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Date: Mon, 28 Oct 2013 04:00:00 -0000
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Subject: Fwd: gdb on Cygwin cannot give correct call stacks for segment faults
From: Pan ruochen <panruochen@gmail.com>
To: gdb@sourceware.org
Content-Type: text/plain; charset=ISO-8859-1
X-SW-Source: 2013-10/txt/msg00162.txt.bz2

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