496 lines
21 KiB
C++
496 lines
21 KiB
C++
/*
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* Cppcheck - A tool for static C/C++ code analysis
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* Copyright (C) 2007-2016 Cppcheck team.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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//---------------------------------------------------------------------------
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#include "checknullpointer.h"
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#include "mathlib.h"
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#include "symboldatabase.h"
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#include "utils.h"
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#include <cctype>
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//---------------------------------------------------------------------------
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// Register this check class (by creating a static instance of it)
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namespace {
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CheckNullPointer instance;
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}
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static const CWE CWE476(476U);
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//---------------------------------------------------------------------------
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static bool checkNullpointerFunctionCallPlausibility(const Function* func, unsigned int arg)
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{
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return !func || (func->argCount() >= arg && func->getArgumentVar(arg - 1) && func->getArgumentVar(arg - 1)->isPointer());
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}
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/**
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* @brief parse a function call and extract information about variable usage
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* @param tok first token
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* @param var variables that the function read / write.
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* @param library --library files data
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* @param value 0 => invalid with null pointers as parameter.
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* 1-.. => only invalid with uninitialized data.
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*/
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void CheckNullPointer::parseFunctionCall(const Token &tok, std::list<const Token *> &var, const Library *library, unsigned char value)
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{
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if (Token::Match(&tok, "%name% ( )") || !tok.tokAt(2))
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return;
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const Token* firstParam = tok.tokAt(2);
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const Token* secondParam = firstParam->nextArgument();
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// 1st parameter..
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if (Token::Match(firstParam, "%var% ,|)") ||
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(value == 0 && Token::Match(firstParam, "0|NULL ,|)"))) {
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if (value == 0 && Token::Match(&tok, "snprintf|vsnprintf|fnprintf|vfnprintf") && secondParam && secondParam->str() != "0") // Only if length (second parameter) is not zero
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var.push_back(firstParam);
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}
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// Library
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if (library) {
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const Token *param = firstParam;
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int argnr = 1;
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while (param) {
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if (Token::Match(param, "%var% ,|)") || (value==0 && Token::Match(param, "0|NULL ,|)"))) {
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if (value == 0 && library->isnullargbad(&tok, argnr) && checkNullpointerFunctionCallPlausibility(tok.function(), argnr))
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var.push_back(param);
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else if (value == 1 && library->isuninitargbad(&tok, argnr))
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var.push_back(param);
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}
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param = param->nextArgument();
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argnr++;
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}
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}
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if (Token::Match(&tok, "printf|sprintf|snprintf|fprintf|fnprintf|scanf|sscanf|fscanf|wprintf|swprintf|fwprintf|wscanf|swscanf|fwscanf")) {
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const Token* argListTok = 0; // Points to first va_list argument
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std::string formatString;
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bool scan = Token::Match(&tok, "scanf|sscanf|fscanf|wscanf|swscanf|fwscanf");
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if (Token::Match(&tok, "printf|scanf|wprintf|wscanf ( %str%")) {
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formatString = firstParam->strValue();
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argListTok = secondParam;
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} else if (Token::Match(&tok, "sprintf|fprintf|sscanf|fscanf|fwprintf|fwscanf|swscanf")) {
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const Token* formatStringTok = secondParam; // Find second parameter (format string)
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if (formatStringTok && formatStringTok->tokType() == Token::eString) {
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argListTok = formatStringTok->nextArgument(); // Find third parameter (first argument of va_args)
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formatString = formatStringTok->strValue();
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}
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} else if (Token::Match(&tok, "snprintf|fnprintf|swprintf") && secondParam) {
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const Token* formatStringTok = secondParam->nextArgument(); // Find third parameter (format string)
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if (formatStringTok && formatStringTok->tokType() == Token::eString) {
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argListTok = formatStringTok->nextArgument(); // Find fourth parameter (first argument of va_args)
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formatString = formatStringTok->strValue();
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}
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}
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if (argListTok) {
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bool percent = false;
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for (std::string::iterator i = formatString.begin(); i != formatString.end(); ++i) {
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if (*i == '%') {
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percent = !percent;
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} else if (percent) {
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percent = false;
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bool _continue = false;
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while (!std::isalpha((unsigned char)*i)) {
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if (*i == '*') {
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if (scan)
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_continue = true;
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else
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argListTok = argListTok->nextArgument();
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}
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++i;
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if (!argListTok || i == formatString.end())
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return;
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}
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if (_continue)
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continue;
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if ((*i == 'n' || *i == 's' || scan) && (!scan || value == 0)) {
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if ((value == 0 && argListTok->str() == "0") || Token::Match(argListTok, "%var% [,)]")) {
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var.push_back(argListTok);
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}
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}
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if (*i != 'm') // %m is a non-standard glibc extension that requires no parameter
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argListTok = argListTok->nextArgument(); // Find next argument
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if (!argListTok)
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break;
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}
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}
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}
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}
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}
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namespace {
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const std::set<std::string> stl_stream = make_container< std::set<std::string> >() <<
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"fstream" << "ifstream" << "iostream" << "istream" <<
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"istringstream" << "ofstream" << "ostream" << "ostringstream" <<
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"stringstream" << "wistringstream" << "wostringstream" << "wstringstream";
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}
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/**
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* Is there a pointer dereference? Everything that should result in
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* a nullpointer dereference error message will result in a true
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* return value. If it's unknown if the pointer is dereferenced false
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* is returned.
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* @param tok token for the pointer
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* @param unknown it is not known if there is a pointer dereference (could be reported as a debug message)
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* @return true => there is a dereference
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*/
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bool CheckNullPointer::isPointerDeRef(const Token *tok, bool &unknown)
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{
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unknown = false;
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const Token* parent = tok->astParent();
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if (!parent)
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return false;
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if (parent->str() == "." && parent->astOperand2() == tok)
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return isPointerDeRef(parent, unknown);
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const bool firstOperand = parent->astOperand1() == tok;
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while (parent->str() == "(" && (parent->astOperand2() == nullptr && parent->strAt(1) != ")")) { // Skip over casts
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parent = parent->astParent();
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if (!parent)
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return false;
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}
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// Dereferencing pointer..
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if (parent->str() == "*" && !parent->astOperand2() && !Token::Match(parent->tokAt(-2), "sizeof|decltype|typeof"))
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return true;
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// array access
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if (firstOperand && parent->str() == "[" && (!parent->astParent() || parent->astParent()->str() != "&"))
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return true;
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// address of member variable / array element
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const Token *parent2 = parent;
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while (Token::Match(parent2, "[|."))
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parent2 = parent2->astParent();
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if (parent2 != parent && parent2 && parent2->str() == "&" && !parent2->astOperand2())
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return false;
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// read/write member variable
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if (firstOperand && parent->str() == "." && (!parent->astParent() || parent->astParent()->str() != "&")) {
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if (!parent->astParent() || parent->astParent()->str() != "(" || parent->astParent() == tok->previous())
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return true;
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unknown = true;
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return false;
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}
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if (Token::Match(tok, "%name% ("))
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return true;
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if (Token::Match(tok, "%var% = %var% .") &&
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tok->varId() == tok->tokAt(2)->varId())
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return true;
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// std::string dereferences nullpointers
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if (Token::Match(parent->tokAt(-3), "std :: string|wstring (") && tok->strAt(1) == ")")
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return true;
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if (Token::Match(parent->previous(), "%name% (") && tok->strAt(1) == ")") {
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const Variable* var = tok->tokAt(-2)->variable();
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if (var && !var->isPointer() && !var->isArray() && var->isStlStringType())
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return true;
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}
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// streams dereference nullpointers
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if (Token::Match(parent, "<<|>>") && !firstOperand) {
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const Variable* var = tok->variable();
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if (var && var->isPointer() && Token::Match(var->typeStartToken(), "char|wchar_t")) { // Only outputting or reading to char* can cause problems
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const Token* tok2 = parent; // Find start of statement
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for (; tok2; tok2 = tok2->previous()) {
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if (Token::Match(tok2->previous(), ";|{|}|:"))
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break;
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}
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if (Token::Match(tok2, "std :: cout|cin|cerr"))
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return true;
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if (tok2 && tok2->varId() != 0) {
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const Variable* var2 = tok2->variable();
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if (var2 && var2->isStlType(stl_stream))
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return true;
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}
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}
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}
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const Variable *ovar = nullptr;
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if (Token::Match(parent, "+|==|!=") || (parent->str() == "=" && !firstOperand)) {
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if (parent->astOperand1() == tok && parent->astOperand2())
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ovar = parent->astOperand2()->variable();
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else if (parent->astOperand1() && parent->astOperand2() == tok)
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ovar = parent->astOperand1()->variable();
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}
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if (ovar && !ovar->isPointer() && !ovar->isArray() && ovar->isStlStringType())
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return true;
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// assume that it's not a dereference (no false positives)
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return false;
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}
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void CheckNullPointer::nullPointerLinkedList()
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{
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if (!_settings->isEnabled("warning"))
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return;
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const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
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// looping through items in a linked list in a inner loop.
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// Here is an example:
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// for (const Token *tok = tokens; tok; tok = tok->next) {
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// if (tok->str() == "hello")
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// tok = tok->next; // <- tok might become a null pointer!
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// }
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for (std::list<Scope>::const_iterator i = symbolDatabase->scopeList.begin(); i != symbolDatabase->scopeList.end(); ++i) {
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const Token* const tok1 = i->classDef;
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// search for a "for" scope..
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if (i->type != Scope::eFor || !tok1)
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continue;
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// is there any dereferencing occurring in the for statement
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const Token* end2 = tok1->linkAt(1);
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for (const Token *tok2 = tok1->tokAt(2); tok2 != end2; tok2 = tok2->next()) {
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// Dereferencing a variable inside the "for" parentheses..
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if (Token::Match(tok2, "%var% . %name%")) {
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// Is this variable a pointer?
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const Variable *var = tok2->variable();
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if (!var || !var->isPointer())
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continue;
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// Variable id for dereferenced variable
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const unsigned int varid(tok2->varId());
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if (Token::Match(tok2->tokAt(-2), "%varid% ?", varid))
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continue;
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// Check usage of dereferenced variable in the loop..
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for (std::list<Scope*>::const_iterator j = i->nestedList.begin(); j != i->nestedList.end(); ++j) {
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Scope* scope = *j;
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if (scope->type != Scope::eWhile)
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continue;
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// TODO: are there false negatives for "while ( %varid% ||"
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if (Token::Match(scope->classDef->next(), "( %varid% &&|)", varid)) {
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// Make sure there is a "break" or "return" inside the loop.
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// Without the "break" a null pointer could be dereferenced in the
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// for statement.
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for (const Token *tok4 = scope->classStart; tok4; tok4 = tok4->next()) {
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if (tok4 == i->classEnd) {
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nullPointerError(tok1, var->name(), scope->classDef, false);
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break;
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}
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// There is a "break" or "return" inside the loop.
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// TODO: there can be false negatives. There could still be
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// execution paths that are not properly terminated
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else if (tok4->str() == "break" || tok4->str() == "return")
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break;
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}
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}
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}
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}
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}
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}
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}
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void CheckNullPointer::nullPointerByDeRefAndChec()
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{
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const bool printWarnings = _settings->isEnabled("warning");
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const bool printInconclusive = (_settings->inconclusive);
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for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
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if (Token::Match(tok, "sizeof|decltype|typeid|typeof (")) {
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tok = tok->next()->link();
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continue;
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}
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const Variable *var = tok->variable();
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if (!var || !var->isPointer() || tok == var->nameToken())
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continue;
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// Can pointer be NULL?
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const ValueFlow::Value *value = tok->getValue(0);
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if (!value)
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continue;
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if (!printInconclusive && value->inconclusive)
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continue;
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// Is pointer used as function parameter?
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if (Token::Match(tok->previous(), "[(,] %name% [,)]")) {
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const Token *ftok = tok->previous();
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while (ftok && ftok->str() != "(") {
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if (ftok->str() == ")")
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ftok = ftok->link();
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ftok = ftok->previous();
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}
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if (!ftok || !ftok->previous())
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continue;
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std::list<const Token *> varlist;
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parseFunctionCall(*ftok->previous(), varlist, &_settings->library, 0);
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if (std::find(varlist.begin(), varlist.end(), tok) != varlist.end()) {
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if (value->condition == nullptr)
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nullPointerError(tok, tok->str(), false, value->defaultArg, !value->isKnown());
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else if (printWarnings)
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nullPointerError(tok, tok->str(), value->condition, value->inconclusive);
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}
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continue;
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}
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// Pointer dereference.
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bool unknown = false;
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if (!isPointerDeRef(tok,unknown)) {
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if (printInconclusive && unknown) {
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if (value->condition == nullptr)
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nullPointerError(tok, tok->str(), true, value->defaultArg, !value->isKnown());
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else
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nullPointerError(tok, tok->str(), value->condition, true);
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}
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continue;
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}
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if (value->condition == nullptr)
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nullPointerError(tok, tok->str(), value->inconclusive, value->defaultArg, !value->isKnown());
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else if (printWarnings)
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nullPointerError(tok, tok->str(), value->condition, value->inconclusive);
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}
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}
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void CheckNullPointer::nullPointer()
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{
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nullPointerLinkedList();
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nullPointerByDeRefAndChec();
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}
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namespace {
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const std::set<std::string> stl_istream = make_container< std::set<std::string> >() <<
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"fstream" << "ifstream" << "iostream" << "istream" <<
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"istringstream" << "stringstream" << "wistringstream" << "wstringstream";
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}
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/** Dereferencing null constant (simplified token list) */
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void CheckNullPointer::nullConstantDereference()
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{
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const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
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const std::size_t functions = symbolDatabase->functionScopes.size();
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for (std::size_t i = 0; i < functions; ++i) {
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const Scope * scope = symbolDatabase->functionScopes[i];
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if (scope->function == 0 || !scope->function->hasBody()) // We only look for functions with a body
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continue;
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const Token *tok = scope->classStart;
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if (scope->function && scope->function->isConstructor())
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tok = scope->function->token; // Check initialization list
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for (; tok != scope->classEnd; tok = tok->next()) {
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if (Token::Match(tok, "sizeof|decltype|typeid|typeof ("))
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tok = tok->next()->link();
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else if (Token::simpleMatch(tok, "* 0")) {
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if (Token::Match(tok->previous(), "return|throw|;|{|}|:|[|(|,") || tok->previous()->isOp()) {
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nullPointerError(tok);
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}
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}
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else if (Token::Match(tok, "0 [") && (tok->previous()->str() != "&" || !Token::Match(tok->next()->link()->next(), "[.(]")))
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nullPointerError(tok);
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else if (Token::Match(tok->previous(), "!!. %name% (") && (tok->previous()->str() != "::" || tok->strAt(-2) == "std")) {
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if (Token::simpleMatch(tok->tokAt(2), "0 )") && tok->varId()) { // constructor call
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const Variable *var = tok->variable();
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if (var && !var->isPointer() && !var->isArray() && var->isStlStringType())
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nullPointerError(tok);
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} else { // function call
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std::list<const Token *> var;
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parseFunctionCall(*tok, var, &_settings->library, 0);
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// is one of the var items a NULL pointer?
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for (std::list<const Token *>::const_iterator it = var.begin(); it != var.end(); ++it) {
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if (Token::Match(*it, "0|NULL [,)]")) {
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nullPointerError(*it);
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}
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}
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}
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} else if (Token::Match(tok, "std :: string|wstring ( 0 )"))
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nullPointerError(tok);
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else if (Token::simpleMatch(tok->previous(), ">> 0")) { // Only checking input stream operations is safe here, because otherwise 0 can be an integer as well
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const Token* tok2 = tok->previous(); // Find start of statement
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for (; tok2; tok2 = tok2->previous()) {
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if (Token::Match(tok2->previous(), ";|{|}|:|("))
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break;
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}
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if (tok2 && tok2->previous() && tok2->previous()->str()=="(")
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continue;
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if (Token::simpleMatch(tok2, "std :: cin"))
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nullPointerError(tok);
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if (tok2 && tok2->varId() != 0) {
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const Variable *var = tok2->variable();
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if (var && var->isStlType(stl_istream))
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nullPointerError(tok);
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}
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}
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const Variable *ovar = nullptr;
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const Token *tokNull = nullptr;
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if (Token::Match(tok, "0 ==|!=|>|>=|<|<= %var%")) {
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if (!Token::Match(tok->tokAt(3),".|[")) {
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ovar = tok->tokAt(2)->variable();
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tokNull = tok;
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}
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} else if (Token::Match(tok, "%var% ==|!=|>|>=|<|<= 0") ||
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Token::Match(tok, "%var% =|+ 0 )|]|,|;|+")) {
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ovar = tok->variable();
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tokNull = tok->tokAt(2);
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}
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if (ovar && !ovar->isPointer() && !ovar->isArray() && ovar->isStlStringType() && tokNull && tokNull->originalName() != "'\\0'")
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nullPointerError(tokNull);
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}
|
|
}
|
|
}
|
|
|
|
void CheckNullPointer::nullPointerError(const Token *tok)
|
|
{
|
|
reportError(tok, Severity::error, "nullPointer", "Null pointer dereference", CWE476, false);
|
|
}
|
|
|
|
void CheckNullPointer::nullPointerError(const Token *tok, const std::string &varname, bool inconclusive, bool defaultArg, bool possible)
|
|
{
|
|
if (defaultArg) {
|
|
if (_settings->isEnabled("warning"))
|
|
reportError(tok, Severity::warning, "nullPointerDefaultArg", "Possible null pointer dereference if the default parameter value is used: " + varname, CWE(0U), inconclusive);
|
|
} else if (possible) {
|
|
if (_settings->isEnabled("warning"))
|
|
reportError(tok, Severity::warning, "nullPointer", "Possible null pointer dereference: " + varname, CWE476, inconclusive);
|
|
} else
|
|
reportError(tok, Severity::error, "nullPointer", "Null pointer dereference: " + varname, CWE476, inconclusive);
|
|
}
|
|
|
|
void CheckNullPointer::nullPointerError(const Token *tok, const std::string &varname, const Token* nullCheck, bool inconclusive)
|
|
{
|
|
std::list<const Token*> callstack;
|
|
callstack.push_back(tok);
|
|
callstack.push_back(nullCheck);
|
|
const std::string errmsg(ValueFlow::eitherTheConditionIsRedundant(nullCheck) + " or there is possible null pointer dereference: " + varname + ".");
|
|
reportError(callstack, Severity::warning, "nullPointerRedundantCheck", errmsg, CWE(0U), inconclusive);
|
|
}
|