Initial implementation of a record-level bitcode fuzzer.

lib/Bitcode/NaCl/TestUtils/NaClBitcodeMungeWriter.cpp

 //===- NaClBitcodeMungeWriter.cpp - Write munged bitcode --------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // Implements method NaClMungedBitcode.write(), which writes out a munged
@@ skipping 359 matching lines @@
       RecoverableError() << "Ignoring abbreviation: " << Record << "\n";
       return Flags.getTryToRecover();
     }
     if (Record.Abbrev != naclbitc::DEFINE_ABBREV) {
       RecoverableError()
           << "Uses illegal abbreviation index in define abbreviation record: "
           << Record << "\n";
       if (!Flags.getTryToRecover())
         return false;
     }
+    if (atOutermostScope()) {
+      // Recover by ignoring abbreviation definition.
+      RecoverableError() << "Defining abbreviation outside block: "
+                         << Record << "\n";
+      return  Flags.getTryToRecover();
+    }
     NaClBitCodeAbbrev *Abbrev = buildAbbrev(Record);
     if (Abbrev == nullptr) {
       markCurrentBlockWithOmittedAbbreviations();
       return Flags.getTryToRecover();
     }
     if (getCurWriteBlockID() == naclbitc::BLOCKINFO_BLOCK_ID) {
       Writer.EmitBlockInfoAbbrev(SetBID, Abbrev);
     } else {
       Writer.EmitAbbrev(Abbrev);
     }
@@ skipping 172 matching lines @@
     NaClWriteHeader(Writer, true);
   }
   for (const NaClBitcodeAbbrevRecord &Record : *this) {
     if (!State.emitRecord(Writer, Record))
       break;
   }
   bool RecoverSilently =
       State.Results.NumErrors > 0 && !Flags.getTryToRecover();
   return State.finish(Writer, RecoverSilently);
 }