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Re: 1.5.6-pre: Occasional bad memory accesses within cygwin1.dll

On Mon, 29 Dec 2003, Christopher Faylor wrote:

> On Sun, Dec 28, 2003 at 03:52:33PM -0000, Max Bowsher wrote:
> >I installed a self-built cygwin HEAD version - mostly it works fine, but it
> >causes odd failures during builds (speculation: race when many processes
> >being created and destroyed?)
> >
> >The most common failure is a Windows error box:
> >
> >The instruction at "0x6108621a" references memory at "0x610030b0". The
> >memory could not be written.
> >
> >(These addresses are constant.)
> >
> >$ addr2line -e /bin/cygwin1.dll 0x6108621a 0x610030b0
> >.../src/winsup/cygwin/
> >.../src/winsup/cygwin/
> This isn't too useful, unfortunately.  The line numbers are an artifact
> of the fact that there is no STABS information in the generated asm in
> 'sigfe.s'.  Can you get an assembly listing of the lines around this
> instruction?
I think this is the same problem.  It shows up all over the place for me
in the testsuite.

$ env
GNU gdb 5.3
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i686-pc-cygwin"...
(gdb) r
Starting program:

Program received signal SIGSEGV, Segmentation fault.
0x6108bcad in _sigfe ()
Current language:  auto; currently c++
(gdb) bt
#0  0x6108bcad in _sigfe ()
#1  0xffffffff in ?? ()
#2  0x00402b1f in cygwin_crt0 (f=0x401134 <main>)
    at ../../../../cygwin/winsup/cygwin/lib/cygwin_crt0.c:24
#3  0x0040103c in mainCRTStartup ()
#4  0x77f1bb7b in _system_dlls__ ()
(gdb) disassemble
Dump of assembler code for function _sigfe:
0x6108bc90 <_sigfe>:    push   %edx
0x6108bc91 <_sigfe+1>:  mov    %fs:0x4,%eax
0x6108bc97 <_sigfe+7>:  mov    $0x4,%edx
0x6108bc9c <_sigfe+12>: xadd   %edx,0xffffeff8(%eax)
0x6108bca3 <_sigfe+19>: lea    0x6108bcb1,%eax
0x6108bca9 <_sigfe+25>: xchg   %eax,0x8(%esp,1)
0x6108bcad <_sigfe+29>: mov    %eax,(%edx)
0x6108bcaf <_sigfe+31>: pop    %edx
0x6108bcb0 <_sigfe+32>: ret
End of assembler dump.

Brian Ford
Senior Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
Phone: 314-551-8460
Fax:   314-551-8444

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