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llvm-project/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp

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//===--- RedundantExpressionCheck.cpp - clang-tidy-------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "RedundantExpressionCheck.h"
#include "../utils/Matchers.h"
#include "../utils/OptionsUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Lex/Lexer.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/FormatVariadic.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <string>
#include <vector>
using namespace clang::ast_matchers;
using namespace clang::tidy::matchers;
namespace clang {
namespace tidy {
namespace misc {
namespace {
using llvm::APSInt;
static constexpr llvm::StringLiteral KnownBannedMacroNames[] = {
"EAGAIN",
"EWOULDBLOCK",
"SIGCLD",
"SIGCHLD",
};
static bool incrementWithoutOverflow(const APSInt &Value, APSInt &Result) {
Result = Value;
++Result;
return Value < Result;
}
static bool areEquivalentNameSpecifier(const NestedNameSpecifier *Left,
const NestedNameSpecifier *Right) {
llvm::FoldingSetNodeID LeftID, RightID;
Left->Profile(LeftID);
Right->Profile(RightID);
return LeftID == RightID;
}
static bool areEquivalentExpr(const Expr *Left, const Expr *Right) {
if (!Left || !Right)
return !Left && !Right;
Left = Left->IgnoreParens();
Right = Right->IgnoreParens();
// Compare classes.
if (Left->getStmtClass() != Right->getStmtClass())
return false;
// Compare children.
Expr::const_child_iterator LeftIter = Left->child_begin();
Expr::const_child_iterator RightIter = Right->child_begin();
while (LeftIter != Left->child_end() && RightIter != Right->child_end()) {
if (!areEquivalentExpr(dyn_cast_or_null<Expr>(*LeftIter),
dyn_cast_or_null<Expr>(*RightIter)))
return false;
++LeftIter;
++RightIter;
}
if (LeftIter != Left->child_end() || RightIter != Right->child_end())
return false;
// Perform extra checks.
switch (Left->getStmtClass()) {
default:
return false;
case Stmt::CharacterLiteralClass:
return cast<CharacterLiteral>(Left)->getValue() ==
cast<CharacterLiteral>(Right)->getValue();
case Stmt::IntegerLiteralClass: {
llvm::APInt LeftLit = cast<IntegerLiteral>(Left)->getValue();
llvm::APInt RightLit = cast<IntegerLiteral>(Right)->getValue();
return LeftLit.getBitWidth() == RightLit.getBitWidth() &&
LeftLit == RightLit;
}
case Stmt::FloatingLiteralClass:
return cast<FloatingLiteral>(Left)->getValue().bitwiseIsEqual(
cast<FloatingLiteral>(Right)->getValue());
case Stmt::StringLiteralClass:
return cast<StringLiteral>(Left)->getBytes() ==
cast<StringLiteral>(Right)->getBytes();
case Stmt::CXXOperatorCallExprClass:
return cast<CXXOperatorCallExpr>(Left)->getOperator() ==
cast<CXXOperatorCallExpr>(Right)->getOperator();
case Stmt::DependentScopeDeclRefExprClass:
if (cast<DependentScopeDeclRefExpr>(Left)->getDeclName() !=
cast<DependentScopeDeclRefExpr>(Right)->getDeclName())
return false;
return areEquivalentNameSpecifier(
cast<DependentScopeDeclRefExpr>(Left)->getQualifier(),
cast<DependentScopeDeclRefExpr>(Right)->getQualifier());
case Stmt::DeclRefExprClass:
return cast<DeclRefExpr>(Left)->getDecl() ==
cast<DeclRefExpr>(Right)->getDecl();
case Stmt::MemberExprClass:
return cast<MemberExpr>(Left)->getMemberDecl() ==
cast<MemberExpr>(Right)->getMemberDecl();
case Stmt::CXXFoldExprClass:
return cast<CXXFoldExpr>(Left)->getOperator() ==
cast<CXXFoldExpr>(Right)->getOperator();
case Stmt::CXXFunctionalCastExprClass:
case Stmt::CStyleCastExprClass:
return cast<ExplicitCastExpr>(Left)->getTypeAsWritten() ==
cast<ExplicitCastExpr>(Right)->getTypeAsWritten();
case Stmt::CallExprClass:
case Stmt::ImplicitCastExprClass:
case Stmt::ArraySubscriptExprClass:
return true;
case Stmt::UnaryOperatorClass:
if (cast<UnaryOperator>(Left)->isIncrementDecrementOp())
return false;
return cast<UnaryOperator>(Left)->getOpcode() ==
cast<UnaryOperator>(Right)->getOpcode();
case Stmt::BinaryOperatorClass:
return cast<BinaryOperator>(Left)->getOpcode() ==
cast<BinaryOperator>(Right)->getOpcode();
case Stmt::UnaryExprOrTypeTraitExprClass:
const auto *LeftUnaryExpr =
cast<UnaryExprOrTypeTraitExpr>(Left);
const auto *RightUnaryExpr =
cast<UnaryExprOrTypeTraitExpr>(Right);
if (LeftUnaryExpr->isArgumentType() && RightUnaryExpr->isArgumentType())
return LeftUnaryExpr->getArgumentType() ==
RightUnaryExpr->getArgumentType();
if (!LeftUnaryExpr->isArgumentType() && !RightUnaryExpr->isArgumentType())
return areEquivalentExpr(LeftUnaryExpr->getArgumentExpr(),
RightUnaryExpr->getArgumentExpr());
return false;
}
}
// For a given expression 'x', returns whether the ranges covered by the
// relational operators are equivalent (i.e. x <= 4 is equivalent to x < 5).
static bool areEquivalentRanges(BinaryOperatorKind OpcodeLHS,
const APSInt &ValueLHS,
BinaryOperatorKind OpcodeRHS,
const APSInt &ValueRHS) {
assert(APSInt::compareValues(ValueLHS, ValueRHS) <= 0 &&
"Values must be ordered");
// Handle the case where constants are the same: x <= 4 <==> x <= 4.
if (APSInt::compareValues(ValueLHS, ValueRHS) == 0)
return OpcodeLHS == OpcodeRHS;
// Handle the case where constants are off by one: x <= 4 <==> x < 5.
APSInt ValueLhsPlus1;
return ((OpcodeLHS == BO_LE && OpcodeRHS == BO_LT) ||
(OpcodeLHS == BO_GT && OpcodeRHS == BO_GE)) &&
incrementWithoutOverflow(ValueLHS, ValueLhsPlus1) &&
APSInt::compareValues(ValueLhsPlus1, ValueRHS) == 0;
}
// For a given expression 'x', returns whether the ranges covered by the
// relational operators are fully disjoint (i.e. x < 4 and x > 7).
static bool areExclusiveRanges(BinaryOperatorKind OpcodeLHS,
const APSInt &ValueLHS,
BinaryOperatorKind OpcodeRHS,
const APSInt &ValueRHS) {
assert(APSInt::compareValues(ValueLHS, ValueRHS) <= 0 &&
"Values must be ordered");
// Handle cases where the constants are the same.
if (APSInt::compareValues(ValueLHS, ValueRHS) == 0) {
switch (OpcodeLHS) {
case BO_EQ:
return OpcodeRHS == BO_NE || OpcodeRHS == BO_GT || OpcodeRHS == BO_LT;
case BO_NE:
return OpcodeRHS == BO_EQ;
case BO_LE:
return OpcodeRHS == BO_GT;
case BO_GE:
return OpcodeRHS == BO_LT;
case BO_LT:
return OpcodeRHS == BO_EQ || OpcodeRHS == BO_GT || OpcodeRHS == BO_GE;
case BO_GT:
return OpcodeRHS == BO_EQ || OpcodeRHS == BO_LT || OpcodeRHS == BO_LE;
default:
return false;
}
}
// Handle cases where the constants are different.
if ((OpcodeLHS == BO_EQ || OpcodeLHS == BO_LT || OpcodeLHS == BO_LE) &&
(OpcodeRHS == BO_EQ || OpcodeRHS == BO_GT || OpcodeRHS == BO_GE))
return true;
// Handle the case where constants are off by one: x > 5 && x < 6.
APSInt ValueLhsPlus1;
if (OpcodeLHS == BO_GT && OpcodeRHS == BO_LT &&
incrementWithoutOverflow(ValueLHS, ValueLhsPlus1) &&
APSInt::compareValues(ValueLhsPlus1, ValueRHS) == 0)
return true;
return false;
}
// Returns whether the ranges covered by the union of both relational
// expressions cover the whole domain (i.e. x < 10 and x > 0).
static bool rangesFullyCoverDomain(BinaryOperatorKind OpcodeLHS,
const APSInt &ValueLHS,
BinaryOperatorKind OpcodeRHS,
const APSInt &ValueRHS) {
assert(APSInt::compareValues(ValueLHS, ValueRHS) <= 0 &&
"Values must be ordered");
// Handle cases where the constants are the same: x < 5 || x >= 5.
if (APSInt::compareValues(ValueLHS, ValueRHS) == 0) {
switch (OpcodeLHS) {
case BO_EQ:
return OpcodeRHS == BO_NE;
case BO_NE:
return OpcodeRHS == BO_EQ;
case BO_LE:
return OpcodeRHS == BO_GT || OpcodeRHS == BO_GE;
case BO_LT:
return OpcodeRHS == BO_GE;
case BO_GE:
return OpcodeRHS == BO_LT || OpcodeRHS == BO_LE;
case BO_GT:
return OpcodeRHS == BO_LE;
default:
return false;
}
}
// Handle the case where constants are off by one: x <= 4 || x >= 5.
APSInt ValueLhsPlus1;
if (OpcodeLHS == BO_LE && OpcodeRHS == BO_GE &&
incrementWithoutOverflow(ValueLHS, ValueLhsPlus1) &&
APSInt::compareValues(ValueLhsPlus1, ValueRHS) == 0)
return true;
// Handle cases where the constants are different: x > 4 || x <= 7.
if ((OpcodeLHS == BO_GT || OpcodeLHS == BO_GE) &&
(OpcodeRHS == BO_LT || OpcodeRHS == BO_LE))
return true;
// Handle cases where constants are different but both ops are !=, like:
// x != 5 || x != 10
if (OpcodeLHS == BO_NE && OpcodeRHS == BO_NE)
return true;
return false;
}
static bool rangeSubsumesRange(BinaryOperatorKind OpcodeLHS,
const APSInt &ValueLHS,
BinaryOperatorKind OpcodeRHS,
const APSInt &ValueRHS) {
int Comparison = APSInt::compareValues(ValueLHS, ValueRHS);
switch (OpcodeLHS) {
case BO_EQ:
return OpcodeRHS == BO_EQ && Comparison == 0;
case BO_NE:
return (OpcodeRHS == BO_NE && Comparison == 0) ||
(OpcodeRHS == BO_EQ && Comparison != 0) ||
(OpcodeRHS == BO_LT && Comparison >= 0) ||
(OpcodeRHS == BO_LE && Comparison > 0) ||
(OpcodeRHS == BO_GT && Comparison <= 0) ||
(OpcodeRHS == BO_GE && Comparison < 0);
case BO_LT:
return ((OpcodeRHS == BO_LT && Comparison >= 0) ||
(OpcodeRHS == BO_LE && Comparison > 0) ||
(OpcodeRHS == BO_EQ && Comparison > 0));
case BO_GT:
return ((OpcodeRHS == BO_GT && Comparison <= 0) ||
(OpcodeRHS == BO_GE && Comparison < 0) ||
(OpcodeRHS == BO_EQ && Comparison < 0));
case BO_LE:
return (OpcodeRHS == BO_LT || OpcodeRHS == BO_LE || OpcodeRHS == BO_EQ) &&
Comparison >= 0;
case BO_GE:
return (OpcodeRHS == BO_GT || OpcodeRHS == BO_GE || OpcodeRHS == BO_EQ) &&
Comparison <= 0;
default:
return false;
}
}
static void transformSubToCanonicalAddExpr(BinaryOperatorKind &Opcode,
APSInt &Value) {
if (Opcode == BO_Sub) {
Opcode = BO_Add;
Value = -Value;
}
}
// to use in the template below
static OverloadedOperatorKind getOp(const BinaryOperator *Op) {
return BinaryOperator::getOverloadedOperator(Op->getOpcode());
}
static OverloadedOperatorKind getOp(const CXXOperatorCallExpr *Op) {
if (Op->getNumArgs() != 2)
return OO_None;
return Op->getOperator();
}
static std::pair<const Expr *, const Expr *>
getOperands(const BinaryOperator *Op) {
return {Op->getLHS()->IgnoreParenImpCasts(),
Op->getRHS()->IgnoreParenImpCasts()};
}
static std::pair<const Expr *, const Expr *>
getOperands(const CXXOperatorCallExpr *Op) {
return {Op->getArg(0)->IgnoreParenImpCasts(),
Op->getArg(1)->IgnoreParenImpCasts()};
}
template <typename TExpr>
static const TExpr *checkOpKind(const Expr *TheExpr,
OverloadedOperatorKind OpKind) {
const auto *AsTExpr = dyn_cast_or_null<TExpr>(TheExpr);
if (AsTExpr && getOp(AsTExpr) == OpKind)
return AsTExpr;
return nullptr;
}
// returns true if a subexpression has two directly equivalent operands and
// is already handled by operands/parametersAreEquivalent
template <typename TExpr, unsigned N>
static bool collectOperands(const Expr *Part,
SmallVector<const Expr *, N> &AllOperands,
OverloadedOperatorKind OpKind) {
if (const auto *BinOp = checkOpKind<TExpr>(Part, OpKind)) {
const std::pair<const Expr *, const Expr *> Operands = getOperands(BinOp);
if (areEquivalentExpr(Operands.first, Operands.second))
return true;
return collectOperands<TExpr>(Operands.first, AllOperands, OpKind) ||
collectOperands<TExpr>(Operands.second, AllOperands, OpKind);
}
AllOperands.push_back(Part);
return false;
}
template <typename TExpr>
static bool hasSameOperatorParent(const Expr *TheExpr,
OverloadedOperatorKind OpKind,
ASTContext &Context) {
// IgnoreParenImpCasts logic in reverse: skip surrounding uninteresting nodes
const DynTypedNodeList Parents = Context.getParents(*TheExpr);
for (DynTypedNode DynParent : Parents) {
if (const auto *Parent = DynParent.get<Expr>()) {
bool Skip = isa<ParenExpr>(Parent) || isa<ImplicitCastExpr>(Parent) ||
isa<FullExpr>(Parent) ||
isa<MaterializeTemporaryExpr>(Parent);
if (Skip && hasSameOperatorParent<TExpr>(Parent, OpKind, Context))
return true;
if (checkOpKind<TExpr>(Parent, OpKind))
return true;
}
}
return false;
}
template <typename TExpr>
static bool
markDuplicateOperands(const TExpr *TheExpr,
ast_matchers::internal::BoundNodesTreeBuilder *Builder,
ASTContext &Context) {
const OverloadedOperatorKind OpKind = getOp(TheExpr);
if (OpKind == OO_None)
return false;
// if there are no nested operators of the same kind, it's handled by
// operands/parametersAreEquivalent
const std::pair<const Expr *, const Expr *> Operands = getOperands(TheExpr);
if (!(checkOpKind<TExpr>(Operands.first, OpKind) ||
checkOpKind<TExpr>(Operands.second, OpKind)))
return false;
// if parent is the same kind of operator, it's handled by a previous call to
// markDuplicateOperands
if (hasSameOperatorParent<TExpr>(TheExpr, OpKind, Context))
return false;
SmallVector<const Expr *, 4> AllOperands;
if (collectOperands<TExpr>(Operands.first, AllOperands, OpKind))
return false;
if (collectOperands<TExpr>(Operands.second, AllOperands, OpKind))
return false;
size_t NumOperands = AllOperands.size();
llvm::SmallBitVector Duplicates(NumOperands);
for (size_t I = 0; I < NumOperands; I++) {
if (Duplicates[I])
continue;
bool FoundDuplicates = false;
for (size_t J = I + 1; J < NumOperands; J++) {
if (AllOperands[J]->HasSideEffects(Context))
break;
if (areEquivalentExpr(AllOperands[I], AllOperands[J])) {
FoundDuplicates = true;
Duplicates.set(J);
Builder->setBinding(SmallString<11>(llvm::formatv("duplicate{0}", J)),
DynTypedNode::create(*AllOperands[J]));
}
}
if (FoundDuplicates)
Builder->setBinding(SmallString<11>(llvm::formatv("duplicate{0}", I)),
DynTypedNode::create(*AllOperands[I]));
}
return Duplicates.any();
}
AST_MATCHER(Expr, isIntegerConstantExpr) {
if (Node.isInstantiationDependent())
return false;
return Node.isIntegerConstantExpr(Finder->getASTContext());
}
AST_MATCHER(BinaryOperator, operandsAreEquivalent) {
return areEquivalentExpr(Node.getLHS(), Node.getRHS());
}
AST_MATCHER(BinaryOperator, nestedOperandsAreEquivalent) {
return markDuplicateOperands(&Node, Builder, Finder->getASTContext());
}
AST_MATCHER(ConditionalOperator, expressionsAreEquivalent) {
return areEquivalentExpr(Node.getTrueExpr(), Node.getFalseExpr());
}
AST_MATCHER(CallExpr, parametersAreEquivalent) {
return Node.getNumArgs() == 2 &&
areEquivalentExpr(Node.getArg(0), Node.getArg(1));
}
AST_MATCHER(CXXOperatorCallExpr, nestedParametersAreEquivalent) {
return markDuplicateOperands(&Node, Builder, Finder->getASTContext());
}
AST_MATCHER(BinaryOperator, binaryOperatorIsInMacro) {
return Node.getOperatorLoc().isMacroID();
}
AST_MATCHER(ConditionalOperator, conditionalOperatorIsInMacro) {
return Node.getQuestionLoc().isMacroID() || Node.getColonLoc().isMacroID();
}
AST_MATCHER(Expr, isMacro) { return Node.getExprLoc().isMacroID(); }
AST_MATCHER_P(Expr, expandedByMacro, ArrayRef<llvm::StringLiteral>, Names) {
const SourceManager &SM = Finder->getASTContext().getSourceManager();
const LangOptions &LO = Finder->getASTContext().getLangOpts();
SourceLocation Loc = Node.getExprLoc();
while (Loc.isMacroID()) {
StringRef MacroName = Lexer::getImmediateMacroName(Loc, SM, LO);
if (llvm::is_contained(Names, MacroName))
return true;
Loc = SM.getImmediateMacroCallerLoc(Loc);
}
return false;
}
// Returns a matcher for integer constant expressions.
static ast_matchers::internal::Matcher<Expr>
matchIntegerConstantExpr(StringRef Id) {
std::string CstId = (Id + "-const").str();
return expr(isIntegerConstantExpr()).bind(CstId);
}
// Retrieves the integer expression matched by 'matchIntegerConstantExpr' with
// name 'Id' and stores it into 'ConstExpr', the value of the expression is
// stored into `Value`.
static bool retrieveIntegerConstantExpr(const MatchFinder::MatchResult &Result,
StringRef Id, APSInt &Value,
const Expr *&ConstExpr) {
std::string CstId = (Id + "-const").str();
ConstExpr = Result.Nodes.getNodeAs<Expr>(CstId);
if (!ConstExpr)
return false;
Optional<llvm::APSInt> R = ConstExpr->getIntegerConstantExpr(*Result.Context);
if (!R)
return false;
Value = *R;
return true;
}
// Overloaded `retrieveIntegerConstantExpr` for compatibility.
static bool retrieveIntegerConstantExpr(const MatchFinder::MatchResult &Result,
StringRef Id, APSInt &Value) {
const Expr *ConstExpr = nullptr;
return retrieveIntegerConstantExpr(Result, Id, Value, ConstExpr);
}
// Returns a matcher for symbolic expressions (matches every expression except
// ingeter constant expressions).
static ast_matchers::internal::Matcher<Expr> matchSymbolicExpr(StringRef Id) {
std::string SymId = (Id + "-sym").str();
return ignoringParenImpCasts(
expr(unless(isIntegerConstantExpr())).bind(SymId));
}
// Retrieves the expression matched by 'matchSymbolicExpr' with name 'Id' and
// stores it into 'SymExpr'.
static bool retrieveSymbolicExpr(const MatchFinder::MatchResult &Result,
StringRef Id, const Expr *&SymExpr) {
std::string SymId = (Id + "-sym").str();
if (const auto *Node = Result.Nodes.getNodeAs<Expr>(SymId)) {
SymExpr = Node;
return true;
}
return false;
}
// Match a binary operator between a symbolic expression and an integer constant
// expression.
static ast_matchers::internal::Matcher<Expr>
matchBinOpIntegerConstantExpr(StringRef Id) {
const auto BinOpCstExpr =
expr(anyOf(binaryOperator(hasAnyOperatorName("+", "|", "&"),
hasOperands(matchSymbolicExpr(Id),
matchIntegerConstantExpr(Id))),
binaryOperator(hasOperatorName("-"),
hasLHS(matchSymbolicExpr(Id)),
hasRHS(matchIntegerConstantExpr(Id)))))
.bind(Id);
return ignoringParenImpCasts(BinOpCstExpr);
}
// Retrieves sub-expressions matched by 'matchBinOpIntegerConstantExpr' with
// name 'Id'.
static bool
retrieveBinOpIntegerConstantExpr(const MatchFinder::MatchResult &Result,
StringRef Id, BinaryOperatorKind &Opcode,
const Expr *&Symbol, APSInt &Value) {
if (const auto *BinExpr = Result.Nodes.getNodeAs<BinaryOperator>(Id)) {
Opcode = BinExpr->getOpcode();
return retrieveSymbolicExpr(Result, Id, Symbol) &&
retrieveIntegerConstantExpr(Result, Id, Value);
}
return false;
}
// Matches relational expressions: 'Expr <op> k' (i.e. x < 2, x != 3, 12 <= x).
static ast_matchers::internal::Matcher<Expr>
matchRelationalIntegerConstantExpr(StringRef Id) {
std::string CastId = (Id + "-cast").str();
std::string SwapId = (Id + "-swap").str();
std::string NegateId = (Id + "-negate").str();
std::string OverloadId = (Id + "-overload").str();
const auto RelationalExpr = ignoringParenImpCasts(binaryOperator(
isComparisonOperator(), expr().bind(Id),
anyOf(allOf(hasLHS(matchSymbolicExpr(Id)),
hasRHS(matchIntegerConstantExpr(Id))),
allOf(hasLHS(matchIntegerConstantExpr(Id)),
hasRHS(matchSymbolicExpr(Id)), expr().bind(SwapId)))));
// A cast can be matched as a comparator to zero. (i.e. if (x) is equivalent
// to if (x != 0)).
const auto CastExpr =
implicitCastExpr(hasCastKind(CK_IntegralToBoolean),
hasSourceExpression(matchSymbolicExpr(Id)))
.bind(CastId);
const auto NegateRelationalExpr =
unaryOperator(hasOperatorName("!"),
hasUnaryOperand(anyOf(CastExpr, RelationalExpr)))
.bind(NegateId);
// Do not bind to double negation.
const auto NegateNegateRelationalExpr =
unaryOperator(hasOperatorName("!"),
hasUnaryOperand(unaryOperator(
hasOperatorName("!"),
hasUnaryOperand(anyOf(CastExpr, RelationalExpr)))));
const auto OverloadedOperatorExpr =
cxxOperatorCallExpr(
hasAnyOverloadedOperatorName("==", "!=", "<", "<=", ">", ">="),
// Filter noisy false positives.
unless(isMacro()), unless(isInTemplateInstantiation()))
.bind(OverloadId);
return anyOf(RelationalExpr, CastExpr, NegateRelationalExpr,
NegateNegateRelationalExpr, OverloadedOperatorExpr);
}
// Checks whether a function param is non constant reference type, and may
// be modified in the function.
static bool isNonConstReferenceType(QualType ParamType) {
return ParamType->isReferenceType() &&
!ParamType.getNonReferenceType().isConstQualified();
}
// Checks whether the arguments of an overloaded operator can be modified in the
// function.
// For operators that take an instance and a constant as arguments, only the
// first argument (the instance) needs to be checked, since the constant itself
// is a temporary expression. Whether the second parameter is checked is
// controlled by the parameter `ParamsToCheckCount`.
static bool
canOverloadedOperatorArgsBeModified(const CXXOperatorCallExpr *OperatorCall,
bool CheckSecondParam) {
const auto *OperatorDecl =
dyn_cast_or_null<FunctionDecl>(OperatorCall->getCalleeDecl());
// if we can't find the declaration, conservatively assume it can modify
// arguments
if (!OperatorDecl)
return true;
unsigned ParamCount = OperatorDecl->getNumParams();
// Overloaded operators declared inside a class have only one param.
// These functions must be declared const in order to not be able to modify
// the instance of the class they are called through.
if (ParamCount == 1 &&
!OperatorDecl->getType()->castAs<FunctionType>()->isConst())
return true;
if (isNonConstReferenceType(OperatorDecl->getParamDecl(0)->getType()))
return true;
return CheckSecondParam && ParamCount == 2 &&
isNonConstReferenceType(OperatorDecl->getParamDecl(1)->getType());
}
// Retrieves sub-expressions matched by 'matchRelationalIntegerConstantExpr'
// with name 'Id'.
static bool retrieveRelationalIntegerConstantExpr(
const MatchFinder::MatchResult &Result, StringRef Id,
const Expr *&OperandExpr, BinaryOperatorKind &Opcode, const Expr *&Symbol,
APSInt &Value, const Expr *&ConstExpr) {
std::string CastId = (Id + "-cast").str();
std::string SwapId = (Id + "-swap").str();
std::string NegateId = (Id + "-negate").str();
std::string OverloadId = (Id + "-overload").str();
if (const auto *Bin = Result.Nodes.getNodeAs<BinaryOperator>(Id)) {
// Operand received with explicit comparator.
Opcode = Bin->getOpcode();
OperandExpr = Bin;
if (!retrieveIntegerConstantExpr(Result, Id, Value, ConstExpr))
return false;
} else if (const auto *Cast = Result.Nodes.getNodeAs<CastExpr>(CastId)) {
// Operand received with implicit comparator (cast).
Opcode = BO_NE;
OperandExpr = Cast;
Value = APSInt(32, false);
} else if (const auto *OverloadedOperatorExpr =
Result.Nodes.getNodeAs<CXXOperatorCallExpr>(OverloadId)) {
if (canOverloadedOperatorArgsBeModified(OverloadedOperatorExpr, false))
return false;
if (const auto *Arg = OverloadedOperatorExpr->getArg(1)) {
if (!Arg->isValueDependent() &&
!Arg->isIntegerConstantExpr(*Result.Context))
return false;
}
Symbol = OverloadedOperatorExpr->getArg(0);
OperandExpr = OverloadedOperatorExpr;
Opcode = BinaryOperator::getOverloadedOpcode(OverloadedOperatorExpr->getOperator());
return BinaryOperator::isComparisonOp(Opcode);
} else {
return false;
}
if (!retrieveSymbolicExpr(Result, Id, Symbol))
return false;
if (Result.Nodes.getNodeAs<Expr>(SwapId))
Opcode = BinaryOperator::reverseComparisonOp(Opcode);
if (Result.Nodes.getNodeAs<Expr>(NegateId))
Opcode = BinaryOperator::negateComparisonOp(Opcode);
return true;
}
// Checks for expressions like (X == 4) && (Y != 9)
static bool areSidesBinaryConstExpressions(const BinaryOperator *&BinOp, const ASTContext *AstCtx) {
const auto *LhsBinOp = dyn_cast<BinaryOperator>(BinOp->getLHS());
const auto *RhsBinOp = dyn_cast<BinaryOperator>(BinOp->getRHS());
if (!LhsBinOp || !RhsBinOp)
return false;
auto IsIntegerConstantExpr = [AstCtx](const Expr *E) {
return !E->isValueDependent() && E->isIntegerConstantExpr(*AstCtx);
};
if ((IsIntegerConstantExpr(LhsBinOp->getLHS()) ||
IsIntegerConstantExpr(LhsBinOp->getRHS())) &&
(IsIntegerConstantExpr(RhsBinOp->getLHS()) ||
IsIntegerConstantExpr(RhsBinOp->getRHS())))
return true;
return false;
}
// Retrieves integer constant subexpressions from binary operator expressions
// that have two equivalent sides.
// E.g.: from (X == 5) && (X == 5) retrieves 5 and 5.
static bool retrieveConstExprFromBothSides(const BinaryOperator *&BinOp,
BinaryOperatorKind &MainOpcode,
BinaryOperatorKind &SideOpcode,
const Expr *&LhsConst,
const Expr *&RhsConst,
const ASTContext *AstCtx) {
assert(areSidesBinaryConstExpressions(BinOp, AstCtx) &&
"Both sides of binary operator must be constant expressions!");
MainOpcode = BinOp->getOpcode();
const auto *BinOpLhs = cast<BinaryOperator>(BinOp->getLHS());
const auto *BinOpRhs = cast<BinaryOperator>(BinOp->getRHS());
auto IsIntegerConstantExpr = [AstCtx](const Expr *E) {
return !E->isValueDependent() && E->isIntegerConstantExpr(*AstCtx);
};
LhsConst = IsIntegerConstantExpr(BinOpLhs->getLHS()) ? BinOpLhs->getLHS()
: BinOpLhs->getRHS();
RhsConst = IsIntegerConstantExpr(BinOpRhs->getLHS()) ? BinOpRhs->getLHS()
: BinOpRhs->getRHS();
if (!LhsConst || !RhsConst)
return false;
assert(BinOpLhs->getOpcode() == BinOpRhs->getOpcode() &&
"Sides of the binary operator must be equivalent expressions!");
SideOpcode = BinOpLhs->getOpcode();
return true;
}
static bool isSameRawIdentifierToken(const Token &T1, const Token &T2,
const SourceManager &SM) {
if (T1.getKind() != T2.getKind())
return false;
if (T1.isNot(tok::raw_identifier))
return true;
if (T1.getLength() != T2.getLength())
return false;
return StringRef(SM.getCharacterData(T1.getLocation()), T1.getLength()) ==
StringRef(SM.getCharacterData(T2.getLocation()), T2.getLength());
}
bool isTokAtEndOfExpr(SourceRange ExprSR, Token T, const SourceManager &SM) {
return SM.getExpansionLoc(ExprSR.getEnd()) == T.getLocation();
}
/// Returns true if both LhsEpxr and RhsExpr are
/// macro expressions and they are expanded
/// from different macros.
static bool areExprsFromDifferentMacros(const Expr *LhsExpr,
const Expr *RhsExpr,
const ASTContext *AstCtx) {
if (!LhsExpr || !RhsExpr)
return false;
SourceRange Lsr = LhsExpr->getSourceRange();
SourceRange Rsr = RhsExpr->getSourceRange();
if (!Lsr.getBegin().isMacroID() || !Rsr.getBegin().isMacroID())
return false;
const SourceManager &SM = AstCtx->getSourceManager();
const LangOptions &LO = AstCtx->getLangOpts();
std::pair<FileID, unsigned> LsrLocInfo =
SM.getDecomposedLoc(SM.getExpansionLoc(Lsr.getBegin()));
std::pair<FileID, unsigned> RsrLocInfo =
SM.getDecomposedLoc(SM.getExpansionLoc(Rsr.getBegin()));
llvm::MemoryBufferRef MB = SM.getBufferOrFake(LsrLocInfo.first);
const char *LTokenPos = MB.getBufferStart() + LsrLocInfo.second;
const char *RTokenPos = MB.getBufferStart() + RsrLocInfo.second;
Lexer LRawLex(SM.getLocForStartOfFile(LsrLocInfo.first), LO,
MB.getBufferStart(), LTokenPos, MB.getBufferEnd());
Lexer RRawLex(SM.getLocForStartOfFile(RsrLocInfo.first), LO,
MB.getBufferStart(), RTokenPos, MB.getBufferEnd());
Token LTok, RTok;
do { // Compare the expressions token-by-token.
LRawLex.LexFromRawLexer(LTok);
RRawLex.LexFromRawLexer(RTok);
} while (!LTok.is(tok::eof) && !RTok.is(tok::eof) &&
isSameRawIdentifierToken(LTok, RTok, SM) &&
!isTokAtEndOfExpr(Lsr, LTok, SM) &&
!isTokAtEndOfExpr(Rsr, RTok, SM));
return (!isTokAtEndOfExpr(Lsr, LTok, SM) ||
!isTokAtEndOfExpr(Rsr, RTok, SM)) ||
!isSameRawIdentifierToken(LTok, RTok, SM);
}
static bool areExprsMacroAndNonMacro(const Expr *&LhsExpr,
const Expr *&RhsExpr) {
if (!LhsExpr || !RhsExpr)
return false;
SourceLocation LhsLoc = LhsExpr->getExprLoc();
SourceLocation RhsLoc = RhsExpr->getExprLoc();
return LhsLoc.isMacroID() != RhsLoc.isMacroID();
}
} // namespace
void RedundantExpressionCheck::registerMatchers(MatchFinder *Finder) {
const auto AnyLiteralExpr = ignoringParenImpCasts(
anyOf(cxxBoolLiteral(), characterLiteral(), integerLiteral()));
const auto BannedIntegerLiteral =
integerLiteral(expandedByMacro(KnownBannedMacroNames));
// Binary with equivalent operands, like (X != 2 && X != 2).
Finder->addMatcher(
traverse(TK_AsIs,
binaryOperator(
anyOf(isComparisonOperator(),
hasAnyOperatorName("-", "/", "%", "|", "&", "^", "&&",
"||", "=")),
operandsAreEquivalent(),
// Filter noisy false positives.
unless(isInTemplateInstantiation()),
unless(binaryOperatorIsInMacro()),
unless(hasType(realFloatingPointType())),
unless(hasEitherOperand(hasType(realFloatingPointType()))),
unless(hasLHS(AnyLiteralExpr)),
unless(hasDescendant(BannedIntegerLiteral)))
.bind("binary")),
this);
// Logical or bitwise operator with equivalent nested operands, like (X && Y
// && X) or (X && (Y && X))
Finder->addMatcher(
binaryOperator(hasAnyOperatorName("|", "&", "||", "&&", "^"),
nestedOperandsAreEquivalent(),
// Filter noisy false positives.
unless(isInTemplateInstantiation()),
unless(binaryOperatorIsInMacro()),
// TODO: if the banned macros are themselves duplicated
unless(hasDescendant(BannedIntegerLiteral)))
.bind("nested-duplicates"),
this);
// Conditional (trenary) operator with equivalent operands, like (Y ? X : X).
Finder->addMatcher(
traverse(TK_AsIs,
conditionalOperator(expressionsAreEquivalent(),
// Filter noisy false positives.
unless(conditionalOperatorIsInMacro()),
unless(isInTemplateInstantiation()))
.bind("cond")),
this);
// Overloaded operators with equivalent operands.
Finder->addMatcher(
traverse(TK_AsIs,
cxxOperatorCallExpr(
hasAnyOverloadedOperatorName("-", "/", "%", "|", "&", "^",
"==", "!=", "<", "<=", ">",
">=", "&&", "||", "="),
parametersAreEquivalent(),
// Filter noisy false positives.
unless(isMacro()), unless(isInTemplateInstantiation()))
.bind("call")),
this);
// Overloaded operators with equivalent operands.
Finder->addMatcher(
cxxOperatorCallExpr(
hasAnyOverloadedOperatorName("|", "&", "||", "&&", "^"),
nestedParametersAreEquivalent(), argumentCountIs(2),
// Filter noisy false positives.
unless(isMacro()), unless(isInTemplateInstantiation()))
.bind("nested-duplicates"),
this);
// Match expressions like: !(1 | 2 | 3)
Finder->addMatcher(
traverse(TK_AsIs,
implicitCastExpr(
hasImplicitDestinationType(isInteger()),
has(unaryOperator(
hasOperatorName("!"),
hasUnaryOperand(ignoringParenImpCasts(binaryOperator(
hasAnyOperatorName("|", "&"),
hasLHS(anyOf(
binaryOperator(hasAnyOperatorName("|", "&")),
integerLiteral())),
hasRHS(integerLiteral())))))
.bind("logical-bitwise-confusion")))),
this);
// Match expressions like: (X << 8) & 0xFF
Finder->addMatcher(
traverse(TK_AsIs,
binaryOperator(
hasOperatorName("&"),
hasOperands(ignoringParenImpCasts(binaryOperator(
hasOperatorName("<<"),
hasRHS(ignoringParenImpCasts(
integerLiteral().bind("shift-const"))))),
ignoringParenImpCasts(
integerLiteral().bind("and-const"))))
.bind("left-right-shift-confusion")),
this);
// Match common expressions and apply more checks to find redundant
// sub-expressions.
// a) Expr <op> K1 == K2
// b) Expr <op> K1 == Expr
// c) Expr <op> K1 == Expr <op> K2
// see: 'checkArithmeticExpr' and 'checkBitwiseExpr'
const auto BinOpCstLeft = matchBinOpIntegerConstantExpr("lhs");
const auto BinOpCstRight = matchBinOpIntegerConstantExpr("rhs");
const auto CstRight = matchIntegerConstantExpr("rhs");
const auto SymRight = matchSymbolicExpr("rhs");
// Match expressions like: x <op> 0xFF == 0xF00.
Finder->addMatcher(
traverse(TK_AsIs, binaryOperator(isComparisonOperator(),
hasOperands(BinOpCstLeft, CstRight))
.bind("binop-const-compare-to-const")),
this);
// Match expressions like: x <op> 0xFF == x.
Finder->addMatcher(
traverse(
TK_AsIs,
binaryOperator(isComparisonOperator(),
anyOf(allOf(hasLHS(BinOpCstLeft), hasRHS(SymRight)),
allOf(hasLHS(SymRight), hasRHS(BinOpCstLeft))))
.bind("binop-const-compare-to-sym")),
this);
// Match expressions like: x <op> 10 == x <op> 12.
Finder->addMatcher(
traverse(TK_AsIs,
binaryOperator(isComparisonOperator(), hasLHS(BinOpCstLeft),
hasRHS(BinOpCstRight),
// Already reported as redundant.
unless(operandsAreEquivalent()))
.bind("binop-const-compare-to-binop-const")),
this);
// Match relational expressions combined with logical operators and find
// redundant sub-expressions.
// see: 'checkRelationalExpr'
// Match expressions like: x < 2 && x > 2.
const auto ComparisonLeft = matchRelationalIntegerConstantExpr("lhs");
const auto ComparisonRight = matchRelationalIntegerConstantExpr("rhs");
Finder->addMatcher(
traverse(TK_AsIs,
binaryOperator(hasAnyOperatorName("||", "&&"),
hasLHS(ComparisonLeft), hasRHS(ComparisonRight),
// Already reported as redundant.
unless(operandsAreEquivalent()))
.bind("comparisons-of-symbol-and-const")),
this);
}
void RedundantExpressionCheck::checkArithmeticExpr(
const MatchFinder::MatchResult &Result) {
APSInt LhsValue, RhsValue;
const Expr *LhsSymbol = nullptr, *RhsSymbol = nullptr;
BinaryOperatorKind LhsOpcode, RhsOpcode;
if (const auto *ComparisonOperator = Result.Nodes.getNodeAs<BinaryOperator>(
"binop-const-compare-to-sym")) {
BinaryOperatorKind Opcode = ComparisonOperator->getOpcode();
if (!retrieveBinOpIntegerConstantExpr(Result, "lhs", LhsOpcode, LhsSymbol,
LhsValue) ||
!retrieveSymbolicExpr(Result, "rhs", RhsSymbol) ||
!areEquivalentExpr(LhsSymbol, RhsSymbol))
return;
// Check expressions: x + k == x or x - k == x.
if (LhsOpcode == BO_Add || LhsOpcode == BO_Sub) {
if ((LhsValue != 0 && Opcode == BO_EQ) ||
(LhsValue == 0 && Opcode == BO_NE))
diag(ComparisonOperator->getOperatorLoc(),
"logical expression is always false");
else if ((LhsValue == 0 && Opcode == BO_EQ) ||
(LhsValue != 0 && Opcode == BO_NE))
diag(ComparisonOperator->getOperatorLoc(),
"logical expression is always true");
}
} else if (const auto *ComparisonOperator =
Result.Nodes.getNodeAs<BinaryOperator>(
"binop-const-compare-to-binop-const")) {
BinaryOperatorKind Opcode = ComparisonOperator->getOpcode();
if (!retrieveBinOpIntegerConstantExpr(Result, "lhs", LhsOpcode, LhsSymbol,
LhsValue) ||
!retrieveBinOpIntegerConstantExpr(Result, "rhs", RhsOpcode, RhsSymbol,
RhsValue) ||
!areEquivalentExpr(LhsSymbol, RhsSymbol))
return;
transformSubToCanonicalAddExpr(LhsOpcode, LhsValue);
transformSubToCanonicalAddExpr(RhsOpcode, RhsValue);
// Check expressions: x + 1 == x + 2 or x + 1 != x + 2.
if (LhsOpcode == BO_Add && RhsOpcode == BO_Add) {
if ((Opcode == BO_EQ && APSInt::compareValues(LhsValue, RhsValue) == 0) ||
(Opcode == BO_NE && APSInt::compareValues(LhsValue, RhsValue) != 0)) {
diag(ComparisonOperator->getOperatorLoc(),
"logical expression is always true");
} else if ((Opcode == BO_EQ &&
APSInt::compareValues(LhsValue, RhsValue) != 0) ||
(Opcode == BO_NE &&
APSInt::compareValues(LhsValue, RhsValue) == 0)) {
diag(ComparisonOperator->getOperatorLoc(),
"logical expression is always false");
}
}
}
}
static bool exprEvaluatesToZero(BinaryOperatorKind Opcode, APSInt Value) {
return (Opcode == BO_And || Opcode == BO_AndAssign) && Value == 0;
}
static bool exprEvaluatesToBitwiseNegatedZero(BinaryOperatorKind Opcode,
APSInt Value) {
return (Opcode == BO_Or || Opcode == BO_OrAssign) && ~Value == 0;
}
static bool exprEvaluatesToSymbolic(BinaryOperatorKind Opcode, APSInt Value) {
return ((Opcode == BO_Or || Opcode == BO_OrAssign) && Value == 0) ||
((Opcode == BO_And || Opcode == BO_AndAssign) && ~Value == 0);
}
void RedundantExpressionCheck::checkBitwiseExpr(
const MatchFinder::MatchResult &Result) {
if (const auto *ComparisonOperator = Result.Nodes.getNodeAs<BinaryOperator>(
"binop-const-compare-to-const")) {
BinaryOperatorKind Opcode = ComparisonOperator->getOpcode();
APSInt LhsValue, RhsValue;
const Expr *LhsSymbol = nullptr;
BinaryOperatorKind LhsOpcode;
if (!retrieveBinOpIntegerConstantExpr(Result, "lhs", LhsOpcode, LhsSymbol,
LhsValue) ||
!retrieveIntegerConstantExpr(Result, "rhs", RhsValue))
return;
uint64_t LhsConstant = LhsValue.getZExtValue();
uint64_t RhsConstant = RhsValue.getZExtValue();
SourceLocation Loc = ComparisonOperator->getOperatorLoc();
// Check expression: x & k1 == k2 (i.e. x & 0xFF == 0xF00)
if (LhsOpcode == BO_And && (LhsConstant & RhsConstant) != RhsConstant) {
if (Opcode == BO_EQ)
diag(Loc, "logical expression is always false");
else if (Opcode == BO_NE)
diag(Loc, "logical expression is always true");
}
// Check expression: x | k1 == k2 (i.e. x | 0xFF == 0xF00)
if (LhsOpcode == BO_Or && (LhsConstant | RhsConstant) != RhsConstant) {
if (Opcode == BO_EQ)
diag(Loc, "logical expression is always false");
else if (Opcode == BO_NE)
diag(Loc, "logical expression is always true");
}
} else if (const auto *IneffectiveOperator =
Result.Nodes.getNodeAs<BinaryOperator>(
"ineffective-bitwise")) {
APSInt Value;
const Expr *Sym = nullptr, *ConstExpr = nullptr;
if (!retrieveSymbolicExpr(Result, "ineffective-bitwise", Sym) ||
!retrieveIntegerConstantExpr(Result, "ineffective-bitwise", Value,
ConstExpr))
return;
if((Value != 0 && ~Value != 0) || Sym->getExprLoc().isMacroID())
return;
SourceLocation Loc = IneffectiveOperator->getOperatorLoc();
BinaryOperatorKind Opcode = IneffectiveOperator->getOpcode();
if (exprEvaluatesToZero(Opcode, Value)) {
diag(Loc, "expression always evaluates to 0");
} else if (exprEvaluatesToBitwiseNegatedZero(Opcode, Value)) {
SourceRange ConstExprRange(ConstExpr->getBeginLoc(),
ConstExpr->getEndLoc());
StringRef ConstExprText = Lexer::getSourceText(
CharSourceRange::getTokenRange(ConstExprRange), *Result.SourceManager,
Result.Context->getLangOpts());
diag(Loc, "expression always evaluates to '%0'") << ConstExprText;
} else if (exprEvaluatesToSymbolic(Opcode, Value)) {
SourceRange SymExprRange(Sym->getBeginLoc(), Sym->getEndLoc());
StringRef ExprText = Lexer::getSourceText(
CharSourceRange::getTokenRange(SymExprRange), *Result.SourceManager,
Result.Context->getLangOpts());
diag(Loc, "expression always evaluates to '%0'") << ExprText;
}
}
}
void RedundantExpressionCheck::checkRelationalExpr(
const MatchFinder::MatchResult &Result) {
if (const auto *ComparisonOperator = Result.Nodes.getNodeAs<BinaryOperator>(
"comparisons-of-symbol-and-const")) {
// Matched expressions are: (x <op> k1) <REL> (x <op> k2).
// E.g.: (X < 2) && (X > 4)
BinaryOperatorKind Opcode = ComparisonOperator->getOpcode();
const Expr *LhsExpr = nullptr, *RhsExpr = nullptr;
const Expr *LhsSymbol = nullptr, *RhsSymbol = nullptr;
const Expr *LhsConst = nullptr, *RhsConst = nullptr;
BinaryOperatorKind LhsOpcode, RhsOpcode;
APSInt LhsValue, RhsValue;
if (!retrieveRelationalIntegerConstantExpr(
Result, "lhs", LhsExpr, LhsOpcode, LhsSymbol, LhsValue, LhsConst) ||
!retrieveRelationalIntegerConstantExpr(
Result, "rhs", RhsExpr, RhsOpcode, RhsSymbol, RhsValue, RhsConst) ||
!areEquivalentExpr(LhsSymbol, RhsSymbol))
return;
// Bring expr to a canonical form: smallest constant must be on the left.
if (APSInt::compareValues(LhsValue, RhsValue) > 0) {
std::swap(LhsExpr, RhsExpr);
std::swap(LhsValue, RhsValue);
std::swap(LhsSymbol, RhsSymbol);
std::swap(LhsOpcode, RhsOpcode);
}
// Constants come from two different macros, or one of them is a macro.
if (areExprsFromDifferentMacros(LhsConst, RhsConst, Result.Context) ||
areExprsMacroAndNonMacro(LhsConst, RhsConst))
return;
if ((Opcode == BO_LAnd || Opcode == BO_LOr) &&
areEquivalentRanges(LhsOpcode, LhsValue, RhsOpcode, RhsValue)) {
diag(ComparisonOperator->getOperatorLoc(),
"equivalent expression on both sides of logical operator");
return;
}
if (Opcode == BO_LAnd) {
if (areExclusiveRanges(LhsOpcode, LhsValue, RhsOpcode, RhsValue)) {
diag(ComparisonOperator->getOperatorLoc(),
"logical expression is always false");
} else if (rangeSubsumesRange(LhsOpcode, LhsValue, RhsOpcode, RhsValue)) {
diag(LhsExpr->getExprLoc(), "expression is redundant");
} else if (rangeSubsumesRange(RhsOpcode, RhsValue, LhsOpcode, LhsValue)) {
diag(RhsExpr->getExprLoc(), "expression is redundant");
}
}
if (Opcode == BO_LOr) {
if (rangesFullyCoverDomain(LhsOpcode, LhsValue, RhsOpcode, RhsValue)) {
diag(ComparisonOperator->getOperatorLoc(),
"logical expression is always true");
} else if (rangeSubsumesRange(LhsOpcode, LhsValue, RhsOpcode, RhsValue)) {
diag(RhsExpr->getExprLoc(), "expression is redundant");
} else if (rangeSubsumesRange(RhsOpcode, RhsValue, LhsOpcode, LhsValue)) {
diag(LhsExpr->getExprLoc(), "expression is redundant");
}
}
}
}
void RedundantExpressionCheck::check(const MatchFinder::MatchResult &Result) {
if (const auto *BinOp = Result.Nodes.getNodeAs<BinaryOperator>("binary")) {
// If the expression's constants are macros, check whether they are
// intentional.
if (areSidesBinaryConstExpressions(BinOp, Result.Context)) {
const Expr *LhsConst = nullptr, *RhsConst = nullptr;
BinaryOperatorKind MainOpcode, SideOpcode;
if (!retrieveConstExprFromBothSides(BinOp, MainOpcode, SideOpcode,
LhsConst, RhsConst, Result.Context))
return;
if (areExprsFromDifferentMacros(LhsConst, RhsConst, Result.Context) ||
areExprsMacroAndNonMacro(LhsConst, RhsConst))
return;
}
diag(BinOp->getOperatorLoc(), "both sides of operator are equivalent");
}
if (const auto *CondOp =
Result.Nodes.getNodeAs<ConditionalOperator>("cond")) {
const Expr *TrueExpr = CondOp->getTrueExpr();
const Expr *FalseExpr = CondOp->getFalseExpr();
if (areExprsFromDifferentMacros(TrueExpr, FalseExpr, Result.Context) ||
areExprsMacroAndNonMacro(TrueExpr, FalseExpr))
return;
diag(CondOp->getColonLoc(),
"'true' and 'false' expressions are equivalent");
}
if (const auto *Call = Result.Nodes.getNodeAs<CXXOperatorCallExpr>("call")) {
if (canOverloadedOperatorArgsBeModified(Call, true))
return;
diag(Call->getOperatorLoc(),
"both sides of overloaded operator are equivalent");
}
if (const auto *Op = Result.Nodes.getNodeAs<Expr>("nested-duplicates")) {
const auto *Call = dyn_cast<CXXOperatorCallExpr>(Op);
if (Call && canOverloadedOperatorArgsBeModified(Call, true))
return;
StringRef Message =
Call ? "overloaded operator has equivalent nested operands"
: "operator has equivalent nested operands";
const auto Diag = diag(Op->getExprLoc(), Message);
for (const auto &KeyValue : Result.Nodes.getMap()) {
if (StringRef(KeyValue.first).startswith("duplicate"))
Diag << KeyValue.second.getSourceRange();
}
}
if (const auto *NegateOperator =
Result.Nodes.getNodeAs<UnaryOperator>("logical-bitwise-confusion")) {
SourceLocation OperatorLoc = NegateOperator->getOperatorLoc();
auto Diag =
diag(OperatorLoc,
"ineffective logical negation operator used; did you mean '~'?");
SourceLocation LogicalNotLocation = OperatorLoc.getLocWithOffset(1);
if (!LogicalNotLocation.isMacroID())
Diag << FixItHint::CreateReplacement(
CharSourceRange::getCharRange(OperatorLoc, LogicalNotLocation), "~");
}
if (const auto *BinaryAndExpr = Result.Nodes.getNodeAs<BinaryOperator>(
"left-right-shift-confusion")) {
const auto *ShiftingConst = Result.Nodes.getNodeAs<Expr>("shift-const");
assert(ShiftingConst && "Expr* 'ShiftingConst' is nullptr!");
Optional<llvm::APSInt> ShiftingValue =
ShiftingConst->getIntegerConstantExpr(*Result.Context);
if (!ShiftingValue)
return;
const auto *AndConst = Result.Nodes.getNodeAs<Expr>("and-const");
assert(AndConst && "Expr* 'AndCont' is nullptr!");
Optional<llvm::APSInt> AndValue =
AndConst->getIntegerConstantExpr(*Result.Context);
if (!AndValue)
return;
// If ShiftingConst is shifted left with more bits than the position of the
// leftmost 1 in the bit representation of AndValue, AndConstant is
// ineffective.
if (AndValue->getActiveBits() > *ShiftingValue)
return;
auto Diag = diag(BinaryAndExpr->getOperatorLoc(),
"ineffective bitwise and operation");
}
// Check for the following bound expressions:
// - "binop-const-compare-to-sym",
// - "binop-const-compare-to-binop-const",
// Produced message:
// -> "logical expression is always false/true"
checkArithmeticExpr(Result);
// Check for the following bound expression:
// - "binop-const-compare-to-const",
// - "ineffective-bitwise"
// Produced message:
// -> "logical expression is always false/true"
// -> "expression always evaluates to ..."
checkBitwiseExpr(Result);
// Check for te following bound expression:
// - "comparisons-of-symbol-and-const",
// Produced messages:
// -> "equivalent expression on both sides of logical operator",
// -> "logical expression is always false/true"
// -> "expression is redundant"
checkRelationalExpr(Result);
}
} // namespace misc
} // namespace tidy
} // namespace clang
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