     START-INFO-DIR-ENTRY
     * Gdb-Internals: (gdbint).	The GNU debugger internals.
     END-INFO-DIR-ENTRY

This file documents the internals of the GNU debugger GDB.

Copyright (C) 1990, 1991, 1992 Free Software Foundation, Inc. Contributed by Cygnus Support.  Written by John Gilmore.

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy or distribute modified versions of this manual under the terms of the GPL (for which purpose this text may be regarded as a program in the language TeX).

This file documents the internals of the GNU debugger GDB.  It is a collection of miscellaneous information with little form at this point. Mostly, it is a repository into which you can put information about GDB as you discover it (or as you design changes to GDB).

The README File
***************

Check the README file, it often has useful information that does not appear anywhere else in the directory.

Defining a New Host or Target Architecture
******************************************

When building support for a new host and/or target, much of the work you need to do is handled by specifying configuration files; see Adding a New Configuration.  Further work can be divided into ``host-dependent'' (see Adding a New Host) and ``target-dependent'' (see Adding a New Target).  The following discussion is meant to explain the difference between hosts and targets.

What is considered ``host-dependent'' versus ``target-dependent''?
==================================================================

Host refers to attributes of the system where GDB runs. Target refers to the system where the program being debugged executes.   In most cases they are the same machine; unfortunately, that means you must add both host and target support for new machines in this category.

The config/mh-*, xm-*.h and *-xdep.c files are for host support.  Similarly, the config/mt-*, tm-*.h and *-tdep.c files are for target support.  The question is, what features or aspects of a debugging or cross-debugging environment are considered to be ``host'' support?

Defines and include files needed to build on the host are host support. Examples are tty support, system defined types, host byte order, host float format.

Unix child process support is considered an aspect of the host.  Since when you fork on the host you are still on the host, the various macros needed for finding the registers in the upage, running ptrace, and such are all in the host-dependent files.

This is still somewhat of a grey area; I (John Gilmore) didn't do the xm-* and tm-* split for gdb (it was done by Jim Kingdon) so I have had to figure out the grounds on which it was split, and make my own choices as I evolve it.  I have moved many things out of the xdep files actually, partly as a result of BFD and partly by removing duplicated code.

Adding a New Configuration
**************************

Most of the work in making GDB compile on a new machine is in specifying the configuration of the machine.  This is done in a dizzying variety of header files and configuration scripts, which we hope to make more sensible soon.  Let's say your new host is called an XXX (e.g. sun4), and its full three-part configuration name is XARCH-XVEND-XOS (e.g.  sparc-sun-sunos4).  In particular:

In the top level directory, edit config.sub and add XARCH, XVEND, and XOS to the lists of supported architectures, vendors, and operating systems near the bottom of the file.  Also, add XXX as an alias that maps to XARCH-XVEND-XOS.  You can test your changes by running

     ./config.sub XXX

and

     ./config.sub XARCH-XVEND-XOS

which should both respond with XARCH-XVEND-XOS and no error messages.

Now, go to the bfd directory and create a new file bfd/hosts/h-XXX.h.  Examine the other h-*.h files as templates, and create one that brings in the right include files for your system, and defines any host-specific macros needed by GDB.

Then edit bfd/configure.in.  Add shell script code to recognize your XARCH-XVEND-XOS configuration, and set my_host to XXX when you recognize it.  This will cause your file h-XXX.h to be linked to sysdep.h at configuration time.

Also, if this host requires any changes to the Makefile, create a file bfd/config/mh-XXX, which includes the required lines.

(If you have the binary utilities and/or GNU ld in the same tree, you'll also have to edit binutils/configure.in or ld/configure.in to match what you've done in the bfd directory.)

It's possible that the libiberty and readline directories won't need any changes for your configuration, but if they do, you can change the configure.in file there to recognize your system and map to an mh-XXX file.  Then add mh-XXX to the config/ subdirectory, to set any makefile variables you need.  The only current options in there are things like -DSYSV.

Aha!  Now to configure GDB itself!  Edit gdb/configure.in to recognize your system and set gdb_host to XXX, and (unless your desired target is already available) also set gdb_target to something appropriate (for instance, XXX).  To handle new hosts, modify the segment after the comment # per-host; to handle new targets, modify after # per-target.

Finally, you'll need to specify and define GDB's host- and target-dependent .h and .c files used for your configuration; the next two chapters discuss those.

Adding a New Host
*****************

Once you have specified a new configuration for your host (see Adding a New Configuration), there are two remaining pieces to making GDB work on a new machine.  First, you have to make it host on the new machine (compile there, handle that machine's terminals properly, etc).  If you will be cross-debugging to some other kind of system that's already supported, you are done.

If you want to use GDB to debug programs that run on the new machine, you have to get it to understand the machine's object files, symbol files, and interfaces to processes.  see Adding a New Target

Several files control GDB's configuration for host systems:

gdb/config/mh-XXX
     Specifies Makefile fragments needed when hosting on machine XXX. In particular, this lists the required machine-dependent object files, by defining XDEPFILES=....  Also specifies the header file which describes host XXX, by defining XM_FILE= xm-XXX.h.  You can also define CC, REGEX and REGEX1, SYSV_DEFINE, XM_CFLAGS, XM_ADD_FILES, XM_CLIBS, XM_CDEPS, etc.; see Makefile.in.

gdb/xm-XXX.h
     (xm.h is a link to this file, created by configure). Contains C macro definitions describing the host system environment, such as byte order, host C compiler and library, ptrace support, and core file structure.  Crib from existing xm-*.h files to create a new one.

gdb/XXX-xdep.c
     Contains any miscellaneous C code required for this machine as a host.  On some machines it doesn't exist at all.

There are some ``generic'' versions of routines that can be used by various host systems.  These can be customized in various ways by macros defined in your xm-XXX.h file.  If these routines work for the XXX host, you can just include the generic file's name (with .o, not .c) in XDEPFILES.

Otherwise, if your machine needs custom support routines, you will need to write routines that perform the same functions as the generic file. Put them into XXX-xdep.c, and put XXX-xdep.o into XDEPFILES.

Generic Host Support Files
--------------------------

infptrace.c
     This is the low level interface to inferior processes for systems using the Unix ptrace call in a vanilla way.

coredep.c::fetch_core_registers()
     Support for reading registers out of a core file.  This routine calls register_addr(), see below. Now that BFD is used to read core files, virtually all machines should use coredep.c, and should just provide fetch_core_registers in XXX-xdep.c (or REGISTER_U_ADDR in xm-XXX.h).

coredep.c::register_addr()
     If your xm-XXX.h file defines the macro REGISTER_U_ADDR(addr, blockend, regno), it should be defined to set addr to the offset within the user struct of GDB register number regno.  blockend is the offset within the ``upage'' of u.u_ar0. If REGISTER_U_ADDR is defined, coredep.c will define the register_addr() function and use the macro in it.  If you do not define REGISTER_U_ADDR, but you are using the standard fetch_core_registers(), you will need to define your own version of register_addr(), put it into your XXX-xdep.c file, and be sure XXX-xdep.o is in the XDEPFILES list.  If you have your own fetch_core_registers(), you may not need a separate register_addr().  Many custom fetch_core_registers() implementations simply locate the registers themselves.

Object files needed when the target system is an XXX are listed in the file config/mt-XXX, in the makefile macro TDEPFILES = ....  The header file that defines the target system should be called tm-XXX.h, and should be specified as the value of TM_FILE in config/mt-XXX.  You can also define TM_CFLAGS, TM_CLIBS, and TM_CDEPS in there; see Makefile.in.

Now, you are now ready to try configuring GDB to compile for your system. From the top level (above bfd, gdb, etc), do:

     ./configure XXX +target=vxworks960

This will configure your system to cross-compile for VxWorks on the Intel 960, which is probably not what you really want, but it's a test case that works at this stage.  (You haven't set up to be able to debug programs that run on XXX yet.)

If this succeeds, you can try building it all with:

     make

Good luck!  Comments and suggestions about this section are particularly welcome; send them to bug-gdb@prep.ai.mit.edu.

When hosting GDB on a new operating system, to make it possible to debug core files, you will need to either write specific code for parsing your OS's core files, or customize bfd/trad-core.c.  First, use whatever #include files your machine uses to define the struct of registers that is accessible (possibly in the u-area) in a core file (rather than machine/reg.h), and an include file that defines whatever header exists on a core file (e.g. the u-area or a struct core).  Then modify trad_unix_core_file_p() to use these values to set up the section information for the data segment, stack segment, any other segments in the core file (perhaps shared library contents or control information), ``registers'' segment, and if there are two discontiguous sets of registers (e.g.  integer and float), the ``reg2'' segment.  This section information basically delimits areas in the core file in a standard way, which the section-reading routines in BFD know how to seek around in.

Then back in GDB, you need a matching routine called fetch_core_registers().  If you can use the generic one, it's in core-dep.c; if not, it's in your XXX-xdep.c file. It will be passed a char pointer to the entire ``registers'' segment, its length, and a zero; or a char pointer to the entire ``regs2'' segment, its length, and a 2.  The routine should suck out the supplied register values and install them into GDB's ``registers'' array. (see Defining a New Host or Target Architecture, for more info about this.)

Adding a New Target
*******************

For a new target called TTT, first specify the configuration as described in Adding a New Configuration.  If your new target is the same as your new host, you've probably already done that.

A variety of files specify attributes of the GDB target environment:

gdb/config/mt-TTT
     Contains a Makefile fragment specific to this target. Specifies what object files are needed for target TTT, by defining TDEPFILES=.... Also specifies the header file which describes TTT, by defining TM_FILE= tm-TTT.h.  You can also define TM_CFLAGS, and other Makefile variables here; see Makefile.in.

gdb/tm-TTT.h
     (tm.h is a link to this file, created by configure). Contains macro definitions about the target machine's registers, stack frame format and instructions. Crib from existing tm-*.h files when building a new one.

gdb/TTT-tdep.c
     Contains any miscellaneous code required for this target machine. On some machines it doesn't exist at all.  Sometimes the macros in tm-TTT.h become very complicated, so they are implemented as functions here instead, and the macro is simply defined to call the function.

gdb/exec.c
     Defines functions for accessing files that are executable on the target system.  These functions open and examine an exec file, extract data from one, write data to one, print information about one, etc.  Now that executable files are handled with BFD, every target should be able to use the generic exec.c rather than its own custom code.

gdb/ARCH-pinsn.c
     Prints (disassembles) the target machine's instructions. This file is usually shared with other target machines which use the same processor, which is why it is ARCH-pinsn.c rather than TTT-pinsn.c.

gdb/ARCH-opcode.h
     Contains some large initialized data structures describing the target machine's instructions. This is a bit strange for a .h file, but it's OK since it is only included in one place.  ARCH-opcode.h is shared between the debugger and the assembler, if the GNU assembler has been ported to the target machine.

gdb/tm-ARCH.h
     This often exists to describe the basic layout of the target machine's processor chip (registers, stack, etc). If used, it is included by tm-XXX.h.  It can be shared among many targets that use the same processor.

gdb/ARCH-tdep.c
     Similarly, there are often common subroutines that are shared by all target machines that use this particular architecture.

When adding support for a new target machine, there are various areas of support that might need change, or might be OK.

If you are using an existing object file format (a.out or COFF), there is probably little to be done.  See bfd/doc/bfd.texinfo for more information on writing new a.out or COFF versions.

If you need to add a new object file format, you are beyond the scope of this document right now.  Look at the structure of the a.out and COFF support, build a transfer vector (xvec) for your new format, and start populating it with routines.  Add it to the list in bfd/targets.c.

If you are adding a new operating system for an existing CPU chip, add a tm-XOS.h file that describes the operating system facilities that are unusual (extra symbol table info; the breakpoint instruction needed; etc).  Then write a tm-XARCH-XOS.h that just #includes tm-XARCH.h and tm-XOS.h.  (Now that we have three-part configuration names, this will probably get revised to separate the XOS configuration from the XARCH configuration.)

Adding a Source Language to GDB
*******************************

To add other languages to GDB's expression parser, follow the following steps:

Create the expression parser.

     This should reside in a file LANG-exp.y.  Routines for building parsed expressions into a union exp_element list are in parse.c.

     Since we can't depend upon everyone having Bison, and YACC produces parsers that define a bunch of global names, the following lines must be included at the top of the YACC parser, to prevent the various parsers from defining the same global names:

          #define yyparse 	LANG_parse
          #define yylex 	LANG_lex
          #define yyerror 	LANG_error
          #define yylval 	LANG_lval
          #define yychar 	LANG_char
          #define yydebug 	LANG_debug
          #define yypact  	LANG_pact
          #define yyr1		LANG_r1
          #define yyr2		LANG_r2
          #define yydef		LANG_def
          #define yychk		LANG_chk
          #define yypgo		LANG_pgo
          #define yyact  	LANG_act
          #define yyexca  	LANG_exca
          #define yyerrflag  	LANG_errflag
          #define yynerrs  	LANG_nerrs

     At the bottom of your parser, define a struct language_defn and initialize it with the right values for your language.  Define an initialize_LANG routine and have it call add_language(LANG_language_defn) to tell the rest of GDB that your language exists.  You'll need some other supporting variables and functions, which will be used via pointers from your LANG_language_defn.  See the declaration of struct language_defn in language.h, and the other *-exp.y files, for more information.

Add any evaluation routines, if necessary

     If you need new opcodes (that represent the operations of the language), add them to the enumerated type in expression.h.  Add support code for these operations in eval.c:evaluate_subexp().  Add cases for new opcodes in two functions from parse.c: prefixify_subexp() and length_of_subexp().  These compute the number of exp_elements that a given operation takes up.

Update some existing code

     Add an enumerated identifier for your language to the enumerated type enum language in defs.h.

     Update the routines in language.c so your language is included.  These routines include type predicates and such, which (in some cases) are language dependent.  If your language does not appear in the switch statement, an error is reported.

     Also included in language.c is the code that updates the variable current_language, and the routines that translate the language_LANG enumerated identifier into a printable string.

     Update the function _initialize_language to include your language.  This function picks the default language upon startup, so is dependent upon which languages that GDB is built for.

     Update allocate_symtab in symfile.c and/or symbol-reading code so that the language of each symtab (source file) is set properly. This is used to determine the language to use at each stack frame level. Currently, the language is set based upon the extension of the source file.  If the language can be better inferred from the symbol information, please set the language of the symtab in the symbol-reading code.

     Add helper code to expprint.c:print_subexp() to handle any new expression opcodes you have added to expression.h.  Also, add the printed representations of your operators to op_print_tab.

Add a place of call

     Add a call to LANG_parse() and LANG_error in parse.c:parse_exp_1().

Use macros to trim code

     The user has the option of building GDB for some or all of the languages.  If the user decides to build GDB for the language LANG, then every file dependent on language.h will have the macro _LANG_LANG defined in it.  Use #ifdefs to leave out large routines that the user won't need if he or she is not using your language.

     Note that you do not need to do this in your YACC parser, since if GDB is not build for LANG, then LANG-exp.tab.o (the compiled form of your parser) is not linked into GDB at all.

     See the file configure.in for how GDB is configured for different languages.

Edit Makefile.in

     Add dependencies in Makefile.in.  Make sure you update the macro variables such as HFILES and OBJS, otherwise your code may not get linked in, or, worse yet, it may not get tarred into the distribution!

Configuring GDB for Release
***************************

From the top level directory (containing gdb, bfd, libiberty, and so on):

     make -f Makefile.in gdb.tar.Z

This will properly configure, clean, rebuild any files that are distributed pre-built (e.g. c-exp.tab.c or refcard.ps), and will then make a tarfile.  (If the top level directory has already beenn configured, you can just do make gdb.tar.Z instead.)

This procedure requires:

  * symbolic links

  * makeinfo (texinfo2 level)

  * TeX

  * dvips

  * yacc or bison

... and the usual slew of utilities (sed, tar, etc.).

TEMPORARY RELEASE PROCEDURE FOR DOCUMENTATION
---------------------------------------------

gdb.texinfo is currently marked up using the texinfo-2 macros, which are not yet a default for anything (but we have to start using them sometime).

For making paper, the only thing this implies is the right generation of texinfo.tex needs to be included in the distribution.

For making info files, however, rather than duplicating the texinfo2 distribution, generate gdb-all.texinfo locally, and include the files gdb.info* in the distribution.  Note the plural; makeinfo will split the document into one overall file and five or so included files.

Partial Symbol Tables
*********************

GDB has three types of symbol tables.

  * full symbol tables (symtabs).  These contain the main information about symbols and addresses.

  * partial symbol tables (psymtabs).  These contain enough information to know when to read the corresponding part of the full symbol table.

  * minimal symbol tables (msymtabs).  These contain information gleaned from non-debugging symbols.

This section describes partial symbol tables.

A psymtab is constructed by doing a very quick pass over an executable file's debugging information.  Small amounts of information are extracted -- enough to identify which parts of the symbol table will need to be re-read and fully digested later, when the user needs the information.  The speed of this pass causes GDB to start up very quickly.  Later, as the detailed rereading occurs, it occurs in small pieces, at various times, and the delay therefrom is mostly invisible to the user.  (see Symbol Reading.)

The symbols that show up in a file's psymtab should be, roughly, those visible to the debugger's user when the program is not running code from that file.  These include external symbols and types, static symbols and types, and enum values declared at file scope.

The psymtab also contains the range of instruction addresses that the full symbol table would represent.

The idea is that there are only two ways for the user (or much of the code in the debugger) to reference a symbol:

  * by its address (e.g. execution stops at some address which is inside a function in this file).  The address will be noticed to be in the range of this psymtab, and the full symtab will be read in. find_pc_function, find_pc_line, and other find_pc_... functions handle this.

  * by its name (e.g. the user asks to print a variable, or set a breakpoint on a function).  Global names and file-scope names will be found in the psymtab, which will cause the symtab to be pulled in.  Local names will have to be qualified by a global name, or a file-scope name, in which case we will have already read in the symtab as we evaluated the qualifier.  Or, a local symbol can be referenced when we are "in" a local scope, in which case the first case applies. lookup_symbol does most of the work here.

The only reason that psymtabs exist is to cause a symtab to be read in at the right moment.  Any symbol that can be elided from a psymtab, while still causing that to happen, should not appear in it.  Since psymtabs don't have the idea of scope, you can't put local symbols in them anyway.  Psymtabs don't have the idea of the type of a symbol, either, so types need not appear, unless they will be referenced by name.

It is a bug for GDB to behave one way when only a psymtab has been read, and another way if the corresponding symtab has been read in.  Such bugs are typically caused by a psymtab that does not contain all the visible symbols, or which has the wrong instruction address ranges.

The psymtab for a particular section of a symbol-file (objfile) could be thrown away after the symtab has been read in.  The symtab should always be searched before the psymtab, so the psymtab will never be used (in a bug-free environment).  Currently, psymtabs are allocated on an obstack, and all the psymbols themselves are allocated in a pair of large arrays on an obstack, so there is little to be gained by trying to free them unless you want to do a lot more work.

Binary File Descriptor Library Support for GDB
**********************************************

BFD provides support for GDB in several ways:

identifying executable and core files
     BFD will identify a variety of file types, including a.out, coff, and several variants thereof, as well as several kinds of core files.

access to sections of files
     BFD parses the file headers to determine the names, virtual addresses, sizes, and file locations of all the various named sections in files (such as the text section or the data section).  GDB simply calls BFD to read or write section X at byte offset Y for length Z.

specialized core file support
     BFD provides routines to determine the failing command name stored in a core file, the signal with which the program failed, and whether a core file matches (i.e. could be a core dump of) a particular executable file.

locating the symbol information
     GDB uses an internal interface of BFD to determine where to find the symbol information in an executable file or symbol-file.  GDB itself handles the reading of symbols, since BFD does not ``understand'' debug symbols, but GDB uses BFD's cached information to find the symbols, string table, etc.

Symbol Reading
**************

GDB reads symbols from "symbol files".  The usual symbol file is the file containing the program which gdb is debugging.  GDB can be directed to use a different file for symbols (with the ``symbol-file'' command), and it can also read more symbols via the ``add-file'' and ``load'' commands, or while reading symbols from shared libraries.

Symbol files are initially opened by symfile.c using the BFD library.  BFD identifies the type of the file by examining its header. symfile_init then uses this identification to locate a set of symbol-reading functions.

Symbol reading modules identify themselves to GDB by calling add_symtab_fns during their module initialization.  The argument to add_symtab_fns is a struct sym_fns which contains the name (or name prefix) of the symbol format, the length of the prefix, and pointers to four functions.  These functions are called at various times to process symbol-files whose identification matches the specified prefix.

The functions supplied by each module are:

XXX_symfile_init(struct sym_fns *sf)

     Called from symbol_file_add when we are about to read a new symbol file.  This function should clean up any internal state (possibly resulting from half-read previous files, for example) and prepare to read a new symbol file. Note that the symbol file which we are reading might be a new "main" symbol file, or might be a secondary symbol file whose symbols are being added to the existing symbol table.

     The argument to XXX_symfile_init is a newly allocated struct sym_fns whose bfd field contains the BFD for the new symbol file being read.  Its private field has been zeroed, and can be modified as desired.  Typically, a struct of private information will be malloc'd, and a pointer to it will be placed in the private field.

     There is no result from XXX_symfile_init, but it can call error if it detects an unavoidable problem.

XXX_new_init()

     Called from symbol_file_add when discarding existing symbols. This function need only handle the symbol-reading module's internal state; the symbol table data structures visible to the rest of GDB will be discarded by symbol_file_add.  It has no arguments and no result. It may be called after XXX_symfile_init, if a new symbol table is being read, or may be called alone if all symbols are simply being discarded.

XXX_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)

     Called from symbol_file_add to actually read the symbols from a symbol-file into a set of psymtabs or symtabs.

     sf points to the struct sym_fns originally passed to XXX_sym_init for possible initialization.  addr is the offset between the file's specified start address and its true address in memory.  mainline is 1 if this is the main symbol table being read, and 0 if a secondary symbol file (e.g. shared library or dynamically loaded file) is being read.

In addition, if a symbol-reading module creates psymtabs when XXX_symfile_read is called, these psymtabs will contain a pointer to a function XXX_psymtab_to_symtab, which can be called from any point in the GDB symbol-handling code.

XXX_psymtab_to_symtab (struct partial_symtab *pst)

     Called from psymtab_to_symtab (or the PSYMTAB_TO_SYMTAB macro) if the psymtab has not already been read in and had its pst->symtab pointer set.  The argument is the psymtab to be fleshed-out into a symtab.  Upon return, pst->readin should have been set to 1, and pst->symtab should contain a pointer to the new corresponding symtab, or zero if there were no symbols in that part of the symbol file.

Cleanups
********

Cleanups are a structured way to deal with things that need to be done later.  When your code does something (like malloc some memory, or open a file) that needs to be undone later (e.g. free the memory or close the file), it can make a cleanup.  The cleanup will be done at some future point:  when the command is finished, when an error occurs, or when your code decides it's time to do cleanups.

You can also discard cleanups, that is, throw them away without doing what they say.  This is only done if you ask that it be done.

Syntax:

OLD_CHAIN = make_cleanup (FUNCTION, ARG);
     Make a cleanup which will cause FUNCTION to be called with ARG (a char *) later.  The result, OLD_CHAIN, is a handle that can be passed to do_cleanups or discard_cleanups later.  Unless you are going to call do_cleanups or discard_cleanups yourself, you can ignore the result from make_cleanup.

do_cleanups (OLD_CHAIN);
     Perform all cleanups done since make_cleanup returned OLD_CHAIN. E.g.:

          make_cleanup (a, 0);
          old = make_cleanup (b, 0);
          do_cleanups (old);

     will call b() but will not call a().  The cleanup that calls a() will remain in the cleanup chain, and will be done later unless otherwise discarded.

discard_cleanups (OLD_CHAIN);
     Same as do_cleanups except that it just removes the cleanups from the chain and does not call the specified functions.

Some functions, e.g. fputs_filtered() or error(), specify that they ``should not be called when cleanups are not in place''.  This means that any actions you need to reverse in the case of an error or interruption must be on the cleanup chain before you call these functions, since they might never return to your code (they longjmp instead).

Wrapping Output Lines
*********************

Output that goes through printf_filtered or fputs_filtered or fputs_demangled needs only to have calls to wrap_here added in places that would be good breaking points.  The utility routines will take care of actually wrapping if the line width is exceeded.

The argument to wrap_here is an indentation string which is printed only if the line breaks there.  This argument is saved away and used later.  It must remain valid until the next call to wrap_here or until a newline has been printed through the *_filtered functions. Don't pass in a local variable and then return!

It is usually best to call wrap_here() after printing a comma or space. If you call it before printing a space, make sure that your indentation properly accounts for the leading space that will print if the line wraps there.

Any function or set of functions that produce filtered output must finish by printing a newline, to flush the wrap buffer, before switching to unfiltered (``printf'') output.  Symbol reading routines that print warnings are a good example.

Frames
******

A frame is a construct that GDB uses to keep track of calling and called functions.

FRAME_FP
     in the machine description has no meaning to the machine-independent part of GDB, except that it is used when setting up a new frame from scratch, as follows:

                create_new_frame (read_register (FP_REGNUM), read_pc ()));

     Other than that, all the meaning imparted to FP_REGNUM is imparted by the machine-dependent code.  So, FP_REGNUM can have any value that is convenient for the code that creates new frames.  (create_new_frame calls INIT_EXTRA_FRAME_INFO if it is defined; that is where you should use the FP_REGNUM value, if your frames are nonstandard.)

FRAME_CHAIN
     Given a GDB frame, determine the address of the calling function's frame.  This will be used to create a new GDB frame struct, and then INIT_EXTRA_FRAME_INFO and INIT_FRAME_PC will be called for the new frame.

Coding Style
************

GDB is generally written using the GNU coding standards, as described in standards.texi, which you can get from the Free Software Foundation.  There are some additional considerations for GDB maintainers that reflect the unique environment and style of GDB maintenance. If you follow these guidelines, GDB will be more consistent and easier to maintain.

GDB's policy on the use of prototypes is that prototypes are used to declare functions but never to define them.  Simple macros are used in the declarations, so that a non-ANSI compiler can compile GDB without trouble.  The simple macro calls are used like this:

     extern int
     memory_remove_breakpoint PARAMS ((CORE_ADDR, char *));

Note the double parentheses around the parameter types.  This allows an arbitrary number of parameters to be described, without freaking out the C preprocessor.  When the function has no parameters, it should be described like:

     void
     noprocess PARAMS ((void));

The PARAMS macro expands to its argument in ANSI C, or to a simple () in traditional C.

All external functions should have a PARAMS declaration in a header file that callers include.  All static functions should have such a declaration near the top of their source file.

We don't have a gcc option that will properly check that these rules have been followed, but it's GDB policy, and we periodically check it using the tools available (plus manual labor), and clean up any remnants.

Host Conditionals
*****************

When GDB is configured and compiled, various macros are defined or left undefined, to control compilation based on the attributes of the host system.  These macros and their meanings are:

NOTE:  For now, both host and target conditionals are here. Eliminate target conditionals from this list as they are identified.

ALIGN_SIZE
     alloca.c

BLOCK_ADDRESS_FUNCTION_RELATIVE
     dbxread.c

GDBINIT_FILENAME
     main.c

KERNELDEBUG
     tm-hppa.h

MEM_FNS_DECLARED
     defs.h

NO_SYS_FILE
     dbxread.c

PYRAMID_CONTROL_FRAME_DEBUGGING
     pyr-xdep.c

SIGWINCH_HANDLER_BODY
     utils.c

1
     buildsym.c

1
     dbxread.c

1
     dbxread.c

1
     buildsym.c

1
     dwarfread.c

1
     valops.c

1
     valops.c

1
     pyr-xdep.c

ADDITIONAL_OPTIONS
     main.c

ADDITIONAL_OPTION_CASES
     main.c

ADDITIONAL_OPTION_HANDLER
     main.c

ADDITIONAL_OPTION_HELP
     main.c

ADDR_BITS_REMOVE
     defs.h

AIX_BUGGY_PTRACE_CONTINUE
     infptrace.c

ALIGN_STACK_ON_STARTUP
     main.c

ALTOS
     altos-xdep.c

ALTOS_AS
     xm-altos.h

ASCII_COFF
     remote-adapt.c

BADMAG
     coffread.c

BCS
     tm-delta88.h

BEFORE_MAIN_LOOP_HOOK
     main.c

BELIEVE_PCC_PROMOTION
     coffread.c

BELIEVE_PCC_PROMOTION_TYPE
     stabsread.c

BIG_ENDIAN
     defs.h

BITS_BIG_ENDIAN
     defs.h

BKPT_AT_MAIN
     solib.c

BLOCK_ADDRESS_ABSOLUTE
     dbxread.c

BPT_VECTOR
     tm-68k.h

BREAKPOINT
     tm-68k.h

BREAKPOINT_DEBUG
     breakpoint.c

BROKEN_LARGE_ALLOCA
     Avoid large alloca's.  For example, on sun's, Large alloca's fail because the attempt to increase the stack limit in main() fails because shared libraries are allocated just below the initial stack limit.  The SunOS kernel will not allow the stack to grow into the area occupied by the shared libraries.

BSTRING
     regex.c

CALL_DUMMY
     valops.c

CALL_DUMMY_LOCATION
     inferior.h

CALL_DUMMY_STACK_ADJUST
     valops.c

CANNOT_FETCH_REGISTER
     hppabsd-xdep.c

CANNOT_STORE_REGISTER
     findvar.c

CFRONT_PRODUCER
     dwarfread.c

CHILD_PREPARE_TO_STORE
     inftarg.c

CLEAR_DEFERRED_STORES
     inflow.c

CLEAR_SOLIB
     objfiles.c

COFF_ENCAPSULATE
     hppabsd-tdep.c

COFF_FORMAT
     symm-tdep.c

COFF_NO_LONG_FILE_NAMES
     coffread.c

CORE_NEEDS_RELOCATION
     stack.c

CPLUS_MARKER
     cplus-dem.c

CREATE_INFERIOR_HOOK
     infrun.c

C_ALLOCA
     regex.c

C_GLBLREG
     coffread.c

DAMON
     xcoffexec.c

DBXREAD_ONLY
     partial-stab.h

DBX_PARM_SYMBOL_CLASS
     stabsread.c

DEBUG
     remote-adapt.c

DEBUG_INFO
     partial-stab.h

DEBUG_PTRACE
     hppabsd-xdep.c

DECR_PC_AFTER_BREAK
     breakpoint.c

DEFAULT_PROMPT
     main.c

DELTA88
     m88k-xdep.c

DEV_TTY
     symmisc.c

DGUX
     m88k-xdep.c

DISABLE_UNSETTABLE_BREAK
     breakpoint.c

DONT_USE_REMOTE
     remote.c

DO_DEFERRED_STORES
     infrun.c

DO_REGISTERS_INFO
     infcmd.c

END_OF_TEXT_DEFAULT
     dbxread.c

EXTERN
     buildsym.h

EXTRACT_RETURN_VALUE
     tm-68k.h

EXTRACT_STRUCT_VALUE_ADDRESS
     values.c

EXTRA_FRAME_INFO
     frame.h

EXTRA_SYMTAB_INFO
     symtab.h

FILES_INFO_HOOK
     target.c

FIXME
     coffread.c

FLOAT_INFO
     infcmd.c

FOPEN_RB
     defs.h

FP0_REGNUM
     a68v-xdep.c

FPC_REGNUM
     mach386-xdep.c

FP_REGNUM
     parse.c

FRAMELESS_FUNCTION_INVOCATION
     blockframe.c

FRAME_ARGS_ADDRESS_CORRECT
     stack.c

FRAME_CHAIN_COMBINE
     blockframe.c

FRAME_CHAIN_VALID
     frame.h

FRAME_CHAIN_VALID_ALTERNATE
     frame.h

FRAME_FIND_SAVED_REGS
     stack.c

FRAME_GET_BASEREG_VALUE
     frame.h

FRAME_NUM_ARGS
     tm-68k.h

FRAME_SPECIFICATION_DYADIC
     stack.c

FUNCTION_EPILOGUE_SIZE
     coffread.c

F_OK
     xm-ultra3.h

GCC2_COMPILED_FLAG_SYMBOL
     dbxread.c

GCC_COMPILED_FLAG_SYMBOL
     dbxread.c

GCC_MANGLE_BUG
     symtab.c

GCC_PRODUCER
     dwarfread.c

GET_SAVED_REGISTER
     findvar.c

GPLUS_PRODUCER
     dwarfread.c

GR64_REGNUM
     remote-adapt.c

GR64_REGNUM
     remote-mm.c

HANDLE_RBRAC
     partial-stab.h

HAVE_68881
     m68k-tdep.c

HAVE_MMAP
     In some cases, use the system call mmap for reading symbol tables.  For some machines this allows for sharing and quick updates.

HAVE_REGISTER_WINDOWS
     findvar.c

HAVE_SIGSETMASK
     main.c

HAVE_TERMIO
     inflow.c

HEADER_SEEK_FD
     arm-tdep.c

HOSTING_ONLY
     xm-rtbsd.h

HOST_BYTE_ORDER
     ieee-float.c

HPUX_ASM
     xm-hp300hpux.h

HPUX_VERSION_5
     hp300ux-xdep.c

HP_OS_BUG
     infrun.c

I80960
     remote-vx.c

IBM6000_HOST
     breakpoint.c

IBM6000_TARGET
     buildsym.c

IEEE_DEBUG
     ieee-float.c

IEEE_FLOAT
     valprint.c

IGNORE_SYMBOL
     dbxread.c

INIT_EXTRA_FRAME_INFO
     blockframe.c

INIT_EXTRA_SYMTAB_INFO
     symfile.c

INIT_FRAME_PC
     blockframe.c

INNER_THAN
     valops.c

INT_MAX
     defs.h

INT_MIN
     defs.h

IN_GDB
     i960-pinsn.c

IN_SIGTRAMP
     infrun.c

IN_SOLIB_TRAMPOLINE
     infrun.c

ISATTY
     main.c

IS_TRAPPED_INTERNALVAR
     values.c

KERNELDEBUG
     dbxread.c

KERNEL_DEBUGGING
     tm-ultra3.h

KERNEL_U_ADDR
     Define this to the address of the u structure (the ``user struct'', also known as the ``u-page'') in kernel virtual memory.  GDB needs to know this so that it can subtract this address from absolute addresses in the upage, that are obtained via ptrace or from core files.  On systems that don't need this value, set it to zero.

KERNEL_U_ADDR_BSD
     Define this to cause GDB to determine the address of u at runtime, by using Berkeley-style nlist on the kernel's image in the root directory.

KERNEL_U_ADDR_HPUX
     Define this to cause GDB to determine the address of u at runtime, by using HP-style nlist on the kernel's image in the root directory.

LCC_PRODUCER
     dwarfread.c

LITTLE_ENDIAN
     defs.h

LOG_FILE
     remote-adapt.c

LONGERNAMES
     cplus-dem.c

LONGEST
     defs.h

LONG_LONG
     defs.h

LONG_MAX
     defs.h

LSEEK_NOT_LINEAR
     source.c

L_LNNO32
     coffread.c

L_SET
     This macro is used as the argument to lseek (or, most commonly, bfd_seek). FIXME, it should be replaced by SEEK_SET instead, which is the POSIX equivalent.

MACHKERNELDEBUG
     hppabsd-tdep.c

MAIN
     cplus-dem.c

MAINTENANCE
     dwarfread.c

MAINTENANCE_CMDS
     breakpoint.c

MAINTENANCE_CMDS
     maint.c

MALLOC_INCOMPATIBLE
     Define this if the system's prototype for malloc differs from the ANSI definition.

MIPSEL
     mips-tdep.c

MMAP_BASE_ADDRESS
     When using HAVE_MMAP, the first mapping should go at this address.

MMAP_INCREMENT
     when using HAVE_MMAP, this is the increment between mappings.

MONO
     ser-go32.c

MOTOROLA
     xm-altos.h

NAMES_HAVE_UNDERSCORE
     coffread.c

NBPG
     altos-xdep.c

NEED_POSIX_SETPGID
     infrun.c

NEED_TEXT_START_END
     exec.c

NFAILURES
     regex.c

NNPC_REGNUM
     infrun.c

NORETURN
     defs.h

NOTDEF
     regex.c

NOTDEF
     remote-adapt.c

NOTDEF
     remote-mm.c

NOTICE_SIGNAL_HANDLING_CHANGE
     infrun.c

NO_DEFINE_SYMBOL
     xcoffread.c

NO_HIF_SUPPORT
     remote-mm.c

NO_JOB_CONTROL
     signals.h

NO_MALLOC_CHECK
     utils.c

NO_MMALLOC
     utils.c

NO_MMALLOC
     objfiles.c

NO_MMALLOC
     utils.c

NO_SIGINTERRUPT
     remote-adapt.c

NO_SINGLE_STEP
     infptrace.c

NO_TYPEDEFS
     xcoffread.c

NO_TYPEDEFS
     xcoffread.c

NPC_REGNUM
     infcmd.c

NS32K_SVC_IMMED_OPERANDS
     ns32k-opcode.h

NUMERIC_REG_NAMES
     mips-tdep.c

N_SETV
     dbxread.c

N_SET_MAGIC
     hppabsd-tdep.c

NaN
     tm-umax.h

ONE_PROCESS_WRITETEXT
     breakpoint.c

O_BINARY
     exec.c

O_RDONLY
     xm-ultra3.h

PC
     convx-opcode.h

PCC_SOL_BROKEN
     dbxread.c

PC_IN_CALL_DUMMY
     inferior.h

PC_LOAD_SEGMENT
     stack.c

PC_REGNUM
     parse.c

PRINT_RANDOM_SIGNAL
     infcmd.c

PRINT_REGISTER_HOOK
     infcmd.c

PRINT_TYPELESS_INTEGER
     valprint.c

PROCESS_LINENUMBER_HOOK
     buildsym.c

PROLOGUE_FIRSTLINE_OVERLAP
     infrun.c

PSIGNAL_IN_SIGNAL_H
     defs.h

PS_REGNUM
     parse.c

PTRACE_ARG3_TYPE
     inferior.h

PTRACE_FP_BUG
     mach386-xdep.c

PT_ATTACH
     hppabsd-xdep.c

PT_DETACH
     hppabsd-xdep.c

PT_KILL
     infptrace.c

PUSH_ARGUMENTS
     valops.c

PYRAMID_CONTROL_FRAME_DEBUGGING
     pyr-xdep.c

PYRAMID_CORE
     pyr-xdep.c

PYRAMID_PTRACE
     pyr-xdep.c

REGISTER_BYTES
     remote.c

REGISTER_NAMES
     tm-29k.h

REG_STACK_SEGMENT
     exec.c

REG_STRUCT_HAS_ADDR
     findvar.c

RE_NREGS
     regex.h

R_FP
     dwarfread.c

R_OK
     xm-altos.h

SDB_REG_TO_REGNUM
     coffread.c

SEEK_END
     state.c

SEEK_SET
     state.c

SEM
     coffread.c

SET_STACK_LIMIT_HUGE
     When defined, stack limits will be raised to their maximum.  Use this if your host supports setrlimit and you have trouble with stringtab in dbxread.c.

     Also used in fork-child.c to return stack limits before child processes are forked.

SHELL_COMMAND_CONCAT
     infrun.c

SHELL_FILE
     infrun.c

SHIFT_INST_REGS
     breakpoint.c

SIGN_EXTEND_CHAR
     regex.c

SIGTRAP_STOP_AFTER_LOAD
     infrun.c

SKIP_PROLOGUE
     tm-68k.h

SKIP_PROLOGUE_FRAMELESS_P
     blockframe.c

SKIP_TRAMPOLINE_CODE
     infrun.c

SOLIB_ADD
     core.c

SOLIB_CREATE_INFERIOR_HOOK
     infrun.c

SOME_NAMES_HAVE_DOT
     minsyms.c

SP_REGNUM
     parse.c

STAB_REG_TO_REGNUM
     stabsread.h

STACK_ALIGN
     valops.c

STACK_DIRECTION
     alloca.c

START_INFERIOR_TRAPS_EXPECTED
     infrun.c

STOP_SIGNAL
     main.c

STORE_RETURN_VALUE
     tm-68k.h

SUN4_COMPILER_FEATURE
     infrun.c

SUN_FIXED_LBRAC_BUG
     dbxread.c

SVR4_SHARED_LIBS
     solib.c

SWITCH_ENUM_BUG
     regex.c

SYM1
     tm-ultra3.h

SYMBOL_RELOADING_DEFAULT
     symfile.c

SYNTAX_TABLE
     regex.c

Sword
     regex.c

TDESC
     infrun.c

TIOCGETC
     inflow.c

TIOCGLTC
     inflow.c

TIOCGPGRP
     inflow.c

TIOCLGET
     inflow.c

TIOCLSET
     inflow.c

TIOCNOTTY
     inflow.c

TM_FILE_OVERRIDE
     defs.h

T_ARG
     coffread.c

T_VOID
     coffread.c

UINT_MAX
     defs.h

UPAGES
     altos-xdep.c

USER
     m88k-tdep.c

USE_GAS
     xm-news.h

USE_O_NOCTTY
     inflow.c

USE_STRUCT_CONVENTION
     values.c

USG
     Means that System V (prior to SVR4) include files are in use. (FIXME:  This symbol is abused in infrun.c, regex.c, remote-nindy.c, and utils.c for other things, at the moment.)

USIZE
     xm-m88k.h

U_FPSTATE
     i386-xdep.c

VARIABLES_INSIDE_BLOCK
     dbxread.c

WRS_ORIG
     remote-vx.c

_LANG_c
     language.c

_LANG_m2
     language.c

__GNUC__
     news-xdep.c

__GO32__
     inflow.c

__HAVE_68881__
     m68k-stub.c

__HPUX_ASM__
     xm-hp300hpux.h

__INT_VARARGS_H
     printcmd.c

__not_on_pyr_yet
     pyr-xdep.c

alloca
     defs.h

const
     defs.h

GOULD_PN
     gould-pinsn.c

emacs
     alloca.c

hp800
     xm-hppabsd.h

hpux
     hppabsd-core.c

lint
     valarith.c

longest_to_int
     defs.h

mc68020
     m68k-stub.c

notdef
     gould-pinsn.c

ns32k_opcodeT
     ns32k-opcode.h

sgi
     mips-tdep.c

sparc
     regex.c

static
     alloca.c

sun
     m68k-tdep.c

sun386
     tm-sun386.h

test
     regex.c

ultrix
     xm-mips.h

volatile
     defs.h

x_name
     coffread.c

x_zeroes
     coffread.c

Target Conditionals
*******************

When GDB is configured and compiled, various macros are defined or left undefined, to control compilation based on the attributes of the target system.  These macros and their meanings are:

NOTE:  For now, both host and target conditionals are here. Eliminate host conditionals from this list as they are identified.

PUSH_DUMMY_FRAME
     Used in call_function_by_hand to create an artificial stack frame.

POP_FRAME
     Used in call_function_by_hand to remove an artificial stack frame.

ALIGN_SIZE
     alloca.c

BLOCK_ADDRESS_FUNCTION_RELATIVE
     dbxread.c

GDBINIT_FILENAME
     main.c

KERNELDEBUG
     tm-hppa.h

MEM_FNS_DECLARED
     defs.h

NO_SYS_FILE
     dbxread.c

PYRAMID_CONTROL_FRAME_DEBUGGING
     pyr-xdep.c

SIGWINCH_HANDLER_BODY
     utils.c

ADDITIONAL_OPTIONS
     main.c

ADDITIONAL_OPTION_CASES
     main.c

ADDITIONAL_OPTION_HANDLER
     main.c

ADDITIONAL_OPTION_HELP
     main.c

ADDR_BITS_REMOVE
     defs.h

ALIGN_STACK_ON_STARTUP
     main.c

ALTOS
     altos-xdep.c

ALTOS_AS
     xm-altos.h

ASCII_COFF
     remote-adapt.c

BADMAG
     coffread.c

BCS
     tm-delta88.h

BEFORE_MAIN_LOOP_HOOK
     main.c

BELIEVE_PCC_PROMOTION
     coffread.c

BELIEVE_PCC_PROMOTION_TYPE
     stabsread.c

BIG_ENDIAN
     defs.h

BITS_BIG_ENDIAN
     defs.h

BKPT_AT_MAIN
     solib.c

BLOCK_ADDRESS_ABSOLUTE
     dbxread.c

BPT_VECTOR
     tm-68k.h

BREAKPOINT
     tm-68k.h

BREAKPOINT_DEBUG
     breakpoint.c

BSTRING
     regex.c

CALL_DUMMY
     valops.c

CALL_DUMMY_LOCATION
     inferior.h

CALL_DUMMY_STACK_ADJUST
     valops.c

CANNOT_FETCH_REGISTER
     hppabsd-xdep.c

CANNOT_STORE_REGISTER
     findvar.c

CFRONT_PRODUCER
     dwarfread.c

CHILD_PREPARE_TO_STORE
     inftarg.c

CLEAR_DEFERRED_STORES
     inflow.c

CLEAR_SOLIB
     objfiles.c

COFF_ENCAPSULATE
     hppabsd-tdep.c

COFF_FORMAT
     symm-tdep.c

COFF_NO_LONG_FILE_NAMES
     coffread.c

CORE_NEEDS_RELOCATION
     stack.c

CPLUS_MARKER
     cplus-dem.c

CREATE_INFERIOR_HOOK
     infrun.c

C_ALLOCA
     regex.c

C_GLBLREG
     coffread.c

DAMON
     xcoffexec.c

DBXREAD_ONLY
     partial-stab.h

DBX_PARM_SYMBOL_CLASS
     stabsread.c

DEBUG
     remote-adapt.c

DEBUG_INFO
     partial-stab.h

DEBUG_PTRACE
     hppabsd-xdep.c

DECR_PC_AFTER_BREAK
     breakpoint.c

DEFAULT_PROMPT
     main.c

DELTA88
     m88k-xdep.c

DEV_TTY
     symmisc.c

DGUX
     m88k-xdep.c

DISABLE_UNSETTABLE_BREAK
     breakpoint.c

DONT_USE_REMOTE
     remote.c

DO_DEFERRED_STORES
     infrun.c

DO_REGISTERS_INFO
     infcmd.c

END_OF_TEXT_DEFAULT
     dbxread.c

EXTERN
     buildsym.h

EXTRACT_RETURN_VALUE
     tm-68k.h

EXTRACT_STRUCT_VALUE_ADDRESS
     values.c

EXTRA_FRAME_INFO
     frame.h

EXTRA_SYMTAB_INFO
     symtab.h

FILES_INFO_HOOK
     target.c

FIXME
     coffread.c

FLOAT_INFO
     infcmd.c

FOPEN_RB
     defs.h

FP0_REGNUM
     a68v-xdep.c

FPC_REGNUM
     mach386-xdep.c

FP_REGNUM
     parse.c

FPU
     Unused?  6-oct-92 rich@cygnus.com.  FIXME.

FRAMELESS_FUNCTION_INVOCATION
     blockframe.c

FRAME_ARGS_ADDRESS_CORRECT
     stack.c

FRAME_CHAIN_COMBINE
     blockframe.c

FRAME_CHAIN_VALID
     frame.h

FRAME_CHAIN_VALID_ALTERNATE
     frame.h

FRAME_FIND_SAVED_REGS
     stack.c

FRAME_GET_BASEREG_VALUE
     frame.h

FRAME_NUM_ARGS
     tm-68k.h

FRAME_SPECIFICATION_DYADIC
     stack.c

FUNCTION_EPILOGUE_SIZE
     coffread.c

F_OK
     xm-ultra3.h

GCC2_COMPILED_FLAG_SYMBOL
     dbxread.c

GCC_COMPILED_FLAG_SYMBOL
     dbxread.c

GCC_MANGLE_BUG
     symtab.c

GCC_PRODUCER
     dwarfread.c

GDB_TARGET_IS_HPPA
     This determines whether horrible kludge code in dbxread.c and partial-stab.h is used to mangle multiple-symbol-table files from HPPA's.  This should all be ripped out, and a scheme like elfread.c used.

GDB_TARGET_IS_MACH386
     mach386-xdep.c

GDB_TARGET_IS_SUN3
     a68v-xdep.c

GDB_TARGET_IS_SUN386
     sun386-xdep.c

GET_LONGJMP_TARGET
     For most machines, this is a target-dependent parameter.  On the DECstation and the Iris, this is a native-dependent parameter, since <setjmp.h> is needed to define it.

     This macro determines the target PC address that longjmp() will jump to, assuming that we have just stopped at a longjmp breakpoint.  It takes a CORE_ADDR * as argument, and stores the target PC value through this pointer.  It examines the current state of the machine as needed.

GET_SAVED_REGISTER
     findvar.c

GPLUS_PRODUCER
     dwarfread.c

GR64_REGNUM
     remote-adapt.c

GR64_REGNUM
     remote-mm.c

HANDLE_RBRAC
     partial-stab.h

HAVE_68881
     m68k-tdep.c

HAVE_REGISTER_WINDOWS
     findvar.c

HAVE_SIGSETMASK
     main.c

HAVE_TERMIO
     inflow.c

HEADER_SEEK_FD
     arm-tdep.c

HOSTING_ONLY
     xm-rtbsd.h

HOST_BYTE_ORDER
     ieee-float.c

HPUX_ASM
     xm-hp300hpux.h

HPUX_VERSION_5
     hp300ux-xdep.c

HP_OS_BUG
     infrun.c

I80960
     remote-vx.c

IBM6000_HOST
     breakpoint.c

IBM6000_TARGET
     buildsym.c

IEEE_DEBUG
     ieee-float.c

IEEE_FLOAT
     valprint.c

IGNORE_SYMBOL
     dbxread.c

INIT_EXTRA_FRAME_INFO
     blockframe.c

INIT_EXTRA_SYMTAB_INFO
     symfile.c

INIT_FRAME_PC
     blockframe.c

INNER_THAN
     valops.c

INT_MAX
     defs.h

INT_MIN
     defs.h

IN_GDB
     i960-pinsn.c

IN_SIGTRAMP
     infrun.c

IN_SOLIB_TRAMPOLINE
     infrun.c

ISATTY
     main.c

IS_TRAPPED_INTERNALVAR
     values.c

KERNELDEBUG
     dbxread.c

KERNEL_DEBUGGING
     tm-ultra3.h

LCC_PRODUCER
     dwarfread.c

LITTLE_ENDIAN
     defs.h

LOG_FILE
     remote-adapt.c

LONGERNAMES
     cplus-dem.c

LONGEST
     defs.h

LONG_LONG
     defs.h

LONG_MAX
     defs.h

L_LNNO32
     coffread.c

MACHKERNELDEBUG
     hppabsd-tdep.c

MAIN
     cplus-dem.c

MAINTENANCE
     dwarfread.c

MAINTENANCE_CMDS
     breakpoint.c

MAINTENANCE_CMDS
     maint.c

MIPSEL
     mips-tdep.c

MOTOROLA
     xm-altos.h

NAMES_HAVE_UNDERSCORE
     coffread.c

NBPG
     altos-xdep.c

NEED_POSIX_SETPGID
     infrun.c

NEED_TEXT_START_END
     exec.c

NFAILURES
     regex.c

NNPC_REGNUM
     infrun.c

NORETURN
     defs.h

NOTDEF
     regex.c

NOTDEF
     remote-adapt.c

NOTDEF
     remote-mm.c

NOTICE_SIGNAL_HANDLING_CHANGE
     infrun.c

NO_DEFINE_SYMBOL
     xcoffread.c

NO_HIF_SUPPORT
     remote-mm.c

NO_JOB_CONTROL
     signals.h

NO_MALLOC_CHECK
     utils.c

NO_MMALLOC
     utils.c

NO_MMALLOC
     objfiles.c

NO_MMALLOC
     utils.c

NO_SIGINTERRUPT
     remote-adapt.c

NO_SINGLE_STEP
     infptrace.c

NO_TYPEDEFS
     xcoffread.c

NO_TYPEDEFS
     xcoffread.c

NPC_REGNUM
     infcmd.c

NS32K_SVC_IMMED_OPERANDS
     ns32k-opcode.h

NUMERIC_REG_NAMES
     mips-tdep.c

N_SETV
     dbxread.c

N_SET_MAGIC
     hppabsd-tdep.c

NaN
     tm-umax.h

ONE_PROCESS_WRITETEXT
     breakpoint.c

PC
     convx-opcode.h

PCC_SOL_BROKEN
     dbxread.c

PC_IN_CALL_DUMMY
     inferior.h

PC_LOAD_SEGMENT
     stack.c

PC_REGNUM
     parse.c

PRINT_RANDOM_SIGNAL
     infcmd.c

PRINT_REGISTER_HOOK
     infcmd.c

PRINT_TYPELESS_INTEGER
     valprint.c

PROCESS_LINENUMBER_HOOK
     buildsym.c

PROLOGUE_FIRSTLINE_OVERLAP
     infrun.c

PSIGNAL_IN_SIGNAL_H
     defs.h

PS_REGNUM
     parse.c

PTRACE_ARG3_TYPE
     inferior.h

PTRACE_FP_BUG
     mach386-xdep.c

PUSH_ARGUMENTS
     valops.c

REGISTER_BYTES
     remote.c

REGISTER_NAMES
     tm-29k.h

REG_STACK_SEGMENT
     exec.c

REG_STRUCT_HAS_ADDR
     findvar.c

RE_NREGS
     regex.h

R_FP
     dwarfread.c

R_OK
     xm-altos.h

SDB_REG_TO_REGNUM
     coffread.c

SEEK_END
     state.c

SEEK_SET
     state.c

SEM
     coffread.c

SET_STACK_LIMIT_HUGE
     infrun.c

SHELL_COMMAND_CONCAT
     infrun.c

SHELL_FILE
     infrun.c

SHIFT_INST_REGS
     breakpoint.c

SIGN_EXTEND_CHAR
     regex.c

SIGTRAP_STOP_AFTER_LOAD
     infrun.c

SKIP_PROLOGUE
     tm-68k.h

SKIP_PROLOGUE_FRAMELESS_P
     blockframe.c

SKIP_TRAMPOLINE_CODE
     infrun.c

SOLIB_ADD
     core.c

SOLIB_CREATE_INFERIOR_HOOK
     infrun.c

SOME_NAMES_HAVE_DOT
     minsyms.c

SP_REGNUM
     parse.c

STAB_REG_TO_REGNUM
     stabsread.h

STACK_ALIGN
     valops.c

STACK_DIRECTION
     alloca.c

START_INFERIOR_TRAPS_EXPECTED
     infrun.c

STOP_SIGNAL
     main.c

STORE_RETURN_VALUE
     tm-68k.h

SUN4_COMPILER_FEATURE
     infrun.c

SUN_FIXED_LBRAC_BUG
     dbxread.c

SVR4_SHARED_LIBS
     solib.c

SWITCH_ENUM_BUG
     regex.c

SYM1
     tm-ultra3.h

SYMBOL_RELOADING_DEFAULT
     symfile.c

SYNTAX_TABLE
     regex.c

Sword
     regex.c

TARGET_BYTE_ORDER
     defs.h

TARGET_CHAR_BIT
     defs.h

TARGET_COMPLEX_BIT
     defs.h

TARGET_DOUBLE_BIT
     defs.h

TARGET_DOUBLE_COMPLEX_BIT
     defs.h

TARGET_FLOAT_BIT
     defs.h

TARGET_INT_BIT
     defs.h

TARGET_LONG_BIT
     defs.h

TARGET_LONG_DOUBLE_BIT
     defs.h

TARGET_LONG_LONG_BIT
     defs.h

TARGET_PTR_BIT
     defs.h

TARGET_SHORT_BIT
     defs.h

TDESC
     infrun.c

TM_FILE_OVERRIDE
     defs.h

T_ARG
     coffread.c

T_VOID
     coffread.c

UINT_MAX
     defs.h

USER
     m88k-tdep.c

USE_GAS
     xm-news.h

USE_STRUCT_CONVENTION
     values.c

USIZE
     xm-m88k.h

U_FPSTATE
     i386-xdep.c

VARIABLES_INSIDE_BLOCK
     dbxread.c

WRS_ORIG
     remote-vx.c

_LANG_c
     language.c

_LANG_m2
     language.c

__GO32__
     inflow.c

__HAVE_68881__
     m68k-stub.c

__HPUX_ASM__
     xm-hp300hpux.h

__INT_VARARGS_H
     printcmd.c

__not_on_pyr_yet
     pyr-xdep.c

GOULD_PN
     gould-pinsn.c

emacs
     alloca.c

hp800
     xm-hppabsd.h

hpux
     hppabsd-core.c

longest_to_int
     defs.h

mc68020
     m68k-stub.c

ns32k_opcodeT
     ns32k-opcode.h

sgi
     mips-tdep.c

sparc
     regex.c

static
     alloca.c

sun
     m68k-tdep.c

sun386
     tm-sun386.h

test
     regex.c

x_name
     coffread.c

x_zeroes
     coffread.c

Native Conditionals
*******************

ATTACH_DETACH
     If defined, then gdb will include support for the attach and detach commands. commands.

FETCH_INFERIOR_REGISTERS
     Define this if the native-dependent code will provide its own routines fetch_inferior_registers and store_inferior_registers in HOST-nat.c. If this symbol is not defined, the default routines in infptrace.c are used for these functions.

GET_LONGJMP_TARGET
     For most machines, this is a target-dependent parameter.  On the DECstation and the Iris, this is a native-dependent parameter, since <setjmp.h> is needed to define it.

     This macro determines the target PC address that longjmp() will jump to, assuming that we have just stopped at a longjmp breakpoint.  It takes a CORE_ADDR * as argument, and stores the target PC value through this pointer.  It examines the current state of the machine as needed.

PROC_NAME_FMT
     Defines the format for the name of a /proc device.  Should be defined in nm.h only in order to override the default definition in procfs.c.

REGISTER_U_ADDR
     Defines the offset of the registers in the ``u area''; see Host.

USE_PROC_FS
     This determines whether small routines that translate register values to GDB's internal representation (from the /proc representation), and vice verse, are compiled.

U_REGS_OFFSET
     This is the offset of the registers in the upage.  It need only be defined if the generic ptrace register access routines in infptrace.c are being used (that is, FETCH_INFERIOR_REGISTERS is not defined).  If the default value from infptrace.c is good enough, leave it undefined.

     The default value means that u.u_ar0 points to the location of the registers.  I'm guessing that #define U_REGS_OFFSET 0 means that u.u_ar0 is the location of the registers.