+#if HAVE_PTHREAD_SIGMASK
+ int ret;
+
+# if PTHREAD_SIGMASK_INEFFECTIVE
+ sigset_t omask, omask_copy;
+ sigset_t *old_mask_ptr = &omask;
+ sigemptyset (&omask);
+ /* Add a signal unlikely to be blocked, so that OMASK_COPY
+ is unlikely to match the actual mask. */
+ sigaddset (&omask, SIGILL);
+ memcpy (&omask_copy, &omask, sizeof omask);
+# else
+ sigset_t *old_mask_ptr = old_mask;
+# endif
+
+ ret = pthread_sigmask (how, new_mask, old_mask_ptr);
+
+# if PTHREAD_SIGMASK_INEFFECTIVE
+ if (ret == 0)
+ {
+ /* Detect whether pthread_sigmask is currently ineffective.
+ Don't cache the information: libpthread.so could be dynamically
+ loaded after the program started and after pthread_sigmask was
+ called for the first time. */
+ if (memcmp (&omask_copy, &omask, sizeof omask) == 0
+ && pthread_sigmask (1729, &omask_copy, NULL) == 0)
+ {
+ /* pthread_sigmask is currently ineffective. The program is not
+ linked to -lpthread. So use sigprocmask instead. */
+ return (sigprocmask (how, new_mask, old_mask) < 0 ? errno : 0);
+ }
+
+ if (old_mask)
+ memcpy (old_mask, &omask, sizeof omask);
+ }
+# endif
+# if PTHREAD_SIGMASK_FAILS_WITH_ERRNO
+ if (ret == -1)
+ return errno;
+# endif
+# if PTHREAD_SIGMASK_UNBLOCK_BUG
+ if (ret == 0
+ && new_mask != NULL
+ && (how == SIG_UNBLOCK || how == SIG_SETMASK))
+ {
+ /* Give the OS the opportunity to raise signals that were pending before
+ the pthread_sigmask call and have now been unblocked. */
+ usleep (1);
+ }
+# endif
+ return ret;
+#else