Eric Blake wrote:
> In the case where oldfd was previously marked O_NOINHERIT, dup2() on mingw
> appears to create newfd as O_NOINHERIT as well. I think we have to rework
> this patch to use DuplicateHandle/_open_osfhandle on both control paths.
No, this is not true in my experiments (done on Windows XP):
$ cat showfd.c
#include <io.h>
#include <stdio.h>
#include <unistd.h>
#include <windows.h>
int main ()
{
int fd;
for (fd = 0; fd < 10; fd++)
printf ("fd %d %s\n", fd,
(HANDLE) _get_osfhandle (fd) == INVALID_HANDLE_VALUE ? "closed" :
"open");
return 0;
}
$ cat main.c
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <process.h>
int main ()
{
int f3 = open ("foo.tmp", O_CREAT | O_TRUNC | O_RDWR, 0600);
printf ("f3 = %d\n", f3);
int f4 = open ("foo.tmp", O_CREAT | O_TRUNC | O_RDWR | O_NOINHERIT, 0600);
printf ("f4 = %d\n", f4);
int f5 = dup2 (f3, 5);
printf ("f5 = %d\n", f5);
int f6 = dup2 (f4, 6);
printf ("f6 = %d\n", f6);
fflush (stdout);
_spawnl (_P_WAIT, "./showfd.exe", "showfd.exe", NULL);
return 0;
}
$ gcc -O -Wall showfd.c -mno-cygwin -o showfd.exe
$ gcc -O -Wall main.c -mno-cygwin -o main.exe
$ ./main.exe
f3 = 3
f4 = 4
f5 = 0
f6 = 0
fd 0 open
fd 1 open
fd 2 open
fd 3 open
fd 4 closed
fd 5 open
fd 6 open
fd 7 closed
fd 8 closed
fd 9 closed
You see, while fd 4 was not inherited by the child process, fd 6 (being a dup2
of fd 4) was inherited. So, dup2 has reset the O_NOINHERIT flag on the newfd.
Just like POSIX says in [1].
Bruno
[1] http://www.opengroup.org/onlinepubs/9699919799/functions/dup.html
