Hi,
Cygwin on Windows 7, seems to exhibit a rather peculiar behavior: Sometimes the
exit status of a Win32 process is incorrectly captured by Cygwin.
I'm running Cygwin 1.7.9(0.237/5/3) on Windows 7 64-bit, but I've reproduced
this behavior with every release of Cygwin 1.7 on both 32-bit and 64-bit
Windows 7. It does not seem to happen in XP 32-bit, and I've not tried any
other environments.
To reproduce, first I wrote a Win32 console application (using Visual Studio
2010 / cl.exe version 16 as my compiler) that exits with the status the user
passes in:
> int _tmain(int argc, _TCHAR* argv[])
> {
> int ret = _ttoi(argv[1]);
> _tprintf(_T("Exiting with %i\n"), ret);
>
> return ret;
> }
Then, I wrote a shell script that called this executable ("exiter.exe") with
argument 0 in an infinite loop:
> #!/bin/sh
> set -e
> while true; do
> /cygdrive/c/exiter.exe 0
> echo $?
> done
>
I expect this script to run forever, as the exit code should always be zero.
However, after running this overnight, I see the script terminate:
> Exiting with 0
> 0
> Exiting with 0
> 0
> Exiting with 0
> 0
> Exiting with 0
> 0
> Exiting with 0
>
> $ echo $?
> 1
>
The last line of output implies that exiter.exe executed "return 0", but
/bin/sh saw a nonzero exit status (of 1) and thus stopped execution due to -e.
Reproducing this seems nondeterministic -- sometimes I can get it to happen in
5 minutes, other times it takes overnight. I've tried using a different shell
(like dash), but it doesn't make a difference, leading me to suspect this to be
a lower-level issue within the Cygwin DLL. It also seems to not happen for
non-zero exit codes (e.g. checking that exiter.exe 1 returns 1 always seems to
succeed), though I'm not 100% confident that I've tested this thoroughly enough.
Again, I've not been able to reproduce this under Windows XP using any version
of Cygwin, but I have been able to reproduce it on both 32-bit and 64-bit
Windows 7. I'm not running anything special on this machine -- it's a fresh
install of Windows 7 Professional, just with Cygwin installed.
Thanks in advance,
John
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