Changeset 202768 in webkit for trunk/Source/JavaScriptCore/parser/Lexer.cpp

Timestamp:

Jul 1, 2016, 5:59:38 PM (9 years ago)

Author:

[email protected]

Message:

fix "ASSERTION FAILED: currentOffset() >= currentLineStartOffset()"
​https://bugs.webkit.org/show_bug.cgi?id=158572
<rdar://problem/26884092>

Reviewed by Mark Lam.

Source/JavaScriptCore:

There is a bug in our lexer when we notice the pattern:
<return|continue|break|...etc> // some comment here
Our code will say that the token for the comment is a semicolon.
This is the correct semantics, however, it would give the semicolon
a start offset of the comment, but it will give its line start offset
the newline after the comment. This breaks the invariant in the lexer/parser
that the offset for the current line starting point must be less than or equal to
than the start offset of any token on that line. This invariant was broken because
the line start offset was greater than the token start offset. To maintain this
invariant, we claim that the semicolon token is located where the comment starts,
and that its line start offset is the line start offset for the line with the
comment on it. There are other solutions that maintain this invariant, but this
solution provides the best error messages.

• parser/Lexer.cpp:

(JSC::Lexer<T>::lex):

• parser/Parser.h:

(JSC::Parser::internalSaveLexerState):

• tests/stress/obscure-error-message-dont-crash.js: Added.

(try.eval.or.catch):

LayoutTests:

• js/parser-syntax-check-expected.txt:
• js/script-tests/parser-syntax-check.js:

(invalid.or.break.catch):
(catch): Deleted.

File:

• trunk/Source/JavaScriptCore/parser/Lexer.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/parser/Lexer.cpp

@@ -1784 +1784 @@
     m_terminator = false;
 
+    auto fillTokenInfo = [&] (int lineNumber, int endOffset, int lineStartOffset, JSTextPosition endPosition) {
+        tokenLocation->line = lineNumber;
+        tokenLocation->endOffset = endOffset;
+        tokenLocation->lineStartOffset = lineStartOffset;
+        ASSERT(tokenLocation->endOffset >= tokenLocation->lineStartOffset);
+        tokenRecord->m_endPosition = endPosition;
+        m_lastToken = token;
+    };
+
 start:
     skipWhitespace();
@@ -2258 +2267 @@
 
 inSingleLineComment:
-    while (!isLineTerminator(m_current)) {
-        if (atEnd())
-            return EOFTOK;
-        shift();
-    }
-    shiftLineTerminator();
-    m_atLineStart = true;
-    m_terminator = true;
-    m_lineStart = m_code;
-    if (!lastTokenWasRestrKeyword())
-        goto start;
-
-    token = SEMICOLON;
-    // Fall through into returnToken.
+    {
+        auto lineNumber = m_lineNumber;
+        auto endOffset = currentOffset();
+        auto lineStartOffset = currentLineStartOffset();
+        auto endPosition = currentPosition();
+
+        while (!isLineTerminator(m_current)) {
+            if (atEnd())
+                return EOFTOK;
+            shift();
+        }
+        shiftLineTerminator();
+        m_atLineStart = true;
+        m_terminator = true;
+        m_lineStart = m_code;
+        if (!lastTokenWasRestrKeyword())
+            goto start;
+
+        token = SEMICOLON;
+        fillTokenInfo(lineNumber, endOffset, lineStartOffset, endPosition);
+        return token;
+    }
 
 returnToken:
-    tokenLocation->line = m_lineNumber;
-    tokenLocation->endOffset = currentOffset();
-    tokenLocation->lineStartOffset = currentLineStartOffset();
-    ASSERT(tokenLocation->endOffset >= tokenLocation->lineStartOffset);
-    tokenRecord->m_endPosition = currentPosition();
-    m_lastToken = token;
+    fillTokenInfo(m_lineNumber, currentOffset(), currentLineStartOffset(), currentPosition());
     return token;
 
 returnError:
     m_error = true;
-    tokenLocation->line = m_lineNumber;
-    tokenLocation->endOffset = currentOffset();
-    tokenLocation->lineStartOffset = currentLineStartOffset();
-    ASSERT(tokenLocation->endOffset >= tokenLocation->lineStartOffset);
-    tokenRecord->m_endPosition = currentPosition();
+    fillTokenInfo(m_lineNumber, currentOffset(), currentLineStartOffset(), currentPosition());
     RELEASE_ASSERT(token & ErrorTokenFlag);
     return token;