OS X 10.10: Fix incorrect check for presence of unsupported MACH_SEND_TRAILER in mach_msg. Partial fix for BZ #343306.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14890 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/NEWS b/NEWS
index 6d82de4..c9f65bd 100644
--- a/NEWS
+++ b/NEWS
@@ -76,6 +76,7 @@
 342795  Internal glibc __GI_mempcpy call should be intercepted
 343012  Unhandled syscall 319 (memfd_create)
 343303  Fix known deliberate memory leak in setenv() on Mac OS X 10.10
+343306  OS X 10.10: UNKNOWN mach_msg unhandled MACH_SEND_TRAILER option (partial fix)
 n-i-bz  Provide implementations of certain compiler builtins to support
         compilers who may not provide those
 n-i-bz  Old STABS code is still being compiled, but never used. Remove it.
diff --git a/coregrind/m_syswrap/syswrap-darwin.c b/coregrind/m_syswrap/syswrap-darwin.c
index 25b5275..2067d8d 100644
--- a/coregrind/m_syswrap/syswrap-darwin.c
+++ b/coregrind/m_syswrap/syswrap-darwin.c
@@ -7903,7 +7903,9 @@
       // (but is this only for too-secure processes?)
       // JRS 11 Nov 2014: this assertion is OK for <= 10.9 but fails on 10.10
 #     if DARWIN_VERS == DARWIN_10_10
-      log_decaying("UNKNOWN mach_msg unhandled MACH_SEND_TRAILER option");
+      if (mh->msgh_bits & MACH_SEND_TRAILER) {
+         log_decaying("UNKNOWN mach_msg unhandled MACH_SEND_TRAILER option");
+      }
 #     else
       vg_assert(! (mh->msgh_bits & MACH_SEND_TRAILER));
 #     endif