1 //===--- RedundantSmartptrGetCheck.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 "RedundantSmartptrGetCheck.h"
10 #include "clang/ASTMatchers/ASTMatchFinder.h"
11 #include "clang/Lex/Lexer.h"
12 
13 using namespace clang::ast_matchers;
14 
15 namespace clang {
16 namespace tidy {
17 namespace readability {
18 
19 namespace {
20 internal::Matcher<Expr> callToGet(const internal::Matcher<Decl> &OnClass) {
21   return expr(
22              anyOf(cxxMemberCallExpr(
23                        on(expr(anyOf(hasType(OnClass),
24                                      hasType(qualType(pointsTo(
25                                          decl(OnClass).bind("ptr_to_ptr"))))))
26                               .bind("smart_pointer")),
27                        unless(callee(
28                            memberExpr(hasObjectExpression(cxxThisExpr())))),
29                        callee(cxxMethodDecl(hasName("get"),
30                                             returns(qualType(pointsTo(
31                                                 type().bind("getType"))))))),
32                    cxxDependentScopeMemberExpr(
33                        hasMemberName("get"),
34                        hasObjectExpression(
35                            expr(hasType(qualType(hasCanonicalType(
36                                     templateSpecializationType(hasDeclaration(
37                                         classTemplateDecl(has(cxxRecordDecl(
38                                             OnClass,
39                                             hasMethod(cxxMethodDecl(
40                                                 hasName("get"),
41                                                 returns(qualType(
42                                                     pointsTo(type().bind(
43                                                         "getType")))))))))))))))
44                                .bind("smart_pointer")))))
45       .bind("redundant_get");
46 }
47 
48 internal::Matcher<Decl> knownSmartptr() {
49   return recordDecl(hasAnyName("::std::unique_ptr", "::std::shared_ptr"));
50 }
51 
52 void registerMatchersForGetArrowStart(MatchFinder *Finder,
53                                       MatchFinder::MatchCallback *Callback) {
54   const auto QuacksLikeASmartptr = recordDecl(
55       recordDecl().bind("duck_typing"),
56       has(cxxMethodDecl(hasName("operator->"),
57                         returns(qualType(pointsTo(type().bind("op->Type")))))),
58       has(cxxMethodDecl(hasName("operator*"), returns(qualType(references(
59                                                   type().bind("op*Type")))))));
60 
61   // Make sure we are not missing the known standard types.
62   const auto Smartptr = anyOf(knownSmartptr(), QuacksLikeASmartptr);
63 
64   // Catch 'ptr.get()->Foo()'
65   Finder->addMatcher(memberExpr(expr().bind("memberExpr"), isArrow(),
66                                 hasObjectExpression(callToGet(Smartptr))),
67                      Callback);
68 
69   // Catch '*ptr.get()' or '*ptr->get()'
70   Finder->addMatcher(
71       unaryOperator(hasOperatorName("*"), hasUnaryOperand(callToGet(Smartptr))),
72       Callback);
73 
74   // Catch '!ptr.get()'
75   const auto CallToGetAsBool = callToGet(
76       recordDecl(Smartptr, has(cxxConversionDecl(returns(booleanType())))));
77   Finder->addMatcher(
78       unaryOperator(hasOperatorName("!"), hasUnaryOperand(CallToGetAsBool)),
79       Callback);
80 
81   // Catch 'if(ptr.get())'
82   Finder->addMatcher(ifStmt(hasCondition(CallToGetAsBool)), Callback);
83 
84   // Catch 'ptr.get() ? X : Y'
85   Finder->addMatcher(conditionalOperator(hasCondition(CallToGetAsBool)),
86                      Callback);
87 
88   Finder->addMatcher(cxxDependentScopeMemberExpr(hasObjectExpression(
89                          callExpr(has(callToGet(Smartptr))).bind("obj"))),
90                      Callback);
91 }
92 
93 void registerMatchersForGetEquals(MatchFinder *Finder,
94                                   MatchFinder::MatchCallback *Callback) {
95   // This one is harder to do with duck typing.
96   // The operator==/!= that we are looking for might be member or non-member,
97   // might be on global namespace or found by ADL, might be a template, etc.
98   // For now, lets keep it to the known standard types.
99 
100   // Matches against nullptr.
101   Finder->addMatcher(
102       binaryOperator(hasAnyOperatorName("==", "!="),
103                      hasOperands(anyOf(cxxNullPtrLiteralExpr(), gnuNullExpr(),
104                                        integerLiteral(equals(0))),
105                                  callToGet(knownSmartptr()))),
106       Callback);
107 
108   // FIXME: Match and fix if (l.get() == r.get()).
109 }
110 
111 } // namespace
112 
113 void RedundantSmartptrGetCheck::storeOptions(
114     ClangTidyOptions::OptionMap &Opts) {
115   Options.store(Opts, "IgnoreMacros", IgnoreMacros);
116 }
117 
118 void RedundantSmartptrGetCheck::registerMatchers(MatchFinder *Finder) {
119   registerMatchersForGetArrowStart(Finder, this);
120   registerMatchersForGetEquals(Finder, this);
121 }
122 
123 namespace {
124 bool allReturnTypesMatch(const MatchFinder::MatchResult &Result) {
125   if (Result.Nodes.getNodeAs<Decl>("duck_typing") == nullptr)
126     return true;
127   // Verify that the types match.
128   // We can't do this on the matcher because the type nodes can be different,
129   // even though they represent the same type. This difference comes from how
130   // the type is referenced (eg. through a typedef, a type trait, etc).
131   const Type *OpArrowType =
132       Result.Nodes.getNodeAs<Type>("op->Type")->getUnqualifiedDesugaredType();
133   const Type *OpStarType =
134       Result.Nodes.getNodeAs<Type>("op*Type")->getUnqualifiedDesugaredType();
135   const Type *GetType =
136       Result.Nodes.getNodeAs<Type>("getType")->getUnqualifiedDesugaredType();
137   return OpArrowType == OpStarType && OpArrowType == GetType;
138 }
139 } // namespace
140 
141 void RedundantSmartptrGetCheck::check(const MatchFinder::MatchResult &Result) {
142   if (!allReturnTypesMatch(Result))
143     return;
144 
145   bool IsPtrToPtr = Result.Nodes.getNodeAs<Decl>("ptr_to_ptr") != nullptr;
146   bool IsMemberExpr = Result.Nodes.getNodeAs<Expr>("memberExpr") != nullptr;
147   const auto *GetCall = Result.Nodes.getNodeAs<Expr>("redundant_get");
148   if (GetCall->getBeginLoc().isMacroID() && IgnoreMacros)
149     return;
150 
151   const auto *Smartptr = Result.Nodes.getNodeAs<Expr>("smart_pointer");
152 
153   if (IsPtrToPtr && IsMemberExpr) {
154     // Ignore this case (eg. Foo->get()->DoSomething());
155     return;
156   }
157 
158   auto SR = GetCall->getSourceRange();
159   // CXXDependentScopeMemberExpr source range does not include parens
160   // Extend the source range of the get call to account for them.
161   if (isa<CXXDependentScopeMemberExpr>(GetCall))
162     SR.setEnd(Lexer::getLocForEndOfToken(SR.getEnd(), 0, *Result.SourceManager,
163                                          getLangOpts())
164                   .getLocWithOffset(1));
165 
166   StringRef SmartptrText = Lexer::getSourceText(
167       CharSourceRange::getTokenRange(Smartptr->getSourceRange()),
168       *Result.SourceManager, getLangOpts());
169   // Replace foo->get() with *foo, and foo.get() with foo.
170   std::string Replacement = Twine(IsPtrToPtr ? "*" : "", SmartptrText).str();
171   diag(GetCall->getBeginLoc(), "redundant get() call on smart pointer")
172       << FixItHint::CreateReplacement(SR, Replacement);
173 }
174 
175 } // namespace readability
176 } // namespace tidy
177 } // namespace clang
178