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PassByValueCheck.cpp
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1 //===--- PassByValueCheck.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
10 #include "PassByValueCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/AST/RecursiveASTVisitor.h"
13 #include "clang/ASTMatchers/ASTMatchFinder.h"
14 #include "clang/ASTMatchers/ASTMatchers.h"
15 #include "clang/Frontend/CompilerInstance.h"
16 #include "clang/Lex/Lexer.h"
17 #include "clang/Lex/Preprocessor.h"
18
19 using namespace clang::ast_matchers;
20 using namespace llvm;
21
22 namespace clang {
23 namespace tidy {
24 namespace modernize {
25
26 /// \brief Matches move-constructible classes.
27 ///
28 /// Given
29 /// \code
30 /// // POD types are trivially move constructible.
31 /// struct Foo { int a; };
32 ///
33 /// struct Bar {
34 /// Bar(Bar &&) = deleted;
35 /// int a;
36 /// };
37 /// \endcode
38 /// recordDecl(isMoveConstructible())
39 /// matches "Foo".
40 AST_MATCHER(CXXRecordDecl, isMoveConstructible) {
41 for (const CXXConstructorDecl *Ctor : Node.ctors()) {
42 if (Ctor->isMoveConstructor() && !Ctor->isDeleted())
43 return true;
44 }
45 return false;
46 }
47
48 static TypeMatcher constRefType() {
49 return lValueReferenceType(pointee(isConstQualified()));
50 }
51
52 static TypeMatcher nonConstValueType() {
53 return qualType(unless(anyOf(referenceType(), isConstQualified())));
54 }
55
56 /// \brief Whether or not \p ParamDecl is used exactly one time in \p Ctor.
57 ///
58 /// Checks both in the init-list and the body of the constructor.
59 static bool paramReferredExactlyOnce(const CXXConstructorDecl *Ctor,
60 const ParmVarDecl *ParamDecl) {
61 /// \brief \c clang::RecursiveASTVisitor that checks that the given
62 /// \c ParmVarDecl is used exactly one time.
63 ///
64 /// \see ExactlyOneUsageVisitor::hasExactlyOneUsageIn()
65 class ExactlyOneUsageVisitor
66 : public RecursiveASTVisitor<ExactlyOneUsageVisitor> {
67 friend class RecursiveASTVisitor<ExactlyOneUsageVisitor>;
68
69 public:
70 ExactlyOneUsageVisitor(const ParmVarDecl *ParamDecl)
71 : ParamDecl(ParamDecl) {}
72
73 /// \brief Whether or not the parameter variable is referred only once in
74 /// the
75 /// given constructor.
76 bool hasExactlyOneUsageIn(const CXXConstructorDecl *Ctor) {
77 Count = 0;
78 TraverseDecl(const_cast<CXXConstructorDecl *>(Ctor));
79 return Count == 1;
80 }
81
82 private:
83 /// \brief Counts the number of references to a variable.
84 ///
85 /// Stops the AST traversal if more than one usage is found.
86 bool VisitDeclRefExpr(DeclRefExpr *D) {
87 if (const ParmVarDecl *To = dyn_cast<ParmVarDecl>(D->getDecl())) {
88 if (To == ParamDecl) {
89 ++Count;
90 if (Count > 1) {
91 // No need to look further, used more than once.
92 return false;
93 }
94 }
95 }
96 return true;
97 }
98
99 const ParmVarDecl *ParamDecl;
100 unsigned Count;
101 };
102
103 return ExactlyOneUsageVisitor(ParamDecl).hasExactlyOneUsageIn(Ctor);
104 }
105
106 /// \brief Find all references to \p ParamDecl across all of the
107 /// redeclarations of \p Ctor.
108 static SmallVector<const ParmVarDecl *, 2>
109 collectParamDecls(const CXXConstructorDecl *Ctor,
110 const ParmVarDecl *ParamDecl) {
111 SmallVector<const ParmVarDecl *, 2> Results;
112 unsigned ParamIdx = ParamDecl->getFunctionScopeIndex();
113
114 for (const FunctionDecl *Redecl : Ctor->redecls())
115 Results.push_back(Redecl->getParamDecl(ParamIdx));
116 return Results;
117 }
118
119 PassByValueCheck::PassByValueCheck(StringRef Name, ClangTidyContext *Context)
120 : ClangTidyCheck(Name, Context),
121 IncludeStyle(IncludeSorter::parseIncludeStyle(
122 Options.get("IncludeStyle", "llvm"))) {}
123
124 void PassByValueCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
125 Options.store(Opts, "IncludeStyle", IncludeSorter::toString(IncludeStyle));
126 }
127
128 void PassByValueCheck::registerMatchers(MatchFinder *Finder) {
129 // Only register the matchers for C++; the functionality currently does not
130 // provide any benefit to other languages, despite being benign.
131 if (getLangOpts().CPlusPlus) {
132 Finder->addMatcher(
133 cxxConstructorDecl(
134 forEachConstructorInitializer(
135 cxxCtorInitializer(
136 // Clang builds a CXXConstructExpr only whin it knows which
137 // constructor will be called. In dependent contexts a
138 // ParenListExpr is generated instead of a CXXConstructExpr,
139 // filtering out templates automatically for us.
140 withInitializer(cxxConstructExpr(
141 has(declRefExpr(to(
142 parmVarDecl(
143 hasType(qualType(
144 // Match only const-ref or a non-const value
145 // parameters. Rvalues and const-values
146 // shouldn't be modified.
147 anyOf(constRefType(),
148 nonConstValueType()))))
149 .bind("Param")))),
150 hasDeclaration(cxxConstructorDecl(
151 isCopyConstructor(), unless(isDeleted()),
152 hasDeclContext(
153 cxxRecordDecl(isMoveConstructible())))))))
154 .bind("Initializer")))
155 .bind("Ctor"),
156 this);
157 }
158 }
159
160 void PassByValueCheck::registerPPCallbacks(CompilerInstance &Compiler) {
161 // Only register the preprocessor callbacks for C++; the functionality
162 // currently does not provide any benefit to other languages, despite being
163 // benign.
164 if (getLangOpts().CPlusPlus) {
165 Inserter.reset(new IncludeInserter(Compiler.getSourceManager(),
166 Compiler.getLangOpts(), IncludeStyle));
167 Compiler.getPreprocessor().addPPCallbacks(Inserter->CreatePPCallbacks());
168 }
169 }
170
171 void PassByValueCheck::check(const MatchFinder::MatchResult &Result) {
172 const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructorDecl>("Ctor");
173 const auto *ParamDecl = Result.Nodes.getNodeAs<ParmVarDecl>("Param");
174 const auto *Initializer =
175 Result.Nodes.getNodeAs<CXXCtorInitializer>("Initializer");
176 SourceManager &SM = *Result.SourceManager;
177
178 // If the parameter is used or anything other than the copy, do not apply
179 // the changes.
180 if (!paramReferredExactlyOnce(Ctor, ParamDecl))
181 return;
182
183 auto Diag = diag(ParamDecl->getLocStart(), "pass by value and use std::move");
184
185 // Iterate over all declarations of the constructor.
186 for (const ParmVarDecl *ParmDecl : collectParamDecls(Ctor, ParamDecl)) {
187 auto ParamTL = ParmDecl->getTypeSourceInfo()->getTypeLoc();
188 auto RefTL = ParamTL.getAs<ReferenceTypeLoc>();
189
190 // Do not replace if it is already a value, skip.
191 if (RefTL.isNull())
192 continue;
193
194 TypeLoc ValueTL = RefTL.getPointeeLoc();
195 auto TypeRange = CharSourceRange::getTokenRange(ParmDecl->getLocStart(),
196 ParamTL.getLocEnd());
197 std::string ValueStr =
198 Lexer::getSourceText(
199 CharSourceRange::getTokenRange(ValueTL.getSourceRange()), SM,
200 Result.Context->getLangOpts())
201 .str();
202 ValueStr += ' ';
203 Diag << FixItHint::CreateReplacement(TypeRange, ValueStr);
204 }
205
206 // Use std::move in the initialization list.
207 Diag << FixItHint::CreateInsertion(Initializer->getRParenLoc(), ")")
208 << FixItHint::CreateInsertion(
209 Initializer->getLParenLoc().getLocWithOffset(1), "std::move(");
210
211 auto Insertion =
212 Inserter->CreateIncludeInsertion(SM.getMainFileID(), "utility",
213 /*IsAngled=*/true);
214 if (Insertion.hasValue())
215 Diag << Insertion.getValue();
216 }
217
218 } // namespace modernize
219 } // namespace tidy
220 } // namespace clang
clang::tidy::modernize::paramReferredExactlyOnce
static bool paramReferredExactlyOnce(const CXXConstructorDecl *Ctor, const ParmVarDecl *ParamDecl)
Whether or not ParamDecl is used exactly one time in Ctor.
Definition: PassByValueCheck.cpp:59
clang::tidy::ClangTidyCheck::getLangOpts
LangOptions getLangOpts() const
Returns the language options from the context.
Definition: ClangTidy.h:162
clang::tidy::modernize::constRefType
static TypeMatcher constRefType()
Definition: PassByValueCheck.cpp:48
Name
StringHandle Name
Definition: PreprocessorTracker.cpp:525
Finder
std::unique_ptr< ast_matchers::MatchFinder > Finder
Definition: ClangTidy.cpp:188
clang::tidy::modernize::nonConstValueType
static TypeMatcher nonConstValueType()
Definition: PassByValueCheck.cpp:52
PassByValueCheck.h
clang::tidy::modernize::AST_MATCHER
AST_MATCHER(CXXRecordDecl, isMoveConstructible)
Matches move-constructible classes.
Definition: PassByValueCheck.cpp:40
clang::tidy::IncludeSorter::toString
static StringRef toString(IncludeStyle Style)
Definition: IncludeSorter.cpp:290
clang::tidy::ClangTidyCheck
Base class for all clang-tidy checks.
Definition: ClangTidy.h:102
clang::tidy::ClangTidyCheck::Options
OptionsView Options
Definition: ClangTidy.h:158
SM
SourceManager & SM
Definition: IncludeOrderCheck.cpp:44
clang::tidy::modernize::PassByValueCheck::registerPPCallbacks
void registerPPCallbacks(clang::CompilerInstance &Compiler) override
Definition: PassByValueCheck.cpp:160
clang::tidy::OptionsView::store
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:344
clang::tidy::ClangTidyOptions::OptionMap
std::map< std::string, std::string > OptionMap
Definition: ClangTidyOptions.h:82
clang::tidy::modernize::PassByValueCheck::registerMatchers
void registerMatchers(ast_matchers::MatchFinder *Finder) override
Override this to register ASTMatchers with Finder.
Definition: PassByValueCheck.cpp:128
clang::tidy::modernize::collectParamDecls
static SmallVector< const ParmVarDecl *, 2 > collectParamDecls(const CXXConstructorDecl *Ctor, const ParmVarDecl *ParamDecl)
Find all references to ParamDecl across all of the redeclarations of Ctor.
Definition: PassByValueCheck.cpp:109
clang::tidy::IncludeSorter
Definition: IncludeSorter.h:23
Context
ClangTidyContext & Context
Definition: ClangTidy.cpp:93
clang::tidy::ClangTidyContext
Every ClangTidyCheck reports errors through a DiagnosticsEngine provided by this context.
Definition: ClangTidyDiagnosticConsumer.h:124
clang::tidy::IncludeInserter
Definition: IncludeInserter.h:47
clang::tidy::modernize::PassByValueCheck::check
void check(const ast_matchers::MatchFinder::MatchResult &Result) override
ClangTidyChecks that register ASTMatchers should do the actual work in here.
Definition: PassByValueCheck.cpp:171
clang::tidy::modernize::PassByValueCheck::storeOptions
void storeOptions(ClangTidyOptions::OptionMap &Opts) override
Should store all options supported by this check with their current values or default values for opti...
Definition: PassByValueCheck.cpp:124
clang::tidy::ClangTidyCheck::diag
DiagnosticBuilder diag(SourceLocation Loc, StringRef Description, DiagnosticIDs::Level Level=DiagnosticIDs::Warning)
Add a diagnostic with the check's name.
Definition: ClangTidy.cpp:323
Result
const NamedDecl * Result
Definition: USRFinder.cpp:121