99 lines · cpp
1//===----------------------------------------------------------------------===//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-exception6//7//===----------------------------------------------------------------------===//8 9#include "StrCatAppendCheck.h"10#include "clang/AST/ASTContext.h"11#include "clang/ASTMatchers/ASTMatchFinder.h"12 13using namespace clang::ast_matchers;14 15namespace clang::tidy::abseil {16 17namespace {18// Skips any combination of temporary materialization, temporary binding and19// implicit casting.20AST_MATCHER_P(Stmt, ignoringTemporaries, ast_matchers::internal::Matcher<Stmt>,21 InnerMatcher) {22 const Stmt *E = &Node;23 while (true) {24 if (const auto *MTE = dyn_cast<MaterializeTemporaryExpr>(E))25 E = MTE->getSubExpr();26 if (const auto *BTE = dyn_cast<CXXBindTemporaryExpr>(E))27 E = BTE->getSubExpr();28 if (const auto *ICE = dyn_cast<ImplicitCastExpr>(E))29 E = ICE->getSubExpr();30 else31 break;32 }33 34 return InnerMatcher.matches(*E, Finder, Builder);35}36 37} // namespace38 39// TODO: str += StrCat(...)40// str.append(StrCat(...))41 42void StrCatAppendCheck::registerMatchers(MatchFinder *Finder) {43 const auto StrCat = functionDecl(hasName("::absl::StrCat"));44 // The arguments of absl::StrCat are implicitly converted to AlphaNum. This45 // matches to the arguments because of that behavior.46 const auto AlphaNum = ignoringTemporaries(cxxConstructExpr(47 argumentCountIs(1), hasType(cxxRecordDecl(hasName("::absl::AlphaNum"))),48 hasArgument(0, ignoringImpCasts(declRefExpr(to(equalsBoundNode("LHS")),49 expr().bind("Arg0"))))));50 51 const auto HasAnotherReferenceToLhs =52 callExpr(hasAnyArgument(expr(hasDescendant(declRefExpr(53 to(equalsBoundNode("LHS")), unless(equalsBoundNode("Arg0")))))));54 55 // Now look for calls to operator= with an object on the LHS and a call to56 // StrCat on the RHS. The first argument of the StrCat call should be the same57 // as the LHS. Ignore calls from template instantiations.58 Finder->addMatcher(59 traverse(TK_AsIs,60 cxxOperatorCallExpr(61 unless(isInTemplateInstantiation()),62 hasOverloadedOperatorName("="),63 hasArgument(0, declRefExpr(to(decl().bind("LHS")))),64 hasArgument(65 1, ignoringTemporaries(66 callExpr(callee(StrCat), hasArgument(0, AlphaNum),67 unless(HasAnotherReferenceToLhs))68 .bind("Call"))))69 .bind("Op")),70 this);71}72 73void StrCatAppendCheck::check(const MatchFinder::MatchResult &Result) {74 const auto *Op = Result.Nodes.getNodeAs<CXXOperatorCallExpr>("Op");75 const auto *Call = Result.Nodes.getNodeAs<CallExpr>("Call");76 assert(Op && Call && "Matcher does not work as expected");77 78 // Handles the case 'x = absl::StrCat(x)', which has no effect.79 if (Call->getNumArgs() == 1) {80 diag(Op->getBeginLoc(), "call to 'absl::StrCat' has no effect");81 return;82 }83 84 // Emit a warning and emit fixits to go from85 // x = absl::StrCat(x, ...)86 // to87 // absl::StrAppend(&x, ...)88 diag(Op->getBeginLoc(),89 "call 'absl::StrAppend' instead of 'absl::StrCat' when appending to a "90 "string to avoid a performance penalty")91 << FixItHint::CreateReplacement(92 CharSourceRange::getTokenRange(Op->getBeginLoc(),93 Call->getCallee()->getEndLoc()),94 "absl::StrAppend")95 << FixItHint::CreateInsertion(Call->getArg(0)->getBeginLoc(), "&");96}97 98} // namespace clang::tidy::abseil99