[rtsan] Intercept aligned_alloc on all versions of OSX if available on the build machine

Author: cjappl

compiler-rt/lib/rtsan/rtsan_interceptors.cpp

@@ -461,7 +461,17 @@ INTERCEPTOR(void *, valloc, SIZE_T size) {
   return REAL(valloc)(size);
 }
 
-#if SANITIZER_INTERCEPT_ALIGNED_ALLOC
+// aligned_alloc was introduced in OSX 10.15
+// Linking will fail when using an older SDK
+#if defined(__MAC_10_15)
+// macOS 10.15 is greater than our minimal deployment target.  To ensure we
+// generate a weak reference so the dylib continues to work on older
+// systems, we need to forward declare the intercepted function as "weak
+// imports".
+SANITIZER_WEAK_IMPORT void *aligned_alloc(SIZE_T __alignment, SIZE_T __size);
+#endif // defined(__MAC_10_15)
+
+#if SANITIZER_INTERCEPT_ALIGNED_ALLOC || SANITIZER_APPLE
 INTERCEPTOR(void *, aligned_alloc, SIZE_T alignment, SIZE_T size) {
   __rtsan_notify_intercepted_call("aligned_alloc");
   return REAL(aligned_alloc)(alignment, size);

compiler-rt/lib/rtsan/tests/rtsan_test_interceptors.cpp

@@ -120,13 +120,17 @@ TEST(TestRtsanInterceptors, VallocDiesWhenRealtime) {
   ExpectNonRealtimeSurvival(Func);
 }
 
-#if SANITIZER_INTERCEPT_ALIGNED_ALLOC
 TEST(TestRtsanInterceptors, AlignedAllocDiesWhenRealtime) {
-  auto Func = []() { EXPECT_NE(nullptr, aligned_alloc(16, 32)); };
-  ExpectRealtimeDeath(Func, "aligned_alloc");
-  ExpectNonRealtimeSurvival(Func);
-}
+#if SANITIZER_APPLE
+  if (__builtin_available(macOS 10.15, *)) {
+#endif // SANITIZER_APPLE
+    auto Func = []() { EXPECT_NE(nullptr, aligned_alloc(16, 32)); };
+    ExpectRealtimeDeath(Func, "aligned_alloc");
+    ExpectNonRealtimeSurvival(Func);
+#if SANITIZER_APPLE
+  }
 #endif
+}
 
 // free_sized and free_aligned_sized (both C23) are not yet supported
 TEST(TestRtsanInterceptors, FreeDiesWhenRealtime) {