[PATCH] pthread_sigmask: fix bug on FreeBSD 9

[Paul Eggert]

I installed this to fix a problem with the Emacs trunk on FreeBSD 9.

---
 ChangeLog             |   13 +++++++++++++
 lib/pthread_sigmask.c |   27 +++++++++++++++++++++++++--
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 169c2ec..1de5899 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2012-07-15  Paul Eggert  <address@hidden>
+
+       pthread_sigmask: fix bug on FreeBSD 9
+       * lib/pthread_sigmask.c [PTHREAD_SIGMASK_INEFFECTIVE]:
+       Include string.h.
+       (pthread_sigmask) [PTHREAD_SIGMASK_INEFFECTIVE]:
+       When calling pthread_sigmask (1729, NEW, OLD), specify non-null NEW;
+       this avoids a bug on FreeBSD 9, where pthread_sigmask is effective
+       but pthread_sigmask (1729, NULL, NULL) returns zero.
+       See <http://bugs.gnu.org/11884>.
+       Avoid the need to call pthread_sigmask (1729, ...) in most cases,
+       by inspecting whether the main call changed the old mask.
+
 2012-07-15  Reuben Thomas  <address@hidden>
 
        README-release: make it more legible
diff --git a/lib/pthread_sigmask.c b/lib/pthread_sigmask.c
index 4a150e7..80ab24b 100644
--- a/lib/pthread_sigmask.c
+++ b/lib/pthread_sigmask.c
@@ -22,6 +22,10 @@
 #include <errno.h>
 #include <stddef.h>
 
+#if PTHREAD_SIGMASK_INEFFECTIVE
+# include <string.h>
+#endif
+
 #if PTHREAD_SIGMASK_UNBLOCK_BUG
 # include <unistd.h>
 #endif
@@ -31,7 +35,22 @@ pthread_sigmask (int how, const sigset_t *new_mask, sigset_t 
*old_mask)
 #undef pthread_sigmask
 {
 #if HAVE_PTHREAD_SIGMASK
-  int ret = pthread_sigmask (how, new_mask, old_mask);
+  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)
     {
@@ -39,12 +58,16 @@ pthread_sigmask (int how, const sigset_t *new_mask, 
sigset_t *old_mask)
          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 (pthread_sigmask (1729, NULL, NULL) == 0)
+      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
-- 
1.7.6.5