Cppcheck report - LibreOffice 2020-06-13 19:58:00 41c465b5ee443ec04441077b5eb80f263336ea8a, CppCheck 2020-06-13 18:19:47 6d5d12f283cf568d2dfe09aa77cb41f34b322d62: compilerplugins/clang/oncevar.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 <unordered_map>
#include <unordered_set>

#include "plugin.hxx"
#include "check.hxx"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/StmtVisitor.h"

// Original idea from tml.
// Look for variables that are (a) initialised from zero or one constants. (b) only used in one spot.
// In which case, we might as well inline it.

namespace
{

Expr const * lookThroughInitListExpr(Expr const * expr) {
    if (auto const ile = dyn_cast<InitListExpr>(expr->IgnoreParenImpCasts())) {
        if (ile->getNumInits() == 1) {
            return ile->getInit(0);
        }
    }
    return expr;
}

class ConstantValueDependentExpressionVisitor:
    public ConstStmtVisitor<ConstantValueDependentExpressionVisitor, bool>
{
    ASTContext const & context_;

public:
    ConstantValueDependentExpressionVisitor(ASTContext const & context):
<--- Class 'ConstantValueDependentExpressionVisitor' has a constructor with 1 argument that is not explicit. [+]
Class 'ConstantValueDependentExpressionVisitor' has a constructor with 1 argument that is not explicit. Such constructors should in general be explicit for type safety reasons. Using the explicit keyword in the constructor means some mistakes when using the class can be avoided.
        context_(context) {}

    bool Visit(Stmt const * stmt) {
        assert(isa<Expr>(stmt));
        auto const expr = cast<Expr>(stmt);
        if (!expr->isValueDependent()) {
            return expr->isEvaluatable(context_);
        }
        return ConstStmtVisitor::Visit(stmt);
    }

    bool VisitParenExpr(ParenExpr const * expr)<--- The function 'VisitParenExpr' is never used.
    { return Visit(expr->getSubExpr()); }

    bool VisitCastExpr(CastExpr const * expr) {<--- The function 'VisitCastExpr' is never used.
        return Visit(expr->getSubExpr());
    }

    bool VisitUnaryOperator(UnaryOperator const * expr)
    { return Visit(expr->getSubExpr()); }

    bool VisitBinaryOperator(BinaryOperator const * expr) {
        return Visit(expr->getLHS()) && Visit(expr->getRHS());
    }

    bool VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr const *) {<--- The function 'VisitUnaryExprOrTypeTraitExpr' is never used.
        return true;
    }
};

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

    virtual void run() override {
        // ignore some files with problematic macros
        std::string fn(handler.getMainFileName());
        loplugin::normalizeDotDotInFilePath(fn);
        // platform-specific stuff
        if (fn == SRCDIR "/sal/osl/unx/thread.cxx"
            || fn == SRCDIR "/sot/source/base/formats.cxx"
<--- Same expression on both sides of '||'. [+]
Finding the same expression on both sides of an operator is suspicious and might indicate a cut and paste or logic error. Please examine this code carefully to determine if it is correct.
            || fn == SRCDIR "/svl/source/config/languageoptions.cxx"
<--- Same expression on both sides of '||'. [+]
Finding the same expression on both sides of an operator is suspicious and might indicate a cut and paste or logic error. Please examine this code carefully to determine if it is correct.
            || fn == SRCDIR "/sfx2/source/appl/appdde.cxx"
<--- Same expression on both sides of '||'. [+]
Finding the same expression on both sides of an operator is suspicious and might indicate a cut and paste or logic error. Please examine this code carefully to determine if it is correct.
            || fn == SRCDIR "/configmgr/source/components.cxx"
<--- Same expression on both sides of '||'. [+]
Finding the same expression on both sides of an operator is suspicious and might indicate a cut and paste or logic error. Please examine this code carefully to determine if it is correct.
            || fn == SRCDIR "/embeddedobj/source/msole/oleembed.cxx")
<--- Same expression on both sides of '||'. [+]
Finding the same expression on both sides of an operator is suspicious and might indicate a cut and paste or logic error. Please examine this code carefully to determine if it is correct.
             return;
        // some of this is necessary
        if (loplugin::hasPathnamePrefix( fn, SRCDIR "/sal/qa/"))
             return;
        if (loplugin::hasPathnamePrefix( fn, SRCDIR "/comphelper/qa/"))
             return;
        // TODO need to check calls via function pointer
        if (fn == SRCDIR "/i18npool/source/textconversion/textconversion_zh.cxx"
            || fn == SRCDIR "/i18npool/source/localedata/localedata.cxx")
<--- Same expression on both sides of '||'. [+]
Finding the same expression on both sides of an operator is suspicious and might indicate a cut and paste or logic error. Please examine this code carefully to determine if it is correct.
             return;
        // debugging stuff
        if (fn == SRCDIR "/sc/source/core/data/dpcache.cxx"
            || fn == SRCDIR "/sw/source/core/layout/dbg_lay.cxx"
<--- Same expression on both sides of '||'. [+]
Finding the same expression on both sides of an operator is suspicious and might indicate a cut and paste or logic error. Please examine this code carefully to determine if it is correct.
            || fn == SRCDIR "/sw/source/core/layout/ftnfrm.cxx")
<--- Same expression on both sides of '||'. [+]
Finding the same expression on both sides of an operator is suspicious and might indicate a cut and paste or logic error. Please examine this code carefully to determine if it is correct.
             return;
        // TODO taking local reference to variable
        if (fn == SRCDIR "/sc/source/filter/excel/xechart.cxx")<--- If condition 'fn==SRCDIR' is true, the function will return/exit
             return;
        // macros managing to generate to a valid warning
        if (fn == SRCDIR "/solenv/bin/concat-deps.c")<--- Testing identical condition 'fn==SRCDIR'<--- If condition 'fn==SRCDIR' is true, the function will return/exit
             return;
        // TODO bug in the plugin
        if (fn == SRCDIR "/vcl/unx/generic/app/saldisp.cxx")<--- Testing identical condition 'fn==SRCDIR'
            return;

        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());

        for (auto const & varDecl : maVarDeclSet)
        {
            if (maVarDeclToIgnoreSet.find(varDecl) != maVarDeclToIgnoreSet.end())
                continue;
            int noUses = 0;
            auto it = maVarUsesMap.find(varDecl);
            if (it != maVarUsesMap.end())
                noUses = it->second;
            if (noUses > 1)
                continue;
            report(DiagnosticsEngine::Warning,
                   "var used only once, should be inlined or declared const",
                   varDecl->getLocation())
                << varDecl->getSourceRange();
            if (it != maVarUsesMap.end())
                report(DiagnosticsEngine::Note,
                       "used here",
                       maVarUseSourceRangeMap[varDecl].getBegin())
                    << maVarUseSourceRangeMap[varDecl];
        }
    }

    bool VisitMemberExpr(MemberExpr const * expr) {
        // ignore cases like:
        //     const OUString("xxx") xxx;
        //     rtl_something(xxx.pData);
        // where we cannot inline the declaration.
        if (isa<FieldDecl>(expr->getMemberDecl())) {
            recordIgnore(expr);
        }
        return true;
    }

    bool VisitUnaryOperator(UnaryOperator const * expr) {
        // if we take the address of it, or we modify it, ignore it
        UnaryOperator::Opcode op = expr->getOpcode();
        if (op == UO_AddrOf || op == UO_PreInc || op == UO_PostInc
            || op == UO_PreDec || op == UO_PostDec)
        {
            recordIgnore(expr->getSubExpr());
        }
        return true;
    }

    bool VisitBinaryOperator(BinaryOperator const * expr) {
        // if we assign it another value, or modify it, ignore it
        BinaryOperator::Opcode op = expr->getOpcode();
        if (op == BO_Assign || op == BO_PtrMemD || op == BO_PtrMemI || op == BO_MulAssign
            || op == BO_DivAssign || op == BO_RemAssign || op == BO_AddAssign
            || op == BO_SubAssign || op == BO_ShlAssign || op == BO_ShrAssign
            || op == BO_AndAssign || op == BO_XorAssign || op == BO_OrAssign)
        {
            recordIgnore(expr->getLHS());
        }
        return true;
    }

    bool VisitCallExpr(CallExpr const * expr) {
        unsigned firstArg = 0;
        if (auto const cmce = dyn_cast<CXXMemberCallExpr>(expr)) {
            if (auto const e1 = cmce->getMethodDecl()) {
                if (!(e1->isConst() || e1->isStatic())) {
                    recordIgnore(cmce->getImplicitObjectArgument());
                }
            } else if (auto const e2 = dyn_cast<BinaryOperator>(
                           cmce->getCallee()->IgnoreParenImpCasts()))
            {
                switch (e2->getOpcode()) {
                case BO_PtrMemD:
                case BO_PtrMemI:
                    if (!e2->getRHS()->getType()->getAs<MemberPointerType>()
                        ->getPointeeType()->getAs<FunctionProtoType>()
                        ->isConst())
                    {
                        recordIgnore(e2->getLHS());
                    }
                    break;
                default:
                    break;
                }
            }
        } else if (auto const coce = dyn_cast<CXXOperatorCallExpr>(expr)) {
            if (auto const cmd = dyn_cast_or_null<CXXMethodDecl>(
                    coce->getDirectCallee()))
            {
                if (!cmd->isStatic()) {
                    assert(coce->getNumArgs() != 0);
                    if (!cmd->isConst()) {
                        recordIgnore(coce->getArg(0));
                    }
                    firstArg = 1;
                }
            }
        }
        // ignore those ones we are passing by reference
        const FunctionDecl* calleeFunctionDecl = expr->getDirectCallee();
        if (calleeFunctionDecl) {
            for (unsigned i = firstArg; i < expr->getNumArgs(); ++i) {
                if (i < calleeFunctionDecl->getNumParams()) {
                    QualType qt { calleeFunctionDecl->getParamDecl(i)->getType() };
                    if (loplugin::TypeCheck(qt).LvalueReference().NonConst()) {
                        recordIgnore(expr->getArg(i));
                    }
                    if (loplugin::TypeCheck(qt).Pointer().NonConst()) {
                        recordIgnore(expr->getArg(i));
                    }
                }
            }
        }
        return true;
    }

    bool VisitCXXConstructExpr(CXXConstructExpr const * expr) {
        // ignore those ones we are passing by reference
        const CXXConstructorDecl* cxxConstructorDecl = expr->getConstructor();
        for (unsigned i = 0; i < expr->getNumArgs(); ++i) {
            if (i < cxxConstructorDecl->getNumParams()) {
                QualType qt { cxxConstructorDecl->getParamDecl(i)->getType() };
                if (loplugin::TypeCheck(qt).LvalueReference().NonConst()) {
                    recordIgnore(expr->getArg(i));
                }
                if (loplugin::TypeCheck(qt).Pointer().NonConst()) {
                    recordIgnore(expr->getArg(i));
                }
            }
        }
        return true;
    }

    bool VisitDeclRefExpr( const DeclRefExpr* );
    bool VisitVarDecl( const VarDecl* );
    bool TraverseFunctionDecl( FunctionDecl* functionDecl );

private:
    std::unordered_set<VarDecl const *> maVarDeclSet;
    std::unordered_set<VarDecl const *> maVarDeclToIgnoreSet;
    std::unordered_map<VarDecl const *, int> maVarUsesMap;
    std::unordered_map<VarDecl const *, SourceRange> maVarUseSourceRangeMap;

    bool isConstantValueDependentExpression(Expr const * expr) {
        return ConstantValueDependentExpressionVisitor(compiler.getASTContext())
            .Visit(expr);
    }

    void recordIgnore(Expr const * expr) {
        for (;;) {
            expr = expr->IgnoreParenImpCasts();
            if (auto const e = dyn_cast<MemberExpr>(expr)) {
                if (isa<FieldDecl>(e->getMemberDecl())) {
                    expr = e->getBase();
                    continue;
                }
            }
            if (auto const e = dyn_cast<ArraySubscriptExpr>(expr)) {
                expr = e->getBase();
                continue;
            }
            if (auto const e = dyn_cast<BinaryOperator>(expr)) {
                if (e->getOpcode() == BO_PtrMemD) {
                    expr = e->getLHS();
                    continue;
                }
            }
            break;
        }
        auto const dre = dyn_cast<DeclRefExpr>(expr);
        if (dre == nullptr) {
            return;
        }
        auto const var = dyn_cast<VarDecl>(dre->getDecl());
        if (var == nullptr) {
            return;
        }
        maVarDeclToIgnoreSet.insert(var);
    }
};

bool OnceVar::TraverseFunctionDecl( FunctionDecl* functionDecl )
{
    // Ignore functions that contains #ifdef-ery, can be quite tricky
    // to make useful changes when this plugin fires in such functions
    if (containsPreprocessingConditionalInclusion(
            functionDecl->getSourceRange()))
        return true;
    return RecursiveASTVisitor::TraverseFunctionDecl(functionDecl);
}

bool OnceVar::VisitVarDecl( const VarDecl* varDecl )
{
    if (ignoreLocation(varDecl)) {
        return true;
    }
    if (auto const init = varDecl->getInit()) {
        recordIgnore(lookThroughInitListExpr(init));
    }
    if (varDecl->isExceptionVariable() || isa<ParmVarDecl>(varDecl)) {
        return true;
    }
    // ignore stuff in header files (which should really not be there, but anyhow)
    if (!compiler.getSourceManager().isInMainFile(varDecl->getLocation())) {
        return true;
    }
    // Ignore macros like FD_ZERO
    if (compiler.getSourceManager().isMacroBodyExpansion(compat::getBeginLoc(varDecl))) {
        return true;
    }
    if (varDecl->hasGlobalStorage()) {
        return true;
    }
    auto const tc = loplugin::TypeCheck(varDecl->getType());
    if (!varDecl->getType().isCXX11PODType(compiler.getASTContext())
        && !tc.Class("OString").Namespace("rtl").GlobalNamespace()
        && !tc.Class("OUString").Namespace("rtl").GlobalNamespace()
        && !tc.Class("OStringBuffer").Namespace("rtl").GlobalNamespace()
        && !tc.Class("OUStringBuffer").Namespace("rtl").GlobalNamespace()
        && !tc.Class("Color").GlobalNamespace()
        && !tc.Class("Pair").GlobalNamespace()
        && !tc.Class("Point").GlobalNamespace()
        && !tc.Class("Size").GlobalNamespace()
        && !tc.Class("Range").GlobalNamespace()
        && !tc.Class("Selection").GlobalNamespace()
        && !tc.Class("Rectangle").Namespace("tools").GlobalNamespace())
    {
        return true;
    }
    if (varDecl->getType()->isPointerType())
        return true;
    // if it's declared const, ignore it, it's there to make the code easier to read
    if (tc.Const())
        return true;

    if (!varDecl->hasInit())
        return true;

    // check for string or scalar literals
    bool foundStringLiteral = false;
    const Expr * initExpr = varDecl->getInit();
    if (auto e = dyn_cast<ExprWithCleanups>(initExpr)) {
        initExpr = e->getSubExpr();
    }
    if (isa<clang::StringLiteral>(initExpr)) {
        foundStringLiteral = true;
    } else if (auto constructExpr = dyn_cast<CXXConstructExpr>(initExpr)) {
        if (constructExpr->getNumArgs() == 0) {
            foundStringLiteral = true; // i.e., empty string
        } else {
            auto stringLit2 = dyn_cast<clang::StringLiteral>(constructExpr->getArg(0));
            foundStringLiteral = stringLit2 != nullptr;
        }
    }
    if (!foundStringLiteral) {
        auto const init = varDecl->getInit();
        if (!(init->isValueDependent()
              ? isConstantValueDependentExpression(init)
              : init->isConstantInitializer(
                  compiler.getASTContext(), false/*ForRef*/)))
        {
            return true;
        }
    }

    maVarDeclSet.insert(varDecl);

    return true;
}

bool OnceVar::VisitDeclRefExpr( const DeclRefExpr* declRefExpr )
{
    if (ignoreLocation(declRefExpr)) {
        return true;
    }
    const Decl* decl = declRefExpr->getDecl();
    if (!isa<VarDecl>(decl) || isa<ParmVarDecl>(decl)) {
        return true;
    }
    const VarDecl * varDecl = dyn_cast<VarDecl>(decl)->getCanonicalDecl();
    // ignore stuff in header files (which should really not be there, but anyhow)
    if (!compiler.getSourceManager().isInMainFile(varDecl->getLocation())) {
        return true;
    }

    if (maVarUsesMap.find(varDecl) == maVarUsesMap.end()) {
        maVarUsesMap[varDecl] = 1;
        maVarUseSourceRangeMap[varDecl] = declRefExpr->getSourceRange();
    } else {
        maVarUsesMap[varDecl]++;
    }

    return true;
}

loplugin::Plugin::Registration< OnceVar > X("oncevar", false);

}

/* vim:set shiftwidth=4 softtabstop=4 expandtab: */