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* Re: [6.2] PROBLEMS file
@ 2004-07-22 12:14 Michael Elizabeth Chastain
  2004-07-22 18:28 ` Joel Brobecker
  0 siblings, 1 reply; 24+ messages in thread
From: Michael Elizabeth Chastain @ 2004-07-22 12:14 UTC (permalink / raw)
  To: eliz, kettenis; +Cc: cagney, gdb

Mark Kettenis writes:
> There will always be cases where GDB will get confused and lose track.
> In that case it will possibly provide an endless or very long backtrace
> containing garbage.

I'm okay with this part, as long as the user can easily get it
out of it at the "press space to continue" prompt.  

It would be nice to have an adjustable cutoff defaulting to perhaps
1000 or 10,000 frames.  I've had some huge gdb.log files
(20 megabytes) because the test suite triggered such a bug and
then gdb wouldn't quit.

> So IMHO there is no regression here.  PR 1505 should be closed.

It's a regression if a specific sequence of commands works with
gdb N and does not work with gdb N+1.  You might have to say
"can't fix" or "won't fix".

Michael C

^ permalink raw reply	[flat|nested] 24+ messages in thread
* Re: [6.2] PROBLEMS file
@ 2004-07-23  5:44 Michael Elizabeth Chastain
  2004-07-23 20:44 ` Andrew Cagney
  0 siblings, 1 reply; 24+ messages in thread
From: Michael Elizabeth Chastain @ 2004-07-23  5:44 UTC (permalink / raw)
  To: brobecker, kettenis; +Cc: cagney, eliz, gdb, hjl

joel> FWIW: As a user, I don't mind when the unwinder goes too far and
joel> displays too many frames.  The info we're looking for is there, and
joel> that's what really counts for me. Not pretty, but good enough.
joel> So I wouldn't mind closing that particular PR, especially since
joel> there doesn't seem to be any accurate way of detecting the top
joel> of the call stack.

There are really two separate problems here.  gdb/1505 is all about
top-of-stack detection.  How about we document the limitation and
live with it.

The existing text is:

  Most programs have a standard user entry point---a place where system
  libraries and startup code transition into user code.  For C this is
  @code{main}.  When @value{GDBN} finds the entry function in a
  backtrace it will terminate the backtrace, to avoid tracing into highly
  system-specific (and generally uninteresting) code.

How about adding something like this:

  @value{GDBN} is not perfect at detecting the top of the call stack.
  For instance, if your program creates multiple threads, then the
  stack of an individual thread may not start with @code{main} at all.
  So you may see strange frames at the top of the stack; it is safe to
  ignore these.

If we document it, I am okay with closing the PR.

(And while I was reading the doco I noticed "set backtrace limit" is
already implemented, which is exactly what I want for callfuncs.exp!)

The other problem is strange frames in the middle that cause the
trace to go bad before it gets to any interesting user code.
That's a different, and much worse, problem, but it's not PR gdb/1505.
See PR gdb/1255 and PR gdb/1253.  Those two particular PR's have been
fixed.

Michael C

^ permalink raw reply	[flat|nested] 24+ messages in thread
* [6.2] PROBLEMS file
@ 2004-07-19  3:51 Andrew Cagney
  2004-07-19 21:01 ` Eli Zaretskii
  0 siblings, 1 reply; 24+ messages in thread
From: Andrew Cagney @ 2004-07-19  3:51 UTC (permalink / raw)
  To: gdb

[-- Attachment #1: Type: text/plain, Size: 34 bytes --]

It needs some updates :-)

Andrew

[-- Attachment #2: PROBLEMS --]
[-- Type: text/plain, Size: 4749 bytes --]


			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.

*** 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.

hppa*-*-*
mips*-*-*

The MIPS and HPPA backtrace code has only very recently been updated
to use GDB's new frame mechanism.  At present there are still a few
problems, in particular backtraces through signal handlers do not
work.

People encountering problems with these architectures should consult
GDB's web pages and mailing lists (http://www.gnu.org/software/gdb/)
to see if there are updates.

powerpc*-*-*

PowerPC architecture support, in 6.1, does not use the new frame code.

Fortunately, PowerPC architecture support, in GDB's mainline sources,
have been updated.  People encountering problems should consider
downloading a more current snapshot of GDB
(http://www.gnu.org/software/gdb/current/).

^ permalink raw reply	[flat|nested] 24+ messages in thread
end of thread, other threads:[~2004-07-23 19:31 UTC | newest]

Thread overview: 24+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2004-07-22 12:14 [6.2] PROBLEMS file Michael Elizabeth Chastain
2004-07-22 18:28 ` Joel Brobecker
2004-07-22 19:26   ` Eli Zaretskii
2004-07-22 20:51     ` Mark Kettenis
2004-07-23  9:24       ` Eli Zaretskii
2004-07-23 11:22         ` Mark Kettenis
2004-07-23 12:03           ` Eli Zaretskii
2004-07-23 12:13             ` Eli Zaretskii
2004-07-23 12:16             ` Dave Korn
2004-07-23 13:36             ` Mark Kettenis
2004-07-23 16:17               ` Eli Zaretskii
  -- strict thread matches above, loose matches on Subject: below --
2004-07-23  5:44 Michael Elizabeth Chastain
2004-07-23 20:44 ` Andrew Cagney
2004-07-19  3:51 Andrew Cagney
2004-07-19 21:01 ` Eli Zaretskii
2004-07-21 21:12   ` Mark Kettenis
2004-07-21 22:05     ` H. J. Lu
2004-07-22 20:58       ` Mark Kettenis
2004-07-22 21:33         ` Joel Brobecker
2004-07-22 21:38         ` H. J. Lu
2004-07-21 22:17     ` Andrew Cagney
2004-07-22  7:13       ` Eli Zaretskii
2004-07-22 13:04     ` Dave Korn
2004-07-22 15:17       ` Daniel Jacobowitz

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