mq_getattr returns -1/EBADF for file descriptors which are not mq.
But we should return 0 in this case.
We first check that fd is a valid fd, so we can assume that if
mq_getattr returns EBADF, it is simply a non-mq fd. There is a slight
race, but there doesn't seem to be a nice way to fix it.
_public_ int sd_is_mq(int fd, const char *path) {
struct mq_attr attr;
- assert_return(fd >= 0, -EBADF);
+ /* Check that the fd is valid */
+ assert_return(fcntl(fd, F_GETFD) >= 0, -errno);
- if (mq_getattr(fd, &attr) < 0)
+ if (mq_getattr(fd, &attr) < 0) {
+ if (errno == EBADF)
+ /* A non-mq fd (or an invalid one, but we ruled that out above) */
+ return 0;
return -errno;
+ }
if (path) {
char fpath[PATH_MAX];