[issue21191] os.fdopen() may eat file descriptor and still raise exception
Dima Tisnek
report at bugs.python.org
Thu Apr 10 19:46:51 CEST 2014
Dima Tisnek added the comment:
I'm not sure if you are referring to Python's C-level fdopen or GNU libc fdopen.
GNU libc fdopen does not consume file descriptor on error:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
int main(int argc, char** argv)
{
int fd = -1;
int rv = 0;
FILE* fh = NULL;
if (argc<3) return 1;
errno = 0;
fd = open(argv[1], O_RDONLY);
printf("got fd %d errno %d text %s\n", fd, errno, strerror(errno));
errno = 0;
fh = fdopen(fd, argv[2]);
printf("got fh %x errno %d text %s\n", fh, errno, strerror(errno));
errno = 0;
rv = close(fd);
printf("got rv %d errno %d text %s\n", rv, errno, strerror(errno));
}
[dima at bmg ~]$ ./a.out /etc/passwd w
got fd 4 errno 0 text Success
got fh 0 errno 22 text Invalid argument
got rv 0 errno 0 text Success
To be fair, GNU libc fdopen doesn't consider it an error to use a file descriptor that refers to a directory, which is the crux of this bug.
Anyhow, point is the semantics change your patch brings in sets Python 2.7+ in contrast with both Python 3.x and GNU libc.
Perhaps if it's too hard to implement properly, it's better to leave this issue as won't fix / technical limitation?
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<http://bugs.python.org/issue21191>
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