sanitizer_common: be more verbose, when symbolizer is not found.

[krasin]

Summary

I have othen been stuck when I got an ASAN report, but no symbols
are resolved. The reasons might be different, and it always
requires a bit of detective work to track down.

These more verbose error messages will help the users like me.

[krasin]

.

[krasin]

Alexey,

friendly ping!

[samsonov]

lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc

386

This is sort of inconsistent - we use VReport(2) if ASAN_OPTIONS=symbolize=0 is used, for example.

465

Don't you need to print error message only if symbolizer list is empty? E.g. it's perfectly fine if we weren't able to find external symbolizer, but internal symbolizer (which takes precedence) is used.

[krasin]

reduce scope

[krasin]

PTAL

lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc

386

Removed for now.

465

That's a good idea. I didn't quite realize the process of the symbolizer selection. Please, take another look. Is it better now?

[samsonov]

LGTM

lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc

 }
 
 void Symbolizer::PlatformPrepareForSandboxing() {}
 
 static SymbolizerTool *ChooseExternalSymbolizer(LowLevelAllocator *allocator) {
   const char *path = common_flags()->external_symbolizer_path;
   const char *binary_name = path ? StripModuleName(path) : "";
   if (path && path[0] == '\0') {
     VReport(2, "External symbolizer is explicitly disabled.\n");
     return nullptr;
   } else if (!internal_strcmp(binary_name, "llvm-symbolizer")) {
     VReport(2, "Using llvm-symbolizer at user-specified path: %s\n", path);
     return new(*allocator) LLVMSymbolizer(path, allocator);
   } else if (!internal_strcmp(binary_name, "atos")) {
 #if SANITIZER_MAC
     VReport(2, "Using atos at user-specified path: %s\n", path);
     return new(*allocator) AtosSymbolizer(path, allocator);
static void ChooseSymbolizerTools(IntrusiveList<SymbolizerTool> *list,
   if (SymbolizerTool *tool = LibbacktraceSymbolizer::get(allocator)) {
     VReport(2, "Using libbacktrace symbolizer.\n");
     list->push_back(tool);
     return;
   }
 
   if (SymbolizerTool *tool = ChooseExternalSymbolizer(allocator)) {
     list->push_back(tool);
-  } else {
-    VReport(2, "No internal or external symbolizer found.\n");
   }
 
 #if SANITIZER_MAC
   VReport(2, "Using dladdr symbolizer.\n");
   list->push_back(new(*allocator) DlAddrSymbolizer());
 #endif  // SANITIZER_MAC
+
+  if (list->size() == 0) {
+    Report("WARNING: no internal or external symbolizer found.\n");
+  }
 }
 
 Symbolizer *Symbolizer::PlatformInit() {
   IntrusiveList<SymbolizerTool> list;
   list.clear();
   ChooseSymbolizerTools(&list, &symbolizer_allocator_);
   return new(symbolizer_allocator_) Symbolizer(list);
 }
 
 }  // namespace __sanitizer
 
 #endif  // SANITIZER_POSIX