Disable the ASan SEGV handler for NaCl processes on Mac.

chrome/app/chrome_exe_main_mac.cc

Index: chrome/app/chrome_exe_main_mac.cc
===================================================================
--- chrome/app/chrome_exe_main_mac.cc	(revision 238326)
+++ chrome/app/chrome_exe_main_mac.cc	(working copy)
@@ -5,8 +5,45 @@
 // The entry point for all Mac Chromium processes, including the outer app
 // bundle (browser) and helper app (renderer, plugin, and friends).
 
+#if defined(ADDRESS_SANITIZER)
+#include <crt_externs.h>  // for _NSGetArgc, _NSGetArgv
+#endif  // ADDRESS_SANITIZER
 #include <stdlib.h>
+#include <string.h>
 
+#if defined(ADDRESS_SANITIZER)
+// NaCl requires its own SEGV handler, so we need to add handle_segv=0 to
+// ASAN_OPTIONS. This is done by injecting __asan_default_options into the
+// executable.
+// Because there's no distinct NaCl executable on OSX, we have to look at the
+// command line arguments to understand whether the process is a NaCl loader.
+
+static const char kNaClDefaultOptions[] = "handle_segv=0";
+static const char kNaClFlag[] = "--type=nacl-loader";
+
+extern "C"
+// __asan_default_options() is called at ASan initialization, so it must
+// not be instrumented with ASan -- thus the "no_sanitize_address" attribute.
+__attribute__((no_sanitize_address))
+// The function isn't referenced from the executable itself. Make sure it isn't
+// stripped by the linker.
+__attribute__((used))
+__attribute__((visibility("default")))
+const char* __asan_default_options()  {
+  char*** argvp = _NSGetArgv();
+  int* argcp = _NSGetArgc();
+  if (!argvp || !argcp) return NULL;
+  char** argv = *argvp;
+  int argc = *argcp;
+  for (int i = 0; i < argc; ++i) {
+    if (strcmp(argv[i], kNaClFlag) == 0) {
+      return kNaClDefaultOptions;
+    }
+  }
+  return NULL;
+}
+#endif  // ADDRESS_SANITIZER
+
 extern "C" {
 int ChromeMain(int argc, char** argv);
 }  // extern "C"