Mail Archives: cygwin/2009/08/14/00:45:14
Further tests with this little program show that the observed error only
occurs when the socket is dup()'ed to STDIN (fd = 0), but not when
dup'ed to any other fd number. To test, replace STDIN_FILENO in the dup
call with any positive integer (except 3 and 4).
Also, explicitly closing STDIN in advance of the dup call has no effect,
as it should since dup should close exisiting fd automatically.
This moves the problem area at least down into dtable::dup_worker and
build_fh_pc()
how is STDIN handled differently?
cygwin wrote:
> I forgot to add that the same binary copy of the executable of the
> test program (compiled under 1.7) works without error if I place the
> cygwin1.dll version 1.5 into the same directory.
>
>
> cygwin wrote:
>>
>> I wrote a small test program to isolate the problem from RSYNC.
>> The problem occurs when a file descriptor obtained from socketpair()
>> is dup2()'ed into STDIN and then closed. The close call fails.
>> Output from the program is as follows:
>>
>> socket 1 = 3
>> socket 2 = 4
>> dup2 socket 1...
>> closing socket 1...
>> close: Socket operation on non-socket
>> closing socket 1 failed
>>
>>
>> It is interesting to note that the close() is successful when the
>> dup2 calling sequence is omitted.
>> Since socketpair() in cygwin appears to use AF_INET sockets to
>> simulate AF_UNIX it might be interesting to try this on a single INET
>> socket.
>>
>>
>>
>> ===============================================
>> #include <stdio.h>
>> #include <stdlib.h>
>> #include <unistd.h>
>> #include <sys/socket.h>
>>
>> main()
>> {
>> int fd[2];
>> int res = socketpair(AF_UNIX, SOCK_STREAM, 0, fd);
>> if (res < 0) {
>> perror("socketpair");
>> fprintf(stderr, "socketpair failed\n");
>> exit(1);
>> }
>>
>> fprintf(stderr, "socket 1 = %d\n", fd[0]);
>> fprintf(stderr, "socket 2 = %d\n", fd[1]);
>>
>> fprintf(stderr, "dup2 socket 1...\n");
>> res = dup2(fd[0], STDIN_FILENO);
>> if (res < 0) {
>> perror("dup2");
>> fprintf(stderr, "dup2 failed\n");
>> }
>>
>> fprintf(stderr, "closing socket 1...\n");
>> res = close(fd[0] < 0);
>> if (res < 0) {
>> perror("close");
>> fprintf(stderr, "closing socket 1 failed\n");
>> }
>> }
>> =====================================================
>>
>
>
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