clang-tools  10.0.0
MoveConstArgCheck.cpp
Go to the documentation of this file.
1 //===--- MoveConstArgCheck.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 
9 #include "MoveConstArgCheck.h"
10 
11 #include "clang/Lex/Lexer.h"
12 
13 using namespace clang::ast_matchers;
14 
15 namespace clang {
16 namespace tidy {
17 namespace performance {
18 
19 static void ReplaceCallWithArg(const CallExpr *Call, DiagnosticBuilder &Diag,
20  const SourceManager &SM,
21  const LangOptions &LangOpts) {
22  const Expr *Arg = Call->getArg(0);
23 
24  CharSourceRange BeforeArgumentsRange = Lexer::makeFileCharRange(
25  CharSourceRange::getCharRange(Call->getBeginLoc(), Arg->getBeginLoc()),
26  SM, LangOpts);
27  CharSourceRange AfterArgumentsRange = Lexer::makeFileCharRange(
28  CharSourceRange::getCharRange(Call->getEndLoc(),
29  Call->getEndLoc().getLocWithOffset(1)),
30  SM, LangOpts);
31 
32  if (BeforeArgumentsRange.isValid() && AfterArgumentsRange.isValid()) {
33  Diag << FixItHint::CreateRemoval(BeforeArgumentsRange)
34  << FixItHint::CreateRemoval(AfterArgumentsRange);
35  }
36 }
37 
38 void MoveConstArgCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
39  Options.store(Opts, "CheckTriviallyCopyableMove", CheckTriviallyCopyableMove);
40 }
41 
42 void MoveConstArgCheck::registerMatchers(MatchFinder *Finder) {
43  if (!getLangOpts().CPlusPlus)
44  return;
45 
46  auto MoveCallMatcher =
47  callExpr(callee(functionDecl(hasName("::std::move"))), argumentCountIs(1),
48  unless(isInTemplateInstantiation()))
49  .bind("call-move");
50 
51  Finder->addMatcher(MoveCallMatcher, this);
52 
53  auto ConstParamMatcher = forEachArgumentWithParam(
54  MoveCallMatcher, parmVarDecl(hasType(references(isConstQualified()))));
55 
56  Finder->addMatcher(callExpr(ConstParamMatcher).bind("receiving-expr"), this);
57  Finder->addMatcher(cxxConstructExpr(ConstParamMatcher).bind("receiving-expr"),
58  this);
59 }
60 
61 void MoveConstArgCheck::check(const MatchFinder::MatchResult &Result) {
62  const auto *CallMove = Result.Nodes.getNodeAs<CallExpr>("call-move");
63  const auto *ReceivingExpr = Result.Nodes.getNodeAs<Expr>("receiving-expr");
64  const Expr *Arg = CallMove->getArg(0);
65  SourceManager &SM = Result.Context->getSourceManager();
66 
67  CharSourceRange MoveRange =
68  CharSourceRange::getCharRange(CallMove->getSourceRange());
69  CharSourceRange FileMoveRange =
70  Lexer::makeFileCharRange(MoveRange, SM, getLangOpts());
71  if (!FileMoveRange.isValid())
72  return;
73 
74  bool IsConstArg = Arg->getType().isConstQualified();
75  bool IsTriviallyCopyable =
76  Arg->getType().isTriviallyCopyableType(*Result.Context);
77 
78  if (IsConstArg || IsTriviallyCopyable) {
79  if (const CXXRecordDecl *R = Arg->getType()->getAsCXXRecordDecl()) {
80  // According to [expr.prim.lambda]p3, "whether the closure type is
81  // trivially copyable" property can be changed by the implementation of
82  // the language, so we shouldn't rely on it when issuing diagnostics.
83  if (R->isLambda())
84  return;
85  // Don't warn when the type is not copyable.
86  for (const auto *Ctor : R->ctors()) {
87  if (Ctor->isCopyConstructor() && Ctor->isDeleted())
88  return;
89  }
90  }
91 
92  if (!IsConstArg && IsTriviallyCopyable && !CheckTriviallyCopyableMove)
93  return;
94 
95  bool IsVariable = isa<DeclRefExpr>(Arg);
96  const auto *Var =
97  IsVariable ? dyn_cast<DeclRefExpr>(Arg)->getDecl() : nullptr;
98  auto Diag = diag(FileMoveRange.getBegin(),
99  "std::move of the %select{|const }0"
100  "%select{expression|variable %4}1 "
101  "%select{|of the trivially-copyable type %5 }2"
102  "has no effect; remove std::move()"
103  "%select{| or make the variable non-const}3")
104  << IsConstArg << IsVariable << IsTriviallyCopyable
105  << (IsConstArg && IsVariable && !IsTriviallyCopyable) << Var
106  << Arg->getType();
107 
108  ReplaceCallWithArg(CallMove, Diag, SM, getLangOpts());
109  } else if (ReceivingExpr) {
110  auto Diag = diag(FileMoveRange.getBegin(),
111  "passing result of std::move() as a const reference "
112  "argument; no move will actually happen");
113 
114  ReplaceCallWithArg(CallMove, Diag, SM, getLangOpts());
115  }
116 }
117 
118 } // namespace performance
119 } // namespace tidy
120 } // namespace clang
std::map< std::string, std::string > OptionMap
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
static void ReplaceCallWithArg(const CallExpr *Call, DiagnosticBuilder &Diag, const SourceManager &SM, const LangOptions &LangOpts)