d2ba5d98ec
...which could never succeed. I became aware of this when Clang 15 trunk -std=c++2b, implementing <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p1328r1.html> "Making std::type_info::operator== constexpr", pointed at two of the broken comparisons with > sw/source/uibase/app/docsh2.cxx:478:25: error: code will never be executed [-Werror,-Wunreachable-code] > pTmpFrame->GetFrame().Appear(); > ^~~~~~~~~ > sw/source/uibase/app/docsh2.cxx:475:33: error: code will never be executed [-Werror,-Wunreachable-code] > bOnly = false; > ^~~~~ (It didn't emit warnings pointing at any of the other broken comparisons, though.) All of these broken comparisons were regressions introduced with89d39bc100"tdf#94559: 4th step to remove rtti.hxx", replacing uses of the IS_TYPE macro (from include/tools/rtti.hxx, meanwhile removed withd64e535fe9"Remove unused rtti.hxx"). I now added loplugin:typeidcomparison to also find the other broken comparisons introduced by that commit. (The remaining cases where that commit replaced uses of TYPE_INFO with typeid comparisons were correct and/or have meanwhile been replaced with code not using typeid, see553ee72041"simplify some use of typeid" andd656da9bc4"~SwModify: do not silently tolerate clients registered past death".) The original IS_TYPE macro made sure not to dereference null pointers, > #define IS_TYPE(T,pObj) \ > ( pObj && (pObj)->Type() == TYPE(T) ) I don't know if any of the pointers now dereferenced in those typeid expressions can legitimately be null. But to be on the safe side, I replicated that check in the newly introduced isType (sw/inc/istype.hxx). (It is interesting to note that none of the static analysis that we routinely employ seems to have noticed these broken comparisons.) Change-Id: I65baffdd27bac1abf744283ff98c2dc864fa63b4 Reviewed-on: https://gerrit.libreoffice.org/c/core/+/129865 Tested-by: Jenkins Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
90 lines
2.7 KiB
C++
90 lines
2.7 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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// Find (in-)equality comparisons between typeid expressions that can never succeed. For now, just
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// detects cases where the two involved types are structurally different, one a pointer type and the
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// other a non-pointer type.
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#ifndef LO_CLANG_SHARED_PLUGINS
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#include "plugin.hxx"
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namespace
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{
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class TypeidComparison final : public loplugin::FilteringPlugin<TypeidComparison>
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{
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public:
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explicit TypeidComparison(loplugin::InstantiationData const& data)
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: FilteringPlugin(data)
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{
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}
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// For CXXRewrittenBinaryOperator `typeid(...) != typeid(...)`:
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bool shouldVisitImplicitCode() const { return true; }
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bool preRun() override { return compiler.getLangOpts().CPlusPlus; }
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void run() override
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{
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if (preRun())
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{
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TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
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}
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}
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bool VisitCXXOperatorCallExpr(CXXOperatorCallExpr const* expr)
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{
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if (ignoreLocation(expr))
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{
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return true;
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}
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auto const op = expr->getOperator();
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if (op != OO_EqualEqual && op != OO_ExclaimEqual)
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{
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return true;
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}
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assert(expr->getNumArgs() == 2);
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auto const e1 = dyn_cast<CXXTypeidExpr>(expr->getArg(0)->IgnoreParenImpCasts());
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if (e1 == nullptr)
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{
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return true;
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}
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auto const e2 = dyn_cast<CXXTypeidExpr>(expr->getArg(1)->IgnoreParenImpCasts());
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if (e2 == nullptr)
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{
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return true;
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}
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auto const t1 = getOperandType(e1);
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auto const t2 = getOperandType(e2);
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if (t1->isPointerType() == t2->isPointerType())
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{
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return true;
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}
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report(DiagnosticsEngine::Warning,
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"comparison of type info of mixed pointer and non-pointer types %0 and %1 can never "
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"succeed",
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expr->getExprLoc())
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<< t1 << t2 << expr->getSourceRange();
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return true;
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}
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private:
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QualType getOperandType(CXXTypeidExpr const* expr)
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{
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return expr->isTypeOperand() ? expr->getTypeOperand(compiler.getASTContext())
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: expr->getExprOperand()->getType();
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}
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};
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static loplugin::Plugin::Registration<TypeidComparison> typeidcomparison("typeidcomparison");
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}
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#endif
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/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
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