Provide default implementations for sanitizer interface functions

[fjricci]

Summary

Adds a few default implementations for weak
interface functions on platforms where weak hooks are not supported.

[kcc]

Does this deserve a test on those platforms?

[fjricci]

Is leak sanitizer currently supported on any platforms that don't support weak hooks? As far as I'm aware, it isn't, although I'm working on adding additional support. This could be tested by adding the stubs necessary for compilation on a platform like Darwin, but I'm not sure whether that's worth the benefits we get.

[fjricci]

Unless the testing infra supports changing these defines at test-time, in which case it probably wouldn't be difficult.

[kcc]

Ok. How about just a test (on all platforms where lsan is supported)?

[fjricci]

The issue is that these SANITIZER_SUPPORTS_WEAK_HOOKS is true on all currently supported platforms (if it wasn't, lsan would fail to link on those platforms, making a test unnecessary anyway). But this patch is required in order to add platforms where SANITIZER_SUPPORTS_WEAK_HOOKS is false. It's also required for consistency with the existing __lsan_is_turned_off() stub.

[kcc]

LGTM

compiler-rt/trunk/lib/lsan/lsan_allocator.cc

 
 SANITIZER_INTERFACE_ATTRIBUTE
 int __sanitizer_get_ownership(const void *p) { return Metadata(p) != nullptr; }
 
 SANITIZER_INTERFACE_ATTRIBUTE
 uptr __sanitizer_get_allocated_size(const void *p) {
   return GetMallocUsableSize(p);
 }
+
+#if !SANITIZER_SUPPORTS_WEAK_HOOKS
+// Provide default (no-op) implementation of malloc hooks.
+SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
+void __sanitizer_malloc_hook(void *ptr, uptr size) {
+  (void)ptr;
+  (void)size;
+}
+SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
+void __sanitizer_free_hook(void *ptr) {
+  (void)ptr;
+}
+#endif
 } // extern "C"

compiler-rt/trunk/lib/lsan/lsan_common.cc

#endif // CAN_SANITIZE_LEAKS
   return 0;
 }
 
 #if !SANITIZER_SUPPORTS_WEAK_HOOKS
 SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 int __lsan_is_turned_off() {
   return 0;
 }
+
+SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
+const char *__lsan_default_suppressions() {
+  return "";
+}
 #endif
 } // extern "C"