Mail Archives: cygwin/2010/12/06/18:07:48
At the end of this message is a short program. It is linked as a
windows-mode executable so when it is launched it does not have a console.
It then allocates one and uses it. The expected behaviour is that when I
run it a fresh DOS-style console appears and I can type a few chars in and
they get echoed.
This happens happily. EXCEPT that if before typing in 5 chars I close the
console either via its file/close menu or by clicking the little "x" at the
right of its title bar and IF I launched the program from cygwin using
execv/execve (as the cygwin bash shell does) the application console winow
closess but the program is instantly relauched. I see this with both the 32
& 64-bit versions of the non-cygwin compilatets - ie replace
x86_64-w64-mingw32-gcc with just "gcc -mno-cygwin" has the same behaviour.
If instead of launching the binary via cygwin's execv I launch it direct
from a plain old DOS shell then closing the console window causes the
program to terminate in the way I expected.
It is not clear to me whether this is an issue of the mingw bits not
handling things and exiting badly or of the cygwin execv behaving
improperly. Eg it I write a very short program that goes basically
execv("./bad0",...) and compile that using cygwin but then run that
executable from a normal DOS shell I get the hydra-like behaviour where
when I cut of a console a fresh one instantly re-grows, even though
launching bad0 directly does not suffer that way. So if mingw people can
confirm that this is a problem on the cygwin side the issue can be
forwarded that way...
When I posted this for mingw64 people to comment on the response I got
back was
"This indicates the problem to be with Cygwin. Have you asked them? I
know that Cygwin doesn't have control of the exec-ed "native" program
but it may be trapping the signals and causing the primary program to
not end so that it reopens the console making it appear to be
"restarting"."
Many thanks,
{I am on Windows 7 64-bit with the x86_64 compiler versions that cygwin
installs for me, but I have tried the bad0 executable on a windows 2000
(virtual) machine and observe the same bad effects in the 32-bit version
there, so actually this is not just a 64-bit issue and not just a Windows 7
one).
Arthur
===========================================================
/*
* x86_64-w64-mingw32-gcc -mno-cygwin bad0.c \
* -Wl,--subsystem=windows -o bad0
* ./bad0
*/
#include <stdio.h>
#include <windows.h>
int main(int argc, char *argv[])
{
int i;
if (AllocConsole())
{ freopen("CONIN$", "r", stdin);
freopen("CONOUT$", "w", stdout);
freopen("CONOUT$", "w", stderr);
}
for (i=0; i<5; i++)
{ int c = getchar();
printf("char %d is %#x\n", i, c);
fflush(stdout);
}
return 0;
}
=============================================================
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