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UnusedRAIICheck.cpp
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1 //===--- UnusedRAIICheck.cpp - clang-tidy ---------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 #include "UnusedRAIICheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/Lex/Lexer.h"
13
14 using namespace clang::ast_matchers;
15
16 namespace clang {
17 namespace {
18 AST_MATCHER(CXXRecordDecl, hasNonTrivialDestructor) {
19 // TODO: If the dtor is there but empty we don't want to warn either.
20 return Node.hasDefinition() && Node.hasNonTrivialDestructor();
21 }
22 } // namespace
23
24 namespace tidy {
25 namespace misc {
26
27 void UnusedRAIICheck::registerMatchers(MatchFinder *Finder) {
28 // Only register the matchers for C++; the functionality currently does not
29 // provide any benefit to other languages, despite being benign.
30 if (!getLangOpts().CPlusPlus)
31 return;
32
33 // Look for temporaries that are constructed in-place and immediately
34 // destroyed. Look for temporaries created by a functional cast but not for
35 // those returned from a call.
36 auto BindTemp = cxxBindTemporaryExpr(unless(has(callExpr()))).bind("temp");
37 Finder->addMatcher(
38 exprWithCleanups(
39 unless(isInTemplateInstantiation()),
40 hasParent(compoundStmt().bind("compound")),
41 hasType(cxxRecordDecl(hasNonTrivialDestructor())),
42 anyOf(has(BindTemp), has(cxxFunctionalCastExpr(has(BindTemp)))))
43 .bind("expr"),
44 this);
45 }
46
47 void UnusedRAIICheck::check(const MatchFinder::MatchResult &Result) {
48 const auto *E = Result.Nodes.getStmtAs<Expr>("expr");
49
50 // We ignore code expanded from macros to reduce the number of false
51 // positives.
52 if (E->getLocStart().isMacroID())
53 return;
54
55 // Don't emit a warning for the last statement in the surrounding compund
56 // statement.
57 const auto *CS = Result.Nodes.getStmtAs<CompoundStmt>("compound");
58 if (E == CS->body_back())
59 return;
60
61 // Emit a warning.
62 auto D = diag(E->getLocStart(), "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.getStmtAs<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 D << FixItHint::CreateInsertion(
84 Lexer::getLocForEndOfToken(TL->getLocEnd(), 0, *Result.SourceManager,
85 Result.Context->getLangOpts()),
86 Replacement);
87 }
88
89 } // namespace misc
90 } // namespace tidy
91 } // namespace clang
Finder
std::unique_ptr< ast_matchers::MatchFinder > Finder
Definition: ClangTidy.cpp:188
clang::tidy::AST_MATCHER
AST_MATCHER(Stmt, isInsideOfRangeBeginEndStmt)
Definition: ProBoundsArrayToPointerDecayCheck.cpp:25
UnusedRAIICheck.h
Result
const NamedDecl * Result
Definition: USRFinder.cpp:121