Add print_unsymbolized_stack_traces gn arg.

This allows using asan_symbolizer.py to get improved stack traces with
line numbers even in non-ASAN, non-debug builds.

Change-Id: I047b7e936c54b79ab057616a9e6a4c013a94b1fc
Reviewed-on: https://chromium-review.googlesource.com/940771Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: James Darpinian <jdarpinian@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540366}

base/third_party/symbolize/BUILD.gn

@@ -2,6 +2,17 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/compiler/compiler.gni")
+
+declare_args() {
+  # Stack traces will not include function names. Instead they will contain
+  # file and offset information that can be used with
+  # tools/valgrind/asan/asan_symbolize.py. By piping stderr through this script,
+  # and also enabling symbol_level = 2, you can get much more detailed stack
+  # traces with file names and line numbers, even in non-ASAN builds.
+  print_unsymbolized_stack_traces = is_asan || is_lsan || is_msan || is_tsan
+}
+
 static_library("symbolize") {
   visibility = [ "//base/*" ]
   sources = [
@@ -15,6 +26,11 @@ static_library("symbolize") {
     "utilities.h",
   ]
 
+  defines = []
+  if (print_unsymbolized_stack_traces) {
+    defines += [ "PRINT_UNSYMBOLIZED_STACK_TRACES" ]
+  }
+
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
 }

base/third_party/symbolize/symbolize.cc

@@ -779,8 +779,7 @@ static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
   }
 
   // Check whether a file name was returned.
-#if !defined(ADDRESS_SANITIZER) && !defined(LEAK_SANITIZER) && \
-    !defined(MEMORY_SANITIZER) && !defined(THREAD_SANITIZER)
+#if !defined(PRINT_UNSYMBOLIZED_STACK_TRACES)
   if (object_fd < 0) {
 #endif
     if (out[1]) {
@@ -796,8 +795,7 @@ static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
     }
     // Failed to determine the object file containing PC.  Bail out.
     return false;
-#if !defined(ADDRESS_SANITIZER) && !defined(LEAK_SANITIZER) && \
-    !defined(MEMORY_SANITIZER) && !defined(THREAD_SANITIZER)
+#if !defined(PRINT_UNSYMBOLIZED_STACK_TRACES)
   }
 #endif
   FileDescriptor wrapped_object_fd(object_fd);