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452 | /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
/*
* 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/.
*/
// A more aggressive check for unused C struct/C++ class members than what plain Clang offers. On
// the one hand, unlike -Wunused-private-field, it warns about all members regardless of access
// specifiers, if all code that can use a class has been seen. On the other hand, it warns about
// all kinds of members. But it uses some heuristics (the type showing up in sizeof, alignof,
// offsetof, certain casts) to determine that seemingly unused data members are probably used after
// all; the used heuristics were enough to not require any explicit [[maybe_unused]] decorations
// across the existing code base.
#include <cassert>
#include <set>
#include "config_clang.h"
#include "check.hxx"
#include "plugin.hxx"
namespace
{
// Whether the CXXRecordDecl itself or one of its enclosing classes is a template:
bool isTemplated(CXXRecordDecl const* decl)
{
if (decl->getDescribedClassTemplate() != nullptr)
{
return true;
}
if (auto const d = dyn_cast<CXXRecordDecl>(decl->getParent()))
{
return isTemplated(d);
}
return false;
}
bool isWarnUnusedType(QualType type)
{
if (auto const t = type->getAs<RecordType>())
{
if (t->getDecl()->hasAttr<WarnUnusedAttr>())
{
return true;
}
}
return loplugin::isExtraWarnUnusedType(type);
}
class UnusedMember final : public loplugin::FilteringPlugin<UnusedMember>
{
public:
explicit UnusedMember(loplugin::InstantiationData const& data)
: FilteringPlugin(data)
{
}
#if CLANG_VERSION < 60000
bool TraverseAlignedAttr(AlignedAttr* attr)
{
bool ret = FilteringPlugin::TraverseAlignedAttr(attr);
PostTraverseAlignedAttr(attr, ret);
return ret;
}
bool PostTraverseAlignedAttr(AlignedAttr* attr, bool run)
{
if (!run)
{
return false;
}
if (attr->isAlignmentExpr())
{
if (!TraverseStmt(attr->getAlignmentExpr()))
{
return false;
}
}
else if (auto const tsi = attr->getAlignmentType())
{
if (!TraverseTypeLoc(tsi->getTypeLoc()))
{
return false;
}
}
return true;
}
#endif
bool VisitCXXRecordDecl(CXXRecordDecl const* decl) //TODO: non-CXX RecordDecl?
{
if (ignoreLocation(decl))
{
return true;
}
if (!decl->isThisDeclarationADefinition())
{
return true;
}
if (!handler.isAllRelevantCodeDefined(decl))
{
return true;
}
if (!compiler.getSourceManager().isInMainFile(decl->getLocation()))
{
// include/rtl/instance.hxx declares entities in an unnamed namespace
return true;
}
if (isTemplated(decl) || isa<ClassTemplatePartialSpecializationDecl>(decl))
{
return true;
}
if (decl->isUnion() && decl->getIdentifier() == nullptr)
{
return true; //TODO
}
for (auto i = decl->decls_begin(); i != decl->decls_end(); ++i)
{
auto const d = *i;
if (d->isImplicit() || isa<AccessSpecDecl>(d) || isa<UsingDecl>(d))
{
//TODO: only filter out UsingDecls that are actually used (if only to silence
// -Woverloaded-virtual)
continue;
}
if (isa<ClassTemplateDecl>(d) || isa<FunctionTemplateDecl>(d))
{
//TODO: only filter out ones that are not instantiated at all
continue;
}
if (auto const d1 = dyn_cast<FriendDecl>(d))
{
//TODO: determine whether the friendship is actually required
auto const d2 = d1->getFriendDecl();
if (d2 == nullptr)
{ // happens for "friend class C;"
continue;
}
if (auto const d3 = dyn_cast<FunctionDecl>(d2))
{
#if 0 //TODO: friend function definitions are not marked as referenced even if used?
if (!d3->isThisDeclarationADefinition()) //TODO: do this check for all kinds?
#endif
{
continue;
}
}
}
if (d->isReferenced())
{
continue;
}
if (d->hasAttr<UnusedAttr>())
{
continue;
}
// Check individual members instead of the whole CXXRecordDecl for coming from a macro,
// as CppUnit's CPPUNIT_TEST_SUITE_END (cppunit/extensions/HelperMacros.h) contains a
// partial member list ending in
//
// private: /* dummy typedef so that the macro can still end with ';'*/
// typedef int CppUnitDummyTypedefForSemiColonEnding__
//
if (compiler.getSourceManager().isMacroBodyExpansion(d->getLocation()))
{
return true;
}
if (auto const d1 = dyn_cast<FieldDecl>(d))
{
if (d1->isUnnamedBitfield())
{
continue;
}
if (!isWarnWhenUnusedType(d1->getType()))
{
continue;
}
deferred_.insert(d1);
continue;
}
if (auto const d1 = dyn_cast<FunctionDecl>(d))
{
if (d1->isDeletedAsWritten()) // TODO: just isDeleted?
{
continue;
}
if (d1->isExplicitlyDefaulted())
{
continue;
}
}
else if (auto const d2 = dyn_cast<TagDecl>(d))
{
if (d2->getIdentifier() == nullptr)
{
continue;
}
if (isa<EnumDecl>(d2))
{
deferred_.insert(d2);
continue;
}
}
else if (auto const d3 = dyn_cast<TypedefNameDecl>(d))
{
// Some types, like (specializations of) std::iterator_traits, have specific
// requirements on their members; only covers std::iterator_traits for now (TODO:
// check that at least some member is actually used)
// (isa<ClassTemplatePartialSpecializationDecl>(decl) is already filtered out
// above):
if (isa<ClassTemplateSpecializationDecl>(decl)
&& loplugin::DeclCheck(decl).Struct("iterator_traits").StdNamespace())
{
auto const id = d3->getIdentifier();
assert(id != nullptr);
auto const n = id->getName();
if (n == "difference_type" || n == "iterator_category" || n == "pointer"
|| n == "reference" || n == "value_type")
{
continue;
}
}
}
report(DiagnosticsEngine::Warning, "unused class member", d->getLocation())
<< d->getSourceRange();
}
return true;
}
bool VisitOffsetOfExpr(OffsetOfExpr const* expr)<--- The function 'VisitOffsetOfExpr' is never used.
{
if (ignoreLocation(expr))
{
return true;
}
recordRecordDeclAndBases(expr->getTypeSourceInfo()->getType()->castAs<RecordType>());
return true;
}
bool VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr const* expr)
{
if (ignoreLocation(expr))
{
return true;
}
switch (expr->getKind())
{
case UETT_SizeOf:
case UETT_AlignOf:
#if CLANG_VERSION >= 80000
case UETT_PreferredAlignOf:
#endif
break;
default:
return true;
}
if (!expr->isArgumentType())
{
return true;
}
auto t = expr->getArgumentType();
if (auto const t1 = t->getAs<ReferenceType>())
{
t = t1->getPointeeType();
}
if (auto const t1 = t->getAsArrayTypeUnsafe())
{
t = compiler.getASTContext().getBaseElementType(t1);
}
if (auto const t1 = t->getAs<RecordType>())
{
recordRecordDeclAndBases(t1);
}
return true;
}
// Handling implicit, C-style, static and reinterpret casts between void* and record types
// (though reinterpret_cast would be ruled out by loplugin:redundantcast):
bool VisitCastExpr(CastExpr const* expr)
{
if (ignoreLocation(expr))
{
return true;
}
auto const t1 = expr->getType();
auto const t2 = expr->getSubExprAsWritten()->getType();
if (loplugin::TypeCheck(t1).Pointer().Void())
{
recordCastedRecordDecl(t2);
}
else if (loplugin::TypeCheck(t2).Pointer().Void())
{
recordCastedRecordDecl(t1);
}
return true;
}
bool VisitCXXReinterpretCastExpr(CXXReinterpretCastExpr const* expr)
{
if (ignoreLocation(expr))
{
return true;
}
recordCastedRecordDecl(expr->getTypeAsWritten());
recordCastedRecordDecl(expr->getSubExprAsWritten()->getType());
return true;
}
bool VisitElaboratedTypeLoc(ElaboratedTypeLoc tloc)<--- The function 'VisitElaboratedTypeLoc' is never used.
{
if (ignoreLocation(tloc))
{
return true;
}
auto const tl = tloc.getNamedTypeLoc().getAs<TagTypeLoc>();
if (tl.isNull())
{
return true;
}
if (tl.isDefinition())
{
return true;
}
if (auto const d = dyn_cast<EnumDecl>(tl.getDecl()))
{
// For some reason, using an elaborated type specifier in (at least) a FieldDecl, as in
//
// enum E { ... };
// enum E e;
//
// doesn't cause the EnumDecl to be marked as referenced. (This should fix it, but note
// the warning at <https://github.com/llvm/llvm-project/commit/
// b96ec568715450106b4f1dd4a20c1c14e9bca6c4#diff-019094457f96a6ed0ee072731d447073R396>:
// "[...] a type written 'struct foo' should be represented as an ElaboratedTypeLoc. We
// currently only do that when C++ is enabled [...]"
deferred_.erase(d->getCanonicalDecl());
}
return true;
}
void postRun() override
{
for (auto const d : deferred_)
{
if (auto const d1 = dyn_cast<FieldDecl>(d))
{
bool layout = false;
for (auto d2 = d1->getParent();;)
{
if (layout_.find(d2->getCanonicalDecl()) != layout_.end())
{
layout = true;
break;
}
// Heuristic to recursively check parent RecordDecl if given RecordDecl is
// unnamed and either an anonymous struct (or union, but which are already
// filtered out anyway), or defined in a non-static data member declaration
// (TODO: which is erroneously approximated here with getTypedefNameForAnonDecl
// for now, which fails to filter out RecordDecls in static data member
// declarations):
if (!(d2->getDeclName().isEmpty()
&& (d2->isAnonymousStructOrUnion()
|| d2->getTypedefNameForAnonDecl() == nullptr)))
{
break;
}
d2 = dyn_cast<RecordDecl>(d2->getParent());
if (d2 == nullptr)
{
break;
}
}
if (layout)
{
continue;
}
}
report(DiagnosticsEngine::Warning, "unused class member", d->getLocation())
<< d->getSourceRange();
}
}
private:
void run() override
{
if (TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()))
{
postRun();
}
}
bool isWarnWhenUnusedType(QualType type)
{
auto t = type;
if (auto const t1 = t->getAs<ReferenceType>())
{
t = t1->getPointeeType();
}
return t.isTrivialType(compiler.getASTContext()) || isWarnUnusedType(t);
}
void recordRecordDeclAndBases(RecordType const* type)
{
auto const d1 = type->getDecl();
if (!layout_.insert(d1->getCanonicalDecl()).second)
{
return;
}
if (auto const d2 = dyn_cast_or_null<CXXRecordDecl>(d1->getDefinition()))
{
for (auto i = d2->bases_begin(); i != d2->bases_end(); ++i)
{
recordRecordDeclAndBases(i->getType()->castAs<RecordType>());
}
//TODO: doesn't iterate vbases, but presence of such would run counter to the layout
// heuristic anyway
}
}
void recordCastedRecordDecl(QualType type)
{
for (auto t = type;;)
{
if (auto const t1 = t->getAs<clang::PointerType>())
{
t = t1->getPointeeType();
continue;
}
if (auto const t1 = t->getAs<RecordType>())
{
recordRecordDeclAndBases(t1);
}
break;
}
}
// RecordDecls whose layout (i.e., contained FieldDecls) must presumably not be changed:
std::set<TagDecl const*> layout_;
std::set<Decl const*> deferred_;
};
loplugin::Plugin::Registration<UnusedMember> unusedmember("unusedmember");
}
/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
|