cppcheck/lib/checkpostfixoperator.cpp

/*
 * Cppcheck - A tool for static C/C++ code analysis
 * Copyright (C) 2007-2018 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/>.
 */

//---------------------------------------------------------------------------
// You should use ++ and -- as prefix whenever possible as these are more
// efficient than postfix operators
//---------------------------------------------------------------------------

#include "checkpostfixoperator.h"

#include "errorlogger.h"
#include "settings.h"
#include "symboldatabase.h"
#include "token.h"

#include <cstddef>

//---------------------------------------------------------------------------


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


// CWE ids used
static const struct CWE CWE398(398U);   // Indicator of Poor Code Quality


void CheckPostfixOperator::postfixOperator()
{
    if (!mSettings->isEnabled(Settings::PERFORMANCE))
        return;

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

    for (const Scope * scope : symbolDatabase->functionScopes) {
        for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) {
            const Variable *var = tok->variable();
            if (!var || !Token::Match(tok, "%var% ++|--"))
                continue;

            const Token* parent = tok->next()->astParent();
            if (!parent || parent->str() == ";" || (parent->str() == "," && (!parent->astParent() || parent->astParent()->str() != "("))) {
                if (var->isPointer() || var->isArray())
                    continue;

                if (Token::Match(var->nameToken()->previous(), "iterator|const_iterator|reverse_iterator|const_reverse_iterator")) {
                    // the variable is an iterator
                    postfixOperatorError(tok);
                } else if (var->type()) {
                    // the variable is an instance of class
                    postfixOperatorError(tok);
                }
            }
        }
    }
}
//---------------------------------------------------------------------------


void CheckPostfixOperator::postfixOperatorError(const Token *tok)
{
    reportError(tok, Severity::performance, "postfixOperator",
                "Prefer prefix ++/-- operators for non-primitive types.\n"
                "Prefix ++/-- operators should be preferred for non-primitive types. "
                "Pre-increment/decrement can be more efficient than "
                "post-increment/decrement. Post-increment/decrement usually "
                "involves keeping a copy of the previous value around and "
                "adds a little extra code.", CWE398, false);
}