Initial implementation of a record-level bitcode fuzzer.

include/llvm/Bitcode/NaCl/NaClBitstreamWriter.h

 //===- NaClBitstreamWriter.h - NaCl bitstream writer ------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This header defines the BitstreamWriter class.  This class can be used to
@@ skipping 413 matching lines @@
       }
     }
     assert(RecordIdx == Vals.size() && "Not all record operands emitted!");
   }
 
 public:
 
   /// Returns a pointer to the abbreviation currently associated with
   /// the abbreviation index. Returns nullptr if no such abbreviation.
   const NaClBitCodeAbbrev *getAbbreviation(unsigned Index) const {
-    if (Index < naclbitc::FIRST_APPLICATION_ABBREV)
-      return nullptr;
-    if (Index >= BlockScope.back().AbbreviationIndexLimit)
+    if (Index < naclbitc::FIRST_APPLICATION_ABBREV
+        || BlockScope.empty()
+        || Index >= BlockScope.back().AbbreviationIndexLimit)
       return nullptr;
     unsigned AbbrevNo = Index - naclbitc::FIRST_APPLICATION_ABBREV;
     if (AbbrevNo >= CurAbbrevs.size())
       return nullptr;
     return CurAbbrevs[AbbrevNo];
   }
 
   /// EmitRecord - Emit the specified record to the stream, using an abbrev if
   /// we have one to compress the output.
   template<typename uintty>
@@ skipping 40 matching lines @@
       }
     }
     flushToByteIfAligned();
   }
 public:
 
   /// EmitAbbrev - This emits an abbreviation to the stream.  Note that this
   /// method takes ownership of the specified abbrev.
   unsigned EmitAbbrev(NaClBitCodeAbbrev *Abbv) {
     assert(Abbv->isValid() && "Can't emit invalid abbreviation!");
+    assert(!BlockScope.empty() && "Can't emit abbreviations outside of blocks");
     // Emit the abbreviation as a record.
     EncodeAbbrev(Abbv);
     CurAbbrevs.push_back(Abbv);
     return static_cast<unsigned>(CurAbbrevs.size())-1 +
       naclbitc::FIRST_APPLICATION_ABBREV;
   }
 
   //===--------------------------------------------------------------------===//
   // BlockInfo Block Emission
   //===--------------------------------------------------------------------===//
@@ skipping 37 matching lines @@
     Info.Abbrevs.push_back(Abbv);
 
     return Info.Abbrevs.size()-1+naclbitc::FIRST_APPLICATION_ABBREV;
   }
 };
 
 
 } // End llvm namespace
 
 #endif