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
registerMatchers(MatchFinder * Finder)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
check(const MatchFinder::MatchResult & Result)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
64