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Diffstat (limited to 'lib/StaticAnalyzer/Checkers/IdenticalExprChecker.cpp')
| -rw-r--r-- | lib/StaticAnalyzer/Checkers/IdenticalExprChecker.cpp | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/lib/StaticAnalyzer/Checkers/IdenticalExprChecker.cpp b/lib/StaticAnalyzer/Checkers/IdenticalExprChecker.cpp new file mode 100644 index 0000000..e696e38 --- /dev/null +++ b/lib/StaticAnalyzer/Checkers/IdenticalExprChecker.cpp @@ -0,0 +1,226 @@ +//== IdenticalExprChecker.cpp - Identical expression checker----------------==// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +/// +/// \file +/// \brief This defines IdenticalExprChecker, a check that warns about +/// unintended use of identical expressions. +/// +/// It checks for use of identical expressions with comparison operators. +/// +//===----------------------------------------------------------------------===// + +#include "ClangSACheckers.h" +#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" +#include "clang/StaticAnalyzer/Core/Checker.h" +#include "clang/StaticAnalyzer/Core/CheckerManager.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" +#include "clang/AST/RecursiveASTVisitor.h" + +using namespace clang; +using namespace ento; + +static bool isIdenticalExpr(const ASTContext &Ctx, const Expr *Expr1, + const Expr *Expr2); +//===----------------------------------------------------------------------===// +// FindIdenticalExprVisitor - Identify nodes using identical expressions. +//===----------------------------------------------------------------------===// + +namespace { +class FindIdenticalExprVisitor + : public RecursiveASTVisitor<FindIdenticalExprVisitor> { +public: + explicit FindIdenticalExprVisitor(BugReporter &B, AnalysisDeclContext *A) + : BR(B), AC(A) {} + // FindIdenticalExprVisitor only visits nodes + // that are binary operators. + bool VisitBinaryOperator(const BinaryOperator *B); + +private: + BugReporter &BR; + AnalysisDeclContext *AC; +}; +} // end anonymous namespace + +bool FindIdenticalExprVisitor::VisitBinaryOperator(const BinaryOperator *B) { + BinaryOperator::Opcode Op = B->getOpcode(); + if (!BinaryOperator::isComparisonOp(Op)) + return true; + // + // Special case for floating-point representation. + // + // If expressions on both sides of comparison operator are of type float, + // then for some comparison operators no warning shall be + // reported even if the expressions are identical from a symbolic point of + // view. Comparison between expressions, declared variables and literals + // are treated differently. + // + // != and == between float literals that have the same value should NOT warn. + // < > between float literals that have the same value SHOULD warn. + // + // != and == between the same float declaration should NOT warn. + // < > between the same float declaration SHOULD warn. + // + // != and == between eq. expressions that evaluates into float + // should NOT warn. + // < > between eq. expressions that evaluates into float + // should NOT warn. + // + const Expr *LHS = B->getLHS()->IgnoreParenImpCasts(); + const Expr *RHS = B->getRHS()->IgnoreParenImpCasts(); + + const DeclRefExpr *DeclRef1 = dyn_cast<DeclRefExpr>(LHS); + const DeclRefExpr *DeclRef2 = dyn_cast<DeclRefExpr>(RHS); + const FloatingLiteral *FloatLit1 = dyn_cast<FloatingLiteral>(LHS); + const FloatingLiteral *FloatLit2 = dyn_cast<FloatingLiteral>(RHS); + if ((DeclRef1) && (DeclRef2)) { + if ((DeclRef1->getType()->hasFloatingRepresentation()) && + (DeclRef2->getType()->hasFloatingRepresentation())) { + if (DeclRef1->getDecl() == DeclRef2->getDecl()) { + if ((Op == BO_EQ) || (Op == BO_NE)) { + return true; + } + } + } + } else if ((FloatLit1) && (FloatLit2)) { + if (FloatLit1->getValue().bitwiseIsEqual(FloatLit2->getValue())) { + if ((Op == BO_EQ) || (Op == BO_NE)) { + return true; + } + } + } else if (LHS->getType()->hasFloatingRepresentation()) { + // If any side of comparison operator still has floating-point + // representation, then it's an expression. Don't warn. + // Here only LHS is checked since RHS will be implicit casted to float. + return true; + } else { + // No special case with floating-point representation, report as usual. + } + + if (isIdenticalExpr(AC->getASTContext(), B->getLHS(), B->getRHS())) { + PathDiagnosticLocation ELoc = + PathDiagnosticLocation::createOperatorLoc(B, BR.getSourceManager()); + StringRef Message; + if (((Op == BO_EQ) || (Op == BO_LE) || (Op == BO_GE))) + Message = "comparison of identical expressions always evaluates to true"; + else + Message = "comparison of identical expressions always evaluates to false"; + BR.EmitBasicReport(AC->getDecl(), "Compare of identical expressions", + categories::LogicError, Message, ELoc); + } + // We want to visit ALL nodes (subexpressions of binary comparison + // expressions too) that contains comparison operators. + // True is always returned to traverse ALL nodes. + return true; +} +/// \brief Determines whether two expression trees are identical regarding +/// operators and symbols. +/// +/// Exceptions: expressions containing macros or functions with possible side +/// effects are never considered identical. +/// Limitations: (t + u) and (u + t) are not considered identical. +/// t*(u + t) and t*u + t*t are not considered identical. +/// +static bool isIdenticalExpr(const ASTContext &Ctx, const Expr *Expr1, + const Expr *Expr2) { + // If Expr1 & Expr2 are of different class then they are not + // identical expression. + if (Expr1->getStmtClass() != Expr2->getStmtClass()) + return false; + // If Expr1 has side effects then don't warn even if expressions + // are identical. + if (Expr1->HasSideEffects(Ctx)) + return false; + // Is expression is based on macro then don't warn even if + // the expressions are identical. + if ((Expr1->getExprLoc().isMacroID()) || (Expr2->getExprLoc().isMacroID())) + return false; + // If all children of two expressions are identical, return true. + Expr::const_child_iterator I1 = Expr1->child_begin(); + Expr::const_child_iterator I2 = Expr2->child_begin(); + while (I1 != Expr1->child_end() && I2 != Expr2->child_end()) { + const Expr *Child1 = dyn_cast<Expr>(*I1); + const Expr *Child2 = dyn_cast<Expr>(*I2); + if (!Child1 || !Child2 || !isIdenticalExpr(Ctx, Child1, Child2)) + return false; + ++I1; + ++I2; + } + // If there are different number of children in the expressions, return false. + // (TODO: check if this is a redundant condition.) + if (I1 != Expr1->child_end()) + return false; + if (I2 != Expr2->child_end()) + return false; + + switch (Expr1->getStmtClass()) { + default: + return false; + case Stmt::ArraySubscriptExprClass: + case Stmt::CStyleCastExprClass: + case Stmt::ImplicitCastExprClass: + case Stmt::ParenExprClass: + return true; + case Stmt::BinaryOperatorClass: { + const BinaryOperator *BinOp1 = dyn_cast<BinaryOperator>(Expr1); + const BinaryOperator *BinOp2 = dyn_cast<BinaryOperator>(Expr2); + return BinOp1->getOpcode() == BinOp2->getOpcode(); + } + case Stmt::CharacterLiteralClass: { + const CharacterLiteral *CharLit1 = dyn_cast<CharacterLiteral>(Expr1); + const CharacterLiteral *CharLit2 = dyn_cast<CharacterLiteral>(Expr2); + return CharLit1->getValue() == CharLit2->getValue(); + } + case Stmt::DeclRefExprClass: { + const DeclRefExpr *DeclRef1 = dyn_cast<DeclRefExpr>(Expr1); + const DeclRefExpr *DeclRef2 = dyn_cast<DeclRefExpr>(Expr2); + return DeclRef1->getDecl() == DeclRef2->getDecl(); + } + case Stmt::IntegerLiteralClass: { + const IntegerLiteral *IntLit1 = dyn_cast<IntegerLiteral>(Expr1); + const IntegerLiteral *IntLit2 = dyn_cast<IntegerLiteral>(Expr2); + return IntLit1->getValue() == IntLit2->getValue(); + } + case Stmt::FloatingLiteralClass: { + const FloatingLiteral *FloatLit1 = dyn_cast<FloatingLiteral>(Expr1); + const FloatingLiteral *FloatLit2 = dyn_cast<FloatingLiteral>(Expr2); + return FloatLit1->getValue().bitwiseIsEqual(FloatLit2->getValue()); + } + case Stmt::MemberExprClass: { + const MemberExpr *MemberExpr1 = dyn_cast<MemberExpr>(Expr1); + const MemberExpr *MemberExpr2 = dyn_cast<MemberExpr>(Expr2); + return MemberExpr1->getMemberDecl() == MemberExpr2->getMemberDecl(); + } + case Stmt::UnaryOperatorClass: { + const UnaryOperator *UnaryOp1 = dyn_cast<UnaryOperator>(Expr1); + const UnaryOperator *UnaryOp2 = dyn_cast<UnaryOperator>(Expr2); + if (UnaryOp1->getOpcode() != UnaryOp2->getOpcode()) + return false; + return !UnaryOp1->isIncrementDecrementOp(); + } + } +} + +//===----------------------------------------------------------------------===// +// FindIdenticalExprChecker +//===----------------------------------------------------------------------===// + +namespace { +class FindIdenticalExprChecker : public Checker<check::ASTCodeBody> { +public: + void checkASTCodeBody(const Decl *D, AnalysisManager &Mgr, + BugReporter &BR) const { + FindIdenticalExprVisitor Visitor(BR, Mgr.getAnalysisDeclContext(D)); + Visitor.TraverseDecl(const_cast<Decl *>(D)); + } +}; +} // end anonymous namespace + +void ento::registerIdenticalExprChecker(CheckerManager &Mgr) { + Mgr.registerChecker<FindIdenticalExprChecker>(); +} |
