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Date: Wed, 09 Nov 2011 18:58:47 -0500
From: Ryan Johnson <ryan DOT johnson AT cs DOT utoronto DOT ca>
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To: cygwin AT cygwin DOT com
Subject: Re: gdb broken inside emacs (again? still?)
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On 09/11/2011 5:32 PM, Ken Brown wrote:
> On 11/9/2011 4:44 PM, Ryan Johnson wrote:
>> Running just `gdb' from emacs allows it to initialize, but
>> attempts to load a file or indeed perform any command hang until a
>> double-^C cancels the attempt (reporting "C-c C-cquit"). Ironically,
>> even `quit' hangs, so you have to use ^D to exit. Debugging anything
>> within emacs is thus completely impossible at this time.
> cgf has already stated that this will be fixed in the next release of 
> gdb; see
>
>   http://cygwin.com/ml/cygwin/2011-10/msg00564.html
Hmm. After dwelling longer on the above post chain... I think cgf was 
only talking about fixing the seg fault. Is this freezing somehow 
related? I didn't think it was.

> P.S. If you're building your own emacs and using a Cygwin snapshot, 
> you'll need to apply my patch to fix the memory allocation problem 
> that we discussed a few months ago.  You can get this by using 
> setup.exe to download the source for emacs-23.3-3.
Built, but unfortunately no improvement in behavior by gdb. Is there 
some possibility those cygwin-specific patches somehow are tied up in 
this? The last time this came up a home-built emacs worked with 
gdb-7.3.50-1.

As others have reported, gud-gdb can load and run binaries, but then 
emacs doesn't sync up its output with source files any more...

BTW, I don't know if this has anything to do with anything, but `strace 
gdb' from the command prompt or inside emacs reports an infinite stream 
of seg faults:
>    25 1231358 [main] gdb 4112 __set_errno: void san::leave():277 val 14
> --- Process 4112, exception C0000005 at 6111AE63
>    71 1231429 [main] gdb 4112 exception::handle: In 
> cygwin_except_handler exc 0xC0000005 at 0x6111AE63 sp 0x149C8F4
>    67 1231496 [main] gdb 4112 exception::handle: In 
> cygwin_except_handler sig 11 at 0x6111AE63
>    82 1231578 [main] gdb 4112 exception::handle: In 
> cygwin_except_handler calling 0x0
>    29 1231607 [main] gdb 4112 __set_errno: void san::leave():277 val 14
> --- Process 4112, exception C0000005 at 6111AE63
>    75 1231682 [main] gdb 4112 exception::handle: In 
> cygwin_except_handler exc 0xC0000005 at 0x6111AE63 sp 0x149C8F4
>    28 1231710 [main] gdb 4112 exception::handle: In 
> cygwin_except_handler sig 11 at 0x6111AE63
>    28 1231738 [main] gdb 4112 exception::handle: In 
> cygwin_except_handler calling 0x0

^C kills the program, but attempting to type any other character hangs 
gdb, strace, and the terminal for good measure.

Is gdb just known-unfriendly to strace?

Ryan


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