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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/.
*/
#ifndef LO_CLANG_SHARED_PLUGINS
#include <string>
#include <unordered_set>
#include "check.hxx"
#include "compat.hxx"
#include "plugin.hxx"
// Find places where parameters 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 referenced 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 PassParamsByRef:
public loplugin::FilteringPlugin<PassParamsByRef>
{
public:
explicit PassParamsByRef(loplugin::InstantiationData const & data): FilteringPlugin(data), mbInsideFunctionDecl(false) {}
virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
// When warning about function params of primitive type that could be passed
// by value instead of by reference, make sure not to warn if the parameter
// is ever bound to a reference; on the one hand, this needs scaffolding in
// all Traverse*Decl functions (indirectly) derived from FunctionDecl; and
// on the other hand, use a hack of ignoring just the DeclRefExprs nested in
// LValueToRValue ImplicitCastExprs when determining whether a param is
// bound to a reference:
bool PreTraverseFunctionDecl(FunctionDecl *);
bool PostTraverseFunctionDecl(FunctionDecl *, bool);
bool TraverseFunctionDecl(FunctionDecl *);
bool PreTraverseImplicitCastExpr(ImplicitCastExpr *);
bool TraverseImplicitCastExpr(ImplicitCastExpr *);
bool VisitBinAssign(BinaryOperator const *);
bool VisitCXXOperatorCallExpr(const CXXOperatorCallExpr *);
private:
bool isFat(QualType type);
bool mbInsideFunctionDecl;
std::unordered_set<ParmVarDecl const *> mParamExclusions;
};
bool PassParamsByRef::PreTraverseFunctionDecl(FunctionDecl* functionDecl)
{
if (ignoreLocation(functionDecl))
return false;
if (functionDecl->isDeleted()
|| functionDecl->isFunctionTemplateSpecialization())
{
return false;
}
// only consider base declarations, not overridden ones, or we warn on methods that
// are overriding stuff from external libraries
const CXXMethodDecl * methodDecl = dyn_cast<CXXMethodDecl>(functionDecl);
if (methodDecl && methodDecl->size_overridden_methods() > 0)
return false;
// Only warn on the definition of the function:
if (!functionDecl->doesThisDeclarationHaveABody())
return false;
mbInsideFunctionDecl = true;
mParamExclusions.clear();
return true;
}
bool PassParamsByRef::PostTraverseFunctionDecl(FunctionDecl* functionDecl, bool)
{
mbInsideFunctionDecl = false;
auto cxxConstructorDecl = dyn_cast<CXXConstructorDecl>(functionDecl);
unsigned n = functionDecl->getNumParams();
for (unsigned i = 0; i != n; ++i) {
const ParmVarDecl * pvDecl = functionDecl->getParamDecl(i);
auto const t = pvDecl->getType();
if (!isFat(t))
continue;
if (mParamExclusions.find(pvDecl) != mParamExclusions.end())
continue;
// Ignore cases where the parameter is std::move'd.
// This is a fairly simple check, might need some more complexity if the parameter is std::move'd
// somewhere else in the constructor.
bool bFoundMove = false;
if (cxxConstructorDecl) {
for (CXXCtorInitializer const * cxxCtorInitializer : cxxConstructorDecl->inits()) {
if (cxxCtorInitializer->isMemberInitializer())
{
auto cxxConstructExpr = dyn_cast<CXXConstructExpr>(cxxCtorInitializer->getInit()->IgnoreParenImpCasts());
if (cxxConstructExpr && cxxConstructExpr->getNumArgs() == 1)
{
if (auto callExpr = dyn_cast<CallExpr>(cxxConstructExpr->getArg(0)->IgnoreParenImpCasts())) {
if (loplugin::DeclCheck(callExpr->getCalleeDecl()).Function("move").StdNamespace()) {
bFoundMove = true;
break;
}
}
}
}
}
}
if (bFoundMove)
continue;
report(
DiagnosticsEngine::Warning,
("passing %0 by value, rather pass by const lvalue reference"),
pvDecl->getLocation())
<< t << pvDecl->getSourceRange();
auto can = functionDecl->getCanonicalDecl();
if (can->getLocation() != functionDecl->getLocation()) {
report(
DiagnosticsEngine::Note, "function is declared here:",
can->getLocation())
<< can->getSourceRange();
}
}
return true;
}
bool PassParamsByRef::TraverseFunctionDecl(FunctionDecl* functionDecl)
{
bool ret = true;
if (PreTraverseFunctionDecl(functionDecl))
{
ret = RecursiveASTVisitor::TraverseFunctionDecl(functionDecl);
PostTraverseFunctionDecl(functionDecl, ret);
}
return ret;
}
bool PassParamsByRef::PreTraverseImplicitCastExpr(ImplicitCastExpr * expr)
{
if (ignoreLocation(expr))
return false;
if (expr->getCastKind() == CK_LValueToRValue
&& isa<DeclRefExpr>(expr->getSubExpr()->IgnoreParenImpCasts()))
return false;
return true;
}
bool PassParamsByRef::TraverseImplicitCastExpr(ImplicitCastExpr * expr)
{
bool ret = true;
if (PreTraverseImplicitCastExpr(expr))
{
ret = RecursiveASTVisitor::TraverseImplicitCastExpr(expr);
}
return ret;
}
bool PassParamsByRef::VisitBinAssign(const BinaryOperator * binaryOperator)
{
if (!mbInsideFunctionDecl)
return true;
// if we are assigning to a parameter, it can be inconvenient to make the param pass-by-ref
if (auto declRefExpr = dyn_cast<DeclRefExpr>(binaryOperator->getLHS()))
{
if (auto parmVarDecl = dyn_cast<ParmVarDecl>(declRefExpr->getDecl()))
mParamExclusions.emplace(parmVarDecl);
}
return true;
}
bool PassParamsByRef::VisitCXXOperatorCallExpr(const CXXOperatorCallExpr * cxxOperatorCallExpr )
{
if (!mbInsideFunctionDecl)
return true;
// if we are assigning to a parameter, it can be inconvenient to make the param pass-by-ref
auto op = cxxOperatorCallExpr->getOperator();
if ( op != clang::OverloadedOperatorKind::OO_Equal
&& op != clang::OverloadedOperatorKind::OO_SlashEqual
&& op != clang::OverloadedOperatorKind::OO_StarEqual
&& op != clang::OverloadedOperatorKind::OO_MinusEqual
&& op != clang::OverloadedOperatorKind::OO_PlusEqual)
return true;
auto declRefExpr = dyn_cast<DeclRefExpr>(cxxOperatorCallExpr->getArg(0));
if (!declRefExpr)
return true;
if (auto parmVarDecl = dyn_cast<ParmVarDecl>(declRefExpr->getDecl()))
mParamExclusions.emplace(parmVarDecl);
return true;
}
bool PassParamsByRef::isFat(QualType type) {
if (!type->isRecordType()) {
return false;
}
loplugin::TypeCheck tc(type);
if ((tc.Class("Reference").Namespace("uno").Namespace("star")
.Namespace("sun").Namespace("com").GlobalNamespace())
|| (tc.Class("Sequence").Namespace("uno").Namespace("star")
.Namespace("sun").Namespace("com").GlobalNamespace())
|| tc.Class("OString").Namespace("rtl").GlobalNamespace()
|| tc.Class("OUString").Namespace("rtl").GlobalNamespace()
|| tc.Class("Reference").Namespace("rtl").GlobalNamespace())
{
return true;
}
if (type->isIncompleteType()) {
return false;
}
clang::Type const * t2 = type.getTypePtrOrNull();
return t2 != nullptr
&& compiler.getASTContext().getTypeSizeInChars(t2).getQuantity() > 64;
}
loplugin::Plugin::Registration< PassParamsByRef > passparamsbyref("passparamsbyref");
} // namespace
#endif // LO_CLANG_SHARED_PLUGINS
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
|
