compilerplugins/clang/unnecessaryvirtual.cxx

/* -*- 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 <cassert>
#include <string>
#include <iostream>
#include <set>
#include <unordered_set>
#include "plugin.hxx"
#include <fstream>

/**
Dump a list of virtual methods and a list of methods overriding virtual methods.
Then we will post-process the 2 lists and find the set of virtual methods which don't need to be virtual.

Also, we look for virtual methods where the bodies of all the overrides are empty i.e. this is leftover code
that no longer has a purpose.

The process goes something like this:
  $ make check
  $ make FORCE_COMPILE_ALL=1 COMPILER_PLUGIN_TOOL='unnecessaryvirtual' check
  $ ./compilerplugins/clang/unnecessaryvirtual.py
  $ for dir in *; do make FORCE_COMPILE_ALL=1 UPDATE_FILES=$dir COMPILER_PLUGIN_TOOL='removevirtuals' $dir; done

Note that the actual process may involve a fair amount of undoing, hand editing, and general messing around
to get it to work :-)

TODO some boost bind stuff appears to confuse it, notably in the xmloff module
*/

namespace {

struct MyFuncInfo
{
    std::string name;
    std::string sourceLocation;

};
bool operator < (const MyFuncInfo &lhs, const MyFuncInfo &rhs)
{
    return lhs.name < rhs.name;
}

// try to limit the voluminous output a little
static std::set<MyFuncInfo> definitionSet;
static std::unordered_set<std::string> overridingSet;
static std::unordered_set<std::string> nonEmptySet;

class UnnecessaryVirtual:
    public RecursiveASTVisitor<UnnecessaryVirtual>, public loplugin::Plugin
{
public:
    explicit UnnecessaryVirtual(loplugin::InstantiationData const & data):
        Plugin(data) {}

    virtual void run() override
    {
        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());

        // dump all our output in one write call - this is to try and limit IO "crosstalk" between multiple processes
        // writing to the same logfile
        std::string output;
        for (const MyFuncInfo & s : definitionSet)
            output += "definition:\t" + s.name + "\t" + s.sourceLocation + "\n";
        for (const std::string & s : overridingSet)
            output += "overriding:\t" + s + "\n";
        for (const std::string & s : nonEmptySet)
            output += "nonempty:\t" + s + "\n";
        std::ofstream myfile;
        myfile.open( WORKDIR "/loplugin.unnecessaryvirtual.log", std::ios::app | std::ios::out);
        myfile << output;
        myfile.close();
    }
    bool shouldVisitTemplateInstantiations () const { return true; }
    bool shouldVisitImplicitCode() const { return true; }

    bool VisitCXXMethodDecl( const CXXMethodDecl* decl );
private:
    void MarkRootOverridesNonEmpty( const CXXMethodDecl* methodDecl );
    std::string toString(SourceLocation loc);
};

std::string niceName(const CXXMethodDecl* cxxMethodDecl)
{
    while (cxxMethodDecl->getTemplateInstantiationPattern())
        cxxMethodDecl = dyn_cast<CXXMethodDecl>(cxxMethodDecl->getTemplateInstantiationPattern());
    while (cxxMethodDecl->getInstantiatedFromMemberFunction())
        cxxMethodDecl = dyn_cast<CXXMethodDecl>(cxxMethodDecl->getInstantiatedFromMemberFunction());
    std::string s = cxxMethodDecl->getReturnType().getCanonicalType().getAsString()
        + " " + cxxMethodDecl->getQualifiedNameAsString() + "(";
    for (const ParmVarDecl *pParmVarDecl : cxxMethodDecl->parameters()) {
        s += pParmVarDecl->getType().getCanonicalType().getAsString();
        s += ",";
    }
    s += ")";
    if (cxxMethodDecl->isConst()) {
        s += "const";
    }
    return s;
}

bool UnnecessaryVirtual::VisitCXXMethodDecl( const CXXMethodDecl* methodDecl )
{
    if (ignoreLocation(methodDecl)) {
        return true;
    }
    if (!methodDecl->isVirtual() || methodDecl->isDeleted()) {
        return true;
    }
    // ignore stuff that forms part of the stable URE interface
    if (isInUnoIncludeFile(methodDecl->getCanonicalDecl())) {
        return true;
    }

    auto body = methodDecl->getBody();
    if (body) {
        auto compoundStmt = dyn_cast<CompoundStmt>(body);
        if (!compoundStmt)
            MarkRootOverridesNonEmpty(methodDecl->getCanonicalDecl());
        else if (compoundStmt->size() > 0)
            MarkRootOverridesNonEmpty(methodDecl->getCanonicalDecl());
    }

    if (!methodDecl->isThisDeclarationADefinition())
        return true;

    methodDecl = methodDecl->getCanonicalDecl();
    std::string aNiceName = niceName(methodDecl);

    // for destructors, we need to check if any of the superclass' destructors are virtual
    if (isa<CXXDestructorDecl>(methodDecl)) {
        const CXXRecordDecl* cxxRecordDecl = methodDecl->getParent();
        if (cxxRecordDecl->getNumBases() == 0) {
            definitionSet.insert( { aNiceName, toString( methodDecl->getLocation() ) } );
            return true;
        }
        for(auto baseSpecifier = cxxRecordDecl->bases_begin();
            baseSpecifier != cxxRecordDecl->bases_end(); ++baseSpecifier)
        {
            if (baseSpecifier->getType()->isRecordType())
            {
                const CXXRecordDecl* superclassCXXRecordDecl = baseSpecifier->getType()->getAsCXXRecordDecl();
                std::string aOverriddenNiceName = niceName(superclassCXXRecordDecl->getDestructor());
                overridingSet.insert(aOverriddenNiceName);
            }
        }
        return true;
    }

    if (methodDecl->size_overridden_methods() == 0) {
        definitionSet.insert( { aNiceName, toString( methodDecl->getLocation() ) } );
    } else {
       for (auto iter = methodDecl->begin_overridden_methods();
            iter != methodDecl->end_overridden_methods(); ++iter)
       {
           const CXXMethodDecl *overriddenMethod = *iter;
           // we only care about the first level override to establish that a virtual qualifier was useful.
           if (overriddenMethod->isPure() || overriddenMethod->size_overridden_methods() == 0)
           {
               std::string aOverriddenNiceName = niceName(overriddenMethod);
               overridingSet.insert(aOverriddenNiceName);
           }
        }
    }
    return true;
}

void UnnecessaryVirtual::MarkRootOverridesNonEmpty( const CXXMethodDecl* methodDecl )
{
    if (methodDecl->size_overridden_methods() == 0) {
        nonEmptySet.insert(niceName(methodDecl));
        return;
    }
    for (auto iter = methodDecl->begin_overridden_methods();
          iter != methodDecl->end_overridden_methods(); ++iter)
    {
        MarkRootOverridesNonEmpty(*iter);
    }
}

std::string UnnecessaryVirtual::toString(SourceLocation loc)
{
    SourceLocation expansionLoc = compiler.getSourceManager().getExpansionLoc( loc );
    StringRef name = getFilenameOfLocation(expansionLoc);
    std::string sourceLocation = std::string(name.substr(strlen(SRCDIR)+1)) + ":" + std::to_string(compiler.getSourceManager().getSpellingLineNumber(expansionLoc));
    loplugin::normalizeDotDotInFilePath(sourceLocation);
    return sourceLocation;
}


loplugin::Plugin::Registration< UnnecessaryVirtual > X("unnecessaryvirtual", false);

}

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