| //===- RedundantStringCStrCheck.cpp - Check for redundant c_str calls -----===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements a check for redundant calls of c_str() on strings. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "RedundantStringCStrCheck.h" |
| #include "clang/Lex/Lexer.h" |
| #include "clang/Tooling/FixIt.h" |
| |
| using namespace clang::ast_matchers; |
| |
| namespace clang { |
| namespace tidy { |
| namespace readability { |
| |
| namespace { |
| |
| // Return true if expr needs to be put in parens when it is an argument of a |
| // prefix unary operator, e.g. when it is a binary or ternary operator |
| // syntactically. |
| bool needParensAfterUnaryOperator(const Expr &ExprNode) { |
| if (isa<clang::BinaryOperator>(&ExprNode) || |
| isa<clang::ConditionalOperator>(&ExprNode)) { |
| return true; |
| } |
| if (const auto *Op = dyn_cast<CXXOperatorCallExpr>(&ExprNode)) { |
| return Op->getNumArgs() == 2 && Op->getOperator() != OO_PlusPlus && |
| Op->getOperator() != OO_MinusMinus && Op->getOperator() != OO_Call && |
| Op->getOperator() != OO_Subscript; |
| } |
| return false; |
| } |
| |
| // Format a pointer to an expression: prefix with '*' but simplify |
| // when it already begins with '&'. Return empty string on failure. |
| std::string |
| formatDereference(const ast_matchers::MatchFinder::MatchResult &Result, |
| const Expr &ExprNode) { |
| if (const auto *Op = dyn_cast<clang::UnaryOperator>(&ExprNode)) { |
| if (Op->getOpcode() == UO_AddrOf) { |
| // Strip leading '&'. |
| return std::string(tooling::fixit::getText( |
| *Op->getSubExpr()->IgnoreParens(), *Result.Context)); |
| } |
| } |
| StringRef Text = tooling::fixit::getText(ExprNode, *Result.Context); |
| |
| if (Text.empty()) |
| return std::string(); |
| // Add leading '*'. |
| if (needParensAfterUnaryOperator(ExprNode)) { |
| return (llvm::Twine("*(") + Text + ")").str(); |
| } |
| return (llvm::Twine("*") + Text).str(); |
| } |
| |
| AST_MATCHER(MaterializeTemporaryExpr, isBoundToLValue) { |
| return Node.isBoundToLvalueReference(); |
| } |
| |
| } // end namespace |
| |
| void RedundantStringCStrCheck::registerMatchers( |
| ast_matchers::MatchFinder *Finder) { |
| // Match expressions of type 'string' or 'string*'. |
| const auto StringDecl = type(hasUnqualifiedDesugaredType(recordType( |
| hasDeclaration(cxxRecordDecl(hasName("::std::basic_string")))))); |
| const auto StringExpr = |
| expr(anyOf(hasType(StringDecl), hasType(qualType(pointsTo(StringDecl))))); |
| |
| // Match string constructor. |
| const auto StringConstructorExpr = expr(anyOf( |
| cxxConstructExpr(argumentCountIs(1), |
| hasDeclaration(cxxMethodDecl(hasName("basic_string")))), |
| cxxConstructExpr( |
| argumentCountIs(2), |
| hasDeclaration(cxxMethodDecl(hasName("basic_string"))), |
| // If present, the second argument is the alloc object which must not |
| // be present explicitly. |
| hasArgument(1, cxxDefaultArgExpr())))); |
| |
| // Match a call to the string 'c_str()' method. |
| const auto StringCStrCallExpr = |
| cxxMemberCallExpr(on(StringExpr.bind("arg")), |
| callee(memberExpr().bind("member")), |
| callee(cxxMethodDecl(hasAnyName("c_str", "data")))) |
| .bind("call"); |
| const auto HasRValueTempParent = |
| hasParent(materializeTemporaryExpr(unless(isBoundToLValue()))); |
| // Detect redundant 'c_str()' calls through a string constructor. |
| // If CxxConstructExpr is the part of some CallExpr we need to |
| // check that matched ParamDecl of the ancestor CallExpr is not rvalue. |
| Finder->addMatcher( |
| traverse( |
| TK_AsIs, |
| cxxConstructExpr( |
| StringConstructorExpr, hasArgument(0, StringCStrCallExpr), |
| unless(anyOf(HasRValueTempParent, hasParent(cxxBindTemporaryExpr( |
| HasRValueTempParent)))))), |
| this); |
| |
| // Detect: 's == str.c_str()' -> 's == str' |
| Finder->addMatcher( |
| cxxOperatorCallExpr( |
| hasAnyOverloadedOperatorName("<", ">", ">=", "<=", "!=", "==", "+"), |
| anyOf(allOf(hasArgument(0, StringExpr), |
| hasArgument(1, StringCStrCallExpr)), |
| allOf(hasArgument(0, StringCStrCallExpr), |
| hasArgument(1, StringExpr)))), |
| this); |
| |
| // Detect: 'dst += str.c_str()' -> 'dst += str' |
| // Detect: 's = str.c_str()' -> 's = str' |
| Finder->addMatcher( |
| cxxOperatorCallExpr(hasAnyOverloadedOperatorName("=", "+="), |
| hasArgument(0, StringExpr), |
| hasArgument(1, StringCStrCallExpr)), |
| this); |
| |
| // Detect: 'dst.append(str.c_str())' -> 'dst.append(str)' |
| Finder->addMatcher( |
| cxxMemberCallExpr(on(StringExpr), callee(decl(cxxMethodDecl(hasAnyName( |
| "append", "assign", "compare")))), |
| argumentCountIs(1), hasArgument(0, StringCStrCallExpr)), |
| this); |
| |
| // Detect: 'dst.compare(p, n, str.c_str())' -> 'dst.compare(p, n, str)' |
| Finder->addMatcher( |
| cxxMemberCallExpr(on(StringExpr), |
| callee(decl(cxxMethodDecl(hasName("compare")))), |
| argumentCountIs(3), hasArgument(2, StringCStrCallExpr)), |
| this); |
| |
| // Detect: 'dst.find(str.c_str())' -> 'dst.find(str)' |
| Finder->addMatcher( |
| cxxMemberCallExpr(on(StringExpr), |
| callee(decl(cxxMethodDecl(hasAnyName( |
| "find", "find_first_not_of", "find_first_of", |
| "find_last_not_of", "find_last_of", "rfind")))), |
| anyOf(argumentCountIs(1), argumentCountIs(2)), |
| hasArgument(0, StringCStrCallExpr)), |
| this); |
| |
| // Detect: 'dst.insert(pos, str.c_str())' -> 'dst.insert(pos, str)' |
| Finder->addMatcher( |
| cxxMemberCallExpr(on(StringExpr), |
| callee(decl(cxxMethodDecl(hasName("insert")))), |
| argumentCountIs(2), hasArgument(1, StringCStrCallExpr)), |
| this); |
| |
| // Detect redundant 'c_str()' calls through a StringRef constructor. |
| Finder->addMatcher( |
| traverse( |
| TK_AsIs, |
| cxxConstructExpr( |
| // Implicit constructors of these classes are overloaded |
| // wrt. string types and they internally make a StringRef |
| // referring to the argument. Passing a string directly to |
| // them is preferred to passing a char pointer. |
| hasDeclaration(cxxMethodDecl(hasAnyName( |
| "::llvm::StringRef::StringRef", "::llvm::Twine::Twine"))), |
| argumentCountIs(1), |
| // The only argument must have the form x.c_str() or p->c_str() |
| // where the method is string::c_str(). StringRef also has |
| // a constructor from string which is more efficient (avoids |
| // strlen), so we can construct StringRef from the string |
| // directly. |
| hasArgument(0, StringCStrCallExpr))), |
| this); |
| } |
| |
| void RedundantStringCStrCheck::check(const MatchFinder::MatchResult &Result) { |
| const auto *Call = Result.Nodes.getNodeAs<CallExpr>("call"); |
| const auto *Arg = Result.Nodes.getNodeAs<Expr>("arg"); |
| const auto *Member = Result.Nodes.getNodeAs<MemberExpr>("member"); |
| bool Arrow = Member->isArrow(); |
| // Replace the "call" node with the "arg" node, prefixed with '*' |
| // if the call was using '->' rather than '.'. |
| std::string ArgText = |
| Arrow ? formatDereference(Result, *Arg) |
| : tooling::fixit::getText(*Arg, *Result.Context).str(); |
| if (ArgText.empty()) |
| return; |
| |
| diag(Call->getBeginLoc(), "redundant call to %0") |
| << Member->getMemberDecl() |
| << FixItHint::CreateReplacement(Call->getSourceRange(), ArgText); |
| } |
| |
| } // namespace readability |
| } // namespace tidy |
| } // namespace clang |
