[CodeView] Healthy paranoia around strings

Make sure strings don't get too big for a record, truncate them if
need-be.

llvm-svn: 273710

llvm/include/llvm/DebugInfo/CodeView/ListRecordBuilder.h

@@ -50,7 +50,7 @@ private:
     return ContinuationOffsets.empty() ? 0 : ContinuationOffsets.back();
   }
   size_t getLastContinuationEnd() const { return Builder.size(); }
-  unsigned getLastContinuationSize() const {
+  size_t getLastContinuationSize() const {
     return getLastContinuationEnd() - getLastContinuationStart();
   }
 

llvm/include/llvm/DebugInfo/CodeView/TypeRecordBuilder.h

@@ -40,7 +40,6 @@ public:
   void writeEncodedInteger(int64_t Value);
   void writeEncodedSignedInteger(int64_t Value);
   void writeEncodedUnsignedInteger(uint64_t Value);
-  void writeNullTerminatedString(const char *Value);
   void writeNullTerminatedString(StringRef Value);
   void writeGuid(StringRef Guid);
   void writeBytes(StringRef Value) { Stream << Value; }

llvm/lib/DebugInfo/CodeView/ListRecordBuilder.cpp

@@ -49,8 +49,10 @@ void ListRecordBuilder::finishSubRecord() {
   // back up and insert a continuation record, sliding the current subrecord
   // down.
   if (getLastContinuationSize() > 65535 - 8) {
+    assert(SubrecordStart != 0 && "can't slide from the start!");
     SmallString<128> SubrecordCopy(
         Builder.str().slice(SubrecordStart, Builder.size()));
+    assert(SubrecordCopy.size() < 65530 && "subrecord is too large to slide!");
     Builder.truncate(SubrecordStart);
 
     // Write a placeholder continuation record.

llvm/lib/DebugInfo/CodeView/TypeRecordBuilder.cpp

@@ -91,15 +91,10 @@ void TypeRecordBuilder::writeEncodedUnsignedInteger(uint64_t Value) {
   }
 }
 
-void TypeRecordBuilder::writeNullTerminatedString(const char *Value) {
-  assert(Value != nullptr);
-
-  size_t Length = strlen(Value);
-  Stream.write(Value, Length);
-  writeUInt8(0);
-}
-
 void TypeRecordBuilder::writeNullTerminatedString(StringRef Value) {
+  // Microsoft's linker seems to have trouble with symbol names longer than
+  // 0xffd8 bytes.
+  Value = Value.substr(0, 0xffd8);
   Stream.write(Value.data(), Value.size());
   writeUInt8(0);
 }