1 //===--- InefficientStringConcatenationCheck.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 "InefficientStringConcatenationCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12
13 using namespace clang::ast_matchers;
14
15 namespace clang::tidy::performance {
16
storeOptions(ClangTidyOptions::OptionMap & Opts)17 void InefficientStringConcatenationCheck::storeOptions(
18 ClangTidyOptions::OptionMap &Opts) {
19 Options.store(Opts, "StrictMode", StrictMode);
20 }
21
InefficientStringConcatenationCheck(StringRef Name,ClangTidyContext * Context)22 InefficientStringConcatenationCheck::InefficientStringConcatenationCheck(
23 StringRef Name, ClangTidyContext *Context)
24 : ClangTidyCheck(Name, Context),
25 StrictMode(Options.getLocalOrGlobal("StrictMode", false)) {}
26
registerMatchers(MatchFinder * Finder)27 void InefficientStringConcatenationCheck::registerMatchers(
28 MatchFinder *Finder) {
29 const auto BasicStringType =
30 hasType(qualType(hasUnqualifiedDesugaredType(recordType(
31 hasDeclaration(cxxRecordDecl(hasName("::std::basic_string")))))));
32
33 const auto BasicStringPlusOperator = cxxOperatorCallExpr(
34 hasOverloadedOperatorName("+"),
35 hasAnyArgument(ignoringImpCasts(declRefExpr(BasicStringType))));
36
37 const auto PlusOperator =
38 cxxOperatorCallExpr(
39 hasOverloadedOperatorName("+"),
40 hasAnyArgument(ignoringImpCasts(declRefExpr(BasicStringType))),
41 hasDescendant(BasicStringPlusOperator))
42 .bind("plusOperator");
43
44 const auto AssignOperator = cxxOperatorCallExpr(
45 hasOverloadedOperatorName("="),
46 hasArgument(0, declRefExpr(BasicStringType,
47 hasDeclaration(decl().bind("lhsStrT")))
48 .bind("lhsStr")),
49 hasArgument(1, stmt(hasDescendant(declRefExpr(
50 hasDeclaration(decl(equalsBoundNode("lhsStrT"))))))),
51 hasDescendant(BasicStringPlusOperator));
52
53 if (StrictMode) {
54 Finder->addMatcher(cxxOperatorCallExpr(anyOf(AssignOperator, PlusOperator)),
55 this);
56 } else {
57 Finder->addMatcher(
58 cxxOperatorCallExpr(anyOf(AssignOperator, PlusOperator),
59 hasAncestor(stmt(anyOf(cxxForRangeStmt(),
60 whileStmt(), forStmt())))),
61 this);
62 }
63 }
64
check(const MatchFinder::MatchResult & Result)65 void InefficientStringConcatenationCheck::check(
66 const MatchFinder::MatchResult &Result) {
67 const auto *LhsStr = Result.Nodes.getNodeAs<DeclRefExpr>("lhsStr");
68 const auto *PlusOperator =
69 Result.Nodes.getNodeAs<CXXOperatorCallExpr>("plusOperator");
70 const char *DiagMsg =
71 "string concatenation results in allocation of unnecessary temporary "
72 "strings; consider using 'operator+=' or 'string::append()' instead";
73
74 if (LhsStr)
75 diag(LhsStr->getExprLoc(), DiagMsg);
76 else if (PlusOperator)
77 diag(PlusOperator->getExprLoc(), DiagMsg);
78 }
79
80 } // namespace clang::tidy::performance
81