Report fatal translator errors to the browser

tools/pnacl-llc/SRPCStreamer.cpp

 //===-- SRPCStreamer.cpp - Stream bitcode over SRPC  ----------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 #if defined(__native_client__)
 #define DEBUG_TYPE "bitcode-stream"
@@ skipping 101 matching lines @@
                                        std::string *ErrMsg) {
   int err = pthread_create(&CompileThread, NULL, Callback, arg);
   if (err) {
     if (ErrMsg) *ErrMsg = std::string(strerror(errno));
     return NULL;
   }
   return &Q;
 }
 
 size_t SRPCStreamer::gotChunk(unsigned char *bytes, size_t len) {
-  if (Error) return 0;
+  if (__sync_fetch_and_add(&Error, 0)) return 0; // Atomic read.
   return Q.PutBytes(bytes, len);
 }
 
 int SRPCStreamer::streamEnd(std::string *ErrMsg) {
   Q.SetDone();
   int err = pthread_join(CompileThread, NULL);
-  if (err) {
+  __sync_synchronize();
+  if (Error) {
+    if (ErrMsg)
+      *ErrMsg = std::string("PNaCl Translator Error: " + ErrorMessage);
+    return 1;
+  } else if (err) {
     if (ErrMsg) *ErrMsg = std::string(strerror(errno));
     return err;
   }
-  if (Error && ErrMsg) *ErrMsg = std::string("compile failed.");
-  return Error;
+  return 0;
+}
+
+void SRPCStreamer::setFatalError(const std::string& message) {
+  __sync_fetch_and_add(&Error, 1);
+  ErrorMessage = message;
+  __sync_synchronize();
+  pthread_exit(NULL);
 }
 
 #endif // __native_client__