Fix an ASSERT in the scanner.

The assert when performing a push back on a two byte string was wrong.

Added a small regression test.
Review URL: http://codereview.chromium.org/173116

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2735 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/scanner.cc

@@ -183,7 +183,8 @@ uc32 TwoByteStringUTF16Buffer::Advance() {
 
 void TwoByteStringUTF16Buffer::PushBack(uc32 ch) {
   pos_--;
-  ASSERT(pos_ >= 0 && raw_data_[pos_] == ch);
+  ASSERT(pos_ >= Scanner::kCharacterLookaheadBufferSize);
+  ASSERT(raw_data_[pos_ - Scanner::kCharacterLookaheadBufferSize] == ch);
 }
 
 

src/scanner.h

@@ -212,6 +212,8 @@ class Scanner {
   static unibrow::Predicate<unibrow::LineTerminator, 128> kIsLineTerminator;
   static unibrow::Predicate<unibrow::WhiteSpace, 128> kIsWhiteSpace;
 
+  static const int kCharacterLookaheadBufferSize = 1;
+
  private:
   CharacterStreamUTF16Buffer char_stream_buffer_;
   TwoByteStringUTF16Buffer two_byte_string_buffer_;
@@ -242,8 +244,6 @@ class Scanner {
   bool has_line_terminator_before_next_;
   bool is_pre_parsing_;
 
-  static const int kCharacterLookaheadBufferSize = 1;
-
   // Literal buffer support
   void StartLiteral();
   void AddChar(uc32 ch);

test/cctest/test-api.cc

@@ -7150,6 +7150,30 @@ THREADED_TEST(MorphCompositeStringTest) {
 }
 
 
+TEST(CompileExternalTwoByteSource) {
+  v8::HandleScope scope;
+  LocalContext context;
+
+  // This is a very short list of sources, which currently is to check for a
+  // regression caused by r2703.
+  const char* ascii_sources[] = {
+    "0.5",
+    "-0.5",   // This mainly testes PushBack in the Scanner.
+    "--0.5",  // This mainly testes PushBack in the Scanner.
+    NULL
+  };
+
+  // Compile the sources as external two byte strings.
+  for (int i = 0; ascii_sources[i] != NULL; i++) {
+    uint16_t* two_byte_string = AsciiToTwoByteString(ascii_sources[i]);
+    UC16VectorResource uc16_resource(
+        i::Vector<const uint16_t>(two_byte_string, strlen(ascii_sources[i])));
+    v8::Local<v8::String> source = v8::String::NewExternal(&uc16_resource);
+    v8::Script::Compile(source);
+  }
+}
+
+
 class RegExpStringModificationTest {
  public:
   RegExpStringModificationTest()