83 lines · cpp
1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#include "SuspiciousMemoryComparisonCheck.h"10#include "clang/AST/ASTContext.h"11#include "clang/ASTMatchers/ASTMatchFinder.h"12#include <optional>13 14using namespace clang::ast_matchers;15 16namespace clang::tidy::bugprone {17 18static std::optional<uint64_t> tryEvaluateSizeExpr(const Expr *SizeExpr,19 const ASTContext &Ctx) {20 Expr::EvalResult Result;21 if (SizeExpr->EvaluateAsRValue(Result, Ctx))22 return Ctx.toBits(23 CharUnits::fromQuantity(Result.Val.getInt().getExtValue()));24 return std::nullopt;25}26 27void SuspiciousMemoryComparisonCheck::registerMatchers(MatchFinder *Finder) {28 Finder->addMatcher(29 callExpr(callee(namedDecl(30 anyOf(hasName("::memcmp"), hasName("::std::memcmp")))),31 unless(isInstantiationDependent()))32 .bind("call"),33 this);34}35 36void SuspiciousMemoryComparisonCheck::check(37 const MatchFinder::MatchResult &Result) {38 const ASTContext &Ctx = *Result.Context;39 const auto *CE = Result.Nodes.getNodeAs<CallExpr>("call");40 41 const Expr *SizeExpr = CE->getArg(2);42 assert(SizeExpr != nullptr && "Third argument of memcmp is mandatory.");43 std::optional<uint64_t> ComparedBits = tryEvaluateSizeExpr(SizeExpr, Ctx);44 45 for (unsigned int ArgIndex = 0; ArgIndex < 2; ++ArgIndex) {46 const Expr *ArgExpr = CE->getArg(ArgIndex);47 const QualType ArgType = ArgExpr->IgnoreImplicit()->getType();48 const Type *PointeeType = ArgType->getPointeeOrArrayElementType();49 assert(PointeeType != nullptr && "PointeeType should always be available.");50 const QualType PointeeQualifiedType(PointeeType, 0);51 52 if (PointeeType->isRecordType()) {53 if (const RecordDecl *RD =54 PointeeType->getAsRecordDecl()->getDefinition()) {55 if (const auto *CXXDecl = dyn_cast<CXXRecordDecl>(RD)) {56 if (!CXXDecl->isStandardLayout()) {57 diag(CE->getBeginLoc(),58 "comparing object representation of non-standard-layout type "59 "%0; consider using a comparison operator instead")60 << PointeeQualifiedType;61 break;62 }63 }64 }65 }66 67 if (!PointeeType->isIncompleteType()) {68 const uint64_t PointeeSize = Ctx.getTypeSize(PointeeType);69 if (ComparedBits && *ComparedBits >= PointeeSize &&70 !Ctx.hasUniqueObjectRepresentations(PointeeQualifiedType)) {71 diag(CE->getBeginLoc(),72 "comparing object representation of type %0 which does not have a "73 "unique object representation; consider comparing %select{the "74 "values|the members of the object}1 manually")75 << PointeeQualifiedType << (PointeeType->isRecordType() ? 1 : 0);76 break;77 }78 }79 }80}81 82} // namespace clang::tidy::bugprone83