1 //===--- CopyConstructorInitCheck.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 "CopyConstructorInitCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/Lex/Lexer.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace bugprone {
19 
20 void CopyConstructorInitCheck::registerMatchers(MatchFinder *Finder) {
21   // In the future this might be extended to move constructors?
22   Finder->addMatcher(
23       cxxConstructorDecl(
24           isCopyConstructor(),
25           hasAnyConstructorInitializer(cxxCtorInitializer(
26               isBaseInitializer(),
27               withInitializer(cxxConstructExpr(hasDeclaration(
28                   cxxConstructorDecl(isDefaultConstructor())))))),
29           unless(isInstantiated()))
30           .bind("ctor"),
31       this);
32 }
33 
34 void CopyConstructorInitCheck::check(const MatchFinder::MatchResult &Result) {
35   const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructorDecl>("ctor");
36   std::string ParamName = Ctor->getParamDecl(0)->getNameAsString();
37 
38   // We want only one warning (and FixIt) for each ctor.
39   std::string FixItInitList;
40   bool HasRelevantBaseInit = false;
41   bool ShouldNotDoFixit = false;
42   bool HasWrittenInitializer = false;
43   SmallVector<FixItHint, 2> SafeFixIts;
44   for (const auto *Init : Ctor->inits()) {
45     bool CtorInitIsWritten = Init->isWritten();
46     HasWrittenInitializer = HasWrittenInitializer || CtorInitIsWritten;
47     if (!Init->isBaseInitializer())
48       continue;
49     const Type *BaseType = Init->getBaseClass();
50     // Do not do fixits if there is a type alias involved or one of the bases
51     // are explicitly initialized. In the latter case we not do fixits to avoid
52     // -Wreorder warnings.
53     if (const auto *TempSpecTy = dyn_cast<TemplateSpecializationType>(BaseType))
54       ShouldNotDoFixit = ShouldNotDoFixit || TempSpecTy->isTypeAlias();
55     ShouldNotDoFixit = ShouldNotDoFixit || isa<TypedefType>(BaseType);
56     ShouldNotDoFixit = ShouldNotDoFixit || CtorInitIsWritten;
57     const CXXRecordDecl *BaseClass =
58         BaseType->getAsCXXRecordDecl()->getDefinition();
59     if (BaseClass->field_empty() &&
60         BaseClass->forallBases(
61             [](const CXXRecordDecl *Class) { return Class->field_empty(); }))
62       continue;
63     bool NonCopyableBase = false;
64     for (const auto *Ctor : BaseClass->ctors()) {
65       if (Ctor->isCopyConstructor() &&
66           (Ctor->getAccess() == AS_private || Ctor->isDeleted())) {
67         NonCopyableBase = true;
68         break;
69       }
70     }
71     if (NonCopyableBase)
72       continue;
73     const auto *CExpr = dyn_cast<CXXConstructExpr>(Init->getInit());
74     if (!CExpr || !CExpr->getConstructor()->isDefaultConstructor())
75       continue;
76     HasRelevantBaseInit = true;
77     if (CtorInitIsWritten) {
78       if (!ParamName.empty())
79         SafeFixIts.push_back(
80             FixItHint::CreateInsertion(CExpr->getEndLoc(), ParamName));
81     } else {
82       if (Init->getSourceLocation().isMacroID() ||
83           Ctor->getLocation().isMacroID() || ShouldNotDoFixit)
84         break;
85       FixItInitList += BaseClass->getNameAsString();
86       FixItInitList += "(" + ParamName + "), ";
87     }
88   }
89   if (!HasRelevantBaseInit)
90     return;
91 
92   auto Diag = diag(Ctor->getLocation(),
93                    "calling a base constructor other than the copy constructor")
94               << SafeFixIts;
95 
96   if (FixItInitList.empty() || ParamName.empty() || ShouldNotDoFixit)
97     return;
98 
99   std::string FixItMsg{FixItInitList.substr(0, FixItInitList.size() - 2)};
100   SourceLocation FixItLoc;
101   // There is no initialization list in this constructor.
102   if (!HasWrittenInitializer) {
103     FixItLoc = Ctor->getBody()->getBeginLoc();
104     FixItMsg = " : " + FixItMsg;
105   } else {
106     // We apply the missing ctors at the beginning of the initialization list.
107     FixItLoc = (*Ctor->init_begin())->getSourceLocation();
108     FixItMsg += ',';
109   }
110   FixItMsg += ' ';
111 
112   Diag << FixItHint::CreateInsertion(FixItLoc, FixItMsg);
113 }
114 
115 } // namespace bugprone
116 } // namespace tidy
117 } // namespace clang
118