UnusedRaiiCheck.cpp
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//===--- UnusedRaiiCheck.cpp - clang-tidy ---------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "UnusedRaiiCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/Lex/Lexer.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace bugprone {
namespace {
AST_MATCHER(CXXRecordDecl, hasNonTrivialDestructor) {
// TODO: If the dtor is there but empty we don't want to warn either.
return Node.hasDefinition() && Node.hasNonTrivialDestructor();
}
} // namespace
void UnusedRaiiCheck::registerMatchers(MatchFinder *Finder) {
// Look for temporaries that are constructed in-place and immediately
// destroyed. Look for temporaries created by a functional cast but not for
// those returned from a call.
auto BindTemp = cxxBindTemporaryExpr(
unless(has(ignoringParenImpCasts(callExpr()))),
unless(has(ignoringParenImpCasts(objcMessageExpr()))))
.bind("temp");
Finder->addMatcher(
traverse(ast_type_traits::TK_AsIs,
exprWithCleanups(
unless(isInTemplateInstantiation()),
hasParent(compoundStmt().bind("compound")),
hasType(cxxRecordDecl(hasNonTrivialDestructor())),
anyOf(has(ignoringParenImpCasts(BindTemp)),
has(ignoringParenImpCasts(cxxFunctionalCastExpr(
has(ignoringParenImpCasts(BindTemp)))))))
.bind("expr")),
this);
}
void UnusedRaiiCheck::check(const MatchFinder::MatchResult &Result) {
const auto *E = Result.Nodes.getNodeAs<Expr>("expr");
// We ignore code expanded from macros to reduce the number of false
// positives.
if (E->getBeginLoc().isMacroID())
return;
// Don't emit a warning for the last statement in the surrounding compound
// statement.
const auto *CS = Result.Nodes.getNodeAs<CompoundStmt>("compound");
if (E == CS->body_back())
return;
// Emit a warning.
auto D = diag(E->getBeginLoc(), "object destroyed immediately after "
"creation; did you mean to name the object?");
const char *Replacement = " give_me_a_name";
// If this is a default ctor we have to remove the parens or we'll introduce a
// most vexing parse.
const auto *BTE = Result.Nodes.getNodeAs<CXXBindTemporaryExpr>("temp");
if (const auto *TOE = dyn_cast<CXXTemporaryObjectExpr>(BTE->getSubExpr()))
if (TOE->getNumArgs() == 0) {
D << FixItHint::CreateReplacement(
CharSourceRange::getTokenRange(TOE->getParenOrBraceRange()),
Replacement);
return;
}
// Otherwise just suggest adding a name. To find the place to insert the name
// find the first TypeLoc in the children of E, which always points to the
// written type.
auto Matches =
match(expr(hasDescendant(typeLoc().bind("t"))), *E, *Result.Context);
const auto *TL = selectFirst<TypeLoc>("t", Matches);
assert(TL);
D << FixItHint::CreateInsertion(
Lexer::getLocForEndOfToken(TL->getEndLoc(), 0, *Result.SourceManager,
getLangOpts()),
Replacement);
}
} // namespace bugprone
} // namespace tidy
} // namespace clang