Fix reading of headers when using a streamable memory object.

Fixes bug where we computed the length of fields buffer on the size of a pointer, rather then the actual length of the field.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3485
R=dschuff@chromium.org

Review URL: https://codereview.chromium.org/17003002

2 files changed, 8 insertions, 6 deletions

diff --git a/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h b/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h
index 6e35f62067..8febf95564 100644
--- a/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h
+++ b/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h
@@ -22,7 +22,7 @@
 #include <vector>
 
 namespace llvm {
-class StreamingMemoryObject;
+class StreamableMemoryObject;
 
 // Class representing a variable-size metadata field in the bitcode header.
 // Also contains the list of known (typed) Tag IDs.
@@ -167,7 +167,7 @@ public:
 
   // \brief Read the PNaCl bitcode header, recording the fields found
   // in the header. Returns false if able to read (all of) the bitcode header.
-  bool Read(StreamingMemoryObject *Bytes);
+  bool Read(StreamableMemoryObject *Bytes);
 
   // \brief Returns the number of bytes read to consume the header.
   size_t getHeaderSize() { return HeaderSize; }
diff --git a/lib/Bitcode/NaCl/Reader/NaClBitcodeHeader.cpp b/lib/Bitcode/NaCl/Reader/NaClBitcodeHeader.cpp
index 5193417619..aa73b9cffa 100644
--- a/lib/Bitcode/NaCl/Reader/NaClBitcodeHeader.cpp
+++ b/lib/Bitcode/NaCl/Reader/NaClBitcodeHeader.cpp
@@ -187,7 +187,7 @@ bool NaClBitcodeHeader::Read(const unsigned char *&BufPtr,
   return false;
 }
 
-bool NaClBitcodeHeader::Read(StreamingMemoryObject *Bytes) {
+bool NaClBitcodeHeader::Read(StreamableMemoryObject *Bytes) {
   unsigned NumFields;
   unsigned NumBytes;
   {
@@ -197,12 +197,14 @@ bool NaClBitcodeHeader::Read(StreamingMemoryObject *Bytes) {
       return true;
   }
   uint8_t *Header = new uint8_t[NumBytes];
-  bool results =
+  bool failed =
       Bytes->readBytes(2 * WordSize, NumBytes, Header, NULL) ||
-      ReadFields(Header, Header + sizeof(Header), NumFields, NumBytes);
+      ReadFields(Header, Header + NumBytes, NumFields, NumBytes);
   delete[] Header;
+  if (failed)
+    return true;
   InstallFields();
-  return results;
+  return false;
 }
 
 NaClBitcodeHeaderField *