 | .stabs "bar:G16=*17=xsfoo:",32,0,0,0 | |
1653 | @end example | |
1654 | ||
1655 | Not all debuggers support the @samp{x} type descriptor, so on some | |
1656 | machines GCC does not use it. I believe that for the above example it | |
1657 | would just emit a reference to type 17 and never define it, but I | |
1658 | haven't verified that. | |
1659 | ||
1660 | Modula-2 imported types, at least on AIX, use the @samp{i} type | |
1661 | descriptor, which is followed by the name of the module from which the | |
1662 | type is imported, followed by @samp{:}, followed by the name of the | |
1663 | type. There is then optionally a comma followed by type information for | |
685a5e86 | 1664 | the type. This differs from merely naming the type (@pxref{Typedefs}) in |
8c59ee11 JK |
1665 | that it identifies the module; I don't understand whether the name of |
1666 | the type given here is always just the same as the name we are giving | |
1667 | it, or whether this type descriptor is used with a nameless stab | |
bf9d2537 | 1668 | (@pxref{String Field}), or what. The symbol ends with @samp{;}. |
e505224d | 1669 | |
8c59ee11 | 1670 | @node Subranges |
bf9d2537 | 1671 | @section Subrange Types |
8c59ee11 JK |
1672 | |
1673 | The @samp{r} type descriptor defines a type as a subrange of another | |
685a5e86 DM |
1674 | type. It is followed by type information for the type of which it is a |
1675 | subrange, a semicolon, an integral lower bound, a semicolon, an | |
8c59ee11 | 1676 | integral upper bound, and a semicolon. The AIX documentation does not |
63cef7d7 JK |
1677 | specify the trailing semicolon, in an effort to specify array indexes |
1678 | more cleanly, but a subrange which is not an array index has always | |
466bdeb2 | 1679 | included a trailing semicolon (@pxref{Arrays}). |
8c59ee11 | 1680 | |
8cfe3beb | 1681 | Instead of an integer, either bound can be one of the following: |
8c59ee11 JK |
1682 | |
1683 | @table @code | |
1684 | @item A @var{offset} | |
1685 | The bound is passed by reference on the stack at offset @var{offset} | |
1686 | from the argument list. @xref{Parameters}, for more information on such | |
1687 | offsets. | |
1688 | ||
1689 | @item T @var{offset} | |
1690 | The bound is passed by value on the stack at offset @var{offset} from | |
1691 | the argument list. | |
1692 | ||
1693 | @item a @var{register-number} | |
1694 | The bound is pased by reference in register number | |
1695 | @var{register-number}. | |
1696 | ||
1697 | @item t @var{register-number} | |
1698 | The bound is passed by value in register number @var{register-number}. | |
1699 | ||
1700 | @item J | |
1701 | There is no bound. | |
1702 | @end table | |
1703 | ||
bf9d2537 | 1704 | Subranges are also used for builtin types; see @ref{Traditional Builtin Types}. |
8c59ee11 JK |
1705 | |
1706 | @node Arrays | |
bf9d2537 | 1707 | @section Array Types |
8c59ee11 JK |
1708 | |
1709 | Arrays use the @samp{a} type descriptor. Following the type descriptor | |
63cef7d7 | 1710 | is the type of the index and the type of the array elements. If the |
685a5e86 DM |
1711 | index type is a range type, it ends in a semicolon; otherwise |
1712 | (for example, if it is a type reference), there does not | |
63cef7d7 JK |
1713 | appear to be any way to tell where the types are separated. In an |
1714 | effort to clean up this mess, IBM documents the two types as being | |
1715 | separated by a semicolon, and a range type as not ending in a semicolon | |
1716 | (but this is not right for range types which are not array indexes, | |
1717 | @pxref{Subranges}). I think probably the best solution is to specify | |
1718 | that a semicolon ends a range type, and that the index type and element | |
1719 | type of an array are separated by a semicolon, but that if the index | |
1720 | type is a range type, the extra semicolon can be omitted. GDB (at least | |
1721 | through version 4.9) doesn't support any kind of index type other than a | |
1722 | range anyway; I'm not sure about dbx. | |
6aa83a79 | 1723 | |
ee59134e | 1724 | It is well established, and widely used, that the type of the index, |
3d4cf720 | 1725 | unlike most types found in the stabs, is merely a type definition, not |
bf9d2537 | 1726 | type information (@pxref{String Field}) (that is, it need not start with |
685a5e86 | 1727 | @samp{@var{type-number}=} if it is defining a new type). According to a |
3d4cf720 JK |
1728 | comment in GDB, this is also true of the type of the array elements; it |
1729 | gives @samp{ar1;1;10;ar1;1;10;4} as a legitimate way to express a two | |
1730 | dimensional array. According to AIX documentation, the element type | |
1731 | must be type information. GDB accepts either. | |
ee59134e | 1732 | |
43603088 JK |
1733 | The type of the index is often a range type, expressed as the type |
1734 | descriptor @samp{r} and some parameters. It defines the size of the | |
1735 | array. In the example below, the range @samp{r1;0;2;} defines an index | |
1736 | type which is a subrange of type 1 (integer), with a lower bound of 0 | |
1737 | and an upper bound of 2. This defines the valid range of subscripts of | |
1738 | a three-element C array. | |
e505224d | 1739 | |
685a5e86 | 1740 | For example, the definition: |
e505224d PB |
1741 | |
1742 | @example | |
8c59ee11 JK |
1743 | char char_vec[3] = @{'a','b','c'@}; |
1744 | @end example | |
e505224d | 1745 | |
8c59ee11 | 1746 | @noindent |
685a5e86 | 1747 | produces the output: |
8c59ee11 JK |
1748 | |
1749 | @example | |
1750 | .stabs "char_vec:G19=ar1;0;2;2",32,0,0,0 | |
1751 | .global _char_vec | |
1752 | .align 4 | |
1753 | _char_vec: | |
1754 | .byte 97 | |
1755 | .byte 98 | |
1756 | .byte 99 | |
1757 | @end example | |
1758 | ||
685a5e86 | 1759 | If an array is @dfn{packed}, the elements are spaced more |
8c59ee11 JK |
1760 | closely than normal, saving memory at the expense of speed. For |
1761 | example, an array of 3-byte objects might, if unpacked, have each | |
1762 | element aligned on a 4-byte boundary, but if packed, have no padding. | |
1763 | One way to specify that something is packed is with type attributes | |
bf9d2537 | 1764 | (@pxref{String Field}). In the case of arrays, another is to use the |
8c59ee11 JK |
1765 | @samp{P} type descriptor instead of @samp{a}. Other than specifying a |
1766 | packed array, @samp{P} is identical to @samp{a}. | |
1767 | ||
1768 | @c FIXME-what is it? A pointer? | |
1769 | An open array is represented by the @samp{A} type descriptor followed by | |
1770 | type information specifying the type of the array elements. | |
1771 | ||
1772 | @c FIXME: what is the format of this type? A pointer to a vector of pointers? | |
1773 | An N-dimensional dynamic array is represented by | |
1774 | ||
1775 | @example | |
1776 | D @var{dimensions} ; @var{type-information} | |
1777 | @end example | |
1778 | ||
1779 | @c Does dimensions really have this meaning? The AIX documentation | |
1780 | @c doesn't say. | |
1781 | @var{dimensions} is the number of dimensions; @var{type-information} | |
1782 | specifies the type of the array elements. | |
1783 | ||
1784 | @c FIXME: what is the format of this type? A pointer to some offsets in | |
1785 | @c another array? | |
1786 | A subarray of an N-dimensional array is represented by | |
1787 | ||
1788 | @example | |
1789 | E @var{dimensions} ; @var{type-information} | |
e505224d PB |
1790 | @end example |
1791 | ||
8c59ee11 JK |
1792 | @c Does dimensions really have this meaning? The AIX documentation |
1793 | @c doesn't say. | |
1794 | @var{dimensions} is the number of dimensions; @var{type-information} | |
1795 | specifies the type of the array elements. | |
1796 | ||
1797 | @node Strings | |
1798 | @section Strings | |
1799 | ||
1800 | Some languages, like C or the original Pascal, do not have string types, | |
1801 | they just have related things like arrays of characters. But most | |
1802 | Pascals and various other languages have string types, which are | |
1803 | indicated as follows: | |
1804 | ||
1805 | @table @code | |
1806 | @item n @var{type-information} ; @var{bytes} | |
1807 | @var{bytes} is the maximum length. I'm not sure what | |
1808 | @var{type-information} is; I suspect that it means that this is a string | |
1809 | of @var{type-information} (thus allowing a string of integers, a string | |
1810 | of wide characters, etc., as well as a string of characters). Not sure | |
1811 | what the format of this type is. This is an AIX feature. | |
1812 | ||
1813 | @item z @var{type-information} ; @var{bytes} | |
1814 | Just like @samp{n} except that this is a gstring, not an ordinary | |
1815 | string. I don't know the difference. | |
1816 | ||
1817 | @item N | |
1818 | Pascal Stringptr. What is this? This is an AIX feature. | |
1819 | @end table | |
1820 | ||
899bafeb | 1821 | @node Enumerations |
6fe91f2c | 1822 | @section Enumerations |
e505224d | 1823 | |
8c59ee11 | 1824 | Enumerations are defined with the @samp{e} type descriptor. |
e505224d | 1825 | |
8c59ee11 JK |
1826 | @c FIXME: Where does this information properly go? Perhaps it is |
1827 | @c redundant with something we already explain. | |
685a5e86 | 1828 | The source line below declares an enumeration type at file scope. |
6fe91f2c DM |
1829 | The type definition is located after the @code{N_RBRAC} that marks the end of |
1830 | the previous procedure's block scope, and before the @code{N_FUN} that marks | |
8c59ee11 | 1831 | the beginning of the next procedure's block scope. Therefore it does not |
6fe91f2c | 1832 | describe a block local symbol, but a file local one. |
8c59ee11 JK |
1833 | |
1834 | The source line: | |
e505224d PB |
1835 | |
1836 | @example | |
8c59ee11 | 1837 | enum e_places @{first,second=3,last@}; |
e505224d PB |
1838 | @end example |
1839 | ||
899bafeb | 1840 | @noindent |
685a5e86 | 1841 | generates the following stab: |
e505224d | 1842 | |
899bafeb | 1843 | @example |
8c59ee11 | 1844 | .stabs "e_places:T22=efirst:0,second:3,last:4,;",128,0,0,0 |
899bafeb | 1845 | @end example |
e505224d | 1846 | |
685a5e86 DM |
1847 | The symbol descriptor (@samp{T}) says that the stab describes a |
1848 | structure, enumeration, or union tag. The type descriptor @samp{e}, | |
1849 | following the @samp{22=} of the type definition narrows it down to an | |
1850 | enumeration type. Following the @samp{e} is a list of the elements of | |
1851 | the enumeration. The format is @samp{@var{name}:@var{value},}. The | |
ae701604 JK |
1852 | list of elements ends with @samp{;}. The fact that @var{value} is |
1853 | specified as an integer can cause problems if the value is large. GCC | |
1854 | 2.5.2 tries to output it in octal in that case with a leading zero, | |
1855 | which is probably a good thing, although GDB 4.11 supports octal only in | |
1856 | cases where decimal is perfectly good. Negative decimal values are | |
1857 | supported by both GDB and dbx. | |
e505224d | 1858 | |
8c59ee11 JK |
1859 | There is no standard way to specify the size of an enumeration type; it |
1860 | is determined by the architecture (normally all enumerations types are | |
ae701604 JK |
1861 | 32 bits). Type attributes can be used to specify an enumeration type of |
1862 | another size for debuggers which support them; see @ref{String Field}. | |
8c59ee11 JK |
1863 | |
1864 | @node Structures | |
1865 | @section Structures | |
e505224d | 1866 | |
685a5e86 | 1867 | The encoding of structures in stabs can be shown with an example. |
e505224d PB |
1868 | |
1869 | The following source code declares a structure tag and defines an | |
685a5e86 DM |
1870 | instance of the structure in global scope. Then a @code{typedef} equates the |
1871 | structure tag with a new type. Seperate stabs are generated for the | |
1872 | structure tag, the structure @code{typedef}, and the structure instance. The | |
1873 | stabs for the tag and the @code{typedef} are emited when the definitions are | |
e505224d PB |
1874 | encountered. Since the structure elements are not initialized, the |
1875 | stab and code for the structure variable itself is located at the end | |
685a5e86 | 1876 | of the program in the bss section. |
e505224d PB |
1877 | |
1878 | @example | |
685a5e86 DM |
1879 | struct s_tag @{ |
1880 | int s_int; | |
1881 | float s_float; | |
1882 | char s_char_vec[8]; | |
1883 | struct s_tag* s_next; | |
1884 | @} g_an_s; | |
e505224d | 1885 | |
685a5e86 DM |
1886 | typedef struct s_tag s_typedef; |
1887 | @end example | |
e505224d | 1888 | |
685a5e86 DM |
1889 | The structure tag has an @code{N_LSYM} stab type because, like the |
1890 | enumeration, the symbol has file scope. Like the enumeration, the | |
1891 | symbol descriptor is @samp{T}, for enumeration, structure, or tag type. | |
43603088 | 1892 | The type descriptor @samp{s} following the @samp{16=} of the type |
685a5e86 | 1893 | definition narrows the symbol type to structure. |
e505224d | 1894 | |
43603088 | 1895 | Following the @samp{s} type descriptor is the number of bytes the |
685a5e86 DM |
1896 | structure occupies, followed by a description of each structure element. |
1897 | The structure element descriptions are of the form @var{name:type, bit | |
1898 | offset from the start of the struct, number of bits in the element}. | |
e505224d | 1899 | |
43603088 JK |
1900 | @c FIXME: phony line break. Can probably be fixed by using an example |
1901 | @c with fewer fields. | |
685a5e86 | 1902 | @example |
43603088 | 1903 | # @r{128 is N_LSYM} |
685a5e86 DM |
1904 | .stabs "s_tag:T16=s20s_int:1,0,32;s_float:12,32,32; |
1905 | s_char_vec:17=ar1;0;7;2,64,64;s_next:18=*16,128,32;;",128,0,0,0 | |
612dbd4c | 1906 | @end example |
6fe91f2c | 1907 | |
685a5e86 DM |
1908 | In this example, the first two structure elements are previously defined |
1909 | types. For these, the type following the @samp{@var{name}:} part of the | |
1910 | element description is a simple type reference. The other two structure | |
e505224d | 1911 | elements are new types. In this case there is a type definition |
685a5e86 DM |
1912 | embedded after the @samp{@var{name}:}. The type definition for the |
1913 | array element looks just like a type definition for a standalone array. | |
1914 | The @code{s_next} field is a pointer to the same kind of structure that | |
1915 | the field is an element of. So the definition of structure type 16 | |
1916 | contains a type definition for an element which is a pointer to type 16. | |
e505224d | 1917 | |
899bafeb | 1918 | @node Typedefs |
bf9d2537 | 1919 | @section Giving a Type a Name |
e505224d | 1920 | |
e7bb76cc | 1921 | To give a type a name, use the @samp{t} symbol descriptor. The type |
bf9d2537 | 1922 | is specified by the type information (@pxref{String Field}) for the stab. |
e7bb76cc | 1923 | For example, |
e505224d | 1924 | |
899bafeb | 1925 | @example |
43603088 | 1926 | .stabs "s_typedef:t16",128,0,0,0 # @r{128 is N_LSYM} |
899bafeb | 1927 | @end example |
e505224d | 1928 | |
8c59ee11 | 1929 | specifies that @code{s_typedef} refers to type number 16. Such stabs |
43603088 | 1930 | have symbol type @code{N_LSYM} (or @code{C_DECL} for XCOFF). |
e505224d | 1931 | |
685a5e86 | 1932 | If you are specifying the tag name for a structure, union, or |
8c59ee11 JK |
1933 | enumeration, use the @samp{T} symbol descriptor instead. I believe C is |
1934 | the only language with this feature. | |
e505224d | 1935 | |
8c59ee11 JK |
1936 | If the type is an opaque type (I believe this is a Modula-2 feature), |
1937 | AIX provides a type descriptor to specify it. The type descriptor is | |
1938 | @samp{o} and is followed by a name. I don't know what the name | |
1939 | means---is it always the same as the name of the type, or is this type | |
bf9d2537 | 1940 | descriptor used with a nameless stab (@pxref{String Field})? There |
8c59ee11 JK |
1941 | optionally follows a comma followed by type information which defines |
1942 | the type of this type. If omitted, a semicolon is used in place of the | |
e7bb76cc | 1943 | comma and the type information, and the type is much like a generic |
8c59ee11 JK |
1944 | pointer type---it has a known size but little else about it is |
1945 | specified. | |
e505224d | 1946 | |
899bafeb | 1947 | @node Unions |
6fe91f2c | 1948 | @section Unions |
e505224d | 1949 | |
e505224d | 1950 | @example |
685a5e86 DM |
1951 | union u_tag @{ |
1952 | int u_int; | |
1953 | float u_float; | |
1954 | char* u_char; | |
1955 | @} an_u; | |
e505224d PB |
1956 | @end example |
1957 | ||
685a5e86 DM |
1958 | This code generates a stab for a union tag and a stab for a union |
1959 | variable. Both use the @code{N_LSYM} stab type. If a union variable is | |
e505224d | 1960 | scoped locally to the procedure in which it is defined, its stab is |
6fe91f2c | 1961 | located immediately preceding the @code{N_LBRAC} for the procedure's block |
e505224d PB |
1962 | start. |
1963 | ||
685a5e86 | 1964 | The stab for the union tag, however, is located preceding the code for |
6fe91f2c | 1965 | the procedure in which it is defined. The stab type is @code{N_LSYM}. This |
e505224d | 1966 | would seem to imply that the union type is file scope, like the struct |
f958d5cd DM |
1967 | type @code{s_tag}. This is not true. The contents and position of the stab |
1968 | for @code{u_type} do not convey any infomation about its procedure local | |
e505224d PB |
1969 | scope. |
1970 | ||
43603088 JK |
1971 | @c FIXME: phony line break. Can probably be fixed by using an example |
1972 | @c with fewer fields. | |
5bc927fb | 1973 | @smallexample |
43603088 | 1974 | # @r{128 is N_LSYM} |
685a5e86 DM |
1975 | .stabs "u_tag:T23=u4u_int:1,0,32;u_float:12,0,32;u_char:21,0,32;;", |
1976 | 128,0,0,0 | |
5bc927fb | 1977 | @end smallexample |
e505224d | 1978 | |
685a5e86 DM |
1979 | The symbol descriptor @samp{T}, following the @samp{name:} means that |
1980 | the stab describes an enumeration, structure, or union tag. The type | |
1981 | descriptor @samp{u}, following the @samp{23=} of the type definition, | |
1982 | narrows it down to a union type definition. Following the @samp{u} is | |
1983 | the number of bytes in the union. After that is a list of union element | |
1984 | descriptions. Their format is @var{name:type, bit offset into the | |
1985 | union, number of bytes for the element;}. | |
e505224d | 1986 | |
685a5e86 | 1987 | The stab for the union variable is: |
e505224d | 1988 | |
899bafeb | 1989 | @example |
43603088 | 1990 | .stabs "an_u:23",128,0,0,-20 # @r{128 is N_LSYM} |
899bafeb | 1991 | @end example |
e505224d | 1992 | |
43603088 | 1993 | @samp{-20} specifies where the variable is stored (@pxref{Stack |
bf9d2537 | 1994 | Variables}). |
43603088 | 1995 | |
bf9d2537 DM |
1996 | @node Function Types |
1997 | @section Function Types | |
e505224d | 1998 | |
685a5e86 DM |
1999 | Various types can be defined for function variables. These types are |
2000 | not used in defining functions (@pxref{Procedures}); they are used for | |
2001 | things like pointers to functions. | |
e505224d | 2002 | |
8c59ee11 JK |
2003 | The simple, traditional, type is type descriptor @samp{f} is followed by |
2004 | type information for the return type of the function, followed by a | |
2005 | semicolon. | |
2006 | ||
685a5e86 DM |
2007 | This does not deal with functions for which the number and types of the |
2008 | parameters are part of the type, as in Modula-2 or ANSI C. AIX provides | |
2009 | extensions to specify these, using the @samp{f}, @samp{F}, @samp{p}, and | |
2010 | @samp{R} type descriptors. | |
8c59ee11 | 2011 | |
685a5e86 | 2012 | First comes the type descriptor. If it is @samp{f} or @samp{F}, this |
43603088 JK |
2013 | type involves a function rather than a procedure, and the type |
2014 | information for the return type of the function follows, followed by a | |
2015 | comma. Then comes the number of parameters to the function and a | |
2016 | semicolon. Then, for each parameter, there is the name of the parameter | |
2017 | followed by a colon (this is only present for type descriptors @samp{R} | |
2018 | and @samp{F} which represent Pascal function or procedure parameters), | |
2019 | type information for the parameter, a comma, 0 if passed by reference or | |
2020 | 1 if passed by value, and a semicolon. The type definition ends with a | |
2021 | semicolon. | |
8c59ee11 | 2022 | |
685a5e86 | 2023 | For example, this variable definition: |
e505224d PB |
2024 | |
2025 | @example | |
8c59ee11 | 2026 | int (*g_pf)(); |
e505224d PB |
2027 | @end example |
2028 | ||
8c59ee11 JK |
2029 | @noindent |
2030 | generates the following code: | |
e505224d | 2031 | |
899bafeb | 2032 | @example |
8c59ee11 JK |
2033 | .stabs "g_pf:G24=*25=f1",32,0,0,0 |
2034 | .common _g_pf,4,"bss" | |
899bafeb | 2035 | @end example |
e505224d | 2036 | |
8c59ee11 | 2037 | The variable defines a new type, 24, which is a pointer to another new |
685a5e86 | 2038 | type, 25, which is a function returning @code{int}. |
e505224d | 2039 | |
bf9d2537 DM |
2040 | @node Symbol Tables |
2041 | @chapter Symbol Information in Symbol Tables | |
e505224d | 2042 | |
6fe91f2c DM |
2043 | This chapter describes the format of symbol table entries |
2044 | and how stab assembler directives map to them. It also describes the | |
2045 | transformations that the assembler and linker make on data from stabs. | |
e505224d | 2046 | |
685a5e86 | 2047 | @menu |
bf9d2537 DM |
2048 | * Symbol Table Format:: |
2049 | * Transformations On Symbol Tables:: | |
685a5e86 DM |
2050 | @end menu |
2051 | ||
bf9d2537 DM |
2052 | @node Symbol Table Format |
2053 | @section Symbol Table Format | |
685a5e86 DM |
2054 | |
2055 | Each time the assembler encounters a stab directive, it puts | |
2056 | each field of the stab into a corresponding field in a symbol table | |
0a95c18c | 2057 | entry of its output file. If the stab contains a string field, the |
e505224d PB |
2058 | symbol table entry for that stab points to a string table entry |
2059 | containing the string data from the stab. Assembler labels become | |
2060 | relocatable addresses. Symbol table entries in a.out have the format: | |
2061 | ||
dd8126d9 | 2062 | @c FIXME: should refer to external, not internal. |
e505224d PB |
2063 | @example |
2064 | struct internal_nlist @{ | |
139741da RP |
2065 | unsigned long n_strx; /* index into string table of name */ |
2066 | unsigned char n_type; /* type of symbol */ | |
2067 | unsigned char n_other; /* misc info (usually empty) */ | |
2068 | unsigned short n_desc; /* description field */ | |
2069 | bfd_vma n_value; /* value of symbol */ | |
e505224d PB |
2070 | @}; |
2071 | @end example | |
2072 | ||
0a95c18c JK |
2073 | If the stab has a string, the @code{n_strx} field holds the offset in |
2074 | bytes of the string within the string table. The string is terminated | |
2075 | by a NUL character. If the stab lacks a string (for example, it was | |
2076 | produced by a @code{.stabn} or @code{.stabd} directive), the | |
2077 | @code{n_strx} field is zero. | |
685a5e86 DM |
2078 | |
2079 | Symbol table entries with @code{n_type} field values greater than 0x1f | |
2080 | originated as stabs generated by the compiler (with one random | |
2081 | exception). The other entries were placed in the symbol table of the | |
2082 | executable by the assembler or the linker. | |
e505224d | 2083 | |
bf9d2537 DM |
2084 | @node Transformations On Symbol Tables |
2085 | @section Transformations on Symbol Tables | |
e505224d PB |
2086 | |
2087 | The linker concatenates object files and does fixups of externally | |
685a5e86 | 2088 | defined symbols. |
e505224d | 2089 | |
685a5e86 DM |
2090 | You can see the transformations made on stab data by the assembler and |
2091 | linker by examining the symbol table after each pass of the build. To | |
2092 | do this, use @samp{nm -ap}, which dumps the symbol table, including | |
6fe91f2c DM |
2093 | debugging information, unsorted. For stab entries the columns are: |
2094 | @var{value}, @var{other}, @var{desc}, @var{type}, @var{string}. For | |
2095 | assembler and linker symbols, the columns are: @var{value}, @var{type}, | |
2096 | @var{string}. | |
e505224d | 2097 | |
43603088 JK |
2098 | The low 5 bits of the stab type tell the linker how to relocate the |
2099 | value of the stab. Thus for stab types like @code{N_RSYM} and | |
2100 | @code{N_LSYM}, where the value is an offset or a register number, the | |
2101 | low 5 bits are @code{N_ABS}, which tells the linker not to relocate the | |
2102 | value. | |
e505224d | 2103 | |
0a95c18c | 2104 | Where the value of a stab contains an assembly language label, |
e505224d PB |
2105 | it is transformed by each build step. The assembler turns it into a |
2106 | relocatable address and the linker turns it into an absolute address. | |
685a5e86 DM |
2107 | |
2108 | @menu | |
bf9d2537 DM |
2109 | * Transformations On Static Variables:: |
2110 | * Transformations On Global Variables:: | |
cd61aa60 | 2111 | * ELF Transformations:: In ELF, things are a bit different. |
685a5e86 DM |
2112 | @end menu |
2113 | ||
bf9d2537 DM |
2114 | @node Transformations On Static Variables |
2115 | @subsection Transformations on Static Variables | |
685a5e86 | 2116 | |
e505224d PB |
2117 | This source line defines a static variable at file scope: |
2118 | ||
899bafeb | 2119 | @example |
685a5e86 | 2120 | static int s_g_repeat |
899bafeb | 2121 | @end example |
e505224d | 2122 | |
899bafeb | 2123 | @noindent |
6fe91f2c | 2124 | The following stab describes the symbol: |
e505224d | 2125 | |
899bafeb | 2126 | @example |
685a5e86 | 2127 | .stabs "s_g_repeat:S1",38,0,0,_s_g_repeat |
899bafeb | 2128 | @end example |
e505224d | 2129 | |
899bafeb | 2130 | @noindent |
e505224d | 2131 | The assembler transforms the stab into this symbol table entry in the |
899bafeb | 2132 | @file{.o} file. The location is expressed as a data segment offset. |
e505224d | 2133 | |
899bafeb | 2134 | @example |
685a5e86 | 2135 | 00000084 - 00 0000 STSYM s_g_repeat:S1 |
899bafeb | 2136 | @end example |
e505224d | 2137 | |
899bafeb | 2138 | @noindent |
685a5e86 | 2139 | In the symbol table entry from the executable, the linker has made the |
e505224d PB |
2140 | relocatable address absolute. |
2141 | ||
899bafeb | 2142 | @example |
685a5e86 | 2143 | 0000e00c - 00 0000 STSYM s_g_repeat:S1 |
899bafeb | 2144 | @end example |
e505224d | 2145 | |
bf9d2537 DM |
2146 | @node Transformations On Global Variables |
2147 | @subsection Transformations on Global Variables | |
685a5e86 | 2148 | |
e505224d | 2149 | Stabs for global variables do not contain location information. In |
685a5e86 | 2150 | this case, the debugger finds location information in the assembler or |
e505224d PB |
2151 | linker symbol table entry describing the variable. The source line: |
2152 | ||
899bafeb | 2153 | @example |
685a5e86 | 2154 | char g_foo = 'c'; |
899bafeb | 2155 | @end example |
e505224d | 2156 | |
899bafeb | 2157 | @noindent |
e505224d PB |
2158 | generates the stab: |
2159 | ||
899bafeb | 2160 | @example |
685a5e86 | 2161 | .stabs "g_foo:G2",32,0,0,0 |
899bafeb | 2162 | @end example |
e505224d | 2163 | |
685a5e86 DM |
2164 | The variable is represented by two symbol table entries in the object |
2165 | file (see below). The first one originated as a stab. The second one | |
2166 | is an external symbol. The upper case @samp{D} signifies that the | |
2167 | @code{n_type} field of the symbol table contains 7, @code{N_DATA} with | |
ac31351a JK |
2168 | local linkage. The stab's value is zero since the value is not used for |
2169 | @code{N_GSYM} stabs. The value of the linker symbol is the relocatable | |
2170 | address corresponding to the variable. | |
e505224d | 2171 | |
899bafeb | 2172 | @example |
685a5e86 DM |
2173 | 00000000 - 00 0000 GSYM g_foo:G2 |
2174 | 00000080 D _g_foo | |
899bafeb | 2175 | @end example |
e505224d | 2176 | |
899bafeb | 2177 | @noindent |
e505224d | 2178 | These entries as transformed by the linker. The linker symbol table |
685a5e86 | 2179 | entry now holds an absolute address: |
e505224d | 2180 | |
899bafeb | 2181 | @example |
685a5e86 | 2182 | 00000000 - 00 0000 GSYM g_foo:G2 |
899bafeb | 2183 | @dots{} |
685a5e86 | 2184 | 0000e008 D _g_foo |
899bafeb | 2185 | @end example |
e505224d | 2186 | |
cd61aa60 JK |
2187 | @node ELF Transformations |
2188 | @subsection Transformations of Stabs in ELF Files | |
2189 | ||
2190 | For ELF files, use @code{objdump --stabs} instead of @code{nm} to show | |
2191 | the stabs in an object or executable file. @code{objdump} is a GNU | |
2192 | utility; Sun does not provide any equivalent. | |
2193 | ||
2194 | The following example is for a stab whose value is an address is | |
2195 | relative to the compilation unit (@pxref{Stabs In ELF}). For example, | |
2196 | if the source line | |
2197 | ||
2198 | @example | |
2199 | static int ld = 5; | |
2200 | @end example | |
2201 | ||
2202 | appears within a function, then the assembly language output from the | |
2203 | compiler contains: | |
2204 | ||
2205 | @example | |
2206 | .Ddata.data: | |
2207 | @dots{} | |
2208 | .stabs "ld:V(0,3)",0x26,0,4,.L18-Ddata.data # @r{0x26 is N_STSYM} | |
2209 | @dots{} | |
2210 | .L18: | |
2211 | .align 4 | |
2212 | .word 0x5 | |
2213 | @end example | |
2214 | ||
2215 | Because the value is formed by subtracting one symbol from another, the | |
2216 | value is absolute, not relocatable, and so the object file contains | |
2217 | ||
2218 | @example | |
2219 | Symnum n_type n_othr n_desc n_value n_strx String | |
2220 | 31 STSYM 0 4 00000004 680 ld:V(0,3) | |
2221 | @end example | |
2222 | ||
2223 | without any relocations, and the executable file also contains | |
2224 | ||
2225 | @example | |
2226 | Symnum n_type n_othr n_desc n_value n_strx String | |
2227 | 31 STSYM 0 4 00000004 680 ld:V(0,3) | |
2228 | @end example | |
2229 | ||
8c59ee11 | 2230 | @node Cplusplus |
bf9d2537 | 2231 | @chapter GNU C++ Stabs |
e505224d PB |
2232 | |
2233 | @menu | |
bb190834 | 2234 | * Class Names:: C++ class names are both tags and typedefs. |
bf9d2537 DM |
2235 | * Basic Cplusplus Types:: |
2236 | * Simple Classes:: | |
2237 | * Class Instance:: | |
8eb5e289 | 2238 | * Methods:: Method definition |
6fe91f2c | 2239 | * Protections:: |
bf9d2537 DM |
2240 | * Method Modifiers:: |
2241 | * Virtual Methods:: | |
6fe91f2c | 2242 | * Inheritence:: |
bf9d2537 DM |
2243 | * Virtual Base Classes:: |
2244 | * Static Members:: | |
e505224d PB |
2245 | @end menu |
2246 | ||
6fe91f2c | 2247 | Type descriptors added for C++ descriptions: |
e505224d PB |
2248 | |
2249 | @table @code | |
2250 | @item # | |
6fe91f2c | 2251 | method type (@code{##} if minimal debug) |
e505224d | 2252 | |
8c59ee11 JK |
2253 | @item @@ |
2254 | Member (class and variable) type. It is followed by type information | |
2255 | for the offset basetype, a comma, and type information for the type of | |
2256 | the field being pointed to. (FIXME: this is acknowledged to be | |
2257 | gibberish. Can anyone say what really goes here?). | |
2258 | ||
2259 | Note that there is a conflict between this and type attributes | |
bf9d2537 | 2260 | (@pxref{String Field}); both use type descriptor @samp{@@}. |
8c59ee11 JK |
2261 | Fortunately, the @samp{@@} type descriptor used in this C++ sense always |
2262 | will be followed by a digit, @samp{(}, or @samp{-}, and type attributes | |
2263 | never start with those things. | |
e505224d PB |
2264 | @end table |
2265 | ||
bb190834 JK |
2266 | @node Class Names |
2267 | @section C++ Class Names | |
2268 | ||
2269 | In C++, a class name which is declared with @code{class}, @code{struct}, | |
2270 | or @code{union}, is not only a tag, as in C, but also a type name. Thus | |
2271 | there should be stabs with both @samp{t} and @samp{T} symbol descriptors | |
2272 | (@pxref{Typedefs}). | |
2273 | ||
2274 | To save space, there is a special abbreviation for this case. If the | |
2275 | @samp{T} symbol descriptor is followed by @samp{t}, then the stab | |
2276 | defines both a type name and a tag. | |
2277 | ||
2278 | For example, the C++ code | |
2279 | ||
2280 | @example | |
2281 | struct foo @{int x;@}; | |
2282 | @end example | |
2283 | ||
2284 | can be represented as either | |
2285 | ||
2286 | @example | |
2287 | .stabs "foo:T19=s4x:1,0,32;;",128,0,0,0 # @r{128 is N_LSYM} | |
2288 | .stabs "foo:t19",128,0,0,0 | |
2289 | @end example | |
2290 | ||
2291 | or | |
2292 | ||
2293 | @example | |
2294 | .stabs "foo:Tt19=s4x:1,0,32;;",128,0,0,0 | |
2295 | @end example | |
2296 | ||
bf9d2537 DM |
2297 | @node Basic Cplusplus Types |
2298 | @section Basic Types For C++ | |
e505224d PB |
2299 | |
2300 | << the examples that follow are based on a01.C >> | |
2301 | ||
2302 | ||
2303 | C++ adds two more builtin types to the set defined for C. These are | |
2304 | the unknown type and the vtable record type. The unknown type, type | |
2305 | 16, is defined in terms of itself like the void type. | |
2306 | ||
2307 | The vtable record type, type 17, is defined as a structure type and | |
6fe91f2c | 2308 | then as a structure tag. The structure has four fields: delta, index, |
e505224d PB |
2309 | pfn, and delta2. pfn is the function pointer. |
2310 | ||
2311 | << In boilerplate $vtbl_ptr_type, what are the fields delta, | |
2312 | index, and delta2 used for? >> | |
2313 | ||
2314 | This basic type is present in all C++ programs even if there are no | |
2315 | virtual methods defined. | |
2316 | ||
899bafeb | 2317 | @display |
e505224d | 2318 | .stabs "struct_name:sym_desc(type)type_def(17)=type_desc(struct)struct_bytes(8) |
139741da RP |
2319 | elem_name(delta):type_ref(short int),bit_offset(0),field_bits(16); |
2320 | elem_name(index):type_ref(short int),bit_offset(16),field_bits(16); | |
2321 | elem_name(pfn):type_def(18)=type_desc(ptr to)type_ref(void), | |
2322 | bit_offset(32),field_bits(32); | |
2323 | elem_name(delta2):type_def(short int);bit_offset(32),field_bits(16);;" | |
2324 | N_LSYM, NIL, NIL | |
899bafeb | 2325 | @end display |
6fe91f2c | 2326 | |
899bafeb | 2327 | @smallexample |
e505224d | 2328 | .stabs "$vtbl_ptr_type:t17=s8 |
139741da RP |
2329 | delta:6,0,16;index:6,16,16;pfn:18=*15,32,32;delta2:6,32,16;;" |
2330 | ,128,0,0,0 | |
899bafeb | 2331 | @end smallexample |
e505224d | 2332 | |
899bafeb | 2333 | @display |
e505224d | 2334 | .stabs "name:sym_dec(struct tag)type_ref($vtbl_ptr_type)",N_LSYM,NIL,NIL,NIL |
899bafeb | 2335 | @end display |
e505224d | 2336 | |
899bafeb | 2337 | @example |
e505224d | 2338 | .stabs "$vtbl_ptr_type:T17",128,0,0,0 |
899bafeb | 2339 | @end example |
e505224d | 2340 | |
bf9d2537 DM |
2341 | @node Simple Classes |
2342 | @section Simple Class Definition | |
e505224d PB |
2343 | |
2344 | The stabs describing C++ language features are an extension of the | |
2345 | stabs describing C. Stabs representing C++ class types elaborate | |
2346 | extensively on the stab format used to describe structure types in C. | |
2347 | Stabs representing class type variables look just like stabs | |
2348 | representing C language variables. | |
2349 | ||
2350 | Consider the following very simple class definition. | |
2351 | ||
2352 | @example | |
2353 | class baseA @{ | |
2354 | public: | |
139741da RP |
2355 | int Adat; |
2356 | int Ameth(int in, char other); | |
e505224d PB |
2357 | @}; |
2358 | @end example | |
2359 | ||
6fe91f2c | 2360 | The class @code{baseA} is represented by two stabs. The first stab describes |
e505224d | 2361 | the class as a structure type. The second stab describes a structure |
6fe91f2c | 2362 | tag of the class type. Both stabs are of stab type @code{N_LSYM}. Since the |
685a5e86 | 2363 | stab is not located between an @code{N_FUN} and an @code{N_LBRAC} stab this indicates |
6fe91f2c | 2364 | that the class is defined at file scope. If it were, then the @code{N_LSYM} |
e505224d PB |
2365 | would signify a local variable. |
2366 | ||
2367 | A stab describing a C++ class type is similar in format to a stab | |
2368 | describing a C struct, with each class member shown as a field in the | |
2369 | structure. The part of the struct format describing fields is | |
2370 | expanded to include extra information relevent to C++ class members. | |
2371 | In addition, if the class has multiple base classes or virtual | |
2372 | functions the struct format outside of the field parts is also | |
2373 | augmented. | |
2374 | ||
2375 | In this simple example the field part of the C++ class stab | |
2376 | representing member data looks just like the field part of a C struct | |
2377 | stab. The section on protections describes how its format is | |
2378 | sometimes extended for member data. | |
2379 | ||
2380 | The field part of a C++ class stab representing a member function | |
2381 | differs substantially from the field part of a C struct stab. It | |
6fe91f2c | 2382 | still begins with @samp{name:} but then goes on to define a new type number |
e505224d PB |
2383 | for the member function, describe its return type, its argument types, |
2384 | its protection level, any qualifiers applied to the method definition, | |
2385 | and whether the method is virtual or not. If the method is virtual | |
2386 | then the method description goes on to give the vtable index of the | |
2387 | method, and the type number of the first base class defining the | |
6fe91f2c | 2388 | method. |
e505224d | 2389 | |
dd8126d9 JK |
2390 | When the field name is a method name it is followed by two colons rather |
2391 | than one. This is followed by a new type definition for the method. | |
2392 | This is a number followed by an equal sign and the type descriptor | |
2393 | @samp{#}, indicating a method type, and a second @samp{#}, indicating | |
2394 | that this is the @dfn{minimal} type of method definition used by GCC2, | |
2395 | not larger method definitions used by earlier versions of GCC. This is | |
2396 | followed by a type reference showing the return type of the method and a | |
e505224d PB |
2397 | semi-colon. |
2398 | ||
dd8126d9 JK |
2399 | The format of an overloaded operator method name differs from that of |
2400 | other methods. It is @samp{op$::@var{operator-name}.} where | |
2401 | @var{operator-name} is the operator name such as @samp{+} or @samp{+=}. | |
2402 | The name ends with a period, and any characters except the period can | |
2403 | occur in the @var{operator-name} string. | |
e505224d | 2404 | |
dd8126d9 JK |
2405 | The next part of the method description represents the arguments to the |
2406 | method, preceeded by a colon and ending with a semi-colon. The types of | |
2407 | the arguments are expressed in the same way argument types are expressed | |
2408 | in C++ name mangling. In this example an @code{int} and a @code{char} | |
6fe91f2c | 2409 | map to @samp{ic}. |
e505224d PB |
2410 | |
2411 | This is followed by a number, a letter, and an asterisk or period, | |
2412 | followed by another semicolon. The number indicates the protections | |
2413 | that apply to the member function. Here the 2 means public. The | |
2414 | letter encodes any qualifier applied to the method definition. In | |
6fe91f2c | 2415 | this case, @samp{A} means that it is a normal function definition. The dot |
e505224d PB |
2416 | shows that the method is not virtual. The sections that follow |
2417 | elaborate further on these fields and describe the additional | |
2418 | information present for virtual methods. | |
2419 | ||
2420 | ||
899bafeb | 2421 | @display |
e505224d | 2422 | .stabs "class_name:sym_desc(type)type_def(20)=type_desc(struct)struct_bytes(4) |
139741da | 2423 | field_name(Adat):type(int),bit_offset(0),field_bits(32); |
e505224d | 2424 | |
139741da | 2425 | method_name(Ameth)::type_def(21)=type_desc(method)return_type(int); |
6fe91f2c | 2426 | :arg_types(int char); |
139741da RP |
2427 | protection(public)qualifier(normal)virtual(no);;" |
2428 | N_LSYM,NIL,NIL,NIL | |
899bafeb | 2429 | @end display |
e505224d | 2430 | |
899bafeb | 2431 | @smallexample |
e505224d PB |
2432 | .stabs "baseA:t20=s4Adat:1,0,32;Ameth::21=##1;:ic;2A.;;",128,0,0,0 |
2433 | ||
2434 | .stabs "class_name:sym_desc(struct tag)",N_LSYM,NIL,NIL,NIL | |
2435 | ||
2436 | .stabs "baseA:T20",128,0,0,0 | |
899bafeb | 2437 | @end smallexample |
e505224d | 2438 | |
bf9d2537 DM |
2439 | @node Class Instance |
2440 | @section Class Instance | |
e505224d PB |
2441 | |
2442 | As shown above, describing even a simple C++ class definition is | |
2443 | accomplished by massively extending the stab format used in C to | |
2444 | describe structure types. However, once the class is defined, C stabs | |
2445 | with no modifications can be used to describe class instances. The | |
2446 | following source: | |
2447 | ||
2448 | @example | |
2449 | main () @{ | |
139741da | 2450 | baseA AbaseA; |
e505224d PB |
2451 | @} |
2452 | @end example | |
2453 | ||
899bafeb RP |
2454 | @noindent |
2455 | yields the following stab describing the class instance. It looks no | |
e505224d PB |
2456 | different from a standard C stab describing a local variable. |
2457 | ||
899bafeb | 2458 | @display |
e505224d | 2459 | .stabs "name:type_ref(baseA)", N_LSYM, NIL, NIL, frame_ptr_offset |
899bafeb | 2460 | @end display |
e505224d | 2461 | |
899bafeb | 2462 | @example |
e505224d | 2463 | .stabs "AbaseA:20",128,0,0,-20 |
899bafeb | 2464 | @end example |
e505224d | 2465 | |
899bafeb | 2466 | @node Methods |
9d719a9c | 2467 | @section Method Definition |
e505224d PB |
2468 | |
2469 | The class definition shown above declares Ameth. The C++ source below | |
2470 | defines Ameth: | |
2471 | ||
2472 | @example | |
6fe91f2c DM |
2473 | int |
2474 | baseA::Ameth(int in, char other) | |
e505224d | 2475 | @{ |
139741da | 2476 | return in; |
e505224d PB |
2477 | @}; |
2478 | @end example | |
2479 | ||
2480 | ||
2481 | This method definition yields three stabs following the code of the | |
3a642a82 JK |
2482 | method. One stab describes the method itself and following two describe |
2483 | its parameters. Although there is only one formal argument all methods | |
6fe91f2c | 2484 | have an implicit argument which is the @code{this} pointer. The @code{this} |
3a642a82 JK |
2485 | pointer is a pointer to the object on which the method was called. Note |
2486 | that the method name is mangled to encode the class name and argument | |
2487 | types. Name mangling is described in the @sc{arm} (@cite{The Annotated | |
2488 | C++ Reference Manual}, by Ellis and Stroustrup, @sc{isbn} | |
2489 | 0-201-51459-1); @file{gpcompare.texi} in Cygnus GCC distributions | |
6fe91f2c | 2490 | describes the differences between GNU mangling and @sc{arm} |
3a642a82 JK |
2491 | mangling. |
2492 | @c FIXME: Use @xref, especially if this is generally installed in the | |
2493 | @c info tree. | |
2494 | @c FIXME: This information should be in a net release, either of GCC or | |
2495 | @c GDB. But gpcompare.texi doesn't seem to be in the FSF GCC. | |
e505224d | 2496 | |
612dbd4c | 2497 | @example |
e505224d | 2498 | .stabs "name:symbol_desriptor(global function)return_type(int)", |
6fe91f2c | 2499 | N_FUN, NIL, NIL, code_addr_of_method_start |
e505224d PB |
2500 | |
2501 | .stabs "Ameth__5baseAic:F1",36,0,0,_Ameth__5baseAic | |
612dbd4c | 2502 | @end example |
e505224d | 2503 | |
6fe91f2c DM |
2504 | Here is the stab for the @code{this} pointer implicit argument. The |
2505 | name of the @code{this} pointer is always @code{this}. Type 19, the | |
2506 | @code{this} pointer is defined as a pointer to type 20, @code{baseA}, | |
2507 | but a stab defining @code{baseA} has not yet been emited. Since the | |
2508 | compiler knows it will be emited shortly, here it just outputs a cross | |
2509 | reference to the undefined symbol, by prefixing the symbol name with | |
2510 | @samp{xs}. | |
e505224d | 2511 | |
612dbd4c | 2512 | @example |
e505224d | 2513 | .stabs "name:sym_desc(register param)type_def(19)= |
139741da | 2514 | type_desc(ptr to)type_ref(baseA)= |
6fe91f2c | 2515 | type_desc(cross-reference to)baseA:",N_RSYM,NIL,NIL,register_number |
e505224d | 2516 | |
c2dc518b | 2517 | .stabs "this:P19=*20=xsbaseA:",64,0,0,8 |
612dbd4c | 2518 | @end example |
e505224d PB |
2519 | |
2520 | The stab for the explicit integer argument looks just like a parameter | |
2521 | to a C function. The last field of the stab is the offset from the | |
2522 | argument pointer, which in most systems is the same as the frame | |
2523 | pointer. | |
2524 | ||
612dbd4c | 2525 | @example |
e505224d | 2526 | .stabs "name:sym_desc(value parameter)type_ref(int)", |
6fe91f2c | 2527 | N_PSYM,NIL,NIL,offset_from_arg_ptr |
e505224d PB |
2528 | |
2529 | .stabs "in:p1",160,0,0,72 | |
612dbd4c | 2530 | @end example |
e505224d PB |
2531 | |
2532 | << The examples that follow are based on A1.C >> | |
2533 | ||
899bafeb | 2534 | @node Protections |
e505224d PB |
2535 | @section Protections |
2536 | ||
2537 | ||
2538 | In the simple class definition shown above all member data and | |
2539 | functions were publicly accessable. The example that follows | |
2540 | contrasts public, protected and privately accessable fields and shows | |
2541 | how these protections are encoded in C++ stabs. | |
2542 | ||
2543 | Protections for class member data are signified by two characters | |
dd8126d9 | 2544 | embedded in the stab defining the class type. These characters are |
bb190834 | 2545 | located after the @samp{name:} part of the string. @samp{/0} means private, |
dd8126d9 JK |
2546 | @samp{/1} means protected, and @samp{/2} means public. If these |
2547 | characters are omited this means that the member is public. The | |
2548 | following C++ source: | |
e505224d PB |
2549 | |
2550 | @example | |
2551 | class all_data @{ | |
6fe91f2c | 2552 | private: |
139741da | 2553 | int priv_dat; |
e505224d | 2554 | protected: |
139741da | 2555 | char prot_dat; |
e505224d | 2556 | public: |
139741da | 2557 | float pub_dat; |
e505224d PB |
2558 | @}; |
2559 | @end example | |
2560 | ||
899bafeb | 2561 | @noindent |
e505224d PB |
2562 | generates the following stab to describe the class type all_data. |
2563 | ||
899bafeb | 2564 | @display |
e505224d | 2565 | .stabs "class_name:sym_desc(type)type_def(19)=type_desc(struct)struct_bytes |
139741da RP |
2566 | data_name:/protection(private)type_ref(int),bit_offset,num_bits; |
2567 | data_name:/protection(protected)type_ref(char),bit_offset,num_bits; | |
2568 | data_name:(/num omited, private)type_ref(float),bit_offset,num_bits;;" | |
2569 | N_LSYM,NIL,NIL,NIL | |
899bafeb | 2570 | @end display |
e505224d | 2571 | |
899bafeb | 2572 | @smallexample |
e505224d | 2573 | .stabs "all_data:t19=s12 |
139741da | 2574 | priv_dat:/01,0,32;prot_dat:/12,32,8;pub_dat:12,64,32;;",128,0,0,0 |
899bafeb | 2575 | @end smallexample |
e505224d PB |
2576 | |
2577 | Protections for member functions are signified by one digit embeded in | |
2578 | the field part of the stab describing the method. The digit is 0 if | |
2579 | private, 1 if protected and 2 if public. Consider the C++ class | |
2580 | definition below: | |
2581 | ||
2582 | @example | |
2583 | class all_methods @{ | |
2584 | private: | |
139741da | 2585 | int priv_meth(int in)@{return in;@}; |
e505224d | 2586 | protected: |
139741da | 2587 | char protMeth(char in)@{return in;@}; |
e505224d | 2588 | public: |
139741da | 2589 | float pubMeth(float in)@{return in;@}; |
e505224d PB |
2590 | @}; |
2591 | @end example | |
2592 | ||
2593 | It generates the following stab. The digit in question is to the left | |
6fe91f2c | 2594 | of an @samp{A} in each case. Notice also that in this case two symbol |
e505224d PB |
2595 | descriptors apply to the class name struct tag and struct type. |
2596 | ||
899bafeb | 2597 | @display |
e505224d | 2598 | .stabs "class_name:sym_desc(struct tag&type)type_def(21)= |
139741da RP |
2599 | sym_desc(struct)struct_bytes(1) |
2600 | meth_name::type_def(22)=sym_desc(method)returning(int); | |
2601 | :args(int);protection(private)modifier(normal)virtual(no); | |
2602 | meth_name::type_def(23)=sym_desc(method)returning(char); | |
2603 | :args(char);protection(protected)modifier(normal)virual(no); | |
2604 | meth_name::type_def(24)=sym_desc(method)returning(float); | |
2605 | :args(float);protection(public)modifier(normal)virtual(no);;", | |
2606 | N_LSYM,NIL,NIL,NIL | |
899bafeb | 2607 | @end display |
6fe91f2c | 2608 | |
899bafeb | 2609 | @smallexample |
e505224d | 2610 | .stabs "all_methods:Tt21=s1priv_meth::22=##1;:i;0A.;protMeth::23=##2;:c;1A.; |
139741da | 2611 | pubMeth::24=##12;:f;2A.;;",128,0,0,0 |
899bafeb | 2612 | @end smallexample |
e505224d | 2613 | |
bf9d2537 DM |
2614 | @node Method Modifiers |
2615 | @section Method Modifiers (@code{const}, @code{volatile}, @code{const volatile}) | |
e505224d PB |
2616 | |
2617 | << based on a6.C >> | |
2618 | ||
2619 | In the class example described above all the methods have the normal | |
2620 | modifier. This method modifier information is located just after the | |
2621 | protection information for the method. This field has four possible | |
6fe91f2c DM |
2622 | character values. Normal methods use @samp{A}, const methods use |
2623 | @samp{B}, volatile methods use @samp{C}, and const volatile methods use | |
2624 | @samp{D}. Consider the class definition below: | |
e505224d PB |
2625 | |
2626 | @example | |
2627 | class A @{ | |
2628 | public: | |
139741da RP |
2629 | int ConstMeth (int arg) const @{ return arg; @}; |
2630 | char VolatileMeth (char arg) volatile @{ return arg; @}; | |
2631 | float ConstVolMeth (float arg) const volatile @{return arg; @}; | |
e505224d PB |
2632 | @}; |
2633 | @end example | |
2634 | ||
2635 | This class is described by the following stab: | |
2636 | ||
899bafeb | 2637 | @display |
e505224d | 2638 | .stabs "class(A):sym_desc(struct)type_def(20)=type_desc(struct)struct_bytes(1) |
139741da RP |
2639 | meth_name(ConstMeth)::type_def(21)sym_desc(method) |
2640 | returning(int);:arg(int);protection(public)modifier(const)virtual(no); | |
2641 | meth_name(VolatileMeth)::type_def(22)=sym_desc(method) | |
2642 | returning(char);:arg(char);protection(public)modifier(volatile)virt(no) | |
2643 | meth_name(ConstVolMeth)::type_def(23)=sym_desc(method) | |
2644 | returning(float);:arg(float);protection(public)modifer(const volatile) | |
2645 | virtual(no);;", @dots{} | |
899bafeb | 2646 | @end display |
6fe91f2c | 2647 | |
899bafeb | 2648 | @example |
e505224d | 2649 | .stabs "A:T20=s1ConstMeth::21=##1;:i;2B.;VolatileMeth::22=##2;:c;2C.; |
139741da | 2650 | ConstVolMeth::23=##12;:f;2D.;;",128,0,0,0 |
612dbd4c | 2651 | @end example |
e505224d | 2652 | |
bf9d2537 DM |
2653 | @node Virtual Methods |
2654 | @section Virtual Methods | |
e505224d | 2655 | |
6fe91f2c | 2656 | << The following examples are based on a4.C >> |
e505224d PB |
2657 | |
2658 | The presence of virtual methods in a class definition adds additional | |
2659 | data to the class description. The extra data is appended to the | |
2660 | description of the virtual method and to the end of the class | |
2661 | description. Consider the class definition below: | |
2662 | ||
2663 | @example | |
2664 | class A @{ | |
2665 | public: | |
139741da RP |
2666 | int Adat; |
2667 | virtual int A_virt (int arg) @{ return arg; @}; | |
e505224d PB |
2668 | @}; |
2669 | @end example | |
6fe91f2c | 2670 | |
e505224d PB |
2671 | This results in the stab below describing class A. It defines a new |
2672 | type (20) which is an 8 byte structure. The first field of the class | |
6fe91f2c DM |
2673 | struct is @samp{Adat}, an integer, starting at structure offset 0 and |
2674 | occupying 32 bits. | |
e505224d PB |
2675 | |
2676 | The second field in the class struct is not explicitly defined by the | |
2677 | C++ class definition but is implied by the fact that the class | |
2678 | contains a virtual method. This field is the vtable pointer. The | |
6fe91f2c | 2679 | name of the vtable pointer field starts with @samp{$vf} and continues with a |
e505224d PB |
2680 | type reference to the class it is part of. In this example the type |
2681 | reference for class A is 20 so the name of its vtable pointer field is | |
6fe91f2c | 2682 | @samp{$vf20}, followed by the usual colon. |
e505224d PB |
2683 | |
2684 | Next there is a type definition for the vtable pointer type (21). | |
6fe91f2c | 2685 | This is in turn defined as a pointer to another new type (22). |
e505224d PB |
2686 | |
2687 | Type 22 is the vtable itself, which is defined as an array, indexed by | |
6aa83a79 JG |
2688 | a range of integers between 0 and 1, and whose elements are of type |
2689 | 17. Type 17 was the vtable record type defined by the boilerplate C++ | |
2690 | type definitions, as shown earlier. | |
e505224d PB |
2691 | |
2692 | The bit offset of the vtable pointer field is 32. The number of bits | |
2693 | in the field are not specified when the field is a vtable pointer. | |
6fe91f2c DM |
2694 | |
2695 | Next is the method definition for the virtual member function @code{A_virt}. | |
e505224d PB |
2696 | Its description starts out using the same format as the non-virtual |
2697 | member functions described above, except instead of a dot after the | |
6fe91f2c | 2698 | @samp{A} there is an asterisk, indicating that the function is virtual. |
e505224d | 2699 | Since is is virtual some addition information is appended to the end |
6fe91f2c | 2700 | of the method description. |
e505224d PB |
2701 | |
2702 | The first number represents the vtable index of the method. This is a | |
2703 | 32 bit unsigned number with the high bit set, followed by a | |
2704 | semi-colon. | |
2705 | ||
2706 | The second number is a type reference to the first base class in the | |
2707 | inheritence hierarchy defining the virtual member function. In this | |
2708 | case the class stab describes a base class so the virtual function is | |
2709 | not overriding any other definition of the method. Therefore the | |
2710 | reference is to the type number of the class that the stab is | |
6fe91f2c | 2711 | describing (20). |
e505224d PB |
2712 | |
2713 | This is followed by three semi-colons. One marks the end of the | |
2714 | current sub-section, one marks the end of the method field, and the | |
2715 | third marks the end of the struct definition. | |
2716 | ||
2717 | For classes containing virtual functions the very last section of the | |
2718 | string part of the stab holds a type reference to the first base | |
6fe91f2c | 2719 | class. This is preceeded by @samp{~%} and followed by a final semi-colon. |
e505224d | 2720 | |
899bafeb | 2721 | @display |
e505224d | 2722 | .stabs "class_name(A):type_def(20)=sym_desc(struct)struct_bytes(8) |
139741da RP |
2723 | field_name(Adat):type_ref(int),bit_offset(0),field_bits(32); |
2724 | field_name(A virt func ptr):type_def(21)=type_desc(ptr to)type_def(22)= | |
6aa83a79 | 2725 | sym_desc(array)index_type_ref(range of int from 0 to 1); |
6fe91f2c | 2726 | elem_type_ref(vtbl elem type), |
139741da RP |
2727 | bit_offset(32); |
2728 | meth_name(A_virt)::typedef(23)=sym_desc(method)returning(int); | |
2729 | :arg_type(int),protection(public)normal(yes)virtual(yes) | |
2730 | vtable_index(1);class_first_defining(A);;;~%first_base(A);", | |
2731 | N_LSYM,NIL,NIL,NIL | |
899bafeb | 2732 | @end display |
e505224d | 2733 | |
3d4cf720 | 2734 | @c FIXME: bogus line break. |
899bafeb | 2735 | @example |
3d4cf720 | 2736 | .stabs "A:t20=s8Adat:1,0,32;$vf20:21=*22=ar1;0;1;17,32; |
6fe91f2c | 2737 | A_virt::23=##1;:i;2A*-2147483647;20;;;~%20;",128,0,0,0 |
612dbd4c | 2738 | @end example |
e505224d | 2739 | |
2dd00294 JG |
2740 | @node Inheritence |
2741 | @section Inheritence | |
e505224d PB |
2742 | |
2743 | Stabs describing C++ derived classes include additional sections that | |
2744 | describe the inheritence hierarchy of the class. A derived class stab | |
2745 | also encodes the number of base classes. For each base class it tells | |
2746 | if the base class is virtual or not, and if the inheritence is private | |
2747 | or public. It also gives the offset into the object of the portion of | |
6fe91f2c | 2748 | the object corresponding to each base class. |
e505224d PB |
2749 | |
2750 | This additional information is embeded in the class stab following the | |
2751 | number of bytes in the struct. First the number of base classes | |
6fe91f2c | 2752 | appears bracketed by an exclamation point and a comma. |
e505224d PB |
2753 | |
2754 | Then for each base type there repeats a series: two digits, a number, | |
6fe91f2c | 2755 | a comma, another number, and a semi-colon. |
e505224d PB |
2756 | |
2757 | The first of the two digits is 1 if the base class is virtual and 0 if | |
2758 | not. The second digit is 2 if the derivation is public and 0 if not. | |
2759 | ||
2760 | The number following the first two digits is the offset from the start | |
6fe91f2c | 2761 | of the object to the part of the object pertaining to the base class. |
e505224d PB |
2762 | |
2763 | After the comma, the second number is a type_descriptor for the base | |
2764 | type. Finally a semi-colon ends the series, which repeats for each | |
2765 | base class. | |
2766 | ||
6fe91f2c DM |
2767 | The source below defines three base classes @code{A}, @code{B}, and |
2768 | @code{C} and the derived class @code{D}. | |
e505224d PB |
2769 | |
2770 | ||
2771 | @example | |
2772 | class A @{ | |
2773 | public: | |
139741da RP |
2774 | int Adat; |
2775 | virtual int A_virt (int arg) @{ return arg; @}; | |
e505224d PB |
2776 | @}; |
2777 | ||
2778 | class B @{ | |
2779 | public: | |
6fe91f2c | 2780 | int B_dat; |
139741da | 2781 | virtual int B_virt (int arg) @{return arg; @}; |
6fe91f2c | 2782 | @}; |
e505224d PB |
2783 | |
2784 | class C @{ | |
6fe91f2c | 2785 | public: |
139741da | 2786 | int Cdat; |
6fe91f2c | 2787 | virtual int C_virt (int arg) @{return arg; @}; |
e505224d PB |
2788 | @}; |
2789 | ||
2790 | class D : A, virtual B, public C @{ | |
2791 | public: | |
139741da RP |
2792 | int Ddat; |
2793 | virtual int A_virt (int arg ) @{ return arg+1; @}; | |
2794 | virtual int B_virt (int arg) @{ return arg+2; @}; | |
2795 | virtual int C_virt (int arg) @{ return arg+3; @}; | |
2796 | virtual int D_virt (int arg) @{ return arg; @}; | |
e505224d PB |
2797 | @}; |
2798 | @end example | |
2799 | ||
2800 | Class stabs similar to the ones described earlier are generated for | |
6fe91f2c | 2801 | each base class. |
e505224d | 2802 | |
5bc927fb RP |
2803 | @c FIXME!!! the linebreaks in the following example probably make the |
2804 | @c examples literally unusable, but I don't know any other way to get | |
2805 | @c them on the page. | |
63cef7d7 JK |
2806 | @c One solution would be to put some of the type definitions into |
2807 | @c separate stabs, even if that's not exactly what the compiler actually | |
2808 | @c emits. | |
899bafeb | 2809 | @smallexample |
5bc927fb RP |
2810 | .stabs "A:T20=s8Adat:1,0,32;$vf20:21=*22=ar1;0;1;17,32; |
2811 | A_virt::23=##1;:i;2A*-2147483647;20;;;~%20;",128,0,0,0 | |
e505224d | 2812 | |
5bc927fb RP |
2813 | .stabs "B:Tt25=s8Bdat:1,0,32;$vf25:21,32;B_virt::26=##1; |
2814 | :i;2A*-2147483647;25;;;~%25;",128,0,0,0 | |
e505224d | 2815 | |
5bc927fb RP |
2816 | .stabs "C:Tt28=s8Cdat:1,0,32;$vf28:21,32;C_virt::29=##1; |
2817 | :i;2A*-2147483647;28;;;~%28;",128,0,0,0 | |
899bafeb | 2818 | @end smallexample |
e505224d | 2819 | |
6fe91f2c | 2820 | In the stab describing derived class @code{D} below, the information about |
e505224d PB |
2821 | the derivation of this class is encoded as follows. |
2822 | ||
899bafeb | 2823 | @display |
e505224d | 2824 | .stabs "derived_class_name:symbol_descriptors(struct tag&type)= |
139741da RP |
2825 | type_descriptor(struct)struct_bytes(32)!num_bases(3), |
2826 | base_virtual(no)inheritence_public(no)base_offset(0), | |
2827 | base_class_type_ref(A); | |
2828 | base_virtual(yes)inheritence_public(no)base_offset(NIL), | |
2829 | base_class_type_ref(B); | |
2830 | base_virtual(no)inheritence_public(yes)base_offset(64), | |
2831 | base_class_type_ref(C); @dots{} | |
899bafeb | 2832 | @end display |
6fe91f2c | 2833 | |
5bc927fb | 2834 | @c FIXME! fake linebreaks. |
899bafeb | 2835 | @smallexample |
5bc927fb RP |
2836 | .stabs "D:Tt31=s32!3,000,20;100,25;0264,28;$vb25:24,128;Ddat: |
2837 | 1,160,32;A_virt::32=##1;:i;2A*-2147483647;20;;B_virt: | |
2838 | :32:i;2A*-2147483647;25;;C_virt::32:i;2A*-2147483647; | |
2839 | 28;;D_virt::32:i;2A*-2147483646;31;;;~%20;",128,0,0,0 | |
899bafeb | 2840 | @end smallexample |
e505224d | 2841 | |
bf9d2537 DM |
2842 | @node Virtual Base Classes |
2843 | @section Virtual Base Classes | |
e505224d | 2844 | |
dd8126d9 JK |
2845 | A derived class object consists of a concatination in memory of the data |
2846 | areas defined by each base class, starting with the leftmost and ending | |
2847 | with the rightmost in the list of base classes. The exception to this | |
2848 | rule is for virtual inheritence. In the example above, class @code{D} | |
2849 | inherits virtually from base class @code{B}. This means that an | |
2850 | instance of a @code{D} object will not contain its own @code{B} part but | |
2851 | merely a pointer to a @code{B} part, known as a virtual base pointer. | |
e505224d PB |
2852 | |
2853 | In a derived class stab, the base offset part of the derivation | |
2854 | information, described above, shows how the base class parts are | |
dd8126d9 JK |
2855 | ordered. The base offset for a virtual base class is always given as 0. |
2856 | Notice that the base offset for @code{B} is given as 0 even though | |
2857 | @code{B} is not the first base class. The first base class @code{A} | |
2858 | starts at offset 0. | |
e505224d | 2859 | |
6fe91f2c DM |
2860 | The field information part of the stab for class @code{D} describes the field |
2861 | which is the pointer to the virtual base class @code{B}. The vbase pointer | |
2862 | name is @samp{$vb} followed by a type reference to the virtual base class. | |
2863 | Since the type id for @code{B} in this example is 25, the vbase pointer name | |
2864 | is @samp{$vb25}. | |
e505224d | 2865 | |
5bc927fb | 2866 | @c FIXME!! fake linebreaks below |
899bafeb | 2867 | @smallexample |
5bc927fb RP |
2868 | .stabs "D:Tt31=s32!3,000,20;100,25;0264,28;$vb25:24,128;Ddat:1, |
2869 | 160,32;A_virt::32=##1;:i;2A*-2147483647;20;;B_virt::32:i; | |
2870 | 2A*-2147483647;25;;C_virt::32:i;2A*-2147483647;28;;D_virt: | |
2871 | :32:i;2A*-2147483646;31;;;~%20;",128,0,0,0 | |
899bafeb | 2872 | @end smallexample |
e505224d PB |
2873 | |
2874 | Following the name and a semicolon is a type reference describing the | |
2875 | type of the virtual base class pointer, in this case 24. Type 24 was | |
6fe91f2c DM |
2876 | defined earlier as the type of the @code{B} class @code{this} pointer. The |
2877 | @code{this} pointer for a class is a pointer to the class type. | |
e505224d | 2878 | |
899bafeb | 2879 | @example |
c2dc518b | 2880 | .stabs "this:P24=*25=xsB:",64,0,0,8 |
899bafeb | 2881 | @end example |
e505224d PB |
2882 | |
2883 | Finally the field offset part of the vbase pointer field description | |
6fe91f2c DM |
2884 | shows that the vbase pointer is the first field in the @code{D} object, |
2885 | before any data fields defined by the class. The layout of a @code{D} | |
2886 | class object is a follows, @code{Adat} at 0, the vtable pointer for | |
2887 | @code{A} at 32, @code{Cdat} at 64, the vtable pointer for C at 96, the | |
2888 | virtual base pointer for @code{B} at 128, and @code{Ddat} at 160. | |
e505224d PB |
2889 | |
2890 | ||
bf9d2537 DM |
2891 | @node Static Members |
2892 | @section Static Members | |
e505224d | 2893 | |
446e5d80 JG |
2894 | The data area for a class is a concatenation of the space used by the |
2895 | data members of the class. If the class has virtual methods, a vtable | |
e505224d | 2896 | pointer follows the class data. The field offset part of each field |
446e5d80 | 2897 | description in the class stab shows this ordering. |
e505224d | 2898 | |
446e5d80 | 2899 | << How is this reflected in stabs? See Cygnus bug #677 for some info. >> |
e505224d | 2900 | |
bf9d2537 DM |
2901 | @node Stab Types |
2902 | @appendix Table of Stab Types | |
e505224d | 2903 | |
0a95c18c JK |
2904 | The following are all the possible values for the stab type field, for |
2905 | @code{a.out} files, in numeric order. This does not apply to XCOFF, but | |
2906 | it does apply to stabs in ELF. Stabs in ECOFF use these values but add | |
2907 | 0x8f300 to distinguish them from non-stab symbols. | |
e505224d | 2908 | |
6fe91f2c DM |
2909 | The symbolic names are defined in the file @file{include/aout/stabs.def}. |
2910 | ||
2911 | @menu | |
bf9d2537 DM |
2912 | * Non-Stab Symbol Types:: Types from 0 to 0x1f |
2913 | * Stab Symbol Types:: Types from 0x20 to 0xff | |
6fe91f2c DM |
2914 | @end menu |
2915 | ||
bf9d2537 DM |
2916 | @node Non-Stab Symbol Types |
2917 | @appendixsec Non-Stab Symbol Types | |
6fe91f2c DM |
2918 | |
2919 | The following types are used by the linker and assembler, not by stab | |
2920 | directives. Since this document does not attempt to describe aspects of | |
2921 | object file format other than the debugging format, no details are | |
2922 | given. | |
e505224d | 2923 | |
3d4cf720 JK |
2924 | @c Try to get most of these to fit on a single line. |
2925 | @iftex | |
2926 | @tableindent=1.5in | |
2927 | @end iftex | |
e505224d | 2928 | |
3d4cf720 | 2929 | @table @code |
6fe91f2c | 2930 | @item 0x0 N_UNDF |
3d4cf720 | 2931 | Undefined symbol |
e505224d | 2932 | |
6fe91f2c | 2933 | @item 0x2 N_ABS |
3d4cf720 | 2934 | File scope absolute symbol |
e505224d | 2935 | |
6fe91f2c | 2936 | @item 0x3 N_ABS | N_EXT |
3d4cf720 JK |
2937 | External absolute symbol |
2938 | ||
6fe91f2c | 2939 | @item 0x4 N_TEXT |
3d4cf720 JK |
2940 | File scope text symbol |
2941 | ||
6fe91f2c | 2942 | @item 0x5 N_TEXT | N_EXT |
3d4cf720 JK |
2943 | External text symbol |
2944 | ||
6fe91f2c | 2945 | @item 0x6 N_DATA |
3d4cf720 JK |
2946 | File scope data symbol |
2947 | ||
6fe91f2c | 2948 | @item 0x7 N_DATA | N_EXT |
3d4cf720 JK |
2949 | External data symbol |
2950 | ||
6fe91f2c | 2951 | @item 0x8 N_BSS |
3d4cf720 JK |
2952 | File scope BSS symbol |
2953 | ||
6fe91f2c | 2954 | @item 0x9 N_BSS | N_EXT |
3d4cf720 JK |
2955 | External BSS symbol |
2956 | ||
6fe91f2c DM |
2957 | @item 0x0c N_FN_SEQ |
2958 | Same as @code{N_FN}, for Sequent compilers | |
3d4cf720 | 2959 | |
6fe91f2c | 2960 | @item 0x0a N_INDR |
3d4cf720 JK |
2961 | Symbol is indirected to another symbol |
2962 | ||
6fe91f2c | 2963 | @item 0x12 N_COMM |
dd8126d9 | 2964 | Common---visible after shared library dynamic link |
3d4cf720 | 2965 | |
6fe91f2c | 2966 | @item 0x14 N_SETA |
3d4cf720 JK |
2967 | Absolute set element |
2968 | ||
6fe91f2c | 2969 | @item 0x16 N_SETT |
3d4cf720 JK |
2970 | Text segment set element |
2971 | ||
6fe91f2c | 2972 | @item 0x18 N_SETD |
3d4cf720 JK |
2973 | Data segment set element |
2974 | ||
6fe91f2c | 2975 | @item 0x1a N_SETB |
3d4cf720 JK |
2976 | BSS segment set element |
2977 | ||
6fe91f2c | 2978 | @item 0x1c N_SETV |
3d4cf720 JK |
2979 | Pointer to set vector |
2980 | ||
6fe91f2c | 2981 | @item 0x1e N_WARNING |
3d4cf720 JK |
2982 | Print a warning message during linking |
2983 | ||
6fe91f2c DM |
2984 | @item 0x1f N_FN |
2985 | File name of a @file{.o} file | |
3d4cf720 JK |
2986 | @end table |
2987 | ||
bf9d2537 DM |
2988 | @node Stab Symbol Types |
2989 | @appendixsec Stab Symbol Types | |
6fe91f2c | 2990 | |
3d4cf720 JK |
2991 | The following symbol types indicate that this is a stab. This is the |
2992 | full list of stab numbers, including stab types that are used in | |
2993 | languages other than C. | |
2994 | ||
2995 | @table @code | |
2996 | @item 0x20 N_GSYM | |
bf9d2537 | 2997 | Global symbol; see @ref{Global Variables}. |
3d4cf720 JK |
2998 | |
2999 | @item 0x22 N_FNAME | |
43603088 | 3000 | Function name (for BSD Fortran); see @ref{Procedures}. |
3d4cf720 | 3001 | |
24dcc707 JK |
3002 | @item 0x24 N_FUN |
3003 | Function name (@pxref{Procedures}) or text segment variable | |
3004 | (@pxref{Statics}). | |
3d4cf720 | 3005 | |
24dcc707 | 3006 | @item 0x26 N_STSYM |
6fe91f2c | 3007 | Data segment file-scope variable; see @ref{Statics}. |
3d4cf720 | 3008 | |
24dcc707 | 3009 | @item 0x28 N_LCSYM |
6fe91f2c | 3010 | BSS segment file-scope variable; see @ref{Statics}. |
3d4cf720 | 3011 | |
6fe91f2c | 3012 | @item 0x2a N_MAIN |
bf9d2537 | 3013 | Name of main routine; see @ref{Main Program}. |
3d4cf720 | 3014 | |
ded6bcab | 3015 | @item 0x2c N_ROSYM |
6fe91f2c | 3016 | Variable in @code{.rodata} section; see @ref{Statics}. |
ded6bcab | 3017 | |
6fe91f2c DM |
3018 | @item 0x30 N_PC |
3019 | Global symbol (for Pascal); see @ref{N_PC}. | |
3d4cf720 | 3020 | |
6fe91f2c DM |
3021 | @item 0x32 N_NSYMS |
3022 | Number of symbols (according to Ultrix V4.0); see @ref{N_NSYMS}. | |
3d4cf720 | 3023 | |
6fe91f2c DM |
3024 | @item 0x34 N_NOMAP |
3025 | No DST map; see @ref{N_NOMAP}. | |
3d4cf720 | 3026 | |
ded6bcab JK |
3027 | @c FIXME: describe this solaris feature in the body of the text (see |
3028 | @c comments in include/aout/stab.def). | |
3029 | @item 0x38 N_OBJ | |
3030 | Object file (Solaris2). | |
3031 | ||
3032 | @c See include/aout/stab.def for (a little) more info. | |
3033 | @item 0x3c N_OPT | |
3034 | Debugger options (Solaris2). | |
3035 | ||
6fe91f2c | 3036 | @item 0x40 N_RSYM |
bf9d2537 | 3037 | Register variable; see @ref{Register Variables}. |
3d4cf720 | 3038 | |
6fe91f2c DM |
3039 | @item 0x42 N_M2C |
3040 | Modula-2 compilation unit; see @ref{N_M2C}. | |
3d4cf720 | 3041 | |
6fe91f2c | 3042 | @item 0x44 N_SLINE |
bf9d2537 | 3043 | Line number in text segment; see @ref{Line Numbers}. |
3d4cf720 | 3044 | |
6fe91f2c | 3045 | @item 0x46 N_DSLINE |
bf9d2537 | 3046 | Line number in data segment; see @ref{Line Numbers}. |
3d4cf720 | 3047 | |
6fe91f2c | 3048 | @item 0x48 N_BSLINE |
bf9d2537 | 3049 | Line number in bss segment; see @ref{Line Numbers}. |
3d4cf720 | 3050 | |
6fe91f2c DM |
3051 | @item 0x48 N_BROWS |
3052 | Sun source code browser, path to @file{.cb} file; see @ref{N_BROWS}. | |
3d4cf720 | 3053 | |
6fe91f2c DM |
3054 | @item 0x4a N_DEFD |
3055 | GNU Modula2 definition module dependency; see @ref{N_DEFD}. | |
3d4cf720 | 3056 | |
ded6bcab JK |
3057 | @item 0x4c N_FLINE |
3058 | Function start/body/end line numbers (Solaris2). | |
3059 | ||
6fe91f2c DM |
3060 | @item 0x50 N_EHDECL |
3061 | GNU C++ exception variable; see @ref{N_EHDECL}. | |
3d4cf720 | 3062 | |
6fe91f2c DM |
3063 | @item 0x50 N_MOD2 |
3064 | Modula2 info "for imc" (according to Ultrix V4.0); see @ref{N_MOD2}. | |
3d4cf720 | 3065 | |
6fe91f2c DM |
3066 | @item 0x54 N_CATCH |
3067 | GNU C++ @code{catch} clause; see @ref{N_CATCH}. | |
3d4cf720 | 3068 | |
6fe91f2c DM |
3069 | @item 0x60 N_SSYM |
3070 | Structure of union element; see @ref{N_SSYM}. | |
3d4cf720 | 3071 | |
ded6bcab JK |
3072 | @item 0x62 N_ENDM |
3073 | Last stab for module (Solaris2). | |
3074 | ||
6fe91f2c | 3075 | @item 0x64 N_SO |
bf9d2537 | 3076 | Path and name of source file; see @ref{Source Files}. |
3d4cf720 | 3077 | |
935d305d | 3078 | @item 0x80 N_LSYM |
bf9d2537 | 3079 | Stack variable (@pxref{Stack Variables}) or type (@pxref{Typedefs}). |
3d4cf720 | 3080 | |
6fe91f2c | 3081 | @item 0x82 N_BINCL |
bf9d2537 | 3082 | Beginning of an include file (Sun only); see @ref{Include Files}. |
3d4cf720 | 3083 | |
6fe91f2c | 3084 | @item 0x84 N_SOL |
bf9d2537 | 3085 | Name of include file; see @ref{Include Files}. |
3d4cf720 | 3086 | |
6fe91f2c DM |
3087 | @item 0xa0 N_PSYM |
3088 | Parameter variable; see @ref{Parameters}. | |
3d4cf720 | 3089 | |
6fe91f2c | 3090 | @item 0xa2 N_EINCL |
bf9d2537 | 3091 | End of an include file; see @ref{Include Files}. |
3d4cf720 | 3092 | |
6fe91f2c DM |
3093 | @item 0xa4 N_ENTRY |
3094 | Alternate entry point; see @ref{N_ENTRY}. | |
3d4cf720 | 3095 | |
6fe91f2c | 3096 | @item 0xc0 N_LBRAC |
bf9d2537 | 3097 | Beginning of a lexical block; see @ref{Block Structure}. |
3d4cf720 | 3098 | |
6fe91f2c | 3099 | @item 0xc2 N_EXCL |
bf9d2537 | 3100 | Place holder for a deleted include file; see @ref{Include Files}. |
3d4cf720 | 3101 | |
6fe91f2c DM |
3102 | @item 0xc4 N_SCOPE |
3103 | Modula2 scope information (Sun linker); see @ref{N_SCOPE}. | |
3d4cf720 | 3104 | |
6fe91f2c | 3105 | @item 0xe0 N_RBRAC |
bf9d2537 | 3106 | End of a lexical block; see @ref{Block Structure}. |
3d4cf720 | 3107 | |
6fe91f2c | 3108 | @item 0xe2 N_BCOMM |
bf9d2537 | 3109 | Begin named common block; see @ref{Common Blocks}. |
3d4cf720 | 3110 | |
6fe91f2c | 3111 | @item 0xe4 N_ECOMM |
bf9d2537 | 3112 | End named common block; see @ref{Common Blocks}. |
3d4cf720 | 3113 | |
6fe91f2c | 3114 | @item 0xe8 N_ECOML |
bf9d2537 | 3115 | Member of a common block; see @ref{Common Blocks}. |
3d4cf720 | 3116 | |
ded6bcab JK |
3117 | @c FIXME: How does this really work? Move it to main body of document. |
3118 | @item 0xea N_WITH | |
3119 | Pascal @code{with} statement: type,,0,0,offset (Solaris2). | |
3120 | ||
6fe91f2c DM |
3121 | @item 0xf0 N_NBTEXT |
3122 | Gould non-base registers; see @ref{Gould}. | |
3d4cf720 | 3123 | |
6fe91f2c DM |
3124 | @item 0xf2 N_NBDATA |
3125 | Gould non-base registers; see @ref{Gould}. | |
3d4cf720 JK |
3126 | |
3127 | @item 0xf4 N_NBBSS | |
6fe91f2c | 3128 | Gould non-base registers; see @ref{Gould}. |
3d4cf720 | 3129 | |
6fe91f2c DM |
3130 | @item 0xf6 N_NBSTS |
3131 | Gould non-base registers; see @ref{Gould}. | |
3d4cf720 | 3132 | |
6fe91f2c DM |
3133 | @item 0xf8 N_NBLCS |
3134 | Gould non-base registers; see @ref{Gould}. | |
3d4cf720 JK |
3135 | @end table |
3136 | ||
3137 | @c Restore the default table indent | |
3138 | @iftex | |
3139 | @tableindent=.8in | |
3140 | @end iftex | |
e505224d | 3141 | |
bf9d2537 DM |
3142 | @node Symbol Descriptors |
3143 | @appendix Table of Symbol Descriptors | |
e505224d | 3144 | |
0a95c18c | 3145 | The symbol descriptor is the character which follows the colon in many |
bf9d2537 | 3146 | stabs, and which tells what kind of stab it is. @xref{String Field}, |
0a95c18c | 3147 | for more information about their use. |
6fe91f2c | 3148 | |
ed9708e2 | 3149 | @c Please keep this alphabetical |
497e44a5 | 3150 | @table @code |
466bdeb2 JK |
3151 | @c In TeX, this looks great, digit is in italics. But makeinfo insists |
3152 | @c on putting it in `', not realizing that @var should override @code. | |
3153 | @c I don't know of any way to make makeinfo do the right thing. Seems | |
3154 | @c like a makeinfo bug to me. | |
3155 | @item @var{digit} | |
8c59ee11 JK |
3156 | @itemx ( |
3157 | @itemx - | |
bf9d2537 | 3158 | Variable on the stack; see @ref{Stack Variables}. |
497e44a5 | 3159 | |
6897f9ec | 3160 | @item a |
bf9d2537 | 3161 | Parameter passed by reference in register; see @ref{Reference Parameters}. |
6897f9ec | 3162 | |
408f6c34 | 3163 | @item b |
f19027a6 | 3164 | Based variable; see @ref{Based Variables}. |
408f6c34 | 3165 | |
6897f9ec | 3166 | @item c |
6fe91f2c | 3167 | Constant; see @ref{Constants}. |
6897f9ec | 3168 | |
ed9708e2 | 3169 | @item C |
43603088 | 3170 | Conformant array bound (Pascal, maybe other languages); @ref{Conformant |
bf9d2537 | 3171 | Arrays}. Name of a caught exception (GNU C++). These can be |
685a5e86 | 3172 | distinguished because the latter uses @code{N_CATCH} and the former uses |
8c59ee11 | 3173 | another symbol type. |
6897f9ec JK |
3174 | |
3175 | @item d | |
bf9d2537 | 3176 | Floating point register variable; see @ref{Register Variables}. |
6897f9ec JK |
3177 | |
3178 | @item D | |
bf9d2537 | 3179 | Parameter in floating point register; see @ref{Register Parameters}. |
ed9708e2 | 3180 | |
497e44a5 | 3181 | @item f |
6fe91f2c | 3182 | File scope function; see @ref{Procedures}. |
497e44a5 JK |
3183 | |
3184 | @item F | |
6fe91f2c | 3185 | Global function; see @ref{Procedures}. |
497e44a5 | 3186 | |
497e44a5 | 3187 | @item G |
bf9d2537 | 3188 | Global variable; see @ref{Global Variables}. |
497e44a5 | 3189 | |
ed9708e2 | 3190 | @item i |
bf9d2537 | 3191 | @xref{Register Parameters}. |
ed9708e2 | 3192 | |
6897f9ec | 3193 | @item I |
bf9d2537 | 3194 | Internal (nested) procedure; see @ref{Nested Procedures}. |
6897f9ec JK |
3195 | |
3196 | @item J | |
bf9d2537 | 3197 | Internal (nested) function; see @ref{Nested Procedures}. |
6897f9ec JK |
3198 | |
3199 | @item L | |
3200 | Label name (documented by AIX, no further information known). | |
3201 | ||
3202 | @item m | |
6fe91f2c | 3203 | Module; see @ref{Procedures}. |
6897f9ec | 3204 | |
ed9708e2 | 3205 | @item p |
6fe91f2c | 3206 | Argument list parameter; see @ref{Parameters}. |
ed9708e2 JK |
3207 | |
3208 | @item pP | |
3209 | @xref{Parameters}. | |
3210 | ||
3211 | @item pF | |
6fe91f2c | 3212 | Fortran Function parameter; see @ref{Parameters}. |
ed9708e2 JK |
3213 | |
3214 | @item P | |
1a8b5668 JK |
3215 | Unfortunately, three separate meanings have been independently invented |
3216 | for this symbol descriptor. At least the GNU and Sun uses can be | |
3217 | distinguished by the symbol type. Global Procedure (AIX) (symbol type | |
685a5e86 DM |
3218 | used unknown); see @ref{Procedures}. Register parameter (GNU) (symbol |
3219 | type @code{N_PSYM}); see @ref{Parameters}. Prototype of function | |
3220 | referenced by this file (Sun @code{acc}) (symbol type @code{N_FUN}). | |
6897f9ec JK |
3221 | |
3222 | @item Q | |
6fe91f2c | 3223 | Static Procedure; see @ref{Procedures}. |
6897f9ec JK |
3224 | |
3225 | @item R | |
bf9d2537 | 3226 | Register parameter; see @ref{Register Parameters}. |
ed9708e2 | 3227 | |
497e44a5 | 3228 | @item r |
bf9d2537 | 3229 | Register variable; see @ref{Register Variables}. |
497e44a5 JK |
3230 | |
3231 | @item S | |
6fe91f2c | 3232 | File scope variable; see @ref{Statics}. |
497e44a5 | 3233 | |
ed9708e2 | 3234 | @item t |
6fe91f2c | 3235 | Type name; see @ref{Typedefs}. |
ed9708e2 JK |
3236 | |
3237 | @item T | |
685a5e86 | 3238 | Enumeration, structure, or union tag; see @ref{Typedefs}. |
ed9708e2 JK |
3239 | |
3240 | @item v | |
bf9d2537 | 3241 | Parameter passed by reference; see @ref{Reference Parameters}. |
ed9708e2 | 3242 | |
497e44a5 | 3243 | @item V |
6fe91f2c | 3244 | Procedure scope static variable; see @ref{Statics}. |
497e44a5 | 3245 | |
6897f9ec | 3246 | @item x |
bf9d2537 | 3247 | Conformant array; see @ref{Conformant Arrays}. |
6897f9ec | 3248 | |
ed9708e2 | 3249 | @item X |
6fe91f2c | 3250 | Function return variable; see @ref{Parameters}. |
497e44a5 | 3251 | @end table |
e505224d | 3252 | |
bf9d2537 DM |
3253 | @node Type Descriptors |
3254 | @appendix Table of Type Descriptors | |
e505224d | 3255 | |
0a95c18c JK |
3256 | The type descriptor is the character which follows the type number and |
3257 | an equals sign. It specifies what kind of type is being defined. | |
bf9d2537 | 3258 | @xref{String Field}, for more information about their use. |
6fe91f2c | 3259 | |
6897f9ec | 3260 | @table @code |
8c59ee11 JK |
3261 | @item @var{digit} |
3262 | @itemx ( | |
bf9d2537 | 3263 | Type reference; see @ref{String Field}. |
8c59ee11 JK |
3264 | |
3265 | @item - | |
bf9d2537 | 3266 | Reference to builtin type; see @ref{Negative Type Numbers}. |
8c59ee11 JK |
3267 | |
3268 | @item # | |
6fe91f2c | 3269 | Method (C++); see @ref{Cplusplus}. |
6897f9ec JK |
3270 | |
3271 | @item * | |
bf9d2537 | 3272 | Pointer; see @ref{Miscellaneous Types}. |
8c59ee11 JK |
3273 | |
3274 | @item & | |
3275 | Reference (C++). | |
6897f9ec JK |
3276 | |
3277 | @item @@ | |
bf9d2537 | 3278 | Type Attributes (AIX); see @ref{String Field}. Member (class and variable) |
6fe91f2c | 3279 | type (GNU C++); see @ref{Cplusplus}. |
e505224d | 3280 | |
6897f9ec | 3281 | @item a |
6fe91f2c | 3282 | Array; see @ref{Arrays}. |
8c59ee11 JK |
3283 | |
3284 | @item A | |
6fe91f2c | 3285 | Open array; see @ref{Arrays}. |
8c59ee11 JK |
3286 | |
3287 | @item b | |
bf9d2537 DM |
3288 | Pascal space type (AIX); see @ref{Miscellaneous Types}. Builtin integer |
3289 | type (Sun); see @ref{Builtin Type Descriptors}. | |
8c59ee11 JK |
3290 | |
3291 | @item B | |
bf9d2537 | 3292 | Volatile-qualified type; see @ref{Miscellaneous Types}. |
8c59ee11 JK |
3293 | |
3294 | @item c | |
bf9d2537 | 3295 | Complex builtin type; see @ref{Builtin Type Descriptors}. |
8c59ee11 JK |
3296 | |
3297 | @item C | |
3298 | COBOL Picture type. See AIX documentation for details. | |
3299 | ||
3300 | @item d | |
bf9d2537 | 3301 | File type; see @ref{Miscellaneous Types}. |
8c59ee11 JK |
3302 | |
3303 | @item D | |
6fe91f2c | 3304 | N-dimensional dynamic array; see @ref{Arrays}. |
6897f9ec JK |
3305 | |
3306 | @item e | |
6fe91f2c | 3307 | Enumeration type; see @ref{Enumerations}. |
8c59ee11 JK |
3308 | |
3309 | @item E | |
6fe91f2c | 3310 | N-dimensional subarray; see @ref{Arrays}. |
6897f9ec JK |
3311 | |
3312 | @item f | |
bf9d2537 | 3313 | Function type; see @ref{Function Types}. |
a03f27c3 JK |
3314 | |
3315 | @item F | |
bf9d2537 | 3316 | Pascal function parameter; see @ref{Function Types} |
8c59ee11 JK |
3317 | |
3318 | @item g | |
bf9d2537 | 3319 | Builtin floating point type; see @ref{Builtin Type Descriptors}. |
8c59ee11 JK |
3320 | |
3321 | @item G | |
3322 | COBOL Group. See AIX documentation for details. | |
3323 | ||
3324 | @item i | |
bf9d2537 | 3325 | Imported type; see @ref{Cross-References}. |
8c59ee11 JK |
3326 | |
3327 | @item k | |
bf9d2537 | 3328 | Const-qualified type; see @ref{Miscellaneous Types}. |
8c59ee11 JK |
3329 | |
3330 | @item K | |
3331 | COBOL File Descriptor. See AIX documentation for details. | |
3332 | ||
a03f27c3 | 3333 | @item M |
bf9d2537 | 3334 | Multiple instance type; see @ref{Miscellaneous Types}. |
a03f27c3 | 3335 | |
8c59ee11 | 3336 | @item n |
6fe91f2c | 3337 | String type; see @ref{Strings}. |
8c59ee11 JK |
3338 | |
3339 | @item N | |
6fe91f2c | 3340 | Stringptr; see @ref{Strings}. |
8c59ee11 | 3341 | |
8c59ee11 | 3342 | @item o |
6fe91f2c | 3343 | Opaque type; see @ref{Typedefs}. |
8c59ee11 | 3344 | |
a03f27c3 | 3345 | @item p |
bf9d2537 | 3346 | Procedure; see @ref{Function Types}. |
a03f27c3 | 3347 | |
8c59ee11 | 3348 | @item P |
6fe91f2c | 3349 | Packed array; see @ref{Arrays}. |
6897f9ec JK |
3350 | |
3351 | @item r | |
6fe91f2c | 3352 | Range type; see @ref{Subranges}. |
8c59ee11 JK |
3353 | |
3354 | @item R | |
bf9d2537 DM |
3355 | Builtin floating type; see @ref{Builtin Type Descriptors} (Sun). Pascal |
3356 | subroutine parameter; see @ref{Function Types} (AIX). Detecting this | |
a03f27c3 JK |
3357 | conflict is possible with careful parsing (hint: a Pascal subroutine |
3358 | parameter type will always contain a comma, and a builtin type | |
3359 | descriptor never will). | |
6897f9ec JK |
3360 | |
3361 | @item s | |
6fe91f2c | 3362 | Structure type; see @ref{Structures}. |
8c59ee11 JK |
3363 | |
3364 | @item S | |
bf9d2537 | 3365 | Set type; see @ref{Miscellaneous Types}. |
6897f9ec JK |
3366 | |
3367 | @item u | |
6fe91f2c | 3368 | Union; see @ref{Unions}. |
8c59ee11 JK |
3369 | |
3370 | @item v | |
3371 | Variant record. This is a Pascal and Modula-2 feature which is like a | |
3372 | union within a struct in C. See AIX documentation for details. | |
3373 | ||
3374 | @item w | |
bf9d2537 | 3375 | Wide character; see @ref{Builtin Type Descriptors}. |
8c59ee11 JK |
3376 | |
3377 | @item x | |
bf9d2537 | 3378 | Cross-reference; see @ref{Cross-References}. |
6897f9ec | 3379 | |
8c59ee11 | 3380 | @item z |
6fe91f2c | 3381 | gstring; see @ref{Strings}. |
6897f9ec | 3382 | @end table |
e505224d | 3383 | |
bf9d2537 DM |
3384 | @node Expanded Reference |
3385 | @appendix Expanded Reference by Stab Type | |
e505224d | 3386 | |
685a5e86 | 3387 | @c FIXME: This appendix should go away; see N_PSYM or N_SO for an example. |
8c59ee11 | 3388 | |
3d4cf720 | 3389 | For a full list of stab types, and cross-references to where they are |
bf9d2537 | 3390 | described, see @ref{Stab Types}. This appendix just duplicates certain |
3d4cf720 JK |
3391 | information from the main body of this document; eventually the |
3392 | information will all be in one place. | |
8c59ee11 | 3393 | |
e505224d | 3394 | Format of an entry: |
6fe91f2c | 3395 | |
685a5e86 | 3396 | The first line is the symbol type (see @file{include/aout/stab.def}). |
e505224d PB |
3397 | |
3398 | The second line describes the language constructs the symbol type | |
3399 | represents. | |
3400 | ||
3401 | The third line is the stab format with the significant stab fields | |
3402 | named and the rest NIL. | |
3403 | ||
3404 | Subsequent lines expand upon the meaning and possible values for each | |
685a5e86 | 3405 | significant stab field. @samp{#} stands in for the type descriptor. |
e505224d PB |
3406 | |
3407 | Finally, any further information. | |
3408 | ||
899bafeb | 3409 | @menu |
8eb5e289 DZ |
3410 | * N_PC:: Pascal global symbol |
3411 | * N_NSYMS:: Number of symbols | |
3412 | * N_NOMAP:: No DST map | |
8eb5e289 DZ |
3413 | * N_M2C:: Modula-2 compilation unit |
3414 | * N_BROWS:: Path to .cb file for Sun source code browser | |
3415 | * N_DEFD:: GNU Modula2 definition module dependency | |
3416 | * N_EHDECL:: GNU C++ exception variable | |
3417 | * N_MOD2:: Modula2 information "for imc" | |
3418 | * N_CATCH:: GNU C++ "catch" clause | |
3419 | * N_SSYM:: Structure or union element | |
8eb5e289 DZ |
3420 | * N_ENTRY:: Alternate entry point |
3421 | * N_SCOPE:: Modula2 scope information (Sun only) | |
3422 | * Gould:: non-base register symbols used on Gould systems | |
3423 | * N_LENG:: Length of preceding entry | |
899bafeb RP |
3424 | @end menu |
3425 | ||
899bafeb | 3426 | @node N_PC |
685a5e86 | 3427 | @section N_PC |
e505224d | 3428 | |
685a5e86 DM |
3429 | @deffn @code{.stabs} N_PC |
3430 | @findex N_PC | |
3431 | Global symbol (for Pascal). | |
e505224d | 3432 | |
899bafeb | 3433 | @example |
e505224d PB |
3434 | "name" -> "symbol_name" <<?>> |
3435 | value -> supposedly the line number (stab.def is skeptical) | |
899bafeb | 3436 | @end example |
e505224d | 3437 | |
899bafeb | 3438 | @display |
f958d5cd | 3439 | @file{stabdump.c} says: |
e505224d | 3440 | |
6fe91f2c | 3441 | global pascal symbol: name,,0,subtype,line |
e505224d | 3442 | << subtype? >> |
899bafeb | 3443 | @end display |
685a5e86 | 3444 | @end deffn |
e505224d | 3445 | |
899bafeb | 3446 | @node N_NSYMS |
685a5e86 DM |
3447 | @section N_NSYMS |
3448 | ||
3449 | @deffn @code{.stabn} N_NSYMS | |
3450 | @findex N_NSYMS | |
3451 | Number of symbols (according to Ultrix V4.0). | |
e505224d | 3452 | |
899bafeb | 3453 | @display |
139741da | 3454 | 0, files,,funcs,lines (stab.def) |
899bafeb | 3455 | @end display |
685a5e86 | 3456 | @end deffn |
e505224d | 3457 | |
899bafeb | 3458 | @node N_NOMAP |
685a5e86 DM |
3459 | @section N_NOMAP |
3460 | ||
3461 | @deffn @code{.stabs} N_NOMAP | |
3462 | @findex N_NOMAP | |
935d305d JK |
3463 | No DST map for symbol (according to Ultrix V4.0). I think this means a |
3464 | variable has been optimized out. | |
e505224d | 3465 | |
899bafeb | 3466 | @display |
139741da | 3467 | name, ,0,type,ignored (stab.def) |
899bafeb | 3468 | @end display |
685a5e86 | 3469 | @end deffn |
e505224d | 3470 | |
899bafeb | 3471 | @node N_M2C |
685a5e86 | 3472 | @section N_M2C |
e505224d | 3473 | |
685a5e86 DM |
3474 | @deffn @code{.stabs} N_M2C |
3475 | @findex N_M2C | |
3476 | Modula-2 compilation unit. | |
e505224d | 3477 | |
899bafeb | 3478 | @example |
685a5e86 | 3479 | "string" -> "unit_name,unit_time_stamp[,code_time_stamp]" |
e505224d PB |
3480 | desc -> unit_number |
3481 | value -> 0 (main unit) | |
139741da | 3482 | 1 (any other unit) |
899bafeb | 3483 | @end example |
685a5e86 | 3484 | @end deffn |
e505224d | 3485 | |
899bafeb | 3486 | @node N_BROWS |
685a5e86 DM |
3487 | @section N_BROWS |
3488 | ||
3489 | @deffn @code{.stabs} N_BROWS | |
3490 | @findex N_BROWS | |
6fe91f2c | 3491 | Sun source code browser, path to @file{.cb} file |
e505224d | 3492 | |
6fe91f2c | 3493 | <<?>> |
685a5e86 | 3494 | "path to associated @file{.cb} file" |
e505224d | 3495 | |
0a95c18c | 3496 | Note: N_BROWS has the same value as N_BSLINE. |
685a5e86 | 3497 | @end deffn |
e505224d | 3498 | |
899bafeb | 3499 | @node N_DEFD |
685a5e86 DM |
3500 | @section N_DEFD |
3501 | ||
3502 | @deffn @code{.stabn} N_DEFD | |
3503 | @findex N_DEFD | |
3504 | GNU Modula2 definition module dependency. | |
e505224d | 3505 | |
0a95c18c JK |
3506 | GNU Modula-2 definition module dependency. The value is the |
3507 | modification time of the definition file. The other field is non-zero | |
3508 | if it is imported with the GNU M2 keyword @code{%INITIALIZE}. Perhaps | |
3509 | @code{N_M2C} can be used if there are enough empty fields? | |
685a5e86 | 3510 | @end deffn |
e505224d | 3511 | |
899bafeb | 3512 | @node N_EHDECL |
685a5e86 | 3513 | @section N_EHDECL |
e505224d | 3514 | |
685a5e86 DM |
3515 | @deffn @code{.stabs} N_EHDECL |
3516 | @findex N_EHDECL | |
3517 | GNU C++ exception variable <<?>>. | |
e505224d | 3518 | |
685a5e86 DM |
3519 | "@var{string} is variable name" |
3520 | ||
3521 | Note: conflicts with @code{N_MOD2}. | |
3522 | @end deffn | |
e505224d | 3523 | |
899bafeb | 3524 | @node N_MOD2 |
685a5e86 DM |
3525 | @section N_MOD2 |
3526 | ||
3527 | @deffn @code{.stab?} N_MOD2 | |
3528 | @findex N_MOD2 | |
899bafeb | 3529 | Modula2 info "for imc" (according to Ultrix V4.0) |
e505224d | 3530 | |
685a5e86 DM |
3531 | Note: conflicts with @code{N_EHDECL} <<?>> |
3532 | @end deffn | |
e505224d | 3533 | |
899bafeb | 3534 | @node N_CATCH |
685a5e86 DM |
3535 | @section N_CATCH |
3536 | ||
3537 | @deffn @code{.stabn} N_CATCH | |
3538 | @findex N_CATCH | |
6fe91f2c | 3539 | GNU C++ @code{catch} clause |
e505224d | 3540 | |
0a95c18c | 3541 | GNU C++ @code{catch} clause. The value is its address. The desc field |
685a5e86 DM |
3542 | is nonzero if this entry is immediately followed by a @code{CAUGHT} stab |
3543 | saying what exception was caught. Multiple @code{CAUGHT} stabs means | |
0a95c18c JK |
3544 | that multiple exceptions can be caught here. If desc is 0, it means all |
3545 | exceptions are caught here. | |
685a5e86 | 3546 | @end deffn |
e505224d | 3547 | |
899bafeb | 3548 | @node N_SSYM |
685a5e86 DM |
3549 | @section N_SSYM |
3550 | ||
3551 | @deffn @code{.stabn} N_SSYM | |
3552 | @findex N_SSYM | |
3553 | Structure or union element. | |
e505224d | 3554 | |
0a95c18c | 3555 | The value is the offset in the structure. |
899bafeb RP |
3556 | |
3557 | <<?looking at structs and unions in C I didn't see these>> | |
685a5e86 | 3558 | @end deffn |
e505224d | 3559 | |
899bafeb | 3560 | @node N_ENTRY |
685a5e86 | 3561 | @section N_ENTRY |
e505224d | 3562 | |
685a5e86 DM |
3563 | @deffn @code{.stabn} N_ENTRY |
3564 | @findex N_ENTRY | |
6fe91f2c | 3565 | Alternate entry point. |
0a95c18c | 3566 | The value is its address. |
e505224d | 3567 | <<?>> |
685a5e86 | 3568 | @end deffn |
e505224d | 3569 | |
899bafeb | 3570 | @node N_SCOPE |
685a5e86 | 3571 | @section N_SCOPE |
e505224d | 3572 | |
685a5e86 DM |
3573 | @deffn @code{.stab?} N_SCOPE |
3574 | @findex N_SCOPE | |
e505224d PB |
3575 | Modula2 scope information (Sun linker) |
3576 | <<?>> | |
685a5e86 | 3577 | @end deffn |
e505224d | 3578 | |
899bafeb RP |
3579 | @node Gould |
3580 | @section Non-base registers on Gould systems | |
ded6bcab | 3581 | |
685a5e86 DM |
3582 | @deffn @code{.stab?} N_NBTEXT |
3583 | @deffnx @code{.stab?} N_NBDATA | |
3584 | @deffnx @code{.stab?} N_NBBSS | |
3585 | @deffnx @code{.stab?} N_NBSTS | |
3586 | @deffnx @code{.stab?} N_NBLCS | |
3587 | @findex N_NBTEXT | |
3588 | @findex N_NBDATA | |
3589 | @findex N_NBBSS | |
3590 | @findex N_NBSTS | |
3591 | @findex N_NBLCS | |
ded6bcab JK |
3592 | These are used on Gould systems for non-base registers syms. |
3593 | ||
3594 | However, the following values are not the values used by Gould; they are | |
3595 | the values which GNU has been documenting for these values for a long | |
3596 | time, without actually checking what Gould uses. I include these values | |
3597 | only because perhaps some someone actually did something with the GNU | |
3598 | information (I hope not, why GNU knowingly assigned wrong values to | |
3599 | these in the header file is a complete mystery to me). | |
e505224d | 3600 | |
899bafeb | 3601 | @example |
139741da RP |
3602 | 240 0xf0 N_NBTEXT ?? |
3603 | 242 0xf2 N_NBDATA ?? | |
3604 | 244 0xf4 N_NBBSS ?? | |
3605 | 246 0xf6 N_NBSTS ?? | |
3606 | 248 0xf8 N_NBLCS ?? | |
899bafeb | 3607 | @end example |
685a5e86 | 3608 | @end deffn |
e505224d | 3609 | |
899bafeb | 3610 | @node N_LENG |
685a5e86 | 3611 | @section N_LENG |
e505224d | 3612 | |
685a5e86 DM |
3613 | @deffn @code{.stabn} N_LENG |
3614 | @findex N_LENG | |
e505224d | 3615 | Second symbol entry containing a length-value for the preceding entry. |
0a95c18c | 3616 | The value is the length. |
685a5e86 | 3617 | @end deffn |
e505224d | 3618 | |
899bafeb | 3619 | @node Questions |
bf9d2537 | 3620 | @appendix Questions and Anomalies |
e505224d PB |
3621 | |
3622 | @itemize @bullet | |
3623 | @item | |
dd8126d9 | 3624 | @c I think this is changed in GCC 2.4.5 to put the line number there. |
6fe91f2c | 3625 | For GNU C stabs defining local and global variables (@code{N_LSYM} and |
0a95c18c JK |
3626 | @code{N_GSYM}), the desc field is supposed to contain the source |
3627 | line number on which the variable is defined. In reality the desc | |
dd8126d9 | 3628 | field is always 0. (This behavior is defined in @file{dbxout.c} and |
0a95c18c | 3629 | putting a line number in desc is controlled by @samp{#ifdef |
dd8126d9 JK |
3630 | WINNING_GDB}, which defaults to false). GDB supposedly uses this |
3631 | information if you say @samp{list @var{var}}. In reality, @var{var} can | |
3632 | be a variable defined in the program and GDB says @samp{function | |
6fe91f2c | 3633 | @var{var} not defined}. |
e505224d PB |
3634 | |
3635 | @item | |
6fe91f2c DM |
3636 | In GNU C stabs, there seems to be no way to differentiate tag types: |
3637 | structures, unions, and enums (symbol descriptor @samp{T}) and typedefs | |
3638 | (symbol descriptor @samp{t}) defined at file scope from types defined locally | |
3639 | to a procedure or other more local scope. They all use the @code{N_LSYM} | |
e505224d | 3640 | stab type. Types defined at procedure scope are emited after the |
6fe91f2c | 3641 | @code{N_RBRAC} of the preceding function and before the code of the |
e505224d PB |
3642 | procedure in which they are defined. This is exactly the same as |
3643 | types defined in the source file between the two procedure bodies. | |
4d7f562d | 3644 | GDB overcompensates by placing all types in block #1, the block for |
6fe91f2c DM |
3645 | symbols of file scope. This is true for default, @samp{-ansi} and |
3646 | @samp{-traditional} compiler options. (Bugs gcc/1063, gdb/1066.) | |
e505224d PB |
3647 | |
3648 | @item | |
6fe91f2c DM |
3649 | What ends the procedure scope? Is it the proc block's @code{N_RBRAC} or the |
3650 | next @code{N_FUN}? (I believe its the first.) | |
e505224d PB |
3651 | |
3652 | @item | |
24dcc707 | 3653 | @c FIXME: This should go with the other stuff about global variables. |
e505224d PB |
3654 | Global variable stabs don't have location information. This comes |
3655 | from the external symbol for the same variable. The external symbol | |
3656 | has a leading underbar on the _name of the variable and the stab does | |
3657 | not. How do we know these two symbol table entries are talking about | |
24dcc707 JK |
3658 | the same symbol when their names are different? (Answer: the debugger |
3659 | knows that external symbols have leading underbars). | |
e505224d | 3660 | |
24dcc707 JK |
3661 | @c FIXME: This is absurdly vague; there all kinds of differences, some |
3662 | @c of which are the same between gnu & sun, and some of which aren't. | |
dd8126d9 JK |
3663 | @c In particular, I'm pretty sure GCC works with Sun dbx by default. |
3664 | @c @item | |
3665 | @c Can GCC be configured to output stabs the way the Sun compiler | |
3666 | @c does, so that their native debugging tools work? <NO?> It doesn't by | |
3667 | @c default. GDB reads either format of stab. (GCC or SunC). How about | |
3668 | @c dbx? | |
e505224d PB |
3669 | @end itemize |
3670 | ||
bf9d2537 DM |
3671 | @node XCOFF Differences |
3672 | @appendix Differences Between GNU Stabs in a.out and GNU Stabs in XCOFF | |
e505224d | 3673 | |
497e44a5 | 3674 | @c FIXME: Merge *all* these into the main body of the document. |
f958d5cd | 3675 | The AIX/RS6000 native object file format is XCOFF with stabs. This |
497e44a5 JK |
3676 | appendix only covers those differences which are not covered in the main |
3677 | body of this document. | |
e505224d PB |
3678 | |
3679 | @itemize @bullet | |
e505224d | 3680 | @item |
dd8126d9 JK |
3681 | BSD a.out stab types correspond to AIX XCOFF storage classes. In general |
3682 | the mapping is @code{N_@var{stabtype}} becomes @code{C_@var{stabtype}}. | |
3683 | Some stab types in a.out are not supported in XCOFF; most of these use | |
3684 | @code{C_DECL}. | |
e505224d | 3685 | |
24dcc707 JK |
3686 | @c FIXME: Get C_* types for the block, figure out whether it is always |
3687 | @c used (I suspect not), explain clearly, and move to node Statics. | |
dd8126d9 JK |
3688 | Exception: initialised static @code{N_STSYM} and un-initialized static |
3689 | @code{N_LCSYM} both map to the @code{C_STSYM} storage class. But the | |
bf9d2537 | 3690 | distinction is preserved because in XCOFF @code{N_STSYM} and |
dd8126d9 JK |
3691 | @code{N_LCSYM} must be emited in a named static block. Begin the block |
3692 | with @samp{.bs s[RW] data_section_name} for @code{N_STSYM} or @samp{.bs | |
3693 | s bss_section_name} for @code{N_LCSYM}. End the block with @samp{.es}. | |
e505224d | 3694 | |
24dcc707 JK |
3695 | @c FIXME: I think they are trying to say something about whether the |
3696 | @c assembler defaults the value to the location counter. | |
e505224d | 3697 | @item |
685a5e86 | 3698 | If the XCOFF stab is an @code{N_FUN} (@code{C_FUN}) then follow the |
dd8126d9 | 3699 | string field with @samp{,.} instead of just @samp{,}. |
e505224d PB |
3700 | @end itemize |
3701 | ||
6fe91f2c | 3702 | I think that's it for @file{.s} file differences. They could stand to be |
e505224d | 3703 | better presented. This is just a list of what I have noticed so far. |
6fe91f2c DM |
3704 | There are a @emph{lot} of differences in the information in the symbol |
3705 | tables of the executable and object files. | |
e505224d | 3706 | |
f958d5cd | 3707 | Mapping of a.out stab types to XCOFF storage classes: |
e505224d PB |
3708 | |
3709 | @example | |
139741da | 3710 | stab type storage class |
e505224d | 3711 | ------------------------------- |
139741da | 3712 | N_GSYM C_GSYM |
43603088 | 3713 | N_FNAME unused |
139741da RP |
3714 | N_FUN C_FUN |
3715 | N_STSYM C_STSYM | |
3716 | N_LCSYM C_STSYM | |
43603088 | 3717 | N_MAIN unknown |
139741da RP |
3718 | N_PC unknown |
3719 | N_RSYM C_RSYM | |
dd8126d9 | 3720 | unknown C_RPSYM |
139741da RP |
3721 | N_M2C unknown |
3722 | N_SLINE unknown | |
3723 | N_DSLINE unknown | |
3724 | N_BSLINE unknown | |
3725 | N_BROWSE unchanged | |
3726 | N_CATCH unknown | |
3727 | N_SSYM unknown | |
3728 | N_SO unknown | |
3729 | N_LSYM C_LSYM | |
dd8126d9 | 3730 | various C_DECL |
139741da RP |
3731 | N_BINCL unknown |
3732 | N_SOL unknown | |
3733 | N_PSYM C_PSYM | |
3734 | N_EINCL unknown | |
3735 | N_ENTRY C_ENTRY | |
3736 | N_LBRAC unknown | |
3737 | N_EXCL unknown | |
3738 | N_SCOPE unknown | |
3739 | N_RBRAC unknown | |
3740 | N_BCOMM C_BCOMM | |
3741 | N_ECOMM C_ECOMM | |
3742 | N_ECOML C_ECOML | |
3743 | ||
3744 | N_LENG unknown | |
e505224d PB |
3745 | @end example |
3746 | ||
bf9d2537 DM |
3747 | @node Sun Differences |
3748 | @appendix Differences Between GNU Stabs and Sun Native Stabs | |
e505224d | 3749 | |
497e44a5 JK |
3750 | @c FIXME: Merge all this stuff into the main body of the document. |
3751 | ||
e505224d PB |
3752 | @itemize @bullet |
3753 | @item | |
6fe91f2c DM |
3754 | GNU C stabs define @emph{all} types, file or procedure scope, as |
3755 | @code{N_LSYM}. Sun doc talks about using @code{N_GSYM} too. | |
e505224d | 3756 | |
e505224d | 3757 | @item |
4e9570e8 JK |
3758 | Sun C stabs use type number pairs in the format |
3759 | (@var{file-number},@var{type-number}) where @var{file-number} is a | |
3760 | number starting with 1 and incremented for each sub-source file in the | |
3761 | compilation. @var{type-number} is a number starting with 1 and | |
6fe91f2c DM |
3762 | incremented for each new type defined in the compilation. GNU C stabs |
3763 | use the type number alone, with no source file number. | |
e505224d PB |
3764 | @end itemize |
3765 | ||
bf9d2537 DM |
3766 | @node Stabs In ELF |
3767 | @appendix Using Stabs With The ELF Object File Format | |
935d305d | 3768 | |
6fe91f2c DM |
3769 | The ELF object file format allows tools to create object files with |
3770 | custom sections containing any arbitrary data. To use stabs in ELF | |
935d305d JK |
3771 | object files, the tools create two custom sections, a section named |
3772 | @code{.stab} which contains an array of fixed length structures, one | |
3773 | struct per stab, and a section named @code{.stabstr} containing all the | |
3774 | variable length strings that are referenced by stabs in the @code{.stab} | |
3775 | section. The byte order of the stabs binary data matches the byte order | |
6fe91f2c DM |
3776 | of the ELF file itself, as determined from the @code{EI_DATA} field in |
3777 | the @code{e_ident} member of the ELF header. | |
935d305d | 3778 | |
4e9570e8 | 3779 | The first stab in the @code{.stab} section for each compilation unit is |
935d305d JK |
3780 | synthetic, generated entirely by the assembler, with no corresponding |
3781 | @code{.stab} directive as input to the assembler. This stab contains | |
3782 | the following fields: | |
cc4fb848 | 3783 | |
935d305d JK |
3784 | @table @code |
3785 | @item n_strx | |
3786 | Offset in the @code{.stabstr} section to the source filename. | |
cc4fb848 | 3787 | |
935d305d JK |
3788 | @item n_type |
3789 | @code{N_UNDF}. | |
cc4fb848 | 3790 | |
935d305d | 3791 | @item n_other |
cc4fb848 FF |
3792 | Unused field, always zero. |
3793 | ||
935d305d | 3794 | @item n_desc |
6fe91f2c | 3795 | Count of upcoming symbols, i.e., the number of remaining stabs for this |
935d305d | 3796 | source file. |
cc4fb848 | 3797 | |
935d305d JK |
3798 | @item n_value |
3799 | Size of the string table fragment associated with this source file, in | |
cc4fb848 | 3800 | bytes. |
935d305d | 3801 | @end table |
cc4fb848 | 3802 | |
935d305d | 3803 | The @code{.stabstr} section always starts with a null byte (so that string |
cc4fb848 FF |
3804 | offsets of zero reference a null string), followed by random length strings, |
3805 | each of which is null byte terminated. | |
3806 | ||
6fe91f2c | 3807 | The ELF section header for the @code{.stab} section has its |
935d305d | 3808 | @code{sh_link} member set to the section number of the @code{.stabstr} |
6fe91f2c | 3809 | section, and the @code{.stabstr} section has its ELF section |
935d305d JK |
3810 | header @code{sh_type} member set to @code{SHT_STRTAB} to mark it as a |
3811 | string table. | |
3812 | ||
31a932d8 | 3813 | To keep linking fast, it is a bad idea to have the linker relocating |
f8cbe518 JK |
3814 | stabs, so (except for a few cases, see below) none of the addresses in |
3815 | the @code{n_value} field of the stabs are relocated by the linker. | |
3816 | Instead they are relative to the source file (or some entity smaller | |
3817 | than a source file, like a function). To find the address of each | |
3818 | section corresponding to a given source file, the compiler puts out | |
31a932d8 | 3819 | symbols giving the address of each section for a given source file. |
f8cbe518 JK |
3820 | Since these are ELF (not stab) symbols, the linker relocates them |
3821 | correctly without having to touch the stabs section. They are named | |
3822 | @code{Bbss.bss} for the bss section, @code{Ddata.data} for the data | |
3823 | section, and @code{Drodata.rodata} for the rodata section. For the text | |
3824 | section, there is no such symbol (but there should be, see below). For | |
cd61aa60 | 3825 | an example of how these symbols work, @xref{ELF Transformations}. GCC |
31a932d8 | 3826 | does not provide these symbols; it instead relies on the stabs getting |
f8cbe518 JK |
3827 | relocated, which slows down linking. Thus addresses which would |
3828 | normally be relative to @code{Bbss.bss}, etc., are already relocated. | |
3829 | The Sun linker provided with Solaris 2.2 and earlier relocates stabs | |
3830 | using normal ELF relocation information, as it would do for any section. | |
3831 | Sun has been threatening to kludge their linker to not do this (to speed | |
3832 | up linking), even though the correct way to avoid having the linker do | |
3833 | these relocations is to have the compiler no longer output relocatable | |
3834 | values. Last I heard they had been talked out of the linker kludge. | |
3835 | See Sun point patch 101052-01 and Sun bug 1142109. This affects | |
3836 | @samp{S} symbol descriptor stabs (@pxref{Statics}) and functions | |
3837 | (@pxref{Procedures}). In the latter case, to adopt the clean solution | |
3838 | (making the value of the stab relative to the start of the compilation | |
3839 | unit), it would be necessary to invent a @code{Ttext.text} symbol, | |
3840 | analogous to the @code{Bbss.bss}, etc., symbols. I recommend this | |
3841 | rather than using a zero value and getting the address from the ELF | |
3842 | symbols. | |
cc4fb848 | 3843 | |
685a5e86 DM |
3844 | @node Symbol Types Index |
3845 | @unnumbered Symbol Types Index | |
3846 | ||
3847 | @printindex fn | |
3848 | ||
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3849 | @contents |
3850 | @bye |