On Tue, Apr 16, 2013 at 6:40 AM, David Blaikie <[email protected]> wrote:
> > On Apr 10, 2013 10:04 AM, "Richard Trieu" <[email protected]> wrote: > > > > Streams commonly overload the << and >> operators for input and output. > However, these operators have higher precedence than comparison operators. > Code written like this: > > > > cout << 5 == 4; > > > > Is interpreted as: > > > > (cout << 5) == 4; > > > > Instead of: > > > > cout << (5 == 4); > > What sort of statistics on success rate do you have with this warning? I > wonder if it would find many intentional uses when dealing with numeric > user defined tyows,. > Prior to this patch, two reports of this type of bug were found and fixed. This warning has not triggered on any other code I've tested, true or false positive. > > > > http://llvm-reviews.chandlerc.com/D650 > > > > Files: > > lib/Sema/SemaExpr.cpp > > test/Sema/parentheses.cpp > > include/clang/Basic/DiagnosticSemaKinds.td > > include/clang/Basic/DiagnosticGroups.td > > > > Index: lib/Sema/SemaExpr.cpp > > =================================================================== > > --- lib/Sema/SemaExpr.cpp > > +++ lib/Sema/SemaExpr.cpp > > @@ -8819,6 +8819,27 @@ > > } > > } > > > > +static void DiagnoseShiftCompare(Sema &S, SourceLocation OpLoc, > > + Expr *LHSExpr, Expr *RHSExpr) { > > + CXXOperatorCallExpr *OCE = dyn_cast<CXXOperatorCallExpr>(LHSExpr); > > + if (!OCE) return; > > These early returns seem a little hard to spot in a fairly dense/flat > piece if code. Might benefit from putting the return on their own line > and/or some comments (or perhaps this is easy enough to read with syntax > highlighting) > > > + FunctionDecl *FD = OCE->getDirectCallee(); > > + if (!FD || !FD->isOverloadedOperator()) return; > > + OverloadedOperatorKind Kind = FD->getOverloadedOperator(); > > + if (Kind != OO_LessLess && Kind != OO_GreaterGreater) return; > > + S.Diag(OpLoc, diag::warn_overloaded_shift_in_comparison) > > + << LHSExpr->getSourceRange() << RHSExpr->getSourceRange() > > + << (Kind == OO_LessLess); > > + SuggestParentheses(S, OpLoc, > > + S.PDiag(diag::note_evaluate_comparison_first), > > + SourceRange(OCE->getArg(1)->getLocStart(), > > + RHSExpr->getLocEnd())); > > + SuggestParentheses(S, OCE->getOperatorLoc(), > > + S.PDiag(diag::note_precedence_silence) > > + << (Kind == OO_LessLess ? "<<" : ">>"), > > + OCE->getSourceRange()); > > +} > > + > > /// DiagnoseBinOpPrecedence - Emit warnings for expressions with tricky > > /// precedence. > > static void DiagnoseBinOpPrecedence(Sema &Self, BinaryOperatorKind Opc, > > @@ -8847,6 +8868,11 @@ > > DiagnoseAdditionInShift(Self, OpLoc, LHSExpr, Shift); > > DiagnoseAdditionInShift(Self, OpLoc, RHSExpr, Shift); > > } > > + > > + // Warn on overloaded shift operators and comparisons, such as: > > + // cout << 5 == 4; > > + if (BinaryOperator::isComparisonOp(Opc)) > > + DiagnoseShiftCompare(Self, OpLoc, LHSExpr, RHSExpr); > > } > > > > // Binary Operators. 'Tok' is the token for the operator. > > Index: test/Sema/parentheses.cpp > > =================================================================== > > --- test/Sema/parentheses.cpp > > +++ test/Sema/parentheses.cpp > > @@ -29,6 +29,12 @@ > > (void)(s << b ? "foo" : "bar"); // expected-warning {{operator '?:' > has lower precedence than '<<'}} \ > > // expected-note {{place parentheses > around the '?:' expression to evaluate it first}} \ > > // expected-note {{place parentheses > around the '<<' expression to silence this warning}} > > + (void)(s << 5 == 1); // expected-warning {{overloaded operator << has > lower precedence than comparison operator}} \ > > + // expected-note {{place parentheses around the > '<<' expression to silence this warning}} \ > > + // expected-note {{place parentheses around > comparison expression to evaluate it first}} > > + (void)(s >> 5 == 1); // expected-warning {{overloaded operator >> has > lower precedence than comparison operator}} \ > > + // expected-note {{place parentheses around the > '>>' expression to silence this warning}} \ > > + // expected-note {{place parentheses around > comparison expression to evaluate it first}} > > } > > > > struct S { > > Index: include/clang/Basic/DiagnosticSemaKinds.td > > =================================================================== > > --- include/clang/Basic/DiagnosticSemaKinds.td > > +++ include/clang/Basic/DiagnosticSemaKinds.td > > @@ -4025,6 +4025,13 @@ > > def warn_logical_and_in_logical_or : Warning< > > "'&&' within '||'">, InGroup<LogicalOpParentheses>; > > > > +def warn_overloaded_shift_in_comparison :Warning< > > + "overloaded operator %select{>>|<<}0 has lower precedence than " > > + "comparison operator">, > > + InGroup<OverloadedShiftOpParentheses>; > > +def note_evaluate_comparison_first :Note< > > + "place parentheses around comparison expression to evaluate it > first">; > > + > > def warn_addition_in_bitshift : Warning< > > "operator '%0' has lower precedence than '%1'; " > > "'%1' will be evaluated first">, InGroup<ShiftOpParentheses>; > > Index: include/clang/Basic/DiagnosticGroups.td > > =================================================================== > > --- include/clang/Basic/DiagnosticGroups.td > > +++ include/clang/Basic/DiagnosticGroups.td > > @@ -122,6 +122,7 @@ > > def BitwiseOpParentheses: DiagGroup<"bitwise-op-parentheses">; > > def LogicalOpParentheses: DiagGroup<"logical-op-parentheses">; > > def ShiftOpParentheses: DiagGroup<"shift-op-parentheses">; > > +def OverloadedShiftOpParentheses: > DiagGroup<"overloaded-shift-op-parentheses">; > > def DanglingElse: DiagGroup<"dangling-else">; > > def DanglingField : DiagGroup<"dangling-field">; > > def DistributedObjectModifiers : > DiagGroup<"distributed-object-modifiers">; > > @@ -352,6 +353,7 @@ > > [LogicalOpParentheses, > > BitwiseOpParentheses, > > ShiftOpParentheses, > > + OverloadedShiftOpParentheses, > > ParenthesesOnEquality, > > DanglingElse]>; > > > > _______________________________________________ > > cfe-commits mailing list > > [email protected] > > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits > > > >
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