From e9440a3a3a21eb5b23d1c7377d043e8d4068b86a Mon Sep 17 00:00:00 2001
From: Jordan Rose <jordan_rose@apple.com>
Date: Thu, 13 Nov 2014 00:08:41 +0000
Subject: [PATCH] [Bitcode] AtEndOfStream should only check against the size if
 it's known.

This avoids an issue where AtEndOfStream mistakenly returns true at the /start/ of
a stream.

(In the rare case that the size is known and actually 0, the slow path will still
handle it correctly.)

llvm-svn: 221840
---
 include/llvm/Bitcode/BitstreamReader.h    |  2 +-
 unittests/Bitcode/BitstreamReaderTest.cpp | 56 +++++++++++++++++++++++
 unittests/Bitcode/CMakeLists.txt          |  1 +
 3 files changed, 58 insertions(+), 1 deletion(-)
 create mode 100644 unittests/Bitcode/BitstreamReaderTest.cpp

diff --git a/include/llvm/Bitcode/BitstreamReader.h b/include/llvm/Bitcode/BitstreamReader.h
index 6b9c858676e..41e50e1690d 100644
--- a/include/llvm/Bitcode/BitstreamReader.h
+++ b/include/llvm/Bitcode/BitstreamReader.h
@@ -227,7 +227,7 @@ public:
   bool AtEndOfStream() {
     if (BitsInCurWord != 0)
       return false;
-    if (Size == NextChar)
+    if (Size != 0 && Size == NextChar)
       return true;
     fillCurWord();
     return BitsInCurWord == 0;
diff --git a/unittests/Bitcode/BitstreamReaderTest.cpp b/unittests/Bitcode/BitstreamReaderTest.cpp
new file mode 100644
index 00000000000..b11d7fde774
--- /dev/null
+++ b/unittests/Bitcode/BitstreamReaderTest.cpp
@@ -0,0 +1,56 @@
+//===- BitstreamReaderTest.cpp - Tests for BitstreamReader ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Bitcode/BitstreamReader.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+TEST(BitstreamReaderTest, AtEndOfStream) {
+  uint8_t Bytes[4] = {
+    0x00, 0x01, 0x02, 0x03
+  };
+  BitstreamReader Reader(std::begin(Bytes), std::end(Bytes));
+  BitstreamCursor Cursor(Reader);
+
+  EXPECT_FALSE(Cursor.AtEndOfStream());
+  (void)Cursor.Read(8);
+  EXPECT_FALSE(Cursor.AtEndOfStream());
+  (void)Cursor.Read(24);
+  EXPECT_TRUE(Cursor.AtEndOfStream());
+
+  Cursor.JumpToBit(0);
+  EXPECT_FALSE(Cursor.AtEndOfStream());
+
+  Cursor.JumpToBit(32);
+  EXPECT_TRUE(Cursor.AtEndOfStream());
+}
+
+TEST(BitstreamReaderTest, AtEndOfStreamJump) {
+  uint8_t Bytes[4] = {
+    0x00, 0x01, 0x02, 0x03
+  };
+  BitstreamReader Reader(std::begin(Bytes), std::end(Bytes));
+  BitstreamCursor Cursor(Reader);
+
+  Cursor.JumpToBit(32);
+  EXPECT_TRUE(Cursor.AtEndOfStream());
+}
+
+TEST(BitstreamReaderTest, AtEndOfStreamEmpty) {
+  uint8_t Dummy = 0xFF;
+  BitstreamReader Reader(&Dummy, &Dummy);
+  BitstreamCursor Cursor(Reader);
+
+  EXPECT_TRUE(Cursor.AtEndOfStream());
+}
+
+} // end anonymous namespace
diff --git a/unittests/Bitcode/CMakeLists.txt b/unittests/Bitcode/CMakeLists.txt
index 7e9d1bc43fe..09cbcdc7284 100644
--- a/unittests/Bitcode/CMakeLists.txt
+++ b/unittests/Bitcode/CMakeLists.txt
@@ -8,4 +8,5 @@ set(LLVM_LINK_COMPONENTS
 
 add_llvm_unittest(BitcodeTests
   BitReaderTest.cpp
+  BitstreamReaderTest.cpp
   )