clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.cpp

   1 //===--- TwineLocalCheck.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 "TwineLocalCheck.h"
  10 #include "clang/AST/ASTContext.h"
  11 #include "clang/ASTMatchers/ASTMatchers.h"
  12 #include "clang/Lex/Lexer.h"
  13
  14 using namespace clang::ast_matchers;
  15
  16 namespace clang::tidy::llvm_check {
  17
  18 void TwineLocalCheck::registerMatchers(MatchFinder *Finder) {
  19   auto TwineType =
  20       qualType(hasDeclaration(cxxRecordDecl(hasName("::llvm::Twine"))));
  21   Finder->addMatcher(
  22       varDecl(unless(parmVarDecl()), hasType(TwineType)).bind("variable"),
  23       this);
  24 }
  25
  26 void TwineLocalCheck::check(const MatchFinder::MatchResult &Result) {
  27   const auto *VD = Result.Nodes.getNodeAs<VarDecl>("variable");
  28   auto Diag = diag(VD->getLocation(),
  29                    "twine variables are prone to use-after-free bugs");
  30
  31   // If this VarDecl has an initializer try to fix it.
  32   if (VD->hasInit()) {
  33     // Peel away implicit constructors and casts so we can see the actual type
  34     // of the initializer.
  35     const Expr *C = VD->getInit()->IgnoreImplicit();
  36
  37     while (isa<CXXConstructExpr>(C)) {
  38       if (cast<CXXConstructExpr>(C)->getNumArgs() == 0)
  39         break;
  40       C = cast<CXXConstructExpr>(C)->getArg(0)->IgnoreParenImpCasts();
  41     }
  42
  43     SourceRange TypeRange =
  44         VD->getTypeSourceInfo()->getTypeLoc().getSourceRange();
  45
  46     // A real Twine, turn it into a std::string.
  47     if (VD->getType()->getCanonicalTypeUnqualified() ==
  48         C->getType()->getCanonicalTypeUnqualified()) {
  49       SourceLocation EndLoc = Lexer::getLocForEndOfToken(
  50           VD->getInit()->getEndLoc(), 0, *Result.SourceManager, getLangOpts());
  51       Diag << FixItHint::CreateReplacement(TypeRange, "std::string")
  52            << FixItHint::CreateInsertion(VD->getInit()->getBeginLoc(), "(")
  53            << FixItHint::CreateInsertion(EndLoc, ").str()");
  54     } else {
  55       // Just an implicit conversion. Insert the real type.
  56       Diag << FixItHint::CreateReplacement(
  57           TypeRange,
  58           C->getType().getAsString(Result.Context->getPrintingPolicy()));
  59     }
  60   }
  61 }
  62
  63 } // namespace clang::tidy::llvm_check