[compiler-rt] r324284 - [Sanitizers, Darwin] Disable SANITIZER_SUPPORTS_WEAK_HOOKS before Mac OS X 10.9

[Vitaly Buka via llvm-commits]

Author: vitalybuka
Date: Mon Feb  5 15:02:09 2018
New Revision: 324284

URL: http://llvm.org/viewvc/llvm-project?rev=324284&view=rev
Log:
[Sanitizers, Darwin] Disable SANITIZER_SUPPORTS_WEAK_HOOKS before Mac OS X 10.9

Summary:
Before Xcode 4.5, undefined weak symbols don't work reliably on Darwin:
https://stackoverflow.com/questions/6009321/weak-symbol-link-on-mac-os-x
Therefore this patch disables their use before Mac OS X 10.9 which is the first version
only supported by Xcode 4.5 and above.

Reviewers: glider, kcc, vitalybuka

Reviewed By: vitalybuka

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D41346

Modified:
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_internal_defs.h

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_internal_defs.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_internal_defs.h?rev=324284&r1=324283&r2=324284&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_internal_defs.h (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_internal_defs.h Mon Feb  5 15:02:09 2018
@@ -65,7 +65,13 @@
 // SANITIZER_SUPPORTS_WEAK_HOOKS means that we support real weak functions that
 // will evaluate to a null pointer when not defined.
 #ifndef SANITIZER_SUPPORTS_WEAK_HOOKS
-#if (SANITIZER_LINUX || SANITIZER_MAC || SANITIZER_SOLARIS) && !SANITIZER_GO
+#if (SANITIZER_LINUX || SANITIZER_SOLARIS) && !SANITIZER_GO
+# define SANITIZER_SUPPORTS_WEAK_HOOKS 1
+// Before Xcode 4.5, the Darwin linker doesn't reliably support undefined
+// weak symbols.  Mac OS X 10.9/Darwin 13 is the first release only supported
+// by Xcode >= 4.5.
+#elif SANITIZER_MAC && \
+    __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 1090 && !SANITIZER_GO
 # define SANITIZER_SUPPORTS_WEAK_HOOKS 1
 #else
 # define SANITIZER_SUPPORTS_WEAK_HOOKS 0