Cppcheck report - LibreOffice 2020-06-13 19:58:00 41c465b5ee443ec04441077b5eb80f263336ea8a, CppCheck 2020-06-13 18:19:47 6d5d12f283cf568d2dfe09aa77cb41f34b322d62: compilerplugins/clang/constfields.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/.
 */

#if !defined _WIN32 //TODO, #include <sys/file.h>

#include <cassert>
#include <string>
#include <iostream>
#include <fstream>
#include <unordered_set>
#include <vector>
#include <algorithm>
#include <sys/file.h>
#include <unistd.h>

#include "config_clang.h"

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

#if CLANG_VERSION >= 110000
#include "clang/AST/ParentMapContext.h"
#endif

/**
Look for fields that are only assigned to in the constructor using field-init, and can therefore be const.

The process goes something like this:
  $ make check
  $ make FORCE_COMPILE_ALL=1 COMPILER_PLUGIN_TOOL='constfields' check
  $ ./compilerplugins/clang/constfields.py

and then
  $ for dir in *; do make $dir FORCE_COMPILE_ALL=1 UPDATE_FILES=$dir COMPILER_PLUGIN_TOOL='constfieldsrewrite' $dir; done
to auto-remove the method declarations

*/

namespace
{
struct MyFieldInfo
{
    const RecordDecl* parentRecord;
    std::string parentClass;
    std::string fieldName;
    std::string fieldType;
    std::string sourceLocation;
    std::string access;
};
bool operator<(const MyFieldInfo& lhs, const MyFieldInfo& rhs)
{
    return std::tie(lhs.parentClass, lhs.fieldName) < std::tie(rhs.parentClass, rhs.fieldName);
}

// try to limit the voluminous output a little
static std::set<MyFieldInfo> cannotBeConstSet;
static std::set<MyFieldInfo> definitionSet;

/**
 * Wrap the different kinds of callable and callee objects in the clang AST so I can define methods that handle everything.
 */
class CallerWrapper
{
    const CallExpr* m_callExpr;
    const CXXConstructExpr* m_cxxConstructExpr;

public:
    CallerWrapper(const CallExpr* callExpr)
<--- Class 'CallerWrapper' has a constructor with 1 argument that is not explicit. [+]
Class 'CallerWrapper' 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.
        : m_callExpr(callExpr)
        , m_cxxConstructExpr(nullptr)
    {
    }
    CallerWrapper(const CXXConstructExpr* cxxConstructExpr)
<--- Class 'CallerWrapper' has a constructor with 1 argument that is not explicit. [+]
Class 'CallerWrapper' 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.
        : m_callExpr(nullptr)
        , m_cxxConstructExpr(cxxConstructExpr)
    {
    }
    unsigned getNumArgs() const
    {
        return m_callExpr ? m_callExpr->getNumArgs() : m_cxxConstructExpr->getNumArgs();
    }
    const Expr* getArg(unsigned i) const
    {
        return m_callExpr ? m_callExpr->getArg(i) : m_cxxConstructExpr->getArg(i);
    }
};
class CalleeWrapper
{
    const FunctionDecl* m_calleeFunctionDecl = nullptr;
    const CXXConstructorDecl* m_cxxConstructorDecl = nullptr;
    const FunctionProtoType* m_functionPrototype = nullptr;

public:
    explicit CalleeWrapper(const FunctionDecl* calleeFunctionDecl)
        : m_calleeFunctionDecl(calleeFunctionDecl)
    {
    }
    explicit CalleeWrapper(const CXXConstructExpr* cxxConstructExpr)
        : m_cxxConstructorDecl(cxxConstructExpr->getConstructor())
    {
    }
    explicit CalleeWrapper(const FunctionProtoType* functionPrototype)
        : m_functionPrototype(functionPrototype)
    {
    }
    unsigned getNumParams() const
    {
        if (m_calleeFunctionDecl)
            return m_calleeFunctionDecl->getNumParams();
        else if (m_cxxConstructorDecl)
            return m_cxxConstructorDecl->getNumParams();
        else if (m_functionPrototype->param_type_begin() == m_functionPrototype->param_type_end())
            // FunctionProtoType will assert if we call getParamTypes() and it has no params
            return 0;
        else
            return m_functionPrototype->getParamTypes().size();
    }
    const QualType getParamType(unsigned i) const
    {
        if (m_calleeFunctionDecl)
            return m_calleeFunctionDecl->getParamDecl(i)->getType();
        else if (m_cxxConstructorDecl)
            return m_cxxConstructorDecl->getParamDecl(i)->getType();
        else
            return m_functionPrototype->getParamTypes()[i];
    }
    std::string getNameAsString() const
    {
        if (m_calleeFunctionDecl)
            return m_calleeFunctionDecl->getNameAsString();
        else if (m_cxxConstructorDecl)
            return m_cxxConstructorDecl->getNameAsString();
        else
            return "";
    }
    CXXMethodDecl const* getAsCXXMethodDecl() const
    {
        if (m_calleeFunctionDecl)
            return dyn_cast<CXXMethodDecl>(m_calleeFunctionDecl);
        return nullptr;
    }
};

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

    virtual void run() override;

    bool shouldVisitTemplateInstantiations() const { return true; }
    bool shouldVisitImplicitCode() const { return true; }

    bool VisitFieldDecl(const FieldDecl*);
    bool VisitMemberExpr(const MemberExpr*);
    bool TraverseCXXConstructorDecl(CXXConstructorDecl*);
    bool TraverseCXXMethodDecl(CXXMethodDecl*);
    bool TraverseFunctionDecl(FunctionDecl*);
    bool TraverseIfStmt(IfStmt*);

private:
    MyFieldInfo niceName(const FieldDecl*);
    void check(const FieldDecl* fieldDecl, const Expr* memberExpr);
    bool isSomeKindOfZero(const Expr* arg);
    bool IsPassedByNonConst(const FieldDecl* fieldDecl, const Stmt* child, CallerWrapper callExpr,
                            CalleeWrapper calleeFunctionDecl);
    llvm::Optional<CalleeWrapper> getCallee(CallExpr const*);

    RecordDecl* insideMoveOrCopyDeclParent = nullptr;
    // For reasons I do not understand, parentFunctionDecl() is not reliable, so
    // we store the parent function on the way down the AST.
    FunctionDecl* insideFunctionDecl = nullptr;
    std::vector<FieldDecl const*> insideConditionalCheckOfMemberSet;
};

void ConstFields::run()
{
    TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());

    if (!isUnitTestMode())
    {
        // 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 MyFieldInfo& s : cannotBeConstSet)
            output += "write-outside-constructor:\t" + s.parentClass + "\t" + s.fieldName + "\n";<--- Consider using std::accumulate algorithm instead of a raw loop.
        for (const MyFieldInfo& s : definitionSet)
            output += "definition:\t" + s.access + "\t" + s.parentClass + "\t" + s.fieldName + "\t"<--- Consider using std::accumulate algorithm instead of a raw loop.
                      + s.fieldType + "\t" + s.sourceLocation + "\n";
        std::ofstream myfile;
        myfile.open(WORKDIR "/loplugin.constfields.log", std::ios::app | std::ios::out);
        myfile << output;
        myfile.close();
    }
    else
    {
        for (const MyFieldInfo& s : cannotBeConstSet)
            report(DiagnosticsEngine::Warning, "notconst %0", compat::getBeginLoc(s.parentRecord))
                << s.fieldName;
    }
}

MyFieldInfo ConstFields::niceName(const FieldDecl* fieldDecl)
{
    MyFieldInfo aInfo;

    const RecordDecl* recordDecl = fieldDecl->getParent();

    if (const CXXRecordDecl* cxxRecordDecl = dyn_cast<CXXRecordDecl>(recordDecl))
    {
        if (cxxRecordDecl->getTemplateInstantiationPattern())
            cxxRecordDecl = cxxRecordDecl->getTemplateInstantiationPattern();
        aInfo.parentRecord = cxxRecordDecl;
        aInfo.parentClass = cxxRecordDecl->getQualifiedNameAsString();
    }
    else
    {
        aInfo.parentRecord = recordDecl;
        aInfo.parentClass = recordDecl->getQualifiedNameAsString();
    }

    aInfo.fieldName = fieldDecl->getNameAsString();
    // sometimes the name (if it's an anonymous thing) contains the full path of the build folder, which we don't need
    size_t idx = aInfo.fieldName.find(SRCDIR);
    if (idx != std::string::npos)
    {
        aInfo.fieldName = aInfo.fieldName.replace(idx, strlen(SRCDIR), "");
    }
    aInfo.fieldType = fieldDecl->getType().getAsString();

    SourceLocation expansionLoc
        = compiler.getSourceManager().getExpansionLoc(fieldDecl->getLocation());
    StringRef name = getFilenameOfLocation(expansionLoc);
    aInfo.sourceLocation
        = std::string(name.substr(strlen(SRCDIR) + 1)) + ":"
          + std::to_string(compiler.getSourceManager().getSpellingLineNumber(expansionLoc));
    loplugin::normalizeDotDotInFilePath(aInfo.sourceLocation);

    switch (fieldDecl->getAccess())
    {
        case AS_public:
            aInfo.access = "public";
            break;
        case AS_private:
            aInfo.access = "private";
            break;
        case AS_protected:
            aInfo.access = "protected";
            break;
        default:
            aInfo.access = "unknown";
            break;
    }

    return aInfo;
}

bool ConstFields::VisitFieldDecl(const FieldDecl* fieldDecl)
{
    fieldDecl = fieldDecl->getCanonicalDecl();
    if (ignoreLocation(fieldDecl))
    {
        return true;
    }
    // ignore stuff that forms part of the stable URE interface
    if (isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(fieldDecl->getLocation())))
    {
        return true;
    }
    definitionSet.insert(niceName(fieldDecl));
    return true;
}

bool ConstFields::TraverseCXXConstructorDecl(CXXConstructorDecl* cxxConstructorDecl)
{
    auto copy = insideMoveOrCopyDeclParent;
    if (!ignoreLocation(cxxConstructorDecl) && cxxConstructorDecl->isThisDeclarationADefinition())
    {
        if (cxxConstructorDecl->isCopyOrMoveConstructor())
            insideMoveOrCopyDeclParent = cxxConstructorDecl->getParent();
    }
    bool ret = RecursiveASTVisitor::TraverseCXXConstructorDecl(cxxConstructorDecl);
    insideMoveOrCopyDeclParent = copy;
    return ret;
}

bool ConstFields::TraverseCXXMethodDecl(CXXMethodDecl* cxxMethodDecl)
{
    auto copy1 = insideMoveOrCopyDeclParent;
    auto copy2 = insideFunctionDecl;
    if (!ignoreLocation(cxxMethodDecl) && cxxMethodDecl->isThisDeclarationADefinition())
    {
        if (cxxMethodDecl->isCopyAssignmentOperator() || cxxMethodDecl->isMoveAssignmentOperator())
            insideMoveOrCopyDeclParent = cxxMethodDecl->getParent();
    }
    insideFunctionDecl = cxxMethodDecl;
    bool ret = RecursiveASTVisitor::TraverseCXXMethodDecl(cxxMethodDecl);
    insideMoveOrCopyDeclParent = copy1;
    insideFunctionDecl = copy2;
    return ret;
}

bool ConstFields::TraverseFunctionDecl(FunctionDecl* functionDecl)
{
    auto copy2 = insideFunctionDecl;
    insideFunctionDecl = functionDecl;
    bool ret = RecursiveASTVisitor::TraverseFunctionDecl(functionDecl);
    insideFunctionDecl = copy2;
    return ret;
}

bool ConstFields::TraverseIfStmt(IfStmt* ifStmt)
{
    FieldDecl const* memberFieldDecl = nullptr;
    Expr const* cond = ifStmt->getCond()->IgnoreParenImpCasts();
    if (auto memberExpr = dyn_cast<MemberExpr>(cond))
    {
        if ((memberFieldDecl = dyn_cast<FieldDecl>(memberExpr->getMemberDecl())))
            insideConditionalCheckOfMemberSet.push_back(memberFieldDecl);
    }
    bool ret = RecursiveASTVisitor::TraverseIfStmt(ifStmt);
    if (memberFieldDecl)
        insideConditionalCheckOfMemberSet.pop_back();
    return ret;
}

bool ConstFields::VisitMemberExpr(const MemberExpr* memberExpr)<--- The function 'VisitMemberExpr' is never used.
{
    const ValueDecl* decl = memberExpr->getMemberDecl();
    const FieldDecl* fieldDecl = dyn_cast<FieldDecl>(decl);
    if (!fieldDecl)
    {
        return true;
    }
    fieldDecl = fieldDecl->getCanonicalDecl();
    if (ignoreLocation(fieldDecl))
    {
        return true;
    }
    // ignore stuff that forms part of the stable URE interface
    if (isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(fieldDecl->getLocation())))
    {
        return true;
    }

    check(fieldDecl, memberExpr);

    return true;
}

void ConstFields::check(const FieldDecl* fieldDecl, const Expr* memberExpr)
{
    auto parentsRange = getParents(*memberExpr);<--- Shadowed declaration
    const Stmt* child = memberExpr;
    const Stmt* parent
        = parentsRange.begin() == parentsRange.end() ? nullptr : parentsRange.begin()->get<Stmt>();
    // walk up the tree until we find something interesting
    bool bCannotBeConst = false;
    bool bDump = false;<--- Assignment 'bDump=false', assigned value is 0
    auto walkUp = [&]() {
        child = parent;
        auto parentsRange = getParents(*parent);
        parent = parentsRange.begin() == parentsRange.end() ? nullptr
                                                            : parentsRange.begin()->get<Stmt>();
    };
    do
    {
        if (!parent)
        {
            // check if we have an expression like
            //    int& r = m_field;
            auto parentsRange = getParents(*child);<--- Shadow variable
            if (parentsRange.begin() != parentsRange.end())
            {
                auto varDecl = dyn_cast_or_null<VarDecl>(parentsRange.begin()->get<Decl>());
                // The isImplicit() call is to avoid triggering when we see the vardecl which is part of a for-range statement,
                // which is of type 'T&&' and also an l-value-ref ?
                if (varDecl && !varDecl->isImplicit()
                    && loplugin::TypeCheck(varDecl->getType()).LvalueReference().NonConst())
                {
                    bCannotBeConst = true;
                }
            }
            break;
        }
        if (isa<CXXReinterpretCastExpr>(parent))
        {
            // once we see one of these, there is not much useful we can know
            bCannotBeConst = true;
            break;
        }
        else if (isa<CastExpr>(parent) || isa<MemberExpr>(parent) || isa<ParenExpr>(parent)
                 || isa<ParenListExpr>(parent) || isa<ArrayInitLoopExpr>(parent)
                 || isa<ExprWithCleanups>(parent))
        {
            walkUp();
        }
        else if (auto unaryOperator = dyn_cast<UnaryOperator>(parent))
        {
            UnaryOperator::Opcode op = unaryOperator->getOpcode();
            if (op == UO_AddrOf || op == UO_PostInc || op == UO_PostDec || op == UO_PreInc
                || op == UO_PreDec)
            {
                bCannotBeConst = true;
            }
            walkUp();
        }
        else if (auto operatorCallExpr = dyn_cast<CXXOperatorCallExpr>(parent))
        {
            auto callee = getCallee(operatorCallExpr);
            if (callee)
            {
                // if calling a non-const operator on the field
                auto calleeMethodDecl = callee->getAsCXXMethodDecl();
                if (calleeMethodDecl && operatorCallExpr->getArg(0) == child
                    && !calleeMethodDecl->isConst())
                {
                    bCannotBeConst = true;
                }
                else if (IsPassedByNonConst(fieldDecl, child, operatorCallExpr, *callee))
                {
                    bCannotBeConst = true;
                }
            }
            else
                bCannotBeConst = true; // conservative, could improve
            walkUp();
        }
        else if (auto cxxMemberCallExpr = dyn_cast<CXXMemberCallExpr>(parent))
        {
            const CXXMethodDecl* calleeMethodDecl = cxxMemberCallExpr->getMethodDecl();
            if (calleeMethodDecl)
            {
                // if calling a non-const method on the field
                const Expr* tmp = dyn_cast<Expr>(child);
                if (tmp->isBoundMemberFunction(compiler.getASTContext()))
                {
                    tmp = dyn_cast<MemberExpr>(tmp)->getBase();
                }
                if (cxxMemberCallExpr->getImplicitObjectArgument() == tmp
                    && !calleeMethodDecl->isConst())
                {
                    bCannotBeConst = true;
                    break;
                }
                if (IsPassedByNonConst(fieldDecl, child, cxxMemberCallExpr,
                                       CalleeWrapper(calleeMethodDecl)))
                    bCannotBeConst = true;
            }
            else
                bCannotBeConst = true; // can happen in templates
            walkUp();
        }
        else if (auto cxxConstructExpr = dyn_cast<CXXConstructExpr>(parent))
        {
            if (IsPassedByNonConst(fieldDecl, child, cxxConstructExpr,
                                   CalleeWrapper(cxxConstructExpr)))
                bCannotBeConst = true;
            walkUp();
        }
        else if (auto callExpr = dyn_cast<CallExpr>(parent))
        {
            auto callee = getCallee(callExpr);
            if (callee)
            {
                if (IsPassedByNonConst(fieldDecl, child, callExpr, *callee))
                    bCannotBeConst = true;
            }
            else
                bCannotBeConst = true; // conservative, could improve
            walkUp();
        }
        else if (auto binaryOp = dyn_cast<BinaryOperator>(parent))
        {
            BinaryOperator::Opcode op = binaryOp->getOpcode();
            const bool assignmentOp = op == BO_Assign || 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;
            if (assignmentOp)
            {
                if (binaryOp->getLHS() == child)
                    bCannotBeConst = true;
                else if (loplugin::TypeCheck(binaryOp->getLHS()->getType())
                             .LvalueReference()
                             .NonConst())
                    // if the LHS is a non-const reference, we could write to the field later on
                    bCannotBeConst = true;
            }
            walkUp();
        }
        else if (isa<ReturnStmt>(parent))
        {
            if (insideFunctionDecl)
            {
                auto tc = loplugin::TypeCheck(insideFunctionDecl->getReturnType());
                if (tc.LvalueReference().NonConst())
                    bCannotBeConst = true;
            }
            break;
        }
        else if (isa<SwitchStmt>(parent) || isa<WhileStmt>(parent) || isa<ForStmt>(parent)
                 || isa<IfStmt>(parent) || isa<DoStmt>(parent) || isa<CXXForRangeStmt>(parent)
                 || isa<DefaultStmt>(parent))
        {
            break;
        }
        else
        {
            walkUp();
        }
    } while (true);

    if (bDump)<--- Condition 'bDump' is always false
    {
        report(DiagnosticsEngine::Warning, "oh dear, what can the matter be? writtenTo=%0",
               compat::getBeginLoc(memberExpr))
            << bCannotBeConst << memberExpr->getSourceRange();
        if (parent)
        {
            report(DiagnosticsEngine::Note, "parent over here", compat::getBeginLoc(parent))
                << parent->getSourceRange();
            parent->dump();
        }
        memberExpr->dump();
        fieldDecl->getType()->dump();
    }

    if (bCannotBeConst)
    {
        cannotBeConstSet.insert(niceName(fieldDecl));
    }
}

bool ConstFields::IsPassedByNonConst(const FieldDecl* fieldDecl, const Stmt* child,
                                     CallerWrapper callExpr, CalleeWrapper calleeFunctionDecl)
<--- Function parameter 'calleeFunctionDecl' should be passed by const reference. [+]
Parameter 'calleeFunctionDecl' is passed by value. It could be passed as a const reference which is usually faster and recommended in C++.
{
    unsigned len = std::min(callExpr.getNumArgs(), calleeFunctionDecl.getNumParams());
    // if it's an array, passing it by value to a method typically means the
    // callee takes a pointer and can modify the array
    if (fieldDecl->getType()->isConstantArrayType())
    {
        for (unsigned i = 0; i < len; ++i)
            if (callExpr.getArg(i) == child)
                if (loplugin::TypeCheck(calleeFunctionDecl.getParamType(i)).Pointer().NonConst())
                    return true;
    }
    else
    {
        for (unsigned i = 0; i < len; ++i)
            if (callExpr.getArg(i) == child)
                if (loplugin::TypeCheck(calleeFunctionDecl.getParamType(i))
                        .LvalueReference()
                        .NonConst())
                    return true;
    }
    return false;
}

llvm::Optional<CalleeWrapper> ConstFields::getCallee(CallExpr const* callExpr)
{
    FunctionDecl const* functionDecl = callExpr->getDirectCallee();
    if (functionDecl)
        return CalleeWrapper(functionDecl);

    // Extract the functionprototype from a type
    clang::Type const* calleeType = callExpr->getCallee()->getType().getTypePtr();
    if (auto pointerType = calleeType->getUnqualifiedDesugaredType()->getAs<clang::PointerType>())
    {
        if (auto prototype = pointerType->getPointeeType()
                                 ->getUnqualifiedDesugaredType()
                                 ->getAs<FunctionProtoType>())
        {
            return CalleeWrapper(prototype);
        }
    }

    return llvm::Optional<CalleeWrapper>();
}

loplugin::Plugin::Registration<ConstFields> X("constfields", false);
}

#endif

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