Fwd: gdb on Cygwin cannot give correct call stacks for segment faults

Fwd: gdb on Cygwin cannot give correct call stacks for segment faults

[Pan ruochen]

Hi All,

I find that my gdb on Cygwin cannot dump correct call stacks while
segment faults arise.

Test code is as follows:
--------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>

void foo()
{
    FILE * volatile dev =NULL;
    fprintf(dev, "Hello World!\n");
}

int main()
{
    foo();
    return 0;
}
--------------------------------------------------------------

And backtrace information is as follows:
Program received signal SIGSEGV, Segmentation fault.
0x61138b61 in _fwrite_r () from /usr/bin/cygwin1.dll
(gdb) backtrace
#0  0x61138b61 in _fwrite_r () from /usr/bin/cygwin1.dll
#1  0x76bd1194 in WaitForSingleObjectEx ()
   from /cygdrive/c/windows/syswow64/kernel32.dll
#2  0x76bd1148 in WaitForSingleObject ()
   from /cygdrive/c/windows/syswow64/kernel32.dll
#3  0x610dd558 in sig_send(_pinfo*, siginfo_t&, _cygtls*) ()
   from /usr/bin/cygwin1.dll
#4  0x610303b4 in exception::handle(_EXCEPTION_RECORD*,
_exception_list*, _CONTEXT*, void*) () from /usr/bin/cygwin1.dll
#5  0x77a5b499 in ntdll!LdrRemoveLoadAsDataTable ()
   from /cygdrive/c/windows/system32/ntdll.dll
#6  0x0028a6ac in ?? ()
#7  0x77a5b46b in ntdll!LdrRemoveLoadAsDataTable ()
   from /cygdrive/c/windows/system32/ntdll.dll
#8  0x0028a6ac in ?? ()
#9  0x77a10133 in ntdll!KiUserExceptionDispatcher ()
   from /cygdrive/c/windows/system32/ntdll.dll
#10 0x0028a6ac in ?? ()
#11 0x61138c75 in fwrite () from /usr/bin/cygwin1.dll
#12 0x610d75e5 in _sigfe () from /usr/bin/cygwin1.dll
#13 0x0000000d in ?? ()
#14 0x00000000 in ?? ()

does not give any useful clues where the segment faults arise.
So what is wrong?

-- BR, Ruochen

Re: Fwd: gdb on Cygwin cannot give correct call stacks for segment faults

[Eli Zaretskii]

> Date: Mon, 28 Oct 2013 12:00:17 +0800
> From: Pan ruochen <panruochen@gmail.com>
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0x61138b61 in _fwrite_r () from /usr/bin/cygwin1.dll
> (gdb) backtrace
> #0  0x61138b61 in _fwrite_r () from /usr/bin/cygwin1.dll
> #1  0x76bd1194 in WaitForSingleObjectEx ()
>    from /cygdrive/c/windows/syswow64/kernel32.dll
> #2  0x76bd1148 in WaitForSingleObject ()
>    from /cygdrive/c/windows/syswow64/kernel32.dll
> #3  0x610dd558 in sig_send(_pinfo*, siginfo_t&, _cygtls*) ()
>    from /usr/bin/cygwin1.dll
> #4  0x610303b4 in exception::handle(_EXCEPTION_RECORD*,
> _exception_list*, _CONTEXT*, void*) () from /usr/bin/cygwin1.dll
> #5  0x77a5b499 in ntdll!LdrRemoveLoadAsDataTable ()
>    from /cygdrive/c/windows/system32/ntdll.dll
> #6  0x0028a6ac in ?? ()
> #7  0x77a5b46b in ntdll!LdrRemoveLoadAsDataTable ()
>    from /cygdrive/c/windows/system32/ntdll.dll
> #8  0x0028a6ac in ?? ()
> #9  0x77a10133 in ntdll!KiUserExceptionDispatcher ()
>    from /cygdrive/c/windows/system32/ntdll.dll
> #10 0x0028a6ac in ?? ()
> #11 0x61138c75 in fwrite () from /usr/bin/cygwin1.dll
> #12 0x610d75e5 in _sigfe () from /usr/bin/cygwin1.dll
> #13 0x0000000d in ?? ()
> #14 0x00000000 in ?? ()
> 
> does not give any useful clues where the segment faults arise.
> So what is wrong?

My crystal ball says you are looking at the wrong thread.  Try "thread
apply all backtrace".

Re: Fwd: gdb on Cygwin cannot give correct call stacks for segment faults

[Christopher Faylor]

On Mon, Oct 28, 2013 at 12:00:17PM +0800, Pan ruochen wrote:
>Hi All,
>
>I find that my gdb on Cygwin cannot dump correct call stacks while
>segment faults arise.

This isn't a failing of gdb.  It's a Cygwin problem.  It can't reliably
show backtraces when a SEGV happens in Cygwin DLL code.  This is a known
issue.

cgf

>Test code is as follows:
>--------------------------------------------------------------
>#include <stdio.h>
>#include <stdlib.h>
>
>void foo()
>{
>    FILE * volatile dev =NULL;
>    fprintf(dev, "Hello World!\n");
>}
>
>int main()
>{
>    foo();
>    return 0;
>}
>--------------------------------------------------------------
>
>And backtrace information is as follows:
>Program received signal SIGSEGV, Segmentation fault.
>0x61138b61 in _fwrite_r () from /usr/bin/cygwin1.dll
>(gdb) backtrace
>#0  0x61138b61 in _fwrite_r () from /usr/bin/cygwin1.dll
>#1  0x76bd1194 in WaitForSingleObjectEx ()
>   from /cygdrive/c/windows/syswow64/kernel32.dll
>#2  0x76bd1148 in WaitForSingleObject ()
>   from /cygdrive/c/windows/syswow64/kernel32.dll
>#3  0x610dd558 in sig_send(_pinfo*, siginfo_t&, _cygtls*) ()
>   from /usr/bin/cygwin1.dll
>#4  0x610303b4 in exception::handle(_EXCEPTION_RECORD*,
>_exception_list*, _CONTEXT*, void*) () from /usr/bin/cygwin1.dll
>#5  0x77a5b499 in ntdll!LdrRemoveLoadAsDataTable ()
>   from /cygdrive/c/windows/system32/ntdll.dll
>#6  0x0028a6ac in ?? ()
>#7  0x77a5b46b in ntdll!LdrRemoveLoadAsDataTable ()
>   from /cygdrive/c/windows/system32/ntdll.dll
>#8  0x0028a6ac in ?? ()
>#9  0x77a10133 in ntdll!KiUserExceptionDispatcher ()
>   from /cygdrive/c/windows/system32/ntdll.dll
>#10 0x0028a6ac in ?? ()
>#11 0x61138c75 in fwrite () from /usr/bin/cygwin1.dll
>#12 0x610d75e5 in _sigfe () from /usr/bin/cygwin1.dll
>#13 0x0000000d in ?? ()
>#14 0x00000000 in ?? ()
>
>does not give any useful clues where the segment faults arise.
>So what is wrong?
>
>-- BR, Ruochen
>