cppcheck/lib/checkbool.cpp

/*
 * Cppcheck - A tool for static C/C++ code analysis
 * Copyright (C) 2007-2014 Daniel Marjamäki and Cppcheck team.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */


//---------------------------------------------------------------------------
#include "checkbool.h"
#include "mathlib.h"
#include "symboldatabase.h"
//---------------------------------------------------------------------------

// Register this check class (by creating a static instance of it)
namespace {
    CheckBool instance;
}


static bool astIsBool(const Token *expr)
{
    return Token::Match(expr, "%comp%|%bool%|%oror%|&&");
}

//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
void CheckBool::checkIncrementBoolean()
{
    if (!_settings->isEnabled("style"))
        return;

    const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
    const std::size_t functions = symbolDatabase->functionScopes.size();
    for (std::size_t i = 0; i < functions; ++i) {
        const Scope * scope = symbolDatabase->functionScopes[i];
        for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
            if (Token::Match(tok, "%var% ++")) {
                if (tok->varId()) {
                    const Variable *var = tok->variable();

                    if (var && var->typeEndToken()->str() == "bool")
                        incrementBooleanError(tok);
                }
            }
        }
    }
}

void CheckBool::incrementBooleanError(const Token *tok)
{
    reportError(
        tok,
        Severity::style,
        "incrementboolean",
        "Incrementing a variable of type 'bool' with postfix operator++ is deprecated by the C++ Standard. You should assign it the value 'true' instead.\n"
        "The operand of a postfix increment operator may be of type bool but it is deprecated by C++ Standard (Annex D-1) and the operand is always set to true. You should assign it the value 'true' instead."
    );
}

//---------------------------------------------------------------------------
// if (bool & bool) -> if (bool && bool)
// if (bool | bool) -> if (bool || bool)
//---------------------------------------------------------------------------
void CheckBool::checkBitwiseOnBoolean()
{
    if (!_settings->isEnabled("style"))
        return;

    // danmar: this is inconclusive because I don't like that there are
    //         warnings for calculations. Example: set_flag(a & b);
    if (!_settings->inconclusive)
        return;

    const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
    const std::size_t functions = symbolDatabase->functionScopes.size();
    for (std::size_t i = 0; i < functions; ++i) {
        const Scope * scope = symbolDatabase->functionScopes[i];
        for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
            if (Token::Match(tok, "(|.|return|&&|%oror%|throw|, %var% [&|]")) {
                const Variable *var = tok->next()->variable();
                if (var && var->typeEndToken()->str() == "bool") {
                    bitwiseOnBooleanError(tok->next(), var->name(), tok->strAt(2) == "&" ? "&&" : "||");
                    tok = tok->tokAt(2);
                }
            } else if (Token::Match(tok, "[&|] %var% )|.|return|&&|%oror%|throw|,") && (!tok->previous() || !tok->previous()->isExtendedOp() || tok->strAt(-1) == ")" || tok->strAt(-1) == "]")) {
                const Variable *var = tok->next()->variable();
                if (var && var->typeEndToken()->str() == "bool") {
                    bitwiseOnBooleanError(tok->next(), var->name(), tok->str() == "&" ? "&&" : "||");
                    tok = tok->tokAt(2);
                }
            }
        }
    }
}

void CheckBool::bitwiseOnBooleanError(const Token *tok, const std::string &varname, const std::string &op)
{
    reportError(tok, Severity::style, "bitwiseOnBoolean",
                "Boolean variable '" + varname + "' is used in bitwise operation. Did you mean '" + op + "'?", true);
}

//---------------------------------------------------------------------------
//    if (!x==3) <- Probably meant to be "x!=3"
//---------------------------------------------------------------------------

static bool isBool(const Variable* var)
{
    return (var && var->typeEndToken()->str() == "bool");
}
static bool isNonBoolStdType(const Variable* var)
{
    return (var && var->typeEndToken()->isStandardType() && var->typeEndToken()->str() != "bool");
}
void CheckBool::checkComparisonOfBoolWithInt()
{
    if (!_settings->isEnabled("warning") || !_tokenizer->isCPP())
        return;

    const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
    const std::size_t functions = symbolDatabase->functionScopes.size();
    for (std::size_t i = 0; i < functions; ++i) {
        const Scope * scope = symbolDatabase->functionScopes[i];
        for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
            if ((!Token::Match(tok->previous(), "%cop%")) && Token::Match(tok->next(), "%comp%") && (!Token::Match(tok->tokAt(3), "%cop%"))) {
                const Token* const right = tok->tokAt(2);
                if ((tok->varId() && right->isNumber()) || (tok->isNumber() && right->varId())) { // Comparing variable with number
                    const Token* varTok = tok;
                    const Token* numTok = right;
                    if (tok->isNumber() && right->varId()) // num with var
                        std::swap(varTok, numTok);
                    if (isBool(varTok->variable()) && // Variable has to be a boolean
                        ((tok->strAt(1) != "==" && tok->strAt(1) != "!=") ||
                         (MathLib::toLongNumber(numTok->str()) != 0 && MathLib::toLongNumber(numTok->str()) != 1))) { // == 0 and != 0 are allowed, for C also == 1 and != 1
                        comparisonOfBoolWithIntError(varTok, numTok->str(), tok->strAt(1) == "==" || tok->strAt(1) == "!=");
                    }
                } else if (tok->isBoolean() && right->varId()) { // Comparing boolean constant with variable
                    if (isNonBoolStdType(right->variable())) { // Variable has to be of non-boolean standard type
                        comparisonOfBoolWithIntError(right, tok->str(), false);
                    } else if (tok->strAt(1) != "==" && tok->strAt(1) != "!=") {
                        comparisonOfBoolWithInvalidComparator(right, tok->str());
                    }
                } else if (tok->varId() && right->isBoolean()) { // Comparing variable with boolean constant
                    if (isNonBoolStdType(tok->variable())) { // Variable has to be of non-boolean standard type
                        comparisonOfBoolWithIntError(tok, right->str(), false);
                    } else if (tok->strAt(1) != "==" && tok->strAt(1) != "!=") {
                        comparisonOfBoolWithInvalidComparator(right, tok->str());
                    }
                } else if (tok->isNumber() && right->isBoolean()) { // number constant with boolean constant
                    comparisonOfBoolWithIntError(tok, right->str(), false);
                } else if (tok->isBoolean() && right->isNumber()) { // number constant with boolean constant
                    comparisonOfBoolWithIntError(tok, tok->str(), false);
                } else if (tok->varId() && right->varId()) { // Comparing two variables, one of them boolean, one of them integer
                    const Variable* var1 = right->variable();
                    const Variable* var2 = tok->variable();
                    if (isBool(var1) && isNonBoolStdType(var2)) // Comparing boolean with non-bool standard type
                        comparisonOfBoolWithIntError(tok, var1->name(), false);
                    else if (isNonBoolStdType(var1) && isBool(var2)) // Comparing non-bool standard type with boolean
                        comparisonOfBoolWithIntError(tok, var2->name(), false);
                }
            }
        }
    }
}

void CheckBool::comparisonOfBoolWithIntError(const Token *tok, const std::string &expression, bool n0o1)
{
    if (n0o1)
        reportError(tok, Severity::warning, "comparisonOfBoolWithInt",
                    "Comparison of a boolean with an integer that is neither 1 nor 0.\n"
                    "The expression '" + expression + "' is of type 'bool' "
                    "and it is compared against an integer value that is "
                    "neither 1 nor 0.");
    else
        reportError(tok, Severity::warning, "comparisonOfBoolWithInt",
                    "Comparison of a boolean with an integer.\n"
                    "The expression '" + expression + "' is of type 'bool' "
                    "and it is compared against an integer value.");
}

void CheckBool::comparisonOfBoolWithInvalidComparator(const Token *tok, const std::string &expression)
{
    reportError(tok, Severity::warning, "comparisonOfBoolWithInvalidComparator",
                "Comparison of a boolean value using relational operator (<, >, <= or >=).\n"
                "The result of the expression '" + expression + "' is of type 'bool'. "
                "Comparing 'bool' value using relational (<, >, <= or >=)"
                " operator could cause unexpected results.");
}

//-------------------------------------------------------------------------------
// Comparing functions which are returning value of type bool
//-------------------------------------------------------------------------------

void CheckBool::checkComparisonOfFuncReturningBool()
{
    if (!_settings->isEnabled("style"))
        return;

    if (!_tokenizer->isCPP())
        return;

    const SymbolDatabase * const symbolDatabase = _tokenizer->getSymbolDatabase();

    const std::size_t functions = symbolDatabase->functionScopes.size();
    for (std::size_t i = 0; i < functions; ++i) {
        const Scope * scope = symbolDatabase->functionScopes[i];
        for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
            if (tok->type() != Token::eComparisonOp || tok->str() == "==" || tok->str() == "!=")
                continue;
            const Token *first_token;
            bool first_token_func_of_type_bool = false;
            if (tok->strAt(-1) == ")") {
                first_token = tok->previous()->link()->previous();
            } else {
                first_token = tok->previous();
            }
            if (Token::Match(first_token, "%var% (") && !Token::Match(first_token->previous(), "::|.")) {
                const Function* func = first_token->function();
                if (func && func->tokenDef && func->tokenDef->strAt(-1) == "bool") {
                    first_token_func_of_type_bool = true;
                }
            }

            Token *second_token = tok->next();
            bool second_token_func_of_type_bool = false;
            while (second_token->str()=="!") {
                second_token = second_token->next();
            }
            if (Token::Match(second_token, "%var% (") && !Token::Match(second_token->previous(), "::|.")) {
                const Function* func = second_token->function();
                if (func && func->tokenDef && func->tokenDef->strAt(-1) == "bool") {
                    second_token_func_of_type_bool = true;
                }
            }

            if ((first_token_func_of_type_bool == true) && (second_token_func_of_type_bool == true)) {
                comparisonOfTwoFuncsReturningBoolError(first_token->next(), first_token->str(), second_token->str());
            } else if (first_token_func_of_type_bool == true) {
                comparisonOfFuncReturningBoolError(first_token->next(), first_token->str());
            } else if (second_token_func_of_type_bool == true) {
                comparisonOfFuncReturningBoolError(second_token->previous(), second_token->str());
            }
        }
    }
}

void CheckBool::comparisonOfFuncReturningBoolError(const Token *tok, const std::string &expression)
{
    reportError(tok, Severity::style, "comparisonOfFuncReturningBoolError",
                "Comparison of a function returning boolean value using relational (<, >, <= or >=) operator.\n"
                "The return type of function '" + expression + "' is 'bool' "
                "and result is of type 'bool'. Comparing 'bool' value using relational (<, >, <= or >=)"
                " operator could cause unexpected results.");
}

void CheckBool::comparisonOfTwoFuncsReturningBoolError(const Token *tok, const std::string &expression1, const std::string &expression2)
{
    reportError(tok, Severity::style, "comparisonOfTwoFuncsReturningBoolError",
                "Comparison of two functions returning boolean value using relational (<, >, <= or >=) operator.\n"
                "The return type of function '" + expression1 + "' and function '" + expression2 + "' is 'bool' "
                "and result is of type 'bool'. Comparing 'bool' value using relational (<, >, <= or >=)"
                " operator could cause unexpected results.");
}

//-------------------------------------------------------------------------------
// Comparison of bool with bool
//-------------------------------------------------------------------------------

void CheckBool::checkComparisonOfBoolWithBool()
{
    // FIXME: This checking is "experimental" because of the false positives
    //        when self checking lib/tokenize.cpp (#2617)
    if (!_settings->experimental)
        return;

    if (!_settings->isEnabled("style"))
        return;

    if (!_tokenizer->isCPP())
        return;

    const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();

    const std::size_t functions = symbolDatabase->functionScopes.size();
    for (std::size_t i = 0; i < functions; ++i) {
        const Scope * scope = symbolDatabase->functionScopes[i];
        for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
            if (tok->type() != Token::eComparisonOp || tok->str() == "==" || tok->str() == "!=")
                continue;
            bool first_token_bool = false;
            bool second_token_bool = false;

            const Token *first_token = tok->previous();
            if (first_token->varId()) {
                if (isBool(first_token->variable())) {
                    first_token_bool = true;
                }
            }
            const Token *second_token = tok->next();
            if (second_token->varId()) {
                if (isBool(second_token->variable())) {
                    second_token_bool = true;
                }
            }
            if ((first_token_bool == true) && (second_token_bool == true)) {
                comparisonOfBoolWithBoolError(first_token->next(), first_token->str());
            }
        }
    }
}

void CheckBool::comparisonOfBoolWithBoolError(const Token *tok, const std::string &expression)
{
    reportError(tok, Severity::style, "comparisonOfBoolWithBoolError",
                "Comparison of a variable having boolean value using relational (<, >, <= or >=) operator.\n"
                "The variable '" + expression + "' is of type 'bool' "
                "and comparing 'bool' value using relational (<, >, <= or >=)"
                " operator could cause unexpected results.");
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
void CheckBool::checkAssignBoolToPointer()
{
    const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
    const std::size_t functions = symbolDatabase->functionScopes.size();
    for (std::size_t i = 0; i < functions; ++i) {
        const Scope * scope = symbolDatabase->functionScopes[i];
        for (const Token* tok = scope->classStart; tok != scope->classEnd; tok = tok->next()) {
            if (tok->str() == "=" && astIsBool(tok->astOperand2())) {
                const Token *lhs = tok->astOperand1();
                while (lhs && lhs->str() == ".")
                    lhs = lhs->astOperand2();
                if (!lhs || !lhs->variable() || !lhs->variable()->isPointer())
                    continue;

                assignBoolToPointerError(tok);
            }
        }
    }
}

void CheckBool::assignBoolToPointerError(const Token *tok)
{
    reportError(tok, Severity::error, "assignBoolToPointer",
                "Boolean value assigned to pointer.");
}

/**
 * @brief Is the result of the LHS expression non-bool?
 * @param tok last token in lhs
 * @return true => lhs result is non-bool. false => lhs result type is unknown or bool
 */
static bool isNonBoolLHSExpr(const Token *tok)
{
    // return value. only return true if we "know" it's a non-bool expression
    bool nonBoolExpr = false;

    for (; tok; tok = tok->previous()) {
        if (tok->str() == ")") {
            if (!Token::Match(tok->link()->previous(), "&&|%oror%|( ("))
                tok = tok->link();
        } else if (tok->str() == "(" || tok->str() == "[")
            break;
        else if (tok->isNumber())
            nonBoolExpr = true;
        else if (tok->isArithmeticalOp()) {
            return true;
        } else if (tok->isComparisonOp() || (tok->str() == "!" && tok->previous()->str()=="("))
            return false;
        else if (Token::Match(tok,"[;{}=?:&|^,]"))
            break;
        else if (Token::Match(tok, "&&|%oror%|and|or"))
            break;
    }

    return nonBoolExpr;
}

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
void CheckBool::checkComparisonOfBoolExpressionWithInt()
{
    if (!_settings->isEnabled("warning"))
        return;

    const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();

    const std::size_t functions = symbolDatabase->functionScopes.size();
    for (std::size_t i = 0; i < functions; ++i) {
        const Scope * scope = symbolDatabase->functionScopes[i];
        for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
            // Skip template parameters
            if (tok->str() == "<" && tok->link()) {
                tok = tok->link();
                continue;
            }

            const Token* numTok = 0;
            const Token* opTok = 0;
            char op = 0;
            if (Token::Match(tok, "&&|%oror% %any% ) %comp% %any%")) {
                numTok = tok->tokAt(4);
                opTok = tok->tokAt(3);
                if (Token::Match(opTok, "<|>"))
                    op = opTok->str()[0];
            } else if (Token::Match(tok, "%any% %comp% ( %any% &&|%oror%")) {
                numTok = tok;
                opTok = tok->next();
                if (Token::Match(opTok, "<|>"))
                    op = opTok->str()[0]=='>'?'<':'>';
            }

            else if (Token::Match(tok, "! %var% %comp% %any%") && !isNonBoolLHSExpr(tok)) {
                numTok = tok->tokAt(3);
                opTok = tok->tokAt(2);
                if (Token::Match(opTok, "<|>"))
                    op = opTok->str()[0];
            } else if (Token::Match(tok->previous(), "(|&&|%oror% %num% %comp% !")) {
                const Token *rhs = tok->tokAt(3);
                while (rhs) {
                    if (rhs->str() == "!") {
                        if (Token::simpleMatch(rhs, "! ("))
                            rhs = rhs->next()->link();
                        rhs = rhs->next();
                    } else if (rhs->isName() || rhs->isNumber())
                        rhs = rhs->next();
                    else
                        break;
                }
                if (Token::Match(rhs, "&&|%oror%|)")) {
                    numTok = tok;
                    opTok = tok->next();
                    if (Token::Match(opTok, "<|>"))
                        op = opTok->str()[0]=='>'?'<':'>';
                }
            }

            // boolean result in lhs compared with <|<=|>|>=
            else if (tok->isComparisonOp() && !Token::Match(tok,"==|!=") && !isNonBoolLHSExpr(tok->previous())) {
                const Token *lhs = tok;
                while (nullptr != (lhs = lhs->previous())) {
                    if ((lhs->isName() && !Token::Match(lhs,"or|and")) || lhs->isNumber())
                        continue;
                    if (lhs->isArithmeticalOp())
                        continue;
                    if (Token::Match(lhs, ")|]")) {
                        if (Token::Match(lhs->link()->previous(), "%var% ("))
                            lhs = lhs->link();
                        continue;
                    }
                    break;
                }
                if (lhs && (lhs->isComparisonOp() || lhs->str() == "!")) {
                    if (_tokenizer->isCPP() && tok->str() == ">" &&
                        (Token::Match(lhs->previous(), "%var% <") || lhs->str() == ">"))
                        continue;
                    while (nullptr != (lhs = lhs->previous())) {
                        if ((lhs->isName() && lhs->str() != "return") || lhs->isNumber())
                            continue;
                        if (Token::Match(lhs,"[+-*/.]"))
                            continue;
                        if (Token::Match(lhs, ")|]")) {
                            lhs = lhs->previous();
                            continue;
                        }
                        break;
                    }

                    std::string expression;
                    for (const Token *t = lhs ? lhs->next() : _tokenizer->tokens(); t != tok; t = t->next()) {
                        if (!expression.empty())
                            expression += ' ';
                        expression += t->str();
                    }

                    comparisonOfBoolWithInvalidComparator(tok, expression);
                }
            }

            if (numTok && opTok) {
                if (numTok->isNumber()) {
                    if (((numTok->str() != "0" && numTok->str() != "1") || !Token::Match(opTok, "!=|==")) && !((op == '<' && numTok->str() == "1") || (op == '>' && numTok->str() == "0")))
                        comparisonOfBoolExpressionWithIntError(tok, true);
                } else if (isNonBoolStdType(numTok->variable()))
                    comparisonOfBoolExpressionWithIntError(tok, false);
            }
        }
    }
}

void CheckBool::comparisonOfBoolExpressionWithIntError(const Token *tok, bool n0o1)
{
    if (n0o1)
        reportError(tok, Severity::warning, "compareBoolExpressionWithInt",
                    "Comparison of a boolean expression with an integer other than 0 or 1.");
    else
        reportError(tok, Severity::warning, "compareBoolExpressionWithInt",
                    "Comparison of a boolean expression with an integer.");
}


void CheckBool::pointerArithBool()
{
    const SymbolDatabase* symbolDatabase = _tokenizer->getSymbolDatabase();

    const std::size_t functions = symbolDatabase->functionScopes.size();
    for (std::size_t i = 0; i < functions; ++i) {
        const Scope * scope = symbolDatabase->functionScopes[i];
        for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
            if (Token::Match(tok, "if|while (")) {
                pointerArithBoolCond(tok->next()->astOperand2());
            }
        }
    }
}

void CheckBool::pointerArithBoolCond(const Token *tok)
{
    if (!tok)
        return;
    if (Token::Match(tok, "&&|%oror%")) {
        pointerArithBoolCond(tok->astOperand1());
        pointerArithBoolCond(tok->astOperand2());
        return;
    }
    if (tok->str() != "+")
        return;

    if (tok->astOperand1() &&
        tok->astOperand1()->isName() &&
        tok->astOperand1()->variable() &&
        tok->astOperand1()->variable()->isPointer() &&
        tok->astOperand2()->isNumber())
        pointerArithBoolError(tok);
}

void CheckBool::pointerArithBoolError(const Token *tok)
{
    reportError(tok,
                Severity::error,
                "pointerArithBool",
                "Converting pointer arithmetic result to bool. The bool is always true unless there is undefined behaviour.\n"
                "Converting pointer arithmetic result to bool. The boolean result is always true unless there is pointer arithmetic overflow, and overflow is undefined behaviour. Probably a dereference is forgotten.");
}