[deliverable/binutils-gdb.git] / gdb / PROBLEMS


			Known problems in GDB 6.2

		See also: http://www.gnu.org/software/gdb/bugs/


*** Build problems

build/1458: compile failed on hpux11

GDB has build problems on HP/UX 11 with some versions of the HP
Ansi C compiler.  (GCC works fine).

The problem happens when compiling intl/bindtextdom.c.
The error is:

  cc: "gettextP.h", line 50: error 1000: Unexpected symbol: "SWAP".
  cc: panic 2017: Cannot recover from earlier errors, terminating.
  *** Error exit code 1

This is a problem with the 'inline' keyword in gettextP.h.
The workaround is to disable 'inline' before building gdb:

  export ac_cv_c_inline=no

This problem happens only with some versions of the HP Ansi C compiler.
Versions A.11.01.25171.GP and B.11.11.28706.GP have both been observed
to work; version B.11.11.04 gets the build error and needs the
workaround.

This problem might also happen with other C compilers.

*** Misc

gdb/1560: Control-C does not always interrupt GDB.

When GDB is busy processing a command which takes a long time to
complete, hitting Control-C does not have the expected effect.
The command execution is not aborted, and the "QUIT" message confirming
the abortion is displayed only after the command has been completed.

*** C++ support

gdb/931: GDB could be more generous when reading types C++ templates on input

When the user types a template, GDB frequently requires the type to be
typed in a certain way (e.g. "const char*" as opposed to "const char *"
or "char const *" or "char const*").

gdb/1512: no canonical way to output names of C++ types

We currently don't have any canonical way to output names of C++ types.
E.g. "const char *" versus "char const *"; more subtleties arise when
dealing with templates.

gdb/1516: [regression] local classes, gcc 2.95.3, dwarf-2

With gcc 2.95.3 and the dwarf-2 debugging format, classes which are
defined locally to a function include the demangled name of the function
as part of their name.  For example, if a function "foobar" contains a
local class definition "Local", gdb will say that the name of the class
type is "foobar__Fi.0:Local".

This applies only to classes where the class type is defined inside a
function, not to variables defined with types that are defined somewhere
outside any function (which most types are).

gdb/1588: names of c++ nested types in casts must be enclosed in quotes

You must type
  (gdb) print ('Foo::Bar') x
or
  (gdb) print ('Foo::Bar' *) y
instead of
  (gdb) print (Foo::Bar) x
or
  (gdb) print (Foo::Bar *) y
respectively.

gdb/1091: Constructor breakpoints ignored
gdb/1193: g++ 3.3 creates multiple constructors: gdb 5.3 can't set breakpoints

When gcc 3.x compiles a C++ constructor or C++ destructor, it generates
2 or 3 different versions of the object code.  These versions have
unique mangled names (they have to, in order for linking to work), but
they have identical source code names, which leads to a great deal of
confusion.  Specifically, if you set a breakpoint in a constructor or a
destructor, gdb will put a breakpoint in one of the versions, but your
program may execute the other version.  This makes it impossible to set
breakpoints reliably in constructors or destructors.

gcc 3.x generates these multiple object code functions in order to
implement virtual base classes.  gcc 2.x generated just one object code
function with a hidden parameter, but gcc 3.x conforms to a multi-vendor
ABI for C++ which requires multiple object code functions.

*** Signal handlers

On many systems an attempt to single-step a system-call instruction
results in two or more instructions being executed (the system-call,
and one or more instructions following).

When attempting to single-step through a signal trampoline, this
problem may result the program unintentionally running to completion,
or re-execute the faulting instruction, or even corrupting the program
counter.

Ref: PR breakpoints/1702.

*** Stack backtraces

GDB's core code base has been updated to use a new backtrace
mechanism.  This mechanism makes it possible to support new features
such DWARF 2 Call Frame Information (which in turn makes possible
backtraces through optimized code).

Since this code is new, it is known to still have a few problems:

gdb/1505: [regression] gdb prints a bad backtrace for a thread

When backtracing a thread, gdb does not stop when it reaches the
outermost frame, instead continuing until it hits garbage.  This is
sensitive to the operating system and thread library.
Commit	Line	Data
e2c9a72c	1
860660cb	2	Known problems in GDB 6.2
e2c9a72c	3
36cc83a3	4	See also: http://www.gnu.org/software/gdb/bugs/
e2c9a72c	5
e6beb428	6
43e2e1a0 AC	7	*** Build problems
43e2e1a0 AC	8
5191de37	9	build/1458: compile failed on hpux11
43e2e1a0	10
5191de37 MC	11	GDB has build problems on HP/UX 11 with some versions of the HP
	12	Ansi C compiler. (GCC works fine).
	13
	14	The problem happens when compiling intl/bindtextdom.c.
	15	The error is:
	16
	17	cc: "gettextP.h", line 50: error 1000: Unexpected symbol: "SWAP".
	18	cc: panic 2017: Cannot recover from earlier errors, terminating.
	19	*** Error exit code 1
	20
	21	This is a problem with the 'inline' keyword in gettextP.h.
	22	The workaround is to disable 'inline' before building gdb:
	23
	24	export ac_cv_c_inline=no
	25
	26	This problem happens only with some versions of the HP Ansi C compiler.
	27	Versions A.11.01.25171.GP and B.11.11.28706.GP have both been observed
	28	to work; version B.11.11.04 gets the build error and needs the
	29	workaround.
	30
	31	This problem might also happen with other C compilers.
43e2e1a0	32
103a0089	33	*** Misc
e6beb428	34
103a0089	35	gdb/1560: Control-C does not always interrupt GDB.
e6beb428	36
103a0089 AC	37	When GDB is busy processing a command which takes a long time to
	38	complete, hitting Control-C does not have the expected effect.
	39	The command execution is not aborted, and the "QUIT" message confirming
	40	the abortion is displayed only after the command has been completed.
	41
	42	*** C++ support
ed47347a	43
ed47347a MC	44	gdb/931: GDB could be more generous when reading types C++ templates on input
	45
	46	When the user types a template, GDB frequently requires the type to be
	47	typed in a certain way (e.g. "const char" as opposed to "const char "
	48	or "char const " or "char const").
	49
ed47347a MC	50	gdb/1512: no canonical way to output names of C++ types
	51
	52	We currently don't have any canonical way to output names of C++ types.
	53	E.g. "const char " versus "char const "; more subtleties arise when
	54	dealing with templates.
	55
c6e06ede MC	56	gdb/1516: [regression] local classes, gcc 2.95.3, dwarf-2
	57
	58	With gcc 2.95.3 and the dwarf-2 debugging format, classes which are
	59	defined locally to a function include the demangled name of the function
	60	as part of their name. For example, if a function "foobar" contains a
	61	local class definition "Local", gdb will say that the name of the class
	62	type is "foobar__Fi.0:Local".
	63
	64	This applies only to classes where the class type is defined inside a
	65	function, not to variables defined with types that are defined somewhere
	66	outside any function (which most types are).
	67
8c691c7a DC	68	gdb/1588: names of c++ nested types in casts must be enclosed in quotes
	69
	70	You must type
	71	(gdb) print ('Foo::Bar') x
	72	or
	73	(gdb) print ('Foo::Bar' *) y
	74	instead of
	75	(gdb) print (Foo::Bar) x
	76	or
	77	(gdb) print (Foo::Bar *) y
	78	respectively.
	79
e8ac10a6 MC	80	gdb/1091: Constructor breakpoints ignored
e8ac10a6 MC	81	gdb/1193: g++ 3.3 creates multiple constructors: gdb 5.3 can't set breakpoints
e2c9a72c	82
e8ac10a6 MC	83	When gcc 3.x compiles a C++ constructor or C++ destructor, it generates
	84	2 or 3 different versions of the object code. These versions have
	85	unique mangled names (they have to, in order for linking to work), but
	86	they have identical source code names, which leads to a great deal of
	87	confusion. Specifically, if you set a breakpoint in a constructor or a
	88	destructor, gdb will put a breakpoint in one of the versions, but your
	89	program may execute the other version. This makes it impossible to set
	90	breakpoints reliably in constructors or destructors.
	91
	92	gcc 3.x generates these multiple object code functions in order to
	93	implement virtual base classes. gcc 2.x generated just one object code
	94	function with a hidden parameter, but gcc 3.x conforms to a multi-vendor
	95	ABI for C++ which requires multiple object code functions.
589ca796	96
73cc75f3 AC	97	*** Signal handlers
	98
	99	On many systems an attempt to single-step a system-call instruction
	100	results in two or more instructions being executed (the system-call,
	101	and one or more instructions following).
	102
	103	When attempting to single-step through a signal trampoline, this
	104	problem may result the program unintentionally running to completion,
	105	or re-execute the faulting instruction, or even corrupting the program
	106	counter.
	107
	108	Ref: PR breakpoints/1702.
	109
103a0089 AC	110	*** Stack backtraces
103a0089 AC	111
72b56458 AC	112	GDB's core code base has been updated to use a new backtrace
	113	mechanism. This mechanism makes it possible to support new features
	114	such DWARF 2 Call Frame Information (which in turn makes possible
	115	backtraces through optimized code).
	116
	117	Since this code is new, it is known to still have a few problems:
	118
103a0089 AC	119	gdb/1505: [regression] gdb prints a bad backtrace for a thread
103a0089 AC	120
72b56458 AC	121	When backtracing a thread, gdb does not stop when it reaches the
	122	outermost frame, instead continuing until it hits garbage. This is
	123	sensitive to the operating system and thread library.