/*
 * Cppcheck - A tool for static C/C++ code analysis
 * Copyright (C) 2007-2020 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/>.
 */


//---------------------------------------------------------------------------
#ifndef checknullpointerH
#define checknullpointerH
//---------------------------------------------------------------------------

#include "check.h"
#include "config.h"
#include "ctu.h"
#include "valueflow.h"

#include <list>
#include <string>

class ErrorLogger;
class Library;
class Settings;
class Token;
class Tokenizer;


/// @addtogroup Checks
/// @{


/** @brief check for null pointer dereferencing */

class CPPCHECKLIB CheckNullPointer : public Check {
public:
 /** @brief This constructor is used when registering the CheckNullPointer */
 CheckNullPointer() : Check(myName()) {
 }

 /** @brief This constructor is used when running checks. */
 CheckNullPointer(const Tokenizer *tokenizer, const Settings *settings, ErrorLogger *errorLogger)
 : Check(myName(), tokenizer, settings, errorLogger) {
 }

 /** @brief Run checks against the normal token list */
 void runChecks(const Tokenizer *tokenizer, const Settings *settings, ErrorLogger *errorLogger) OVERRIDE {
 CheckNullPointer checkNullPointer(tokenizer, settings, errorLogger);
 checkNullPointer.nullPointer();
 checkNullPointer.arithmetic();
 checkNullPointer.nullConstantDereference();
 }

 /**
 * @brief parse a function call and extract information about variable usage
 * @param tok first token
 * @param var variables that the function read / write.
 * @param library --library files data
 */
 static void parseFunctionCall(const Token &tok,
 std::list<const Token *> &var,
 const Library *library);

 /**
 * Is there a pointer dereference? Everything that should result in
 * a nullpointer dereference error message will result in a true
 * return value. If it's unknown if the pointer is dereferenced false
 * is returned.
 * @param tok token for the pointer
 * @param unknown it is not known if there is a pointer dereference (could be reported as a debug message)
 * @return true => there is a dereference
 */
 bool isPointerDeRef(const Token *tok, bool &unknown) const;

 static bool isPointerDeRef(const Token *tok, bool &unknown, const Settings *settings);

 /** @brief possible null pointer dereference */
 void nullPointer();

 /** @brief dereferencing null constant (after Tokenizer::simplifyKnownVariables) */
 void nullConstantDereference();

 void nullPointerError(const Token *tok) {
 ValueFlow::Value v(0);
 v.setKnown();
 nullPointerError(tok, "", &v, false);
 }
 void nullPointerError(const Token *tok, const std::string &varname, const ValueFlow::Value* value, bool inconclusive);

 /* data for multifile checking */
 class MyFileInfo : public Check::FileInfo {
 public:
 /** function arguments that are dereferenced without checking if they are null */
 std::list<CTU::FileInfo::UnsafeUsage> unsafeUsage;

 /** Convert MyFileInfo data into xml string */
 std::string toString() const OVERRIDE;
 };

 /** @brief Parse current TU and extract file info */
 Check::FileInfo *getFileInfo(const Tokenizer *tokenizer, const Settings *settings) const OVERRIDE;

 Check::FileInfo * loadFileInfoFromXml(const tinyxml2::XMLElement *xmlElement) const OVERRIDE;

 /** @brief Analyse all file infos for all TU */
 bool analyseWholeProgram(const CTU::FileInfo *ctu, const std::list<Check::FileInfo*> &fileInfo, const Settings& settings, ErrorLogger &errorLogger) OVERRIDE;

private:
 /** Get error messages. Used by --errorlist */
 void getErrorMessages(ErrorLogger *errorLogger, const Settings *settings) const OVERRIDE {
 CheckNullPointer c(nullptr, settings, errorLogger);
 c.nullPointerError(nullptr, "pointer", nullptr, false);
 c.pointerArithmeticError(nullptr, nullptr, false);
 c.redundantConditionWarning(nullptr, nullptr, nullptr, false);
 }

 /** Name of check */
 static std::string myName() {
 return "Null pointer";
 }

 /** class info in WIKI format. Used by --doc */
 std::string classInfo() const OVERRIDE {
 return "Null pointers\n"
 "- null pointer dereferencing\n"
 "- undefined null pointer arithmetic\n";
 }

 /**
 * @brief Does one part of the check for nullPointer().
 * Dereferencing a pointer and then checking if it's NULL..
 */
 void nullPointerByDeRefAndChec();

 /** undefined null pointer arithmetic */
 void arithmetic();
 void pointerArithmeticError(const Token* tok, const ValueFlow::Value *value, bool inconclusive);
 void redundantConditionWarning(const Token* tok, const ValueFlow::Value *value, const Token *condition, bool inconclusive);
};
/// @}
//---------------------------------------------------------------------------
#endif // checknullpointerH