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

On Wed, 31 Dec 2003, Christopher Faylor wrote:

> On Wed, Dec 31, 2003 at 10:02:44AM -0500, Pierre A. Humblet wrote:
> >Christopher Faylor wrote:
> >>This should be fixed now.  I'm uploading a snapshot.
> >
> >CYGWIN_ME-4.90 hpn5170x 1.5.6s(0.108/3/2) 20031231 01:31:40 i686 unknown
> >unknown Cygwin
> >
> >Now virtually every cygwin program (/bin/true, ls, uname,...) almost
> >always ends with the popup about causing an error in Cygwin1.dll.
> Did you look at the changes I made?  It's difficult to believe that minor
> changes to cygwin.din would cause a popup on every access, although I can
> believe that the stuff in CVS previously would work that way.  If anything,
> I'd expect that there would be no change rather than actual worsening.
> Are you sure you're up to date?
Yep.  That change just wasn't enough.  Here's the next spot.

$ env PATH="../../cygwin:${PATH}" gdb ./checksignal.exe
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  0x6108a683 in shared_info::initialize() (this=0xa000000)
    at ../../../../cygwin/winsup/cygwin/
#3  0x6108a77d in memory_init() ()
    at ../../../../cygwin/winsup/cygwin/
#4  0x61005c75 in dll_crt0_1(char*) ()
    at ../../../../cygwin/winsup/cygwin/
#5  0x6100615a in _dll_crt0 () at
#6  0x61006256 in *_dll_crt0 (uptr=0x0)
    at ../../../../cygwin/winsup/cygwin/
(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.
(gdb) p $edx
$1 = 0

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

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