[scudo] Add default implementations for weak functions

[cryptoad]

Summary

This is in preparation for platforms where SANITIZER_SUPPORTS_WEAK_HOOKS is 0.
They require a default implementation.

lib/scudo/scudo_allocator.cpp

 int __sanitizer_get_ownership(const void *Ptr) {
   return Instance.isValidPointer(Ptr);
 }
 
 uptr __sanitizer_get_allocated_size(const void *Ptr) {
   return Instance.getUsableSize(Ptr);
 }
 
+#if !SANITIZER_SUPPORTS_WEAK_HOOKS
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_malloc_hook,
+                             void *Ptr, uptr Size) {
+  (void)Ptr;
+  (void)Size;
+}
+
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_free_hook, void *Ptr) {
+  (void)Ptr;
+}
+#endif
+
 // Interface functions
 
 void __scudo_set_rss_limit(uptr LimitMb, s32 HardLimit) {
   if (!SCUDO_CAN_USE_PUBLIC_INTERFACE)
     return;
   Instance.setRssLimit(LimitMb, !!HardLimit);
 }

lib/scudo/scudo_flags.cpp

 //===-- scudo_flags.cpp -----------------------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// Hardened Allocator flag parsing logic.
 ///
 //===----------------------------------------------------------------------===//
 
 #include "scudo_flags.h"
+#include "scudo_interface_internal.h"
 #include "scudo_utils.h"
 
 #include "sanitizer_common/sanitizer_flags.h"
 #include "sanitizer_common/sanitizer_flag_parser.h"
 
-SANITIZER_INTERFACE_WEAK_DEF(const char*, __scudo_default_options, void);
-
 namespace __scudo {
 
 static Flags ScudoFlags;  // Use via getFlags().
 
 void Flags::setDefaults() {
 #define SCUDO_FLAG(Type, Name, DefaultValue, Description) Name = DefaultValue;
 #include "scudo_flags.inc"
 #undef SCUDO_FLAG
void initFlags() {
   }
 }
 
 Flags *getFlags() {
   return &ScudoFlags;
 }
 
 }  // namespace __scudo
+
+#if !SANITIZER_SUPPORTS_WEAK_HOOKS
+SANITIZER_INTERFACE_WEAK_DEF(const char*, __scudo_default_options, void) {
+  return "";
+}
+#endif

lib/scudo/scudo_interface_internal.h

 #define SCUDO_INTERFACE_INTERNAL_H_
 
 #include "sanitizer_common/sanitizer_internal_defs.h"
 
 using __sanitizer::uptr;
 using __sanitizer::s32;
 
 extern "C" {
+SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
+const char* __scudo_default_options();
+
 SANITIZER_INTERFACE_ATTRIBUTE
 void __scudo_set_rss_limit(uptr LimitMb, s32 HardLimit);
 }  // extern "C"
 
 #endif  // SCUDO_INTERFACE_INTERNAL_H_