forked from OSchip/llvm-project
491 lines
18 KiB
C++
491 lines
18 KiB
C++
//== IdenticalExprChecker.cpp - Identical expression checker----------------==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// \brief This defines IdenticalExprChecker, a check that warns about
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/// unintended use of identical expressions.
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///
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/// It checks for use of identical expressions with comparison operators and
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/// inside conditional expressions.
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///
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//===----------------------------------------------------------------------===//
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#include "ClangSACheckers.h"
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#include "clang/AST/RecursiveASTVisitor.h"
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#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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using namespace clang;
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using namespace ento;
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static bool isIdenticalStmt(const ASTContext &Ctx, const Stmt *Stmt1,
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const Stmt *Stmt2, bool IgnoreSideEffects = false);
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//===----------------------------------------------------------------------===//
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// FindIdenticalExprVisitor - Identify nodes using identical expressions.
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//===----------------------------------------------------------------------===//
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namespace {
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class FindIdenticalExprVisitor
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: public RecursiveASTVisitor<FindIdenticalExprVisitor> {
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BugReporter &BR;
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const CheckerBase *Checker;
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AnalysisDeclContext *AC;
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public:
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explicit FindIdenticalExprVisitor(BugReporter &B,
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const CheckerBase *Checker,
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AnalysisDeclContext *A)
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: BR(B), Checker(Checker), AC(A) {}
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// FindIdenticalExprVisitor only visits nodes
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// that are binary operators, if statements or
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// conditional operators.
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bool VisitBinaryOperator(const BinaryOperator *B);
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bool VisitIfStmt(const IfStmt *I);
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bool VisitConditionalOperator(const ConditionalOperator *C);
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private:
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void reportIdenticalExpr(const BinaryOperator *B, bool CheckBitwise,
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ArrayRef<SourceRange> Sr);
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void checkBitwiseOrLogicalOp(const BinaryOperator *B, bool CheckBitwise);
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void checkComparisonOp(const BinaryOperator *B);
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};
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} // end anonymous namespace
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void FindIdenticalExprVisitor::reportIdenticalExpr(const BinaryOperator *B,
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bool CheckBitwise,
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ArrayRef<SourceRange> Sr) {
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StringRef Message;
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if (CheckBitwise)
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Message = "identical expressions on both sides of bitwise operator";
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else
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Message = "identical expressions on both sides of logical operator";
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PathDiagnosticLocation ELoc =
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PathDiagnosticLocation::createOperatorLoc(B, BR.getSourceManager());
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BR.EmitBasicReport(AC->getDecl(), Checker,
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"Use of identical expressions",
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categories::LogicError,
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Message, ELoc, Sr);
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}
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void FindIdenticalExprVisitor::checkBitwiseOrLogicalOp(const BinaryOperator *B,
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bool CheckBitwise) {
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SourceRange Sr[2];
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const Expr *LHS = B->getLHS();
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const Expr *RHS = B->getRHS();
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// Split operators as long as we still have operators to split on. We will
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// get called for every binary operator in an expression so there is no need
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// to check every one against each other here, just the right most one with
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// the others.
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while (const BinaryOperator *B2 = dyn_cast<BinaryOperator>(LHS)) {
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if (B->getOpcode() != B2->getOpcode())
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break;
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if (isIdenticalStmt(AC->getASTContext(), RHS, B2->getRHS())) {
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Sr[0] = RHS->getSourceRange();
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Sr[1] = B2->getRHS()->getSourceRange();
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reportIdenticalExpr(B, CheckBitwise, Sr);
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}
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LHS = B2->getLHS();
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}
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if (isIdenticalStmt(AC->getASTContext(), RHS, LHS)) {
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Sr[0] = RHS->getSourceRange();
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Sr[1] = LHS->getSourceRange();
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reportIdenticalExpr(B, CheckBitwise, Sr);
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}
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}
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bool FindIdenticalExprVisitor::VisitIfStmt(const IfStmt *I) {
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const Stmt *Stmt1 = I->getThen();
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const Stmt *Stmt2 = I->getElse();
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// Check for identical conditions:
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//
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// if (b) {
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// foo1();
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// } else if (b) {
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// foo2();
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// }
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if (Stmt1 && Stmt2) {
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const Expr *Cond1 = I->getCond();
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const Stmt *Else = Stmt2;
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while (const IfStmt *I2 = dyn_cast_or_null<IfStmt>(Else)) {
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const Expr *Cond2 = I2->getCond();
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if (isIdenticalStmt(AC->getASTContext(), Cond1, Cond2, false)) {
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SourceRange Sr = Cond1->getSourceRange();
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PathDiagnosticLocation ELoc(Cond2, BR.getSourceManager(), AC);
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BR.EmitBasicReport(AC->getDecl(), Checker, "Identical conditions",
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categories::LogicError,
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"expression is identical to previous condition",
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ELoc, Sr);
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}
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Else = I2->getElse();
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}
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}
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if (!Stmt1 || !Stmt2)
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return true;
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// Special handling for code like:
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//
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// if (b) {
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// i = 1;
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// } else
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// i = 1;
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if (const CompoundStmt *CompStmt = dyn_cast<CompoundStmt>(Stmt1)) {
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if (CompStmt->size() == 1)
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Stmt1 = CompStmt->body_back();
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}
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if (const CompoundStmt *CompStmt = dyn_cast<CompoundStmt>(Stmt2)) {
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if (CompStmt->size() == 1)
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Stmt2 = CompStmt->body_back();
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}
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if (isIdenticalStmt(AC->getASTContext(), Stmt1, Stmt2, true)) {
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PathDiagnosticLocation ELoc =
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PathDiagnosticLocation::createBegin(I, BR.getSourceManager(), AC);
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BR.EmitBasicReport(AC->getDecl(), Checker,
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"Identical branches",
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categories::LogicError,
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"true and false branches are identical", ELoc);
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}
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return true;
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}
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bool FindIdenticalExprVisitor::VisitBinaryOperator(const BinaryOperator *B) {
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BinaryOperator::Opcode Op = B->getOpcode();
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if (BinaryOperator::isBitwiseOp(Op))
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checkBitwiseOrLogicalOp(B, true);
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if (BinaryOperator::isLogicalOp(Op))
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checkBitwiseOrLogicalOp(B, false);
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if (BinaryOperator::isComparisonOp(Op))
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checkComparisonOp(B);
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// We want to visit ALL nodes (subexpressions of binary comparison
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// expressions too) that contains comparison operators.
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// True is always returned to traverse ALL nodes.
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return true;
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}
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void FindIdenticalExprVisitor::checkComparisonOp(const BinaryOperator *B) {
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BinaryOperator::Opcode Op = B->getOpcode();
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//
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// Special case for floating-point representation.
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//
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// If expressions on both sides of comparison operator are of type float,
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// then for some comparison operators no warning shall be
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// reported even if the expressions are identical from a symbolic point of
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// view. Comparison between expressions, declared variables and literals
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// are treated differently.
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//
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// != and == between float literals that have the same value should NOT warn.
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// < > between float literals that have the same value SHOULD warn.
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//
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// != and == between the same float declaration should NOT warn.
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// < > between the same float declaration SHOULD warn.
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//
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// != and == between eq. expressions that evaluates into float
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// should NOT warn.
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// < > between eq. expressions that evaluates into float
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// should NOT warn.
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//
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const Expr *LHS = B->getLHS()->IgnoreParenImpCasts();
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const Expr *RHS = B->getRHS()->IgnoreParenImpCasts();
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const DeclRefExpr *DeclRef1 = dyn_cast<DeclRefExpr>(LHS);
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const DeclRefExpr *DeclRef2 = dyn_cast<DeclRefExpr>(RHS);
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const FloatingLiteral *FloatLit1 = dyn_cast<FloatingLiteral>(LHS);
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const FloatingLiteral *FloatLit2 = dyn_cast<FloatingLiteral>(RHS);
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if ((DeclRef1) && (DeclRef2)) {
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if ((DeclRef1->getType()->hasFloatingRepresentation()) &&
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(DeclRef2->getType()->hasFloatingRepresentation())) {
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if (DeclRef1->getDecl() == DeclRef2->getDecl()) {
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if ((Op == BO_EQ) || (Op == BO_NE)) {
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return;
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}
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}
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}
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} else if ((FloatLit1) && (FloatLit2)) {
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if (FloatLit1->getValue().bitwiseIsEqual(FloatLit2->getValue())) {
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if ((Op == BO_EQ) || (Op == BO_NE)) {
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return;
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}
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}
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} else if (LHS->getType()->hasFloatingRepresentation()) {
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// If any side of comparison operator still has floating-point
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// representation, then it's an expression. Don't warn.
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// Here only LHS is checked since RHS will be implicit casted to float.
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return;
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} else {
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// No special case with floating-point representation, report as usual.
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}
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if (isIdenticalStmt(AC->getASTContext(), B->getLHS(), B->getRHS())) {
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PathDiagnosticLocation ELoc =
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PathDiagnosticLocation::createOperatorLoc(B, BR.getSourceManager());
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StringRef Message;
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if (((Op == BO_EQ) || (Op == BO_LE) || (Op == BO_GE)))
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Message = "comparison of identical expressions always evaluates to true";
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else
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Message = "comparison of identical expressions always evaluates to false";
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BR.EmitBasicReport(AC->getDecl(), Checker,
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"Compare of identical expressions",
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categories::LogicError, Message, ELoc);
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}
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}
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bool FindIdenticalExprVisitor::VisitConditionalOperator(
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const ConditionalOperator *C) {
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// Check if expressions in conditional expression are identical
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// from a symbolic point of view.
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if (isIdenticalStmt(AC->getASTContext(), C->getTrueExpr(),
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C->getFalseExpr(), true)) {
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PathDiagnosticLocation ELoc =
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PathDiagnosticLocation::createConditionalColonLoc(
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C, BR.getSourceManager());
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SourceRange Sr[2];
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Sr[0] = C->getTrueExpr()->getSourceRange();
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Sr[1] = C->getFalseExpr()->getSourceRange();
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BR.EmitBasicReport(
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AC->getDecl(), Checker,
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"Identical expressions in conditional expression",
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categories::LogicError,
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"identical expressions on both sides of ':' in conditional expression",
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ELoc, Sr);
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}
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// We want to visit ALL nodes (expressions in conditional
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// expressions too) that contains conditional operators,
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// thus always return true to traverse ALL nodes.
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return true;
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}
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/// \brief Determines whether two statement trees are identical regarding
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/// operators and symbols.
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///
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/// Exceptions: expressions containing macros or functions with possible side
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/// effects are never considered identical.
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/// Limitations: (t + u) and (u + t) are not considered identical.
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/// t*(u + t) and t*u + t*t are not considered identical.
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///
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static bool isIdenticalStmt(const ASTContext &Ctx, const Stmt *Stmt1,
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const Stmt *Stmt2, bool IgnoreSideEffects) {
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if (!Stmt1 || !Stmt2) {
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if (!Stmt1 && !Stmt2)
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return true;
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return false;
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}
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// If Stmt1 & Stmt2 are of different class then they are not
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// identical statements.
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if (Stmt1->getStmtClass() != Stmt2->getStmtClass())
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return false;
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const Expr *Expr1 = dyn_cast<Expr>(Stmt1);
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const Expr *Expr2 = dyn_cast<Expr>(Stmt2);
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if (Expr1 && Expr2) {
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// If Stmt1 has side effects then don't warn even if expressions
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// are identical.
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if (!IgnoreSideEffects && Expr1->HasSideEffects(Ctx))
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return false;
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// If either expression comes from a macro then don't warn even if
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// the expressions are identical.
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if ((Expr1->getExprLoc().isMacroID()) || (Expr2->getExprLoc().isMacroID()))
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return false;
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// If all children of two expressions are identical, return true.
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Expr::const_child_iterator I1 = Expr1->child_begin();
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Expr::const_child_iterator I2 = Expr2->child_begin();
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while (I1 != Expr1->child_end() && I2 != Expr2->child_end()) {
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if (!*I1 || !*I2 || !isIdenticalStmt(Ctx, *I1, *I2, IgnoreSideEffects))
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return false;
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++I1;
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++I2;
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}
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// If there are different number of children in the statements, return
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// false.
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if (I1 != Expr1->child_end())
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return false;
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if (I2 != Expr2->child_end())
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return false;
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}
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switch (Stmt1->getStmtClass()) {
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default:
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return false;
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case Stmt::CallExprClass:
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case Stmt::ArraySubscriptExprClass:
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case Stmt::ImplicitCastExprClass:
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case Stmt::ParenExprClass:
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case Stmt::BreakStmtClass:
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case Stmt::ContinueStmtClass:
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case Stmt::NullStmtClass:
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return true;
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case Stmt::CStyleCastExprClass: {
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const CStyleCastExpr* CastExpr1 = cast<CStyleCastExpr>(Stmt1);
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const CStyleCastExpr* CastExpr2 = cast<CStyleCastExpr>(Stmt2);
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return CastExpr1->getTypeAsWritten() == CastExpr2->getTypeAsWritten();
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}
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case Stmt::ReturnStmtClass: {
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const ReturnStmt *ReturnStmt1 = cast<ReturnStmt>(Stmt1);
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const ReturnStmt *ReturnStmt2 = cast<ReturnStmt>(Stmt2);
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return isIdenticalStmt(Ctx, ReturnStmt1->getRetValue(),
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ReturnStmt2->getRetValue(), IgnoreSideEffects);
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}
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case Stmt::ForStmtClass: {
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const ForStmt *ForStmt1 = cast<ForStmt>(Stmt1);
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const ForStmt *ForStmt2 = cast<ForStmt>(Stmt2);
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if (!isIdenticalStmt(Ctx, ForStmt1->getInit(), ForStmt2->getInit(),
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IgnoreSideEffects))
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return false;
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if (!isIdenticalStmt(Ctx, ForStmt1->getCond(), ForStmt2->getCond(),
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IgnoreSideEffects))
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return false;
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if (!isIdenticalStmt(Ctx, ForStmt1->getInc(), ForStmt2->getInc(),
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IgnoreSideEffects))
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return false;
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if (!isIdenticalStmt(Ctx, ForStmt1->getBody(), ForStmt2->getBody(),
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IgnoreSideEffects))
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return false;
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return true;
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}
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case Stmt::DoStmtClass: {
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const DoStmt *DStmt1 = cast<DoStmt>(Stmt1);
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const DoStmt *DStmt2 = cast<DoStmt>(Stmt2);
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if (!isIdenticalStmt(Ctx, DStmt1->getCond(), DStmt2->getCond(),
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IgnoreSideEffects))
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return false;
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if (!isIdenticalStmt(Ctx, DStmt1->getBody(), DStmt2->getBody(),
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IgnoreSideEffects))
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return false;
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return true;
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}
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case Stmt::WhileStmtClass: {
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const WhileStmt *WStmt1 = cast<WhileStmt>(Stmt1);
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const WhileStmt *WStmt2 = cast<WhileStmt>(Stmt2);
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if (!isIdenticalStmt(Ctx, WStmt1->getCond(), WStmt2->getCond(),
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IgnoreSideEffects))
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return false;
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if (!isIdenticalStmt(Ctx, WStmt1->getBody(), WStmt2->getBody(),
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IgnoreSideEffects))
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return false;
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return true;
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}
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case Stmt::IfStmtClass: {
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const IfStmt *IStmt1 = cast<IfStmt>(Stmt1);
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const IfStmt *IStmt2 = cast<IfStmt>(Stmt2);
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if (!isIdenticalStmt(Ctx, IStmt1->getCond(), IStmt2->getCond(),
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IgnoreSideEffects))
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return false;
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if (!isIdenticalStmt(Ctx, IStmt1->getThen(), IStmt2->getThen(),
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IgnoreSideEffects))
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return false;
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if (!isIdenticalStmt(Ctx, IStmt1->getElse(), IStmt2->getElse(),
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IgnoreSideEffects))
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return false;
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return true;
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}
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case Stmt::CompoundStmtClass: {
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const CompoundStmt *CompStmt1 = cast<CompoundStmt>(Stmt1);
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const CompoundStmt *CompStmt2 = cast<CompoundStmt>(Stmt2);
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if (CompStmt1->size() != CompStmt2->size())
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return false;
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CompoundStmt::const_body_iterator I1 = CompStmt1->body_begin();
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CompoundStmt::const_body_iterator I2 = CompStmt2->body_begin();
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while (I1 != CompStmt1->body_end() && I2 != CompStmt2->body_end()) {
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if (!isIdenticalStmt(Ctx, *I1, *I2, IgnoreSideEffects))
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return false;
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++I1;
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++I2;
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}
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return true;
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}
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case Stmt::CompoundAssignOperatorClass:
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case Stmt::BinaryOperatorClass: {
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const BinaryOperator *BinOp1 = cast<BinaryOperator>(Stmt1);
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const BinaryOperator *BinOp2 = cast<BinaryOperator>(Stmt2);
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return BinOp1->getOpcode() == BinOp2->getOpcode();
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}
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case Stmt::CharacterLiteralClass: {
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const CharacterLiteral *CharLit1 = cast<CharacterLiteral>(Stmt1);
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const CharacterLiteral *CharLit2 = cast<CharacterLiteral>(Stmt2);
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return CharLit1->getValue() == CharLit2->getValue();
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}
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case Stmt::DeclRefExprClass: {
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const DeclRefExpr *DeclRef1 = cast<DeclRefExpr>(Stmt1);
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const DeclRefExpr *DeclRef2 = cast<DeclRefExpr>(Stmt2);
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return DeclRef1->getDecl() == DeclRef2->getDecl();
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}
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case Stmt::IntegerLiteralClass: {
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const IntegerLiteral *IntLit1 = cast<IntegerLiteral>(Stmt1);
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const IntegerLiteral *IntLit2 = cast<IntegerLiteral>(Stmt2);
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return IntLit1->getValue() == IntLit2->getValue();
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}
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case Stmt::FloatingLiteralClass: {
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const FloatingLiteral *FloatLit1 = cast<FloatingLiteral>(Stmt1);
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const FloatingLiteral *FloatLit2 = cast<FloatingLiteral>(Stmt2);
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return FloatLit1->getValue().bitwiseIsEqual(FloatLit2->getValue());
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}
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case Stmt::StringLiteralClass: {
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const StringLiteral *StringLit1 = cast<StringLiteral>(Stmt1);
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const StringLiteral *StringLit2 = cast<StringLiteral>(Stmt2);
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return StringLit1->getString() == StringLit2->getString();
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}
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case Stmt::MemberExprClass: {
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const MemberExpr *MemberStmt1 = cast<MemberExpr>(Stmt1);
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const MemberExpr *MemberStmt2 = cast<MemberExpr>(Stmt2);
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return MemberStmt1->getMemberDecl() == MemberStmt2->getMemberDecl();
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}
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case Stmt::UnaryOperatorClass: {
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const UnaryOperator *UnaryOp1 = cast<UnaryOperator>(Stmt1);
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const UnaryOperator *UnaryOp2 = cast<UnaryOperator>(Stmt2);
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return UnaryOp1->getOpcode() == UnaryOp2->getOpcode();
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}
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}
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}
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//===----------------------------------------------------------------------===//
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// FindIdenticalExprChecker
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//===----------------------------------------------------------------------===//
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namespace {
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class FindIdenticalExprChecker : public Checker<check::ASTCodeBody> {
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public:
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void checkASTCodeBody(const Decl *D, AnalysisManager &Mgr,
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BugReporter &BR) const {
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FindIdenticalExprVisitor Visitor(BR, this, Mgr.getAnalysisDeclContext(D));
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Visitor.TraverseDecl(const_cast<Decl *>(D));
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}
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};
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} // end anonymous namespace
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void ento::registerIdenticalExprChecker(CheckerManager &Mgr) {
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Mgr.registerChecker<FindIdenticalExprChecker>();
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}
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