nullptr.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:https://mozilla.org/MPL/2.0/.
 */

#include <cassert>
#include <cstdlib>
#include <limits>
#include <set>

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

namespace {

char const * kindName(Expr::NullPointerConstantKind kind) {
    switch (kind) {
    case Expr::NPCK_ZeroExpression:
        return "ZeroExpression";
    case Expr::NPCK_ZeroLiteral:
        return "ZeroLiteral";
    case Expr::NPCK_CXX11_nullptr:
        return "CXX11_nullptr";
    case Expr::NPCK_GNUNull:
        return "GNUNull";
    case Expr::NPCK_NotNull:
        break; // cannot happen
    }
    llvm_unreachable("unknown null pointer kind");
}

bool isAnyKindOfPointerType(QualType type) {
    return type->isAnyPointerType() || type->isFunctionPointerType()
        || type->isMemberPointerType();
}

bool isNullPointerCast(CastExpr const * expr) {
    switch (expr->getCastKind()) {
    case CK_NullToPointer:
    case CK_NullToMemberPointer:
        return true;
    default:
        return false;
    }
}

class Nullptr:
    public loplugin::FilteringRewritePlugin<Nullptr>
{
public:
    explicit Nullptr(loplugin::InstantiationData const & data):
        FilteringRewritePlugin(data) {}

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

    bool VisitImplicitCastExpr(CastExpr const * expr);

    bool VisitGNUNullExpr(GNUNullExpr const * expr);

    bool VisitBinaryOperator(BinaryOperator const * expr);

    bool VisitCXXOperatorCallExpr(CXXOperatorCallExpr const * expr);

    bool VisitParmVarDecl(ParmVarDecl const * decl);

    bool TraverseConstructorInitializer(CXXCtorInitializer * init);

    bool TraverseLinkageSpecDecl(LinkageSpecDecl * decl);

    bool TraverseInitListExpr(InitListExpr * expr, DataRecursionQueue * queue = nullptr);

    bool shouldVisitTemplateInstantiations() const { return true; }

private:
    bool isInLokIncludeFile(SourceLocation spellingLocation) const;

    bool isFromCIncludeFile(SourceLocation spellingLocation) const;

    bool isSharedCAndCppCode(SourceLocation location) const;

    void visitCXXCtorInitializer(CXXCtorInitializer const * init);

    void handleZero(Expr const * expr);

    void handleNull(
        Expr const * expr, char const * castKind,
        Expr::NullPointerConstantKind nullPointerKind);

    void rewriteOrWarn(
        Expr const * expr, char const * castKind,
        Expr::NullPointerConstantKind nullPointerKind,
        char const * replacement);

    std::set<Expr const *> gnuNulls_;
    unsigned int externCContexts_ = 0;
};

bool Nullptr::VisitImplicitCastExpr(CastExpr const * expr) {
    if (ignoreLocation(expr)) {
        return true;
    }
    if (!isNullPointerCast(expr)) {
        return true;
    }
    Expr::NullPointerConstantKind k = expr->isNullPointerConstant(
        compiler.getASTContext(), Expr::NPC_ValueDependentIsNotNull);
    switch (k) {
    case Expr::NPCK_NotNull:
        k = expr->isNullPointerConstant(
            compiler.getASTContext(), Expr::NPC_ValueDependentIsNull);
        switch (k) {
        case Expr::NPCK_NotNull:
            break;
        case Expr::NPCK_ZeroExpression:
        case Expr::NPCK_ZeroLiteral:
            report(
                DiagnosticsEngine::Warning,
                "suspicious ValueDependentIsNull %0", expr->getBeginLoc())
                << kindName(k) << expr->getSourceRange();
            break;
        default:
            assert(false); // cannot happen
        }
        break;
    case Expr::NPCK_CXX11_nullptr:
        break;
    default:
        auto const tc = loplugin::TypeCheck(expr->getType());
        if (tc.Typedef("locale_t")
            .GlobalNamespace())
        {
            break; // POSIX locale_t is left unspecified
        }
        // Hack to handle libc++ and stdlibc++ `std::strong_ordering x; x < 0` etc.:
        if (tc.MemberPointerOf().ClassOrStruct("_CmpUnspecifiedParam").StdNamespace()
            || tc.Pointer().ClassOrStruct("__unspec").Namespace("__cmp_cat").StdNamespace())
        {
            break;
        }
        handleNull(expr->getSubExpr(), expr->getCastKindName(), k);
        break;
    }
    return true;
}

bool Nullptr::VisitGNUNullExpr(GNUNullExpr const * expr) {
    if (ignoreLocation(expr)) {
        return true;
    }
    handleNull(expr, nullptr, Expr::NPCK_GNUNull);
    return true;
}

bool Nullptr::VisitBinaryOperator(BinaryOperator const * expr) {
    if (ignoreLocation(expr)) {
        return true;
    }
    Expr const * e;
    switch (expr->getOpcode()) {
    case BO_EQ:
    case BO_NE:
        if (isAnyKindOfPointerType(expr->getRHS()->getType())) {
            e = expr->getLHS();
            break;
        }
        // fall through
    case BO_Assign:
        if (isAnyKindOfPointerType(expr->getLHS()->getType())) {
            e = expr->getRHS();
            break;
        }
        // fall through
    default:
        return true;
    }
    handleZero(e);
    return true;
}

bool Nullptr::VisitCXXOperatorCallExpr(CXXOperatorCallExpr const * expr) {
    if (ignoreLocation(expr)) {
        return true;
    }
    Expr const * e;
    switch (expr->getOperator()) {
    case OO_EqualEqual:
    case OO_ExclaimEqual:
        if (isAnyKindOfPointerType(expr->getArg(1)->getType())) {
            e = expr->getArg(0);
            break;
        }
        // fall through
    case OO_Equal:
        if (isAnyKindOfPointerType(expr->getArg(0)->getType())) {
            e = expr->getArg(1);
            break;
        }
        // fall through
    default:
        return true;
    }
    handleZero(e);
    return true;
}

bool Nullptr::VisitParmVarDecl(ParmVarDecl const * decl) {
    if (ignoreLocation(decl)) {
        return true;
    }
    if (!isAnyKindOfPointerType(decl->getType())) {
        return true;
    }
    if (decl->hasUninstantiatedDefaultArg()) {
        return true; //TODO
    }
    auto e = decl->getDefaultArg();
    if (e == nullptr) {
        return true;
    }
    handleZero(e);
    return true;
}

bool Nullptr::TraverseConstructorInitializer(CXXCtorInitializer * init) {
    visitCXXCtorInitializer(init);
    return RecursiveASTVisitor::TraverseConstructorInitializer(init);
}

bool Nullptr::TraverseLinkageSpecDecl(LinkageSpecDecl * decl) {
    assert(externCContexts_ != std::numeric_limits<unsigned int>::max()); //TODO
    ++externCContexts_;
    bool ret = RecursiveASTVisitor::TraverseLinkageSpecDecl(decl);
    assert(externCContexts_ != 0);
    --externCContexts_;
    return ret;
}

bool Nullptr::TraverseInitListExpr(InitListExpr * expr, DataRecursionQueue * queue) {
    return WalkUpFromInitListExpr(expr)
        && TraverseSynOrSemInitListExpr(
            expr->isSemanticForm() ? expr : expr->getSemanticForm(), queue);
}

bool Nullptr::isInLokIncludeFile(SourceLocation spellingLocation) const {
    return loplugin::hasPathnamePrefix(
        getFilenameOfLocation(spellingLocation),
        SRCDIR "/include/LibreOfficeKit/");
}

bool Nullptr::isFromCIncludeFile(SourceLocation spellingLocation) const {
    return !compiler.getSourceManager().isInMainFile(spellingLocation)
        && compat::ends_with(
            StringRef(compiler.getSourceManager().getPresumedLoc(spellingLocation).getFilename()),
            ".h");
}

bool Nullptr::isSharedCAndCppCode(SourceLocation location) const {
    // Assume that code is intended to be shared between C and C++ if it comes
    // from an include file ending in .h, and is either in an extern "C" context
    // or the body of a macro definition:
    return
        isFromCIncludeFile(compiler.getSourceManager().getSpellingLoc(location))
        && (externCContexts_ != 0
            || compiler.getSourceManager().isMacroBodyExpansion(location));
}

void Nullptr::visitCXXCtorInitializer(CXXCtorInitializer const * init) {
    if (!init->isWritten()) {
        return;
    }
    auto e = init->getInit();
    if (ignoreLocation(e)) {
        return;
    }
    auto d = init->getAnyMember();
    if (d == nullptr || !isAnyKindOfPointerType(d->getType())) {
        return;
    }
    if (auto e2 = dyn_cast<ParenListExpr>(e)) {
        if (e2->getNumExprs() != 1) {
            return;
        }
        e = e2->getExpr(0);
    } else if (auto e2 = dyn_cast<InitListExpr>(e)) {
        if (e2->getNumInits() != 1) {
            return;
        }
        e = e2->getInit(0);
    }
    handleZero(e);
}

void Nullptr::handleZero(Expr const * expr) {
    //TODO: detect NPCK_ZeroExpression where appropriate
    // Filter out ImplicitCastExpr that will be handled by
    // VisitImplicitCastExpr:
    if (auto ice = dyn_cast<ImplicitCastExpr>(expr)) {
        if (isNullPointerCast(ice)) {
            return;
        }
    }
    auto const lit = dyn_cast<IntegerLiteral>(expr->IgnoreParenImpCasts());
    if (lit != nullptr && !lit->getValue().getBoolValue()) {
        handleNull(expr, nullptr, Expr::NPCK_ZeroLiteral);
    }
}

void Nullptr::handleNull(
    Expr const * expr, char const * castKind,
    Expr::NullPointerConstantKind nullPointerKind)
{
    auto e = expr;
    SourceLocation loc;
    for (;;) {
        e = e->IgnoreImpCasts();
        loc = e->getBeginLoc();
        while (compiler.getSourceManager().isMacroArgExpansion(loc)) {
            loc = compiler.getSourceManager().getImmediateMacroCallerLoc(loc);
        }
        if (compiler.getSourceManager().isMacroBodyExpansion(loc)) {
            if (Lexer::getImmediateMacroName(
                    loc, compiler.getSourceManager(), compiler.getLangOpts())
                == "NULL")
            {
                if (!compiler.getLangOpts().CPlusPlus) {
                    //TODO: if !castKind, warn if NULL is passed into fn call
                    // ellipsis, cast to void*
                    return;
                }
                loc = compat::getImmediateExpansionRange(compiler.getSourceManager(), loc).first;
                if (ignoreLocation(
                        compiler.getSourceManager().getSpellingLoc(loc)))
                {
                    return;
                }
                if (isInUnoIncludeFile(
                        compiler.getSourceManager().getSpellingLoc(loc))
                    || isInLokIncludeFile(
                        compiler.getSourceManager().getSpellingLoc(loc))
                    || isSharedCAndCppCode(loc))
                {
                    //TODO: if !castKind, warn if NULL is passed into fn call
                    // ellipsis, cast to void*
                    return;
                }
            } else if (ignoreLocation(
                           compiler.getSourceManager().getSpellingLoc(loc)))
            {
                return;
            }
        }
        ParenExpr const * pe = dyn_cast<ParenExpr>(e);
        if (pe == nullptr) {
            break;
        }
        e = pe->getSubExpr();
    }
    if (nullPointerKind == Expr::NPCK_GNUNull) {
        if (castKind == nullptr) {
            if (gnuNulls_.erase(expr) == 1) {
                return;
            }
        } else {
            auto const ok = gnuNulls_.insert(expr).second;
            assert(ok); (void) ok;
        }
    }
    auto const asMacro = !compiler.getLangOpts().CPlusPlus
        || isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(loc))
        || isInLokIncludeFile(compiler.getSourceManager().getSpellingLoc(loc))
        || isSharedCAndCppCode(loc);
    assert(!asMacro || nullPointerKind != Expr::NPCK_GNUNull);
    rewriteOrWarn(e, castKind, nullPointerKind, asMacro ? "NULL" : "nullptr");
}

void Nullptr::rewriteOrWarn(
    Expr const * expr, char const * castKind,
    Expr::NullPointerConstantKind nullPointerKind, char const * replacement)
{
    if (rewriter != nullptr) {
        SourceLocation locStart(expr->getBeginLoc());
        while (compiler.getSourceManager().isMacroArgExpansion(locStart)) {
            locStart = compiler.getSourceManager()
                .getImmediateMacroCallerLoc(locStart);
        }
        if (compiler.getLangOpts().CPlusPlus
            && compiler.getSourceManager().isMacroBodyExpansion(locStart)
            && (Lexer::getImmediateMacroName(
                    locStart, compiler.getSourceManager(),
                    compiler.getLangOpts())
                == "NULL"))
        {
            locStart = compat::getImmediateExpansionRange(compiler.getSourceManager(), locStart)
                .first;
        }
        SourceLocation locEnd(expr->getEndLoc());
        while (compiler.getSourceManager().isMacroArgExpansion(locEnd)) {
            locEnd = compiler.getSourceManager()
                .getImmediateMacroCallerLoc(locEnd);
        }
        if (compiler.getLangOpts().CPlusPlus
            && compiler.getSourceManager().isMacroBodyExpansion(locEnd)
            && (Lexer::getImmediateMacroName(
                    locEnd, compiler.getSourceManager(),
                    compiler.getLangOpts())
                == "NULL"))
        {
            locEnd = compat::getImmediateExpansionRange(compiler.getSourceManager(), locEnd).first;
        }
        if (replaceText(SourceRange(compiler.getSourceManager().getSpellingLoc(locStart), compiler.getSourceManager().getSpellingLoc(locEnd)), replacement)) {
            return;
        }
    }
    if (castKind == nullptr) {
        report(DiagnosticsEngine::Warning, "%0 -> %1", expr->getBeginLoc())
            << kindName(nullPointerKind) << replacement
            << expr->getSourceRange();
    } else {
        report(
            DiagnosticsEngine::Warning, "%0 ValueDependentIsNotNull %1 -> %2",
            expr->getBeginLoc())
            << castKind << kindName(nullPointerKind) << replacement
            << expr->getSourceRange();
    }
}

loplugin::Plugin::Registration<Nullptr> X("nullptr", true);

}

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