From 355094ef06a3d47f0600e85744f6e995706b12d3 Mon Sep 17 00:00:00 2001
From: Argyrios Kyrtzidis <akyrtzi@gmail.com>
Date: Thu, 17 Jun 2010 10:52:18 +0000
Subject: [PATCH] Make sure parens/braces/brackets are correctly balanced.

In a line like:

(;

the semicolon leaves Parser:ParenCount unbalanced (it's 1 even though we stopped looking for a right paren).
This may affect later parsing and result in bad recovery for parsing errors.

llvm-svn: 106213
---
 clang/include/clang/Parse/Parser.h     |  1 +
 clang/lib/Parse/ParseDecl.cpp          |  2 ++
 clang/lib/Parse/ParseStmt.cpp          |  2 ++
 clang/lib/Parse/Parser.cpp             | 13 ++++++++++++-
 clang/lib/Parse/RAIIObjectsForParser.h | 17 +++++++++++++++++
 5 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
index 233ed1c0b83b..0ba348159ff1 100644
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -72,6 +72,7 @@ namespace prec {
 class Parser {
   friend class PragmaUnusedHandler;
   friend class ColonProtectionRAIIObject;
+  friend class ParenBraceBracketBalancer;
   PrettyStackTraceParserEntry CrashInfo;
 
   Preprocessor &PP;
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 65c42193f66e..ad1a690b4246 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -309,6 +309,8 @@ AttributeList* Parser::ParseMicrosoftTypeAttributes(AttributeList *CurrAttr) {
 Parser::DeclGroupPtrTy Parser::ParseDeclaration(unsigned Context,
                                                 SourceLocation &DeclEnd,
                                                 CXX0XAttributeList Attr) {
+  ParenBraceBracketBalancer BalancerRAIIObj(*this);
+  
   DeclPtrTy SingleDecl;
   switch (Tok.getKind()) {
   case tok::kw_template:
diff --git a/clang/lib/Parse/ParseStmt.cpp b/clang/lib/Parse/ParseStmt.cpp
index f0930a0a1a44..266b858109fa 100644
--- a/clang/lib/Parse/ParseStmt.cpp
+++ b/clang/lib/Parse/ParseStmt.cpp
@@ -77,6 +77,8 @@ Parser::OwningStmtResult
 Parser::ParseStatementOrDeclaration(bool OnlyStatement) {
   const char *SemiError = 0;
   OwningStmtResult Res(Actions);
+  
+  ParenBraceBracketBalancer BalancerRAIIObj(*this);
 
   CXX0XAttributeList Attr;
   if (getLang().CPlusPlus0x && isCXX0XAttributeSpecifier())
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
index 225a793af53a..7d999ac40846 100644
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -127,7 +127,16 @@ SourceLocation Parser::MatchRHSPunctuation(tok::TokenKind RHSTok,
   }
   Diag(Tok, DID);
   Diag(LHSLoc, diag::note_matching) << LHSName;
-  SkipUntil(RHSTok);
+  if (!SkipUntil(RHSTok)) {
+    // We stopped before finding a RHS token, e.g. we encountered a ';'.
+    // Balance Paren/Brace/Bracket counting. 
+    switch (RHSTok) {
+    default: break;
+    case tok::r_paren : assert(ParenCount > 0); --ParenCount; break;
+    case tok::r_brace : assert(BraceCount > 0); --BraceCount; break;
+    case tok::r_square: assert(BracketCount > 0); --BracketCount; break;
+    }
+  }
   return R;
 }
 
@@ -401,6 +410,8 @@ void Parser::ParseTranslationUnit() {
 ///
 /// [C++0x/GNU] 'extern' 'template' declaration
 Parser::DeclGroupPtrTy Parser::ParseExternalDeclaration(CXX0XAttributeList Attr) {
+  ParenBraceBracketBalancer BalancerRAIIObj(*this);
+  
   DeclPtrTy SingleDecl;
   switch (Tok.getKind()) {
   case tok::semi:
diff --git a/clang/lib/Parse/RAIIObjectsForParser.h b/clang/lib/Parse/RAIIObjectsForParser.h
index 06bbbc23a010..addc79508399 100644
--- a/clang/lib/Parse/RAIIObjectsForParser.h
+++ b/clang/lib/Parse/RAIIObjectsForParser.h
@@ -80,6 +80,23 @@ namespace clang {
     }
   };
   
+  /// \brief RAII object that makes sure paren/bracket/brace count is correct
+  /// after declaration/statement parsing, even when there's a parsing error.
+  class ParenBraceBracketBalancer {
+    Parser &P;
+    unsigned short ParenCount, BracketCount, BraceCount;
+  public:
+    ParenBraceBracketBalancer(Parser &p)
+      : P(p), ParenCount(p.ParenCount), BracketCount(p.BracketCount),
+        BraceCount(p.BraceCount) { }
+    
+    ~ParenBraceBracketBalancer() {
+      P.ParenCount = ParenCount;
+      P.BracketCount = BracketCount;
+      P.BraceCount = BraceCount;
+    }
+  };
+  
 } // end namespace clang
 
 #endif