[compiler-rt] Define as weak, functions that are declared as weak.

[mpividori]

I updated the diff to use the new macro SANITIZER_INTERFACE_WEAK_DEF() and also add that symbols to the list of weak symbols in: weak_symbols.txt.

Ready to land?

compiler-rt/trunk/lib/asan/asan_win_dll_thunk.cc

 INTERFACE_FUNCTION(__sanitizer_get_total_unique_coverage)
 INTERFACE_FUNCTION(__sanitizer_get_unmapped_bytes)
 INTERFACE_FUNCTION(__sanitizer_maybe_open_cov_file)
 INTERFACE_FUNCTION(__sanitizer_print_stack_trace)
 INTERFACE_FUNCTION(__sanitizer_symbolize_pc)
 INTERFACE_FUNCTION(__sanitizer_symbolize_global)
 INTERFACE_FUNCTION(__sanitizer_ptr_cmp)
 INTERFACE_FUNCTION(__sanitizer_ptr_sub)
-INTERFACE_FUNCTION(__sanitizer_report_error_summary)
 INTERFACE_FUNCTION(__sanitizer_reset_coverage)
 INTERFACE_FUNCTION(__sanitizer_get_number_of_counters)
 INTERFACE_FUNCTION(__sanitizer_update_counter_bitset_and_clear_counters)
-INTERFACE_FUNCTION(__sanitizer_sandbox_on_notify)
 INTERFACE_FUNCTION(__sanitizer_set_death_callback)
 INTERFACE_FUNCTION(__sanitizer_set_report_path)
 INTERFACE_FUNCTION(__sanitizer_set_report_fd)
 INTERFACE_FUNCTION(__sanitizer_unaligned_load16)
 INTERFACE_FUNCTION(__sanitizer_unaligned_load32)
 INTERFACE_FUNCTION(__sanitizer_unaligned_load64)
 INTERFACE_FUNCTION(__sanitizer_unaligned_store16)
 INTERFACE_FUNCTION(__sanitizer_unaligned_store32)

compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.cc

void __sanitizer_set_report_path(const char *path) {
   report_file.SetReportPath(path);
 }
 
 void __sanitizer_set_report_fd(void *fd) {
   report_file.fd = (fd_t)reinterpret_cast<uptr>(fd);
   report_file.fd_pid = internal_getpid();
 }
 
-void __sanitizer_report_error_summary(const char *error_summary) {
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_report_error_summary,
+                             const char *error_summary) {
   Printf("%s\n", error_summary);
 }
 
 SANITIZER_INTERFACE_ATTRIBUTE
 void __sanitizer_set_death_callback(void (*callback)(void)) {
   SetUserDieCallback(callback);
 }
 

compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_libcdep.cc

if (!common_flags()->hard_rss_limit_mb &&
       !common_flags()->heap_profile) return;
   if (!&real_pthread_create) return;  // Can't spawn the thread anyway.
   internal_start_thread(BackgroundThread, nullptr);
 #endif
 }
 
 }  // namespace __sanitizer
 
-void NOINLINE
-__sanitizer_sandbox_on_notify(__sanitizer_sandbox_arguments *args) {
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_sandbox_on_notify,
+                             __sanitizer_sandbox_arguments *args) {
   __sanitizer::PrepareForSandboxing(args);
   if (__sanitizer::sandboxing_callback)
     __sanitizer::sandboxing_callback();
 }

compiler-rt/trunk/lib/sanitizer_common/weak_symbols.txt

 ___sanitizer_free_hook
 ___sanitizer_malloc_hook
+___sanitizer_report_error_summary
+___sanitizer_sandbox_on_notify
 ___sanitizer_symbolize_code
 ___sanitizer_symbolize_data
 ___sanitizer_symbolize_demangle
 ___sanitizer_symbolize_flush