clang-tools  3.9.0
MoveConstructorInitCheck.cpp
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1 //===--- MoveConstructorInitCheck.cpp - clang-tidy-------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
11 #include "../utils/Matchers.h"
12 #include "clang/AST/ASTContext.h"
13 #include "clang/ASTMatchers/ASTMatchFinder.h"
14 #include "clang/Frontend/CompilerInstance.h"
15 #include "clang/Lex/Lexer.h"
16 #include "clang/Lex/Preprocessor.h"
17 
18 using namespace clang::ast_matchers;
19 
20 namespace clang {
21 namespace tidy {
22 namespace misc {
23 
24 namespace {
25 
26 unsigned int
27 parmVarDeclRefExprOccurences(const ParmVarDecl &MovableParam,
28  const CXXConstructorDecl &ConstructorDecl,
29  ASTContext &Context) {
30  unsigned int Occurrences = 0;
31  auto AllDeclRefs =
32  findAll(declRefExpr(to(parmVarDecl(equalsNode(&MovableParam)))));
33  Occurrences += match(AllDeclRefs, *ConstructorDecl.getBody(), Context).size();
34  for (const auto *Initializer : ConstructorDecl.inits()) {
35  Occurrences += match(AllDeclRefs, *Initializer->getInit(), Context).size();
36  }
37  return Occurrences;
38 }
39 
40 } // namespace
41 
42 MoveConstructorInitCheck::MoveConstructorInitCheck(StringRef Name,
43  ClangTidyContext *Context)
44  : ClangTidyCheck(Name, Context),
45  IncludeStyle(utils::IncludeSorter::parseIncludeStyle(
46  Options.get("IncludeStyle", "llvm"))),
47  UseCERTSemantics(Options.get("UseCERTSemantics", 0) != 0) {}
48 
50  // Only register the matchers for C++11; the functionality currently does not
51  // provide any benefit to other languages, despite being benign.
52  if (!getLangOpts().CPlusPlus11)
53  return;
54 
55  Finder->addMatcher(
56  cxxConstructorDecl(
57  unless(isImplicit()),
58  allOf(isMoveConstructor(),
59  hasAnyConstructorInitializer(
60  cxxCtorInitializer(
61  withInitializer(cxxConstructExpr(hasDeclaration(
62  cxxConstructorDecl(isCopyConstructor())
63  .bind("ctor")))))
64  .bind("move-init")))),
65  this);
66 
67  auto NonConstValueMovableAndExpensiveToCopy =
68  qualType(allOf(unless(pointerType()), unless(isConstQualified()),
69  hasDeclaration(cxxRecordDecl(hasMethod(cxxConstructorDecl(
70  isMoveConstructor(), unless(isDeleted()))))),
72 
73  // This checker is also used to implement cert-oop11-cpp, but when using that
74  // form of the checker, we do not want to diagnose movable parameters.
75  if (!UseCERTSemantics) {
76  Finder->addMatcher(
77  cxxConstructorDecl(
78  allOf(
79  unless(isMoveConstructor()),
80  hasAnyConstructorInitializer(withInitializer(cxxConstructExpr(
81  hasDeclaration(cxxConstructorDecl(isCopyConstructor())),
82  hasArgument(
83  0,
84  declRefExpr(
85  to(parmVarDecl(
86  hasType(
87  NonConstValueMovableAndExpensiveToCopy))
88  .bind("movable-param")))
89  .bind("init-arg")))))))
90  .bind("ctor-decl"),
91  this);
92  }
93 }
94 
95 void MoveConstructorInitCheck::check(const MatchFinder::MatchResult &Result) {
96  if (Result.Nodes.getNodeAs<CXXCtorInitializer>("move-init") != nullptr)
97  handleMoveConstructor(Result);
98  if (Result.Nodes.getNodeAs<ParmVarDecl>("movable-param") != nullptr)
99  handleParamNotMoved(Result);
100 }
101 
102 void MoveConstructorInitCheck::handleParamNotMoved(
103  const MatchFinder::MatchResult &Result) {
104  const auto *MovableParam =
105  Result.Nodes.getNodeAs<ParmVarDecl>("movable-param");
106  const auto *ConstructorDecl =
107  Result.Nodes.getNodeAs<CXXConstructorDecl>("ctor-decl");
108  const auto *InitArg = Result.Nodes.getNodeAs<DeclRefExpr>("init-arg");
109  // If the parameter is referenced more than once it is not safe to move it.
110  if (parmVarDeclRefExprOccurences(*MovableParam, *ConstructorDecl,
111  *Result.Context) > 1)
112  return;
113  auto DiagOut = diag(InitArg->getLocStart(),
114  "value argument %0 can be moved to avoid copy")
115  << MovableParam;
116  DiagOut << FixItHint::CreateReplacement(
117  InitArg->getSourceRange(),
118  (Twine("std::move(") + MovableParam->getName() + ")").str());
119  if (auto IncludeFixit = Inserter->CreateIncludeInsertion(
120  Result.SourceManager->getFileID(InitArg->getLocStart()), "utility",
121  /*IsAngled=*/true)) {
122  DiagOut << *IncludeFixit;
123  }
124 }
125 
126 void MoveConstructorInitCheck::handleMoveConstructor(
127  const MatchFinder::MatchResult &Result) {
128  const auto *CopyCtor = Result.Nodes.getNodeAs<CXXConstructorDecl>("ctor");
129  const auto *Initializer = Result.Nodes.getNodeAs<CXXCtorInitializer>("move-init");
130 
131  // Do not diagnose if the expression used to perform the initialization is a
132  // trivially-copyable type.
133  QualType QT = Initializer->getInit()->getType();
134  if (QT.isTriviallyCopyableType(*Result.Context))
135  return;
136 
137  const auto *RD = QT->getAsCXXRecordDecl();
138  if (RD && RD->isTriviallyCopyable())
139  return;
140 
141  // Diagnose when the class type has a move constructor available, but the
142  // ctor-initializer uses the copy constructor instead.
143  const CXXConstructorDecl *Candidate = nullptr;
144  for (const auto *Ctor : CopyCtor->getParent()->ctors()) {
145  if (Ctor->isMoveConstructor() && Ctor->getAccess() <= AS_protected &&
146  !Ctor->isDeleted()) {
147  // The type has a move constructor that is at least accessible to the
148  // initializer.
149  //
150  // FIXME: Determine whether the move constructor is a viable candidate
151  // for the ctor-initializer, perhaps provide a fixit that suggests
152  // using std::move().
153  Candidate = Ctor;
154  break;
155  }
156  }
157 
158  if (Candidate) {
159  // There's a move constructor candidate that the caller probably intended
160  // to call instead.
161  diag(Initializer->getSourceLocation(),
162  "move constructor initializes %0 by calling a copy constructor")
163  << (Initializer->isBaseInitializer() ? "base class" : "class member");
164  diag(CopyCtor->getLocation(), "copy constructor being called",
165  DiagnosticIDs::Note);
166  diag(Candidate->getLocation(), "candidate move constructor here",
167  DiagnosticIDs::Note);
168  }
169 }
170 
171 void MoveConstructorInitCheck::registerPPCallbacks(CompilerInstance &Compiler) {
172  Inserter.reset(new utils::IncludeInserter(
173  Compiler.getSourceManager(), Compiler.getLangOpts(), IncludeStyle));
174  Compiler.getPreprocessor().addPPCallbacks(Inserter->CreatePPCallbacks());
175 }
176 
178  Options.store(Opts, "IncludeStyle",
179  utils::IncludeSorter::toString(IncludeStyle));
180  Options.store(Opts, "UseCERTSemantics", UseCERTSemantics ? 1 : 0);
181 }
182 
183 } // namespace misc
184 } // namespace tidy
185 } // namespace clang
const std::string Name
Definition: USRFinder.cpp:140
LangOptions getLangOpts() const
Returns the language options from the context.
Definition: ClangTidy.h:170
std::unique_ptr< ast_matchers::MatchFinder > Finder
Definition: ClangTidy.cpp:210
static StringRef toString(IncludeStyle Style)
Converts IncludeStyle to string representation.
Base class for all clang-tidy checks.
Definition: ClangTidy.h:110
void registerPPCallbacks(clang::CompilerInstance &Compiler) override
void registerMatchers(ast_matchers::MatchFinder *Finder) override
Override this to register AST matchers with Finder.
void storeOptions(ClangTidyOptions::OptionMap &Opts) override
Should store all options supported by this check with their current values or default values for opti...
llvm::Optional< bool > isExpensiveToCopy(QualType Type, const ASTContext &Context)
Returns true if Type is expensive to copy.
Definition: TypeTraits.cpp:42
void store(ClangTidyOptions::OptionMap &Options, StringRef LocalName, StringRef Value) const
Stores an option with the check-local name LocalName with string value Value to Options.
Definition: ClangTidy.cpp:385
std::map< std::string, std::string > OptionMap
Produces fixes to insert specified includes to source files, if not yet present.
ClangTidyContext & Context
Definition: ClangTidy.cpp:93
Every ClangTidyCheck reports errors through a DiagnosticsEngine provided by this context.
void check(const ast_matchers::MatchFinder::MatchResult &Result) override
ClangTidyChecks that register ASTMatchers should do the actual work in here.
DiagnosticBuilder diag(SourceLocation Loc, StringRef Description, DiagnosticIDs::Level Level=DiagnosticIDs::Warning)
Add a diagnostic with the check's name.
Definition: ClangTidy.cpp:352
const NamedDecl * Result
Definition: USRFinder.cpp:137