hwasan: Bring back operator {new,delete} interceptors on Android.

[pcc]

Summary

It turns out that we can't remove the operator new and delete
interceptors on Android without breaking ABI, so bring them back
as forwards to the malloc and free functions.

[eugenis]

LGTM

compiler-rt/lib/hwasan/hwasan_new_delete.cpp

 // Interceptors for operators new and delete.
 //===----------------------------------------------------------------------===//
 
 #include "hwasan.h"
 #include "interception/interception.h"
 #include "sanitizer_common/sanitizer_allocator.h"
 #include "sanitizer_common/sanitizer_allocator_report.h"
 
+#include <stddef.h>
+#include <stdlib.h>
+
 #if HWASAN_REPLACE_OPERATORS_NEW_AND_DELETE
 
-#include <stddef.h>
+// TODO(alekseys): throw std::bad_alloc instead of dying on OOM.
+#define OPERATOR_NEW_BODY(nothrow) \
+  GET_MALLOC_STACK_TRACE; \
+  void *res = hwasan_malloc(size, &stack);\
+  if (!nothrow && UNLIKELY(!res)) ReportOutOfMemory(size, &stack);\
+  return res
+
+#define OPERATOR_DELETE_BODY \
+  GET_MALLOC_STACK_TRACE; \
+  if (ptr) hwasan_free(ptr, &stack)
+
+#elif defined(__ANDROID__)
+
+// We don't actually want to intercept operator new and delete on Android, but
+// since we previously released a runtime that intercepted these functions,
+// removing the interceptors would break ABI. Therefore we simply forward to
+// malloc and free.
+#define OPERATOR_NEW_BODY(nothrow) return malloc(size)
+#define OPERATOR_DELETE_BODY free(ptr)
+
+#endif
+
+#ifdef OPERATOR_NEW_BODY
 
 using namespace __hwasan;
 
 // Fake std::nothrow_t to avoid including <new>.
 namespace std {
   struct nothrow_t {};
 }  // namespace std
 
 
-// TODO(alekseys): throw std::bad_alloc instead of dying on OOM.
-#define OPERATOR_NEW_BODY(nothrow) \
-  GET_MALLOC_STACK_TRACE; \
-  void *res = hwasan_malloc(size, &stack);\
-  if (!nothrow && UNLIKELY(!res)) ReportOutOfMemory(size, &stack);\
-  return res
 
 INTERCEPTOR_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 void *operator new(size_t size) { OPERATOR_NEW_BODY(false /*nothrow*/); }
 INTERCEPTOR_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 void *operator new[](size_t size) { OPERATOR_NEW_BODY(false /*nothrow*/); }
 INTERCEPTOR_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 void *operator new(size_t size, std::nothrow_t const&) {
   OPERATOR_NEW_BODY(true /*nothrow*/);
 }
 INTERCEPTOR_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 void *operator new[](size_t size, std::nothrow_t const&) {
   OPERATOR_NEW_BODY(true /*nothrow*/);
 }
 
-#define OPERATOR_DELETE_BODY \
-  GET_MALLOC_STACK_TRACE; \
-  if (ptr) hwasan_free(ptr, &stack)
-
 INTERCEPTOR_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 void operator delete(void *ptr) NOEXCEPT { OPERATOR_DELETE_BODY; }
 INTERCEPTOR_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 void operator delete[](void *ptr) NOEXCEPT { OPERATOR_DELETE_BODY; }
 INTERCEPTOR_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 void operator delete(void *ptr, std::nothrow_t const&) { OPERATOR_DELETE_BODY; }
 INTERCEPTOR_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 void operator delete[](void *ptr, std::nothrow_t const&) {
   OPERATOR_DELETE_BODY;
 }
 
-#endif // HWASAN_REPLACE_OPERATORS_NEW_AND_DELETE
+#endif // OPERATOR_NEW_BODY