clang-tools 6.0.0

UseEqualsDefaultCheck.cpp
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1 //===--- UseEqualsDefaultCheck.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 "UseEqualsDefaultCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/Lex/Lexer.h"
14
15 using namespace clang::ast_matchers;
16
17 namespace clang {
18 namespace tidy {
19 namespace modernize {
20
21 static const char SpecialFunction[] = "SpecialFunction";
22
23 /// \brief Finds all the named non-static fields of \p Record.
24 static std::set<const FieldDecl *>
25 getAllNamedFields(const CXXRecordDecl *Record) {
26 std::set<const FieldDecl *> Result;
27 for (const auto *Field : Record->fields()) {
28 // Static data members are not in this range.
29 if (Field->isUnnamedBitfield())
30 continue;
31 Result.insert(Field);
32 }
33 return Result;
34 }
35
36 /// \brief Returns the names of the direct bases of \p Record, both virtual and
37 /// non-virtual.
38 static std::set<const Type *> getAllDirectBases(const CXXRecordDecl *Record) {
39 std::set<const Type *> Result;
40 for (auto Base : Record->bases()) {
41 // CXXBaseSpecifier.
42 const auto *BaseType = Base.getTypeSourceInfo()->getType().getTypePtr();
43 Result.insert(BaseType);
44 }
45 return Result;
46 }
47
48 /// \brief Returns a matcher that matches member expressions where the base is
49 /// the variable declared as \p Var and the accessed member is the one declared
50 /// as \p Field.
51 internal::Matcher<Expr> accessToFieldInVar(const FieldDecl *Field,
52 const ValueDecl *Var) {
53 return ignoringImpCasts(
54 memberExpr(hasObjectExpression(declRefExpr(to(varDecl(equalsNode(Var))))),
55 member(fieldDecl(equalsNode(Field)))));
56 }
57
58 /// \brief Check that the given constructor has copy signature and that it
59 /// copy-initializes all its bases and members.
60 static bool isCopyConstructorAndCanBeDefaulted(ASTContext *Context,
61 const CXXConstructorDecl *Ctor) {
62 // An explicitly-defaulted constructor cannot have default arguments.
63 if (Ctor->getMinRequiredArguments() != 1)
64 return false;
65
66 const auto *Record = Ctor->getParent();
67 const auto *Param = Ctor->getParamDecl(0);
68
69 // Base classes and members that have to be copied.
70 auto BasesToInit = getAllDirectBases(Record);
71 auto FieldsToInit = getAllNamedFields(Record);
72
73 // Ensure that all the bases are copied.
74 for (const auto *Base : BasesToInit) {
75 // The initialization of a base class should be a call to a copy
76 // constructor of the base.
77 if (match(
78 cxxConstructorDecl(forEachConstructorInitializer(cxxCtorInitializer(
79 isBaseInitializer(),
80 withInitializer(cxxConstructExpr(allOf(
81 hasType(equalsNode(Base)),
82 hasDeclaration(cxxConstructorDecl(isCopyConstructor())),
83 argumentCountIs(1),
84 hasArgument(
85 0, declRefExpr(to(varDecl(equalsNode(Param))))))))))),
86 *Ctor, *Context)
87 .empty())
88 return false;
89 }
90
91 // Ensure that all the members are copied.
92 for (const auto *Field : FieldsToInit) {
93 auto AccessToFieldInParam = accessToFieldInVar(Field, Param);
94 // The initialization is a CXXConstructExpr for class types.
95 if (match(
96 cxxConstructorDecl(forEachConstructorInitializer(cxxCtorInitializer(
97 isMemberInitializer(), forField(equalsNode(Field)),
98 withInitializer(anyOf(
99 AccessToFieldInParam,
100 cxxConstructExpr(allOf(
101 hasDeclaration(cxxConstructorDecl(isCopyConstructor())),
102 argumentCountIs(1),
103 hasArgument(0, AccessToFieldInParam)))))))),
104 *Ctor, *Context)
105 .empty())
106 return false;
107 }
108
109 // Ensure that we don't do anything else, like initializing an indirect base.
110 return Ctor->getNumCtorInitializers() ==
111 BasesToInit.size() + FieldsToInit.size();
112 }
113
114 /// \brief Checks that the given method is an overloading of the assignment
115 /// operator, has copy signature, returns a reference to "*this" and copies
116 /// all its members and subobjects.
117 static bool isCopyAssignmentAndCanBeDefaulted(ASTContext *Context,
118 const CXXMethodDecl *Operator) {
119 const auto *Record = Operator->getParent();
120 const auto *Param = Operator->getParamDecl(0);
121
122 // Base classes and members that have to be copied.
123 auto BasesToInit = getAllDirectBases(Record);
124 auto FieldsToInit = getAllNamedFields(Record);
125
126 const auto *Compound = cast<CompoundStmt>(Operator->getBody());
127
128 // The assignment operator definition has to end with the following return
129 // statement:
130 // return *this;
131 if (Compound->body_empty() ||
132 match(returnStmt(has(ignoringParenImpCasts(unaryOperator(
133 hasOperatorName("*"), hasUnaryOperand(cxxThisExpr()))))),
134 *Compound->body_back(), *Context)
135 .empty())
136 return false;
137
138 // Ensure that all the bases are copied.
139 for (const auto *Base : BasesToInit) {
140 // Assignment operator of a base class:
141 // Base::operator=(Other);
142 //
143 // Clang translates this into:
144 // ((Base*)this)->operator=((Base)Other);
145 //
146 // So we are looking for a member call that fulfills:
147 if (match(compoundStmt(has(ignoringParenImpCasts(cxxMemberCallExpr(allOf(
148 // - The object is an implicit cast of 'this' to a pointer to
149 // a base class.
150 onImplicitObjectArgument(
151 implicitCastExpr(hasImplicitDestinationType(
152 pointsTo(type(equalsNode(Base)))),
153 hasSourceExpression(cxxThisExpr()))),
154 // - The called method is the operator=.
155 callee(cxxMethodDecl(isCopyAssignmentOperator())),
156 // - The argument is (an implicit cast to a Base of) the
157 // argument taken by "Operator".
158 argumentCountIs(1),
159 hasArgument(0,
160 declRefExpr(to(varDecl(equalsNode(Param)))))))))),
161 *Compound, *Context)
162 .empty())
163 return false;
164 }
165
166 // Ensure that all the members are copied.
167 for (const auto *Field : FieldsToInit) {
168 // The assignment of data members:
169 // Field = Other.Field;
170 // Is a BinaryOperator in non-class types, and a CXXOperatorCallExpr
171 // otherwise.
172 auto LHS = memberExpr(hasObjectExpression(cxxThisExpr()),
173 member(fieldDecl(equalsNode(Field))));
174 auto RHS = accessToFieldInVar(Field, Param);
175 if (match(
176 compoundStmt(has(ignoringParenImpCasts(stmt(anyOf(
177 binaryOperator(hasOperatorName("="), hasLHS(LHS), hasRHS(RHS)),
178 cxxOperatorCallExpr(hasOverloadedOperatorName("="),
179 argumentCountIs(2), hasArgument(0, LHS),
180 hasArgument(1, RHS))))))),
181 *Compound, *Context)
182 .empty())
183 return false;
184 }
185
186 // Ensure that we don't do anything else.
187 return Compound->size() == BasesToInit.size() + FieldsToInit.size() + 1;
188 }
189
190 /// \brief Returns false if the body has any non-whitespace character.
191 static bool bodyEmpty(const ASTContext *Context, const CompoundStmt *Body) {
192 bool Invalid = false;
193 StringRef Text = Lexer::getSourceText(
194 CharSourceRange::getCharRange(Body->getLBracLoc().getLocWithOffset(1),
195 Body->getRBracLoc()),
196 Context->getSourceManager(), Context->getLangOpts(), &Invalid);
197 return !Invalid && std::strspn(Text.data(), " \t\r\n") == Text.size();
198 }
199
200 UseEqualsDefaultCheck::UseEqualsDefaultCheck(StringRef Name,
201 ClangTidyContext *Context)
202 : ClangTidyCheck(Name, Context),
203 IgnoreMacros(Options.getLocalOrGlobal("IgnoreMacros", true) != 0) {}
204
205 void UseEqualsDefaultCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
206 Options.store(Opts, "IgnoreMacros", IgnoreMacros);
207 }
208
209 void UseEqualsDefaultCheck::registerMatchers(MatchFinder *Finder) {
210 if (!getLangOpts().CPlusPlus)
211 return;
212
213 // Destructor.
214 Finder->addMatcher(cxxDestructorDecl(isDefinition()).bind(SpecialFunction),
215 this);
216 Finder->addMatcher(
217 cxxConstructorDecl(
218 isDefinition(),
219 anyOf(
220 // Default constructor.
221 allOf(unless(hasAnyConstructorInitializer(isWritten())),
222 parameterCountIs(0)),
223 // Copy constructor.
224 allOf(isCopyConstructor(),
225 // Discard constructors that can be used as a copy
226 // constructor because all the other arguments have
227 // default values.
228 parameterCountIs(1))))
229 .bind(SpecialFunction),
230 this);
231 // Copy-assignment operator.
232 Finder->addMatcher(
233 cxxMethodDecl(isDefinition(), isCopyAssignmentOperator(),
234 // isCopyAssignmentOperator() allows the parameter to be
235 // passed by value, and in this case it cannot be
236 // defaulted.
237 hasParameter(0, hasType(lValueReferenceType())))
238 .bind(SpecialFunction),
239 this);
240 }
241
242 void UseEqualsDefaultCheck::check(const MatchFinder::MatchResult &Result) {
243 std::string SpecialFunctionName;
244
245 // Both CXXConstructorDecl and CXXDestructorDecl inherit from CXXMethodDecl.
246 const auto *SpecialFunctionDecl =
247 Result.Nodes.getNodeAs<CXXMethodDecl>(SpecialFunction);
248
249 if (IgnoreMacros && SpecialFunctionDecl->getLocation().isMacroID())
250 return;
251
252 // Discard explicitly deleted/defaulted special member functions and those
253 // that are not user-provided (automatically generated).
254 if (SpecialFunctionDecl->isDeleted() ||
255 SpecialFunctionDecl->isExplicitlyDefaulted() ||
256 SpecialFunctionDecl->isLateTemplateParsed() ||
257 SpecialFunctionDecl->isTemplateInstantiation() ||
258 !SpecialFunctionDecl->isUserProvided() || !SpecialFunctionDecl->hasBody())
259 return;
260
261 const auto *Body = dyn_cast<CompoundStmt>(SpecialFunctionDecl->getBody());
262 if (!Body)
263 return;
264
265 // If there is code inside the body, don't warn.
266 if (!SpecialFunctionDecl->isCopyAssignmentOperator() && !Body->body_empty())
267 return;
268
269 // If there are comments inside the body, don't do the change.
270 bool ApplyFix = SpecialFunctionDecl->isCopyAssignmentOperator() ||
271 bodyEmpty(Result.Context, Body);
272
273 std::vector<FixItHint> RemoveInitializers;
274
275 if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(SpecialFunctionDecl)) {
276 if (Ctor->getNumParams() == 0) {
277 SpecialFunctionName = "default constructor";
278 } else {
279 if (!isCopyConstructorAndCanBeDefaulted(Result.Context, Ctor))
280 return;
281 SpecialFunctionName = "copy constructor";
282 // If there are constructor initializers, they must be removed.
283 for (const auto *Init : Ctor->inits()) {
284 RemoveInitializers.emplace_back(
285 FixItHint::CreateRemoval(Init->getSourceRange()));
286 }
287 }
288 } else if (isa<CXXDestructorDecl>(SpecialFunctionDecl)) {
289 SpecialFunctionName = "destructor";
290 } else {
291 if (!isCopyAssignmentAndCanBeDefaulted(Result.Context, SpecialFunctionDecl))
292 return;
293 SpecialFunctionName = "copy-assignment operator";
294 }
295
296 // The location of the body is more useful inside a macro as spelling and
297 // expansion locations are reported.
298 SourceLocation Location = SpecialFunctionDecl->getLocation();
299 if (Location.isMacroID())
300 Location = Body->getLocStart();
301
302 auto Diag = diag(Location, "use '= default' to define a trivial " +
303 SpecialFunctionName);
304
305 if (ApplyFix)
306 Diag << FixItHint::CreateReplacement(Body->getSourceRange(), "= default;")
307 << RemoveInitializers;
308 }
309
310 } // namespace modernize
311 } // namespace tidy
312 } // namespace clang
clang::tidy::modernize::isCopyAssignmentAndCanBeDefaulted
static bool isCopyAssignmentAndCanBeDefaulted(ASTContext *Context, const CXXMethodDecl *Operator)
Checks that the given method is an overloading of the assignment operator, has copy signature...
Definition: UseEqualsDefaultCheck.cpp:117
clang::ast_matchers
Definition: ClangTidyDiagnosticConsumer.h:27
clang::tidy::modernize::SpecialFunction
static const char SpecialFunction[]
Definition: UseEqualsDefaultCheck.cpp:21
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:449
Name
StringHandle Name
Definition: PreprocessorTracker.cpp:525
clang::tidy::ClangTidyCheck::getLangOpts
LangOptions getLangOpts() const
Returns the language options from the context.
Definition: ClangTidy.h:187
clang::tidy::ClangTidyCheck
Base class for all clang-tidy checks.
Definition: ClangTidy.h:127
clang::tidy::ClangTidyCheck::Options
OptionsView Options
Definition: ClangTidy.h:183
clang::tidy::modernize::bodyEmpty
static bool bodyEmpty(const ASTContext *Context, const CompoundStmt *Body)
Returns false if the body has any non-whitespace character.
Definition: UseEqualsDefaultCheck.cpp:191
clang::tidy::modernize::UseEqualsDefaultCheck::registerMatchers
void registerMatchers(ast_matchers::MatchFinder *Finder) override
Override this to register AST matchers with Finder.
Definition: UseEqualsDefaultCheck.cpp:209
clang::tidy::ClangTidyOptions::OptionMap
std::map< std::string, std::string > OptionMap
Definition: ClangTidyOptions.h:99
UseEqualsDefaultCheck.h
clang
Definition: AndroidTidyModule.cpp:28
clang::tidy::modernize::accessToFieldInVar
internal::Matcher< Expr > accessToFieldInVar(const FieldDecl *Field, const ValueDecl *Var)
Returns a matcher that matches member expressions where the base is the variable declared as Var and ...
Definition: UseEqualsDefaultCheck.cpp:51
clang::tidy::ClangTidyContext
Every ClangTidyCheck reports errors through a DiagnosticsEngine provided by this context.
Definition: ClangTidyDiagnosticConsumer.h:104
clang::tidy::modernize::UseEqualsDefaultCheck::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: UseEqualsDefaultCheck.cpp:205
clang::tidy::modernize::isCopyConstructorAndCanBeDefaulted
static bool isCopyConstructorAndCanBeDefaulted(ASTContext *Context, const CXXConstructorDecl *Ctor)
Check that the given constructor has copy signature and that it copy-initializes all its bases and me...
Definition: UseEqualsDefaultCheck.cpp:60
clang::tidy::modernize::getAllDirectBases
static std::set< const Type * > getAllDirectBases(const CXXRecordDecl *Record)
Returns the names of the direct bases of Record, both virtual and non-virtual.
Definition: UseEqualsDefaultCheck.cpp:38
clang::tidy::modernize::getAllNamedFields
static std::set< const FieldDecl * > getAllNamedFields(const CXXRecordDecl *Record)
Finds all the named non-static fields of Record.
Definition: UseEqualsDefaultCheck.cpp:25
clang::tidy::ClangTidyCheck::diag
DiagnosticBuilder diag(SourceLocation Loc, StringRef Description, DiagnosticIDs::Level Level=DiagnosticIDs::Warning)
Add a diagnostic with the check&#39;s name.
Definition: ClangTidy.cpp:416
clang::tidy::modernize::UseEqualsDefaultCheck::check
void check(const ast_matchers::MatchFinder::MatchResult &Result) override
ClangTidyChecks that register ASTMatchers should do the actual work in here.
Definition: UseEqualsDefaultCheck.cpp:242
Location
Definition: Modularize.cpp:384