1 //===-- StringCompareCheck.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 "StringCompareCheck.h"
10 #include "../utils/FixItHintUtils.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/Tooling/FixIt.h"
14 
15 using namespace clang::ast_matchers;
16 
17 namespace clang {
18 namespace tidy {
19 namespace readability {
20 
21 static const StringRef CompareMessage = "do not use 'compare' to test equality "
22                                         "of strings; use the string equality "
23                                         "operator instead";
24 
25 void StringCompareCheck::registerMatchers(MatchFinder *Finder) {
26   if (!getLangOpts().CPlusPlus)
27     return;
28 
29   const auto StrCompare = cxxMemberCallExpr(
30       callee(cxxMethodDecl(hasName("compare"),
31                            ofClass(classTemplateSpecializationDecl(
32                                hasName("::std::basic_string"))))),
33       hasArgument(0, expr().bind("str2")), argumentCountIs(1),
34       callee(memberExpr().bind("str1")));
35 
36   // First and second case: cast str.compare(str) to boolean.
37   Finder->addMatcher(implicitCastExpr(hasImplicitDestinationType(booleanType()),
38                                       has(StrCompare))
39                          .bind("match1"),
40                      this);
41 
42   // Third and fourth case: str.compare(str) == 0 and str.compare(str) != 0.
43   Finder->addMatcher(
44       binaryOperator(anyOf(hasOperatorName("=="), hasOperatorName("!=")),
45                      hasEitherOperand(StrCompare.bind("compare")),
46                      hasEitherOperand(integerLiteral(equals(0)).bind("zero")))
47           .bind("match2"),
48       this);
49 }
50 
51 void StringCompareCheck::check(const MatchFinder::MatchResult &Result) {
52   if (const auto *Matched = Result.Nodes.getNodeAs<Stmt>("match1")) {
53     diag(Matched->getBeginLoc(), CompareMessage);
54     return;
55   }
56 
57   if (const auto *Matched = Result.Nodes.getNodeAs<Stmt>("match2")) {
58     const ASTContext &Ctx = *Result.Context;
59 
60     if (const auto *Zero = Result.Nodes.getNodeAs<Stmt>("zero")) {
61       const auto *Str1 = Result.Nodes.getNodeAs<MemberExpr>("str1");
62       const auto *Str2 = Result.Nodes.getNodeAs<Stmt>("str2");
63       const auto *Compare = Result.Nodes.getNodeAs<Stmt>("compare");
64 
65       auto Diag = diag(Matched->getBeginLoc(), CompareMessage);
66 
67       if (Str1->isArrow())
68         Diag << FixItHint::CreateInsertion(Str1->getBeginLoc(), "*");
69 
70       Diag << tooling::fixit::createReplacement(*Zero, *Str2, Ctx)
71            << tooling::fixit::createReplacement(*Compare, *Str1->getBase(),
72                                                 Ctx);
73     }
74   }
75 
76   // FIXME: Add fixit to fix the code for case one and two (match1).
77 }
78 
79 } // namespace readability
80 } // namespace tidy
81 } // namespace clang
82