122 lines
4.2 KiB
C++
122 lines
4.2 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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* 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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#include <string>
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#include <set>
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#include "plugin.hxx"
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// Find places where various things are passed by value.
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// It's not very efficient, because we generally end up copying it twice - once into the parameter and
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// again into the destination.
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// They should rather be passed by reference.
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//
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// Generally recommending lambda capture by-ref rather than by-copy is even more
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// problematic than with function parameters, as a lambda instance can easily
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// outlive a referrenced variable. So once lambdas start to get used in more
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// sophisticated ways than passing them into standard algorithms, this plugin's
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// advice, at least for explicit captures, will need to be revisited.
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namespace {
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class PassStuffByRef:
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public RecursiveASTVisitor<PassStuffByRef>, public loplugin::Plugin
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{
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public:
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explicit PassStuffByRef(InstantiationData const & data): Plugin(data) {}
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virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
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bool VisitFunctionDecl(const FunctionDecl * decl);
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bool VisitLambdaExpr(const LambdaExpr * expr);
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private:
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bool isFat(QualType type, std::string * name);
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};
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bool PassStuffByRef::VisitFunctionDecl(const FunctionDecl * functionDecl) {
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if (ignoreLocation(functionDecl)) {
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return true;
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}
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// only warn on the definition/prototype of the function,
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// not on the function implementation
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if ((functionDecl->isThisDeclarationADefinition()
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&& functionDecl->getPreviousDecl() != nullptr)
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|| functionDecl->isDeleted())
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{
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return true;
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}
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// only consider base declarations, not overriden ones, or we warn on methods that
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// are overriding stuff from external libraries
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if (isa<CXXMethodDecl>(functionDecl)) {
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CXXMethodDecl const * m = dyn_cast<CXXMethodDecl>(functionDecl);
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if (m->size_overridden_methods() > 0)
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return true;
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}
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unsigned n = functionDecl->getNumParams();
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for (unsigned i = 0; i != n; ++i) {
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const ParmVarDecl * pvDecl = functionDecl->getParamDecl(i);
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std::string name;
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if (isFat(pvDecl->getType(), &name)) {
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report(
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DiagnosticsEngine::Warning,
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("passing '%0' by value, rather pass by reference, e.g., '%0"
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" const &'"),
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pvDecl->getLocation())
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<< name << pvDecl->getSourceRange();
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}
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}
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return true;
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}
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bool PassStuffByRef::VisitLambdaExpr(const LambdaExpr * expr) {
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if (ignoreLocation(expr)) {
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return true;
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}
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for (auto i(expr->capture_begin()); i != expr->capture_end(); ++i) {
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if (i->getCaptureKind() == LambdaCaptureKind::LCK_ByCopy) {
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std::string name;
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if (isFat(i->getCapturedVar()->getType(), &name)) {
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report(
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DiagnosticsEngine::Warning,
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("%0 capture of '%1' variable by copy, rather use capture"
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" by reference---UNLESS THE LAMBDA OUTLIVES THE VARIABLE"),
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i->getLocation())
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<< (i->isImplicit() ? "implicit" : "explicit") << name
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<< expr->getSourceRange();
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}
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}
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}
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return true;
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}
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bool PassStuffByRef::isFat(QualType type, std::string * name) {
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if (!type->isRecordType()) {
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return false;
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}
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*name = type.getUnqualifiedType().getCanonicalType().getAsString();
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if (*name == "class rtl::OUString" || *name == "class rtl::OString"
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|| name->find("class com::sun::star::uno::Sequence") == 0)
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{
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return true;
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}
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if (type->isIncompleteType()) {
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return false;
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}
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Type const * t2 = type.getTypePtrOrNull();
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return t2 != nullptr
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&& compiler.getASTContext().getTypeSizeInChars(t2).getQuantity() > 64;
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}
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loplugin::Plugin::Registration< PassStuffByRef > X("passstuffbyref");
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}
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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