Fix pnacl-sz to return with staus 0 in report_fatal_error.

Fixes pnacl-sz to return with exit status 0 in report_fatal_error, if
command line flag --exit-status is specified. The importance of this
is that it allows afl-fuzz to not report the mutation as a crash.

In addition, afl-fuzz doesn't record crash paths in its search
history.  By returning success, afl-fuzz can continue to apply
additional mutations to the bad input. This allows afl-fuzz to add
errors that require multiple changes to occur on the input.

BUG=None
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1382653002 .

diff --git a/src/IceCompileServer.cpp b/src/IceCompileServer.cpp
index db0694b..e2d7e38 100644 (file)
--- a/src/IceCompileServer.cpp
+++ b/src/IceCompileServer.cpp
@@ -93,6 +93,33 @@ ErrorCodes getReturnValue(const Ice::ClFlagsExtra &Flags, ErrorCodes Val) {
   return Val;
 }
 
+// Reports fatal error message, and then exits with success status 0.
+void reportFatalErrorThenExitSuccess(void * UserData,
+                                     const std::string &Reason,
+                                     bool GenCrashDag) {
+  (void)UserData;
+  (void)GenCrashDag;
+
+  // Note: This code is (mostly) copied from llvm/lib/Support/ErrorHandling.cpp
+
+  // Blast the result out to stderr.  We don't try hard to make sure this
+  // succeeds (e.g. handling EINTR) and we can't use errs() here because
+  // raw ostreams can call report_fatal_error.
+  llvm::SmallVector<char, 64> Buffer;
+  llvm::raw_svector_ostream OS(Buffer);
+  OS << "LLVM ERROR: " << Reason << "\n";
+  llvm::StringRef MessageStr = OS.str();
+  ssize_t written = ::write(2, MessageStr.data(), MessageStr.size());
+  (void)written; // If something went wrong, we deliberately just give up.
+
+  // If we reached here, we are failing ungracefully. Run the interrupt handlers
+  // to make sure any special cleanups get done, in particular that we remove
+  // files registered with RemoveFileOnSignal.
+  llvm::sys::RunInterruptHandlers();
+
+  exit(0);
+}
+
 } // end of anonymous namespace
 
 void CLCompileServer::run() {
@@ -105,6 +132,10 @@ void CLCompileServer::run() {
   ClFlags::getParsedClFlags(Flags);
   ClFlags::getParsedClFlagsExtra(ExtraFlags);
 
+  // Override report_fatal_error if we want to exit with 0 status.
+  if (ExtraFlags.getAlwaysExitSuccess())
+    llvm::install_fatal_error_handler(reportFatalErrorThenExitSuccess, this);
+
   std::error_code EC;
   std::unique_ptr<Ostream> Ls = makeStream(ExtraFlags.getLogFilename(), EC);
   if (EC) {