office-gobmx/compilerplugins/clang/conststringvar.cxx

/* -*- 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/.
 */
#ifndef LO_CLANG_SHARED_PLUGINS

#include <set>
#include <stack>

#include "check.hxx"
#include "plugin.hxx"

// Find non-const vars of 'char const *' type initialized with a const expr,
// that could likely be const (and will then probably trigger further
// loplugin:stringconstant findings).

namespace {

class ConstStringVar:
    public loplugin::FilteringPlugin<ConstStringVar>
{
public:
    explicit ConstStringVar(loplugin::InstantiationData const & data):
        FilteringPlugin(data) {}

    bool preRun() override {
        return compiler.getLangOpts().CPlusPlus;
            // clang::Expr::isCXX11ConstantExpr only works for C++
    }

    void postRun() override {
        for (auto v: vars_) {
            report(
                DiagnosticsEngine::Warning,
                "variable is only used as rvalue, should be const",
                v->getLocation())
                << v->getSourceRange();
        }
    }

    void run() override {
        if (preRun() && TraverseDecl(compiler.getASTContext().getTranslationUnitDecl())) {
            postRun();
        }
    }

    bool PreTraverseImplicitCastExpr(ImplicitCastExpr * expr) {
        bool match;
        switch (expr->getCastKind()) {
        case CK_NoOp:
            // OString CharPtrDetector ctor:
            match = bool(
                loplugin::TypeCheck(expr->getType()).Const().Pointer().Const()
                .Char());
            break;
        case CK_LValueToRValue:
            match = true;
            break;
        default:
            match = false;
            break;
        }
        bool pushed = false;
        if (match) {
            if (auto dr = dyn_cast<DeclRefExpr>(
                    expr->getSubExpr()->IgnoreParenImpCasts()))
            {
                if (auto vd = dyn_cast<VarDecl>(dr->getDecl())) {
                    if (vars_.find(vd->getCanonicalDecl()) != vars_.end()) {
                        casted_.push(dr);
                        pushed = true;
                    }
                }
            }
        }
        pushed_.push(pushed);
        return true;
    }
    bool PostTraverseImplicitCastExpr(ImplicitCastExpr *, bool) {
        bool pushed = pushed_.top();
        pushed_.pop();
        if (pushed) {
            casted_.pop();
        }
        return true;
    }
    bool TraverseImplicitCastExpr(ImplicitCastExpr * expr) {
        bool ret = true;
        if (PreTraverseImplicitCastExpr(expr))
        {
            ret = FilteringPlugin::TraverseImplicitCastExpr(expr);
            PostTraverseImplicitCastExpr(expr, ret);
        }
       return ret;
    }

    bool VisitVarDecl(VarDecl const * decl) {
        if (ignoreLocation(decl)) {
            return true;
        }
        if (decl != decl->getCanonicalDecl()) {
            return true;
        }
        if (isa<ParmVarDecl>(decl) || loplugin::hasExternalLinkage(decl)) {
            return true;
        }
        if (!loplugin::TypeCheck(decl->getType()).NonConstVolatile().Pointer()
            .Const().Char())
        {
            return true;
        }
        auto init = decl->getAnyInitializer();
        if (init == nullptr) {
            return true;
        }
        if (init->isInstantiationDependent()) {
            // avoid problems with isCXX11ConstantExpr in template code
            return true;
        }
        APValue v;
        if (!init->isCXX11ConstantExpr(compiler.getASTContext(), &v)) {
            return true;
        }
        vars_.insert(decl);
        return true;
    }

    bool VisitDeclRefExpr(DeclRefExpr const * expr) {
        if (!casted_.empty() && expr == casted_.top()) {
            return true;
        }
        auto vd = dyn_cast<VarDecl>(expr->getDecl());
        if (vd == nullptr) {
            return true;
        }
        vars_.erase(vd->getCanonicalDecl());
        return true;
    }

private:
    std::set<VarDecl const *> vars_;
    std::stack<DeclRefExpr const *> casted_;
    std::stack<bool> pushed_;
};

loplugin::Plugin::Registration<ConstStringVar> conststringvar("conststringvar");

}

#endif // LO_CLANG_SHARED_PLUGINS

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