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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
#include <string>
#include <set>
#include "plugin.hxx"
// Find places where various things are passed by value.
// It's not very efficient, because we generally end up copying it twice - once into the parameter and
// again into the destination.
// They should rather be passed by reference.
//
// Generally recommending lambda capture by-ref rather than by-copy is even more
// problematic than with function parameters, as a lambda instance can easily
// outlive a referrenced variable. So once lambdas start to get used in more
// sophisticated ways than passing them into standard algorithms, this plugin's
// advice, at least for explicit captures, will need to be revisited.
namespace {
class PassStuffByRef:
public RecursiveASTVisitor<PassStuffByRef>, public loplugin::Plugin
{
public:
explicit PassStuffByRef(InstantiationData const & data): Plugin(data) {}
virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
bool VisitFunctionDecl(const FunctionDecl * decl);
bool VisitLambdaExpr(const LambdaExpr * expr);
private:
bool isFat(QualType type, std::string * name);
};
bool PassStuffByRef::VisitFunctionDecl(const FunctionDecl * functionDecl) {
if (ignoreLocation(functionDecl)) {
return true;
}
// only warn on the definition/prototype of the function,
// not on the function implementation
if ((functionDecl->isThisDeclarationADefinition()
&& functionDecl->getPreviousDecl() != nullptr)
|| functionDecl->isDeleted())
{
return true;
}
// only consider base declarations, not overriden ones, or we warn on methods that
// are overriding stuff from external libraries
if (isa<CXXMethodDecl>(functionDecl)) {
CXXMethodDecl const * m = dyn_cast<CXXMethodDecl>(functionDecl);
if (m->size_overridden_methods() > 0)
return true;
}
unsigned n = functionDecl->getNumParams();
for (unsigned i = 0; i != n; ++i) {
const ParmVarDecl * pvDecl = functionDecl->getParamDecl(i);
std::string name;
if (isFat(pvDecl->getType(), &name)) {
report(
DiagnosticsEngine::Warning,
("passing '%0' by value, rather pass by reference, e.g., '%0"
" const &'"),
pvDecl->getLocation())
<< name << pvDecl->getSourceRange();
}
}
return true;
}
bool PassStuffByRef::VisitLambdaExpr(const LambdaExpr * expr) {
if (ignoreLocation(expr)) {
return true;
}
for (auto i(expr->capture_begin()); i != expr->capture_end(); ++i) {
if (i->getCaptureKind() == LambdaCaptureKind::LCK_ByCopy) {
std::string name;
if (isFat(i->getCapturedVar()->getType(), &name)) {
report(
DiagnosticsEngine::Warning,
("%0 capture of '%1' variable by copy, rather use capture"
" by reference---UNLESS THE LAMBDA OUTLIVES THE VARIABLE"),
i->getLocation())
<< (i->isImplicit() ? "implicit" : "explicit") << name
<< expr->getSourceRange();
}
}
}
return true;
}
bool PassStuffByRef::isFat(QualType type, std::string * name) {
if (!type->isRecordType()) {
return false;
}
*name = type.getUnqualifiedType().getCanonicalType().getAsString();
if (*name == "class rtl::OUString" || *name == "class rtl::OString"
|| name->find("class com::sun::star::uno::Sequence") == 0)
{
return true;
}
if (type->isIncompleteType()) {
return false;
}
Type const * t2 = type.getTypePtrOrNull();
return t2 != nullptr
&& compiler.getASTContext().getTypeSizeInChars(t2).getQuantity() > 64;
}
loplugin::Plugin::Registration< PassStuffByRef > X("passstuffbyref");
}
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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