Index: lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc
===================================================================
--- lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc
+++ lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cc
@@ -50,6 +50,13 @@
 
 // Attempts to demangle the name via __cxa_demangle from __cxxabiv1.
 const char *DemangleCXXABI(const char *name) {
+  if (!name) return nullptr;
+
+  // Check if we are dealing with a C++ mangled name first.
+  if (name[0] != '_' || name[1] != 'Z') {
+    return nullptr;
+  }
+
   // FIXME: __cxa_demangle aggressively insists on allocating memory.
   // There's not much we can do about that, short of providing our
   // own demangler (libc++abi's implementation could be adapted so that
@@ -60,7 +67,7 @@
           __cxxabiv1::__cxa_demangle(name, 0, 0, 0))
       return demangled_name;
 
-  return name;
+  return nullptr;
 }
 
 // As of now, there are no headers for the Swift runtime. Once they are
@@ -98,7 +105,9 @@
   if (!name) return nullptr;
   if (const char *swift_demangled_name = DemangleSwift(name))
     return swift_demangled_name;
-  return DemangleCXXABI(name);
+  if (const char *cxx_demangled_name = DemangleCXXABI(name))
+    return cxx_demangled_name;
+  return name;
 }
 
 bool SymbolizerProcess::StartSymbolizerSubprocess() {