Fix the NaCl bitstream reader to report fatal errors.

lib/Bitcode/NaCl/TestUtils/NaClBitcodeMunge.cpp

Index: lib/Bitcode/NaCl/TestUtils/NaClBitcodeMunge.cpp
diff --git a/lib/Bitcode/NaCl/TestUtils/NaClBitcodeMunge.cpp b/lib/Bitcode/NaCl/TestUtils/NaClBitcodeMunge.cpp
index 7ed2dc8f3e875480681af7ab9c9b222ceb71e881..d7f51bc30eef52c3606971dc0113c1b62f324331 100644
--- a/lib/Bitcode/NaCl/TestUtils/NaClBitcodeMunge.cpp
+++ b/lib/Bitcode/NaCl/TestUtils/NaClBitcodeMunge.cpp
@@ -218,6 +218,8 @@ void NaClBitcodeMunger::emitRecord(unsigned AbbrevIndex,
               << Values.size();
       ReportFatalError();
     }
+    uint64_t MaxAbbrev = (uint64_t(1) << NumBits) - 1;
+    AbbrevIndexLimitStack.push_back(MaxAbbrev);
     if (WriteBlockID == naclbitc::BLOCKINFO_BLOCK_ID) {
       if (NumBits != naclbitc::DEFAULT_MAX_ABBREV) {
         Fatal()
@@ -227,7 +229,8 @@ void NaClBitcodeMunger::emitRecord(unsigned AbbrevIndex,
       }
       Writer->EnterBlockInfoBlock();
     } else {
-      Writer->EnterSubblock(WriteBlockID, NumBits);
+      NaClBitcodeSelectorAbbrev CurCodeLen(MaxAbbrev);
+      Writer->EnterSubblock(WriteBlockID, CurCodeLen);
     }
     return;
   }
@@ -242,6 +245,8 @@ void NaClBitcodeMunger::emitRecord(unsigned AbbrevIndex,
               << Values.size() << "\n";
       ReportFatalError();
     }
+    if (!AbbrevIndexLimitStack.empty())
+      AbbrevIndexLimitStack.pop_back();
     Writer->ExitBlock();
     return;
   case naclbitc::BLK_CODE_DEFINE_ABBREV: {
@@ -270,9 +275,26 @@ void NaClBitcodeMunger::emitRecord(unsigned AbbrevIndex,
   default:
     if ((AbbrevIndex != naclbitc::UNABBREV_RECORD
          && !Writer->isUserRecordAbbreviation(AbbrevIndex))) {
-      Fatal() << "Error: Record code " << RecordCode
-              << " uses illegal abbreviation index " << AbbrevIndex << "\n";
-      ReportFatalError();
+      uint64_t BlockAbbrevIndexLimit = 0;
+      if (!AbbrevIndexLimitStack.empty())
+        BlockAbbrevIndexLimit = AbbrevIndexLimitStack.back();
+      if (AbbrevIndex > BlockAbbrevIndexLimit) {
+        Fatal() << "Error: Record code " << RecordCode
+                << " uses illegal abbreviation index " << AbbrevIndex
+                << ". Must not exceed " << BlockAbbrevIndexLimit << "\n";
+        ReportFatalError();
+      }
+      errs() << "Warning: Record code " << RecordCode
+             << " uses illegal abbreviation index " << AbbrevIndex << "\n";
+      // Fake writing out record using default abbreviation pattern.

[jvoung (off chromium), 2015/02/20 00:12:42]

When is this sort of error recovery needed?

Can you just abort either way?

[Karl, 2015/02/20 21:41:17]

The purpose of the munger is to be able to introduce "errors" in bitcode files.
One of them is abbreviations. This code allows illegal abbreviations to be put
in the bitcode file, so that the reader can be tested and report the error.

Updated the comment to reflect this.

+      Writer->EmitCode(AbbrevIndex);
+      Writer->EmitVBR(RecordCode, 6);
+      uint32_t NumValues = uint32_t(Values.size());

[jvoung (off chromium), 2015/02/20 00:12:42]

static_cast<uint32_t>()?

[Karl, 2015/02/20 21:41:17]

Done.

+      Writer->EmitVBR(NumValues, 6);
+      for (uint32_t i = 0; i < NumValues; ++i) {
+        Writer->EmitVBR64(Values[i], 6);
+      }
+      return;
     }
     if (AbbrevIndex == naclbitc::UNABBREV_RECORD)
       Writer->EmitRecord(RecordCode, Values);
@@ -348,7 +370,12 @@ bool NaClObjDumpMunger::runTestWithFlags(
     const char *Name, const uint64_t Munges[], size_t MungesSize,
     bool AddHeader, bool NoRecords, bool NoAssembly) {
   setupTest(Name, Munges, MungesSize, AddHeader);
-  if (NaClObjDump(MungedInput.get(), *DumpStream, NoRecords, NoAssembly))
+
+  /// If running in death mode, redirect output directly to the
+  /// error stream (rather than buffering in DumpStream), so that
+  /// output can be seen in gtest death test.
+  raw_ostream &Output = RunAsDeathTest ? errs() : *DumpStream;
+  if (NaClObjDump(MungedInput.get(), Output, NoRecords, NoAssembly))
     FoundErrors = true;
   cleanupTest();
   return !FoundErrors;