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

compiler-rt/lib/rtsan/rtsan_interceptors_posix.cpp

@@ -464,10 +464,13 @@ INTERCEPTOR(void *, valloc, SIZE_T size) {
 }
 
 #if SANITIZER_INTERCEPT_ALIGNED_ALLOC
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunguarded-availability-new"
 INTERCEPTOR(void *, aligned_alloc, SIZE_T alignment, SIZE_T size) {
   __rtsan_notify_intercepted_call("aligned_alloc");
   return REAL(aligned_alloc)(alignment, size);
 }
+#pragma clang diagnostic pop
 #define RTSAN_MAYBE_INTERCEPT_ALIGNED_ALLOC INTERCEPT_FUNCTION(aligned_alloc)
 #else
 #define RTSAN_MAYBE_INTERCEPT_ALIGNED_ALLOC

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

@@ -122,13 +122,20 @@ TEST(TestRtsanInterceptors, VallocDiesWhenRealtime) {
   ExpectNonRealtimeSurvival(Func);
 }
 
-#if SANITIZER_INTERCEPT_ALIGNED_ALLOC
+#if __has_builtin(__builtin_available) && SANITIZER_APPLE
+#define ALIGNED_ALLOC_AVAILABLE() (__builtin_available(macOS 10.15, *))
+#else
+// We are going to assume this is true until we hit systems where it isn't
+#define ALIGNED_ALLOC_AVAILABLE() (true)
+#endif
+
 TEST(TestRtsanInterceptors, AlignedAllocDiesWhenRealtime) {
-  auto Func = []() { EXPECT_NE(nullptr, aligned_alloc(16, 32)); };
-  ExpectRealtimeDeath(Func, "aligned_alloc");
-  ExpectNonRealtimeSurvival(Func);
+  if (ALIGNED_ALLOC_AVAILABLE()) {
+    auto Func = []() { EXPECT_NE(nullptr, aligned_alloc(16, 32)); };
+    ExpectRealtimeDeath(Func, "aligned_alloc");
+    ExpectNonRealtimeSurvival(Func);
+  }
 }
-#endif
 
 // free_sized and free_aligned_sized (both C23) are not yet supported
 TEST(TestRtsanInterceptors, FreeDiesWhenRealtime) {

compiler-rt/lib/sanitizer_common/sanitizer_platform_interceptors.h

@@ -84,6 +84,25 @@
 #define SI_NOT_MAC 1
 #endif
 
+#if SANITIZER_APPLE
+#  include <Availability.h>
+
+// 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(__sanitizer::usize __alignment,
+                                          __sanitizer::usize __size);
+#    define SI_MAC_SDK_10_15_AVAILABLE 1
+#  else
+#    define SI_MAC_SDK_10_15_AVAILABLE 0
+#  endif  // defined(__MAC_10_15)
+
+#endif  // SANITIZER_APPLE
+
 #if SANITIZER_IOS
 #define SI_IOS 1
 #else
@@ -500,7 +519,8 @@
 #define SANITIZER_INTERCEPT_PVALLOC (SI_GLIBC || SI_ANDROID)
 #define SANITIZER_INTERCEPT_CFREE (SI_GLIBC && !SANITIZER_RISCV64)
 #define SANITIZER_INTERCEPT_REALLOCARRAY SI_POSIX
-#define SANITIZER_INTERCEPT_ALIGNED_ALLOC (!SI_MAC)
+#define SANITIZER_INTERCEPT_ALIGNED_ALLOC \
+  (!SI_MAC || SI_MAC_SDK_10_15_AVAILABLE)
 #define SANITIZER_INTERCEPT_MALLOC_USABLE_SIZE (!SI_MAC && !SI_NETBSD)
 #define SANITIZER_INTERCEPT_MCHECK_MPROBE SI_LINUX_NOT_ANDROID
 #define SANITIZER_INTERCEPT_WCSLEN 1