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