clang-tools  11.0.0
UnusedRaiiCheck.cpp
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1 //===--- UnusedRaiiCheck.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 "UnusedRaiiCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/Lex/Lexer.h"
12 
13 using namespace clang::ast_matchers;
14 
15 namespace clang {
16 namespace tidy {
17 namespace bugprone {
18 
19 namespace {
20 AST_MATCHER(CXXRecordDecl, hasNonTrivialDestructor) {
21  // TODO: If the dtor is there but empty we don't want to warn either.
22  return Node.hasDefinition() && Node.hasNonTrivialDestructor();
23 }
24 } // namespace
25 
26 void UnusedRaiiCheck::registerMatchers(MatchFinder *Finder) {
27  // Look for temporaries that are constructed in-place and immediately
28  // destroyed. Look for temporaries created by a functional cast but not for
29  // those returned from a call.
30  auto BindTemp = cxxBindTemporaryExpr(
31  unless(has(ignoringParenImpCasts(callExpr()))),
32  unless(has(ignoringParenImpCasts(objcMessageExpr()))))
33  .bind("temp");
34  Finder->addMatcher(
35  traverse(ast_type_traits::TK_AsIs,
36  exprWithCleanups(
37  unless(isInTemplateInstantiation()),
38  hasParent(compoundStmt().bind("compound")),
39  hasType(cxxRecordDecl(hasNonTrivialDestructor())),
40  anyOf(has(ignoringParenImpCasts(BindTemp)),
41  has(ignoringParenImpCasts(cxxFunctionalCastExpr(
42  has(ignoringParenImpCasts(BindTemp)))))))
43  .bind("expr")),
44  this);
45 }
46 
47 void UnusedRaiiCheck::check(const MatchFinder::MatchResult &Result) {
48  const auto *E = Result.Nodes.getNodeAs<Expr>("expr");
49 
50  // We ignore code expanded from macros to reduce the number of false
51  // positives.
52  if (E->getBeginLoc().isMacroID())
53  return;
54 
55  // Don't emit a warning for the last statement in the surrounding compound
56  // statement.
57  const auto *CS = Result.Nodes.getNodeAs<CompoundStmt>("compound");
58  if (E == CS->body_back())
59  return;
60 
61  // Emit a warning.
62  auto D = diag(E->getBeginLoc(), "object destroyed immediately after "
63  "creation; did you mean to name the object?");
64  const char *Replacement = " give_me_a_name";
65 
66  // If this is a default ctor we have to remove the parens or we'll introduce a
67  // most vexing parse.
68  const auto *BTE = Result.Nodes.getNodeAs<CXXBindTemporaryExpr>("temp");
69  if (const auto *TOE = dyn_cast<CXXTemporaryObjectExpr>(BTE->getSubExpr()))
70  if (TOE->getNumArgs() == 0) {
71  D << FixItHint::CreateReplacement(
72  CharSourceRange::getTokenRange(TOE->getParenOrBraceRange()),
73  Replacement);
74  return;
75  }
76 
77  // Otherwise just suggest adding a name. To find the place to insert the name
78  // find the first TypeLoc in the children of E, which always points to the
79  // written type.
80  auto Matches =
81  match(expr(hasDescendant(typeLoc().bind("t"))), *E, *Result.Context);
82  const auto *TL = selectFirst<TypeLoc>("t", Matches);
83  assert(TL);
84  D << FixItHint::CreateInsertion(
85  Lexer::getLocForEndOfToken(TL->getEndLoc(), 0, *Result.SourceManager,
86  getLangOpts()),
87  Replacement);
88 }
89 
90 } // namespace bugprone
91 } // namespace tidy
92 } // namespace clang
E
const Expr * E
Definition: AvoidBindCheck.cpp:88
clang::ast_matchers
Definition: AbseilMatcher.h:14
clang::clangd::match
std::vector< std::string > match(const SymbolIndex &I, const FuzzyFindRequest &Req, bool *Incomplete)
Definition: TestIndex.cpp:94
clang::ast_matchers::AST_MATCHER
AST_MATCHER(Expr, isMacroID)
Definition: PreferIsaOrDynCastInConditionalsCheck.cpp:19
clang
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Definition: ApplyReplacements.h:27
UnusedRaiiCheck.h