clang-tools  14.0.0git
SuspiciousMemoryComparisonCheck.cpp
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1 //===--- SuspiciousMemoryComparisonCheck.cpp - clang-tidy -----------------===//
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-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 
13 using namespace clang::ast_matchers;
14 
15 namespace clang {
16 namespace tidy {
17 namespace bugprone {
18 
19 static llvm::Optional<uint64_t> tryEvaluateSizeExpr(const Expr *SizeExpr,
20  const ASTContext &Ctx) {
21  Expr::EvalResult Result;
22  if (SizeExpr->EvaluateAsRValue(Result, Ctx))
23  return Ctx.toBits(
24  CharUnits::fromQuantity(Result.Val.getInt().getExtValue()));
25  return None;
26 }
27 
28 void SuspiciousMemoryComparisonCheck::registerMatchers(MatchFinder *Finder) {
29  Finder->addMatcher(
30  callExpr(allOf(callee(namedDecl(
31  anyOf(hasName("::memcmp"), hasName("::std::memcmp")))),
32  unless(isInstantiationDependent())))
33  .bind("call"),
34  this);
35 }
36 
38  const MatchFinder::MatchResult &Result) {
39  const ASTContext &Ctx = *Result.Context;
40  const auto *CE = Result.Nodes.getNodeAs<CallExpr>("call");
41 
42  const Expr *SizeExpr = CE->getArg(2);
43  assert(SizeExpr != nullptr && "Third argument of memcmp is mandatory.");
44  llvm::Optional<uint64_t> ComparedBits = tryEvaluateSizeExpr(SizeExpr, Ctx);
45 
46  for (unsigned int ArgIndex = 0; ArgIndex < 2; ++ArgIndex) {
47  const Expr *ArgExpr = CE->getArg(ArgIndex);
48  QualType ArgType = ArgExpr->IgnoreImplicit()->getType();
49  const Type *PointeeType = ArgType->getPointeeOrArrayElementType();
50  assert(PointeeType != nullptr && "PointeeType should always be available.");
51  QualType PointeeQualifiedType(PointeeType, 0);
52 
53  if (PointeeType->isRecordType()) {
54  if (const RecordDecl *RD =
55  PointeeType->getAsRecordDecl()->getDefinition()) {
56  if (const auto *CXXDecl = dyn_cast<CXXRecordDecl>(RD)) {
57  if (!CXXDecl->isStandardLayout()) {
58  diag(CE->getBeginLoc(),
59  "comparing object representation of non-standard-layout type "
60  "%0; consider using a comparison operator instead")
61  << PointeeQualifiedType;
62  break;
63  }
64  }
65  }
66  }
67 
68  if (!PointeeType->isIncompleteType()) {
69  uint64_t PointeeSize = Ctx.getTypeSize(PointeeType);
70  if (ComparedBits.hasValue() && *ComparedBits >= PointeeSize &&
71  !Ctx.hasUniqueObjectRepresentations(PointeeQualifiedType)) {
72  diag(CE->getBeginLoc(),
73  "comparing object representation of type %0 which does not have a "
74  "unique object representation; consider comparing %select{the "
75  "values|the members of the object}1 manually")
76  << PointeeQualifiedType << (PointeeType->isRecordType() ? 1 : 0);
77  break;
78  }
79  }
80  }
81 }
82 
83 } // namespace bugprone
84 } // namespace tidy
85 } // namespace clang
Type
NodeType Type
Definition: HTMLGenerator.cpp:73
Ctx
Context Ctx
Definition: TUScheduler.cpp:460
clang::ast_matchers
Definition: AbseilMatcher.h:14
clang::clangd::check
bool check(llvm::StringRef File, llvm::function_ref< bool(const Position &)> ShouldCheckLine, const ThreadsafeFS &TFS, const ClangdLSPServer::Options &Opts, bool EnableCodeCompletion)
Definition: Check.cpp:259
CE
CaptureExpr CE
Definition: AvoidBindCheck.cpp:67
SuspiciousMemoryComparisonCheck.h
clang
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Definition: ApplyReplacements.h:27
clang::tidy::bugprone::tryEvaluateSizeExpr
static llvm::Optional< uint64_t > tryEvaluateSizeExpr(const Expr *SizeExpr, const ASTContext &Ctx)
Definition: SuspiciousMemoryComparisonCheck.cpp:19