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5de20e45e4
to find my previous attempt at this, which only obscured the problem <noelgrandin> I'm such an idiot <noelgrandin> I changed a whole bunch of code to avoid calling const methods on a non-const object <noelgrandin> from p->foo() to std::as_const(*p).foo() <noelgrandin> can you spot the mistake? <bubli> Is this a job interview question? :D <vmiklos> noelgrandin: you did the opposite, now you always call const member functions, while you wanted to always call non-const member functions? <noelgrandin> more like a "why didn't the smart people on this channel tell me I was an idiot" :-) <noelgrandin> in this case, we have o3tl::cow_wrapper, which overrides operator* and operator-> <vmiklos> ah, and by the time you would add/remove the const, cow_wrapper already did the expensive task of copying based on const/non-const <noelgrandin> exactly <thorsten> heh Change-Id: I5366e6a87c414b862668b61e6adfbccfdd9d3b04 Reviewed-on: https://gerrit.libreoffice.org/c/core/+/126473 Tested-by: Jenkins Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
122 lines
3.7 KiB
C++
122 lines
3.7 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* Based on LLVM/Clang.
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*
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* This file is distributed under the University of Illinois Open Source
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* License. See LICENSE.TXT for details.
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*
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*/
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#ifndef LO_CLANG_SHARED_PLUGINS
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#include <cassert>
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#include <string>
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#include <iostream>
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#include <fstream>
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#include <set>
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#include <unordered_set>
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#include "plugin.hxx"
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#include "check.hxx"
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/*
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Look for places where we are using cow_wrapper, but we are calling a const method on the impl object
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with a non-const pointer, which means we will unnnecessarily trigger a copy.
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*/
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namespace
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{
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class Cow_Wrapper : public loplugin::FilteringPlugin<Cow_Wrapper>
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{
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public:
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explicit Cow_Wrapper(loplugin::InstantiationData const& data)
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: FilteringPlugin(data)
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{
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}
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virtual bool preRun() override { return true; }
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virtual void run() override
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{
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if (preRun())
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TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
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}
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bool VisitCXXMemberCallExpr(const CXXMemberCallExpr*);
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};
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bool Cow_Wrapper::VisitCXXMemberCallExpr(const CXXMemberCallExpr* memberCallExpr)
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{
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if (ignoreLocation(memberCallExpr))
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return true;
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auto methodDecl = memberCallExpr->getMethodDecl();
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if (!methodDecl || !methodDecl->isConst())
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return true;
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auto expr = compat::IgnoreImplicit(memberCallExpr->getImplicitObjectArgument())->IgnoreParens();
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auto operatorCallExpr = dyn_cast<CXXOperatorCallExpr>(expr);
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if (operatorCallExpr && operatorCallExpr->getOperator() == OO_Arrow)
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{
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auto arrowMethodDecl = dyn_cast_or_null<CXXMethodDecl>(operatorCallExpr->getDirectCallee());
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if (!arrowMethodDecl)
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return true;
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if (arrowMethodDecl->isConst())
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return true;
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auto dc = loplugin::DeclCheck(arrowMethodDecl->getParent())
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.Class("cow_wrapper")
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.Namespace("o3tl")
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.GlobalNamespace();
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if (!dc)
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return true;
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}
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else if (operatorCallExpr)
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{
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auto methodDecl2 = dyn_cast_or_null<CXXMethodDecl>(operatorCallExpr->getDirectCallee());
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if (!methodDecl2)
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return true;
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auto dc = loplugin::DeclCheck(methodDecl2->getParent())
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.Class("cow_wrapper")
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.Namespace("o3tl")
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.GlobalNamespace();
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if (!dc)
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return true;
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}
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else if (auto callExpr = dyn_cast<CallExpr>(expr))
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{
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if (!isa<ImplicitCastExpr>(callExpr->getCallee())) // std::as_const shows up as this
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return true;
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if (callExpr->getNumArgs() < 1)
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return true;
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auto arg0 = dyn_cast<CXXOperatorCallExpr>(callExpr->getArg(0));
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if (!arg0)
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return true;
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auto starMethodDecl = dyn_cast_or_null<CXXMethodDecl>(arg0->getDirectCallee());
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if (!starMethodDecl)
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return true;
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auto dc = loplugin::DeclCheck(starMethodDecl->getParent())
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.Class("cow_wrapper")
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.Namespace("o3tl")
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.GlobalNamespace();
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if (!dc)
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return true;
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}
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else
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return true;
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report(DiagnosticsEngine::Warning,
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"calling const method on o3tl::cow_wrapper impl class via non-const pointer, rather use "
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"std::as_const to prevent triggering an unnecessary copy",
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compat::getBeginLoc(memberCallExpr))
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<< memberCallExpr->getSourceRange();
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return true;
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}
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loplugin::Plugin::Registration<Cow_Wrapper> cow_wrapper("cow_wrapper", true);
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} // namespace
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#endif // LO_CLANG_SHARED_PLUGINS
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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