[compiler-rt] [rtsan] Intercept aligned_alloc on all versions of OSX if available on build machine (PR #112780)

[Chris Apple via llvm-commits]

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@@ -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
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cjappl wrote:

My proposal is get feedback on this change to make sure it looks good, integrate it, then follow it up with a review that makes this true for all of the sanitizers

https://github.com/llvm/llvm-project/pull/112780