Replace C++ bitfields with our own BitFields

src/scanner.cc

Index: src/scanner.cc
diff --git a/src/scanner.cc b/src/scanner.cc
index 8062faa2447403af9354c1304200401521ebb123..8fd1077bbf29125b6b569519bc65ea363ed89080 100644
--- a/src/scanner.cc
+++ b/src/scanner.cc
@@ -245,6 +245,8 @@ bool Scanner::SkipWhiteSpace() {
 
   while (true) {
     while (true) {
+      // The unicode cache accepts unsigned inputs.
+      if (c0_ < 0) break;

[Sven Panne, 2014/11/05 09:11:49]

How is this related to the bitfield fiddling?

[Jakob Kummerow, 2014/11/05 12:13:46]

As the comment says, the unicode_cache_ only accepts unsigned inputs. Since it's
now using BitField, it trips over a DCHECK that the implicitly-converted -1
(which signals EOS) can actually be stored.

       // Advance as long as character is a WhiteSpace or LineTerminator.
       // Remember if the latter is the case.
       if (unicode_cache_->IsLineTerminator(c0_)) {
@@ -625,14 +627,14 @@ void Scanner::Scan() {
         break;
 
       default:
-        if (unicode_cache_->IsIdentifierStart(c0_)) {
+        if (c0_ < 0) {
+          token = Token::EOS;

[Sven Panne, 2014/11/05 09:11:49]

Same here...

+        } else if (unicode_cache_->IsIdentifierStart(c0_)) {
           token = ScanIdentifierOrKeyword();
         } else if (IsDecimalDigit(c0_)) {
           token = ScanNumber(false);
         } else if (SkipWhiteSpace()) {
           token = Token::WHITESPACE;
-        } else if (c0_ < 0) {
-          token = Token::EOS;
         } else {
           token = Select(Token::ILLEGAL);
         }