634 lines
25 KiB
C++
634 lines
25 KiB
C++
/*
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* Cppcheck - A tool for static C/C++ code analysis
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* Copyright (C) 2007-2022 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 "astutils.h"
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#include "errorlogger.h"
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#include "errortypes.h"
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#include "library.h"
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#include "mathlib.h"
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#include "settings.h"
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#include "symboldatabase.h"
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#include "token.h"
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#include "tokenize.h"
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#include <algorithm>
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#include <cctype>
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#include <map>
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#include <memory>
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#include <set>
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#include <vector>
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//---------------------------------------------------------------------------
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// CWE ids used:
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static const struct CWE CWE_NULL_POINTER_DEREFERENCE(476U);
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static const struct CWE CWE_INCORRECT_CALCULATION(682U);
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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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//---------------------------------------------------------------------------
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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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*/
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void CheckNullPointer::parseFunctionCall(const Token &tok, std::list<const Token *> &var, const Library *library)
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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 std::vector<const Token *> args = getArguments(&tok);
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if (library || tok.function() != nullptr) {
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for (int argnr = 1; argnr <= args.size(); ++argnr) {
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const Token *param = args[argnr - 1];
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if (library && library->isnullargbad(&tok, argnr) && checkNullpointerFunctionCallPlausibility(tok.function(), argnr))
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var.push_back(param);
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else if (tok.function()) {
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const Variable* argVar = tok.function()->getArgumentVar(argnr-1);
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if (argVar && argVar->isStlStringType() && !argVar->isArrayOrPointer())
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var.push_back(param);
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}
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}
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}
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if (library && library->formatstr_function(&tok)) {
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const int formatStringArgNr = library->formatstr_argno(&tok);
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if (formatStringArgNr < 0 || formatStringArgNr >= args.size())
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return;
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// 1st parameter..
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if (Token::Match(&tok, "snprintf|vsnprintf|fnprintf|vfnprintf") && args.size() > 1 && !(args[1] && args[1]->hasKnownIntValue() && args[1]->getKnownIntValue() == 0)) // Only if length (second parameter) is not zero
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var.push_back(args[0]);
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if (args[formatStringArgNr]->tokType() != Token::eString)
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return;
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const std::string &formatString = args[formatStringArgNr]->strValue();
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int argnr = formatStringArgNr + 1;
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const bool scan = library->formatstr_scan(&tok);
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bool percent = false;
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for (std::string::const_iterator i = formatString.cbegin(); i != formatString.cend(); ++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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argnr++;
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}
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++i;
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if (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 (argnr < args.size() && (*i == 'n' || *i == 's' || scan))
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var.push_back(args[argnr]);
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if (*i != 'm') // %m is a non-standard glibc extension that requires no parameter
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argnr++;
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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 = {
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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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/**
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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) const
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{
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return isPointerDeRef(tok, unknown, mSettings);
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}
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static bool isUnevaluatedOperator(const Token* tok)
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{
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return Token::Match(tok, "sizeof|decltype|typeid|typeof|alignof|_Alignof|_alignof|__alignof|__alignof__ (");
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}
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bool CheckNullPointer::isPointerDeRef(const Token *tok, bool &unknown, const Settings *settings)
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{
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unknown = false;
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// Is pointer used as function parameter?
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if (Token::Match(tok->previous(), "[(,] %name% [,)]") && settings) {
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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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std::list<const Token *> varlist;
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parseFunctionCall(*ftok->previous(), varlist, &settings->library);
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if (std::find(varlist.begin(), varlist.end(), tok) != varlist.end()) {
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return true;
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}
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}
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}
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if (tok->str() == "(" && !tok->scope()->isExecutable())
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return 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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const bool addressOf = parent->astParent() && parent->astParent()->str() == "&";
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if (parent->str() == "." && astIsRHS(tok))
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return isPointerDeRef(parent, unknown, settings);
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const bool firstOperand = parent->astOperand1() == tok;
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parent = astParentSkipParens(tok);
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if (!parent)
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return false;
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// Dereferencing pointer..
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const Token* grandParent = parent->astParent();
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if (parent->isUnaryOp("*") && !(grandParent && isUnevaluatedOperator(grandParent->previous()))) {
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// declaration of function pointer
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if (tok->variable() && tok->variable()->nameToken() == tok)
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return false;
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if (!addressOf)
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return true;
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}
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// array access
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if (firstOperand && parent->str() == "[" && !addressOf)
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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->isUnaryOp("&"))
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return false;
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// read/write member variable
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if (firstOperand && parent->originalName() == "->" && !addressOf)
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return true;
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// If its a function pointer then check if its called
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if (tok->variable() && tok->variable()->isPointer() && Token::Match(tok->variable()->nameToken(), "%name% ) (") &&
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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 (|{ %name% )|}"))
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return true;
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if (Token::Match(parent->previous(), "%name% (|{ %name% )|}")) {
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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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static bool isNullablePointer(const Token* tok, const Settings* settings)
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{
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if (!tok)
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return false;
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if (Token::simpleMatch(tok, "new") && tok->varId() == 0)
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return false;
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if (astIsPointer(tok))
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return true;
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if (astIsSmartPointer(tok))
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return true;
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if (Token::simpleMatch(tok, "."))
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return isNullablePointer(tok->astOperand2(), settings);
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if (const Variable* var = tok->variable()) {
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return (var->isPointer() || var->isSmartPointer());
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}
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return false;
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}
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void CheckNullPointer::nullPointerByDeRefAndChec()
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{
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const bool printInconclusive = (mSettings->certainty.isEnabled(Certainty::inconclusive));
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for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
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if (isUnevaluatedOperator(tok)) {
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tok = tok->next()->link();
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continue;
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}
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if (Token::Match(tok, "%num%|%char%|%str%"))
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continue;
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if (!isNullablePointer(tok, mSettings) ||
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(tok->str() == "." && isNullablePointer(tok->astOperand2(), mSettings) && tok->astOperand2()->getValue(0))) // avoid duplicate warning
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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->isInconclusive())
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continue;
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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 (unknown)
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nullPointerError(tok, tok->expressionString(), value, true);
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continue;
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}
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nullPointerError(tok, tok->expressionString(), value, value->isInconclusive());
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}
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}
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void CheckNullPointer::nullPointer()
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{
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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 = {
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"fstream", "ifstream", "iostream", "istream",
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"istringstream", "stringstream", "wistringstream", "wstringstream"
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};
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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 = mTokenizer->getSymbolDatabase();
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for (const Scope * scope : symbolDatabase->functionScopes) {
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if (scope->function == nullptr || !scope->function->hasBody()) // We only look for functions with a body
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continue;
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const Token *tok = scope->bodyStart;
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if (scope->function->isConstructor())
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tok = scope->function->token; // Check initialization list
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for (; tok != scope->bodyEnd; tok = tok->next()) {
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if (isUnevaluatedOperator(tok))
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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::Match(tok->tokAt(2), "0|NULL|nullptr )|}") && 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, &mSettings->library);
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// is one of the var items a NULL pointer?
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for (const Token *vartok : var) {
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if (vartok->hasKnownIntValue() && vartok->getKnownIntValue() == 0)
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nullPointerError(vartok);
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}
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}
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} else if (Token::Match(tok, "std :: string|wstring ( 0|NULL|nullptr )"))
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nullPointerError(tok);
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else if (Token::Match(tok->previous(), "::|. %name% (")) {
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const std::vector<const Token *> &args = getArguments(tok);
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for (int argnr = 0; argnr < args.size(); ++argnr) {
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const Token *argtok = args[argnr];
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if (!argtok->hasKnownIntValue())
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continue;
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if (argtok->values().front().intvalue != 0)
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continue;
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if (mSettings->library.isnullargbad(tok, argnr+1))
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nullPointerError(argtok);
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}
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}
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else if (Token::Match(tok->previous(), ">> 0|NULL|nullptr")) { // 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|NULL|nullptr ==|!=|>|>=|<|<= %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|NULL|nullptr") ||
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Token::Match(tok, "%var% =|+ 0|NULL|nullptr )|]|,|;|+")) {
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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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}
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}
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}
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void CheckNullPointer::nullPointerError(const Token *tok, const std::string &varname, const ValueFlow::Value *value, bool inconclusive)
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{
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const std::string errmsgcond("$symbol:" + varname + '\n' + ValueFlow::eitherTheConditionIsRedundant(value ? value->condition : nullptr) + " or there is possible null pointer dereference: $symbol.");
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const std::string errmsgdefarg("$symbol:" + varname + "\nPossible null pointer dereference if the default parameter value is used: $symbol");
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if (!tok) {
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reportError(tok, Severity::error, "nullPointer", "Null pointer dereference", CWE_NULL_POINTER_DEREFERENCE, Certainty::normal);
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reportError(tok, Severity::warning, "nullPointerDefaultArg", errmsgdefarg, CWE_NULL_POINTER_DEREFERENCE, Certainty::normal);
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reportError(tok, Severity::warning, "nullPointerRedundantCheck", errmsgcond, CWE_NULL_POINTER_DEREFERENCE, Certainty::normal);
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return;
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}
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if (!value) {
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reportError(tok, Severity::error, "nullPointer", "Null pointer dereference", CWE_NULL_POINTER_DEREFERENCE, inconclusive ? Certainty::inconclusive : Certainty::normal);
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return;
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}
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if (!mSettings->isEnabled(value, inconclusive))
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return;
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const ErrorPath errorPath = getErrorPath(tok, value, "Null pointer dereference");
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if (value->condition) {
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reportError(errorPath, Severity::warning, "nullPointerRedundantCheck", errmsgcond, CWE_NULL_POINTER_DEREFERENCE, inconclusive || value->isInconclusive() ? Certainty::inconclusive : Certainty::normal);
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} else if (value->defaultArg) {
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reportError(errorPath, Severity::warning, "nullPointerDefaultArg", errmsgdefarg, CWE_NULL_POINTER_DEREFERENCE, inconclusive || value->isInconclusive() ? Certainty::inconclusive : Certainty::normal);
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} else {
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std::string errmsg;
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errmsg = std::string(value->isKnown() ? "Null" : "Possible null") + " pointer dereference";
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if (!varname.empty())
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errmsg = "$symbol:" + varname + '\n' + errmsg + ": $symbol";
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reportError(errorPath,
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value->isKnown() ? Severity::error : Severity::warning,
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"nullPointer",
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errmsg,
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CWE_NULL_POINTER_DEREFERENCE, inconclusive || value->isInconclusive() ? Certainty::inconclusive : Certainty::normal);
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}
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}
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void CheckNullPointer::arithmetic()
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{
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const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
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for (const Scope * scope : symbolDatabase->functionScopes) {
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for (const Token* tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) {
|
|
if (!Token::Match(tok, "-|+|+=|-=|++|--"))
|
|
continue;
|
|
const Token *pointerOperand;
|
|
const Token *numericOperand;
|
|
if (tok->astOperand1() && tok->astOperand1()->valueType() && tok->astOperand1()->valueType()->pointer != 0) {
|
|
pointerOperand = tok->astOperand1();
|
|
numericOperand = tok->astOperand2();
|
|
} else if (tok->astOperand2() && tok->astOperand2()->valueType() && tok->astOperand2()->valueType()->pointer != 0) {
|
|
pointerOperand = tok->astOperand2();
|
|
numericOperand = tok->astOperand1();
|
|
} else
|
|
continue;
|
|
if (numericOperand && numericOperand->valueType() && !numericOperand->valueType()->isIntegral())
|
|
continue;
|
|
const ValueFlow::Value* numValue = numericOperand ? numericOperand->getValue(0) : nullptr;
|
|
if (numValue && numValue->intvalue == 0) // don't warn for arithmetic with 0
|
|
continue;
|
|
const ValueFlow::Value* value = pointerOperand->getValue(0);
|
|
if (!value)
|
|
continue;
|
|
if (!mSettings->certainty.isEnabled(Certainty::inconclusive) && value->isInconclusive())
|
|
continue;
|
|
if (value->condition && !mSettings->severity.isEnabled(Severity::warning))
|
|
continue;
|
|
if (value->condition)
|
|
redundantConditionWarning(tok, value, value->condition, value->isInconclusive());
|
|
else
|
|
pointerArithmeticError(tok, value, value->isInconclusive());
|
|
}
|
|
}
|
|
}
|
|
|
|
static std::string arithmeticTypeString(const Token *tok)
|
|
{
|
|
if (tok && tok->str()[0] == '-')
|
|
return "subtraction";
|
|
else if (tok && tok->str()[0] == '+')
|
|
return "addition";
|
|
else
|
|
return "arithmetic";
|
|
}
|
|
|
|
void CheckNullPointer::pointerArithmeticError(const Token* tok, const ValueFlow::Value *value, bool inconclusive)
|
|
{
|
|
std::string arithmetic = arithmeticTypeString(tok);
|
|
std::string errmsg;
|
|
if (tok && tok->str()[0] == '-') {
|
|
errmsg = "Overflow in pointer arithmetic, NULL pointer is subtracted.";
|
|
} else {
|
|
errmsg = "Pointer " + arithmetic + " with NULL pointer.";
|
|
}
|
|
const ErrorPath errorPath = getErrorPath(tok, value, "Null pointer " + arithmetic);
|
|
reportError(errorPath,
|
|
Severity::error,
|
|
"nullPointerArithmetic",
|
|
errmsg,
|
|
CWE_INCORRECT_CALCULATION,
|
|
inconclusive ? Certainty::inconclusive : Certainty::normal);
|
|
}
|
|
|
|
void CheckNullPointer::redundantConditionWarning(const Token* tok, const ValueFlow::Value *value, const Token *condition, bool inconclusive)
|
|
{
|
|
std::string arithmetic = arithmeticTypeString(tok);
|
|
std::string errmsg;
|
|
if (tok && tok->str()[0] == '-') {
|
|
errmsg = ValueFlow::eitherTheConditionIsRedundant(condition) + " or there is overflow in pointer " + arithmetic + ".";
|
|
} else {
|
|
errmsg = ValueFlow::eitherTheConditionIsRedundant(condition) + " or there is pointer arithmetic with NULL pointer.";
|
|
}
|
|
const ErrorPath errorPath = getErrorPath(tok, value, "Null pointer " + arithmetic);
|
|
reportError(errorPath,
|
|
Severity::warning,
|
|
"nullPointerArithmeticRedundantCheck",
|
|
errmsg,
|
|
CWE_INCORRECT_CALCULATION,
|
|
inconclusive ? Certainty::inconclusive : Certainty::normal);
|
|
}
|
|
|
|
std::string CheckNullPointer::MyFileInfo::toString() const
|
|
{
|
|
return CTU::toString(unsafeUsage);
|
|
}
|
|
|
|
// NOLINTNEXTLINE(readability-non-const-parameter) - used as callback so we need to preserve the signature
|
|
static bool isUnsafeUsage(const Check *check, const Token *vartok, MathLib::bigint *value)
|
|
{
|
|
(void)value;
|
|
const CheckNullPointer *checkNullPointer = dynamic_cast<const CheckNullPointer *>(check);
|
|
bool unknown = false;
|
|
return checkNullPointer && checkNullPointer->isPointerDeRef(vartok, unknown);
|
|
}
|
|
|
|
Check::FileInfo *CheckNullPointer::getFileInfo(const Tokenizer *tokenizer, const Settings *settings) const
|
|
{
|
|
CheckNullPointer check(tokenizer, settings, nullptr);
|
|
const std::list<CTU::FileInfo::UnsafeUsage> &unsafeUsage = CTU::getUnsafeUsage(tokenizer, settings, &check, ::isUnsafeUsage);
|
|
if (unsafeUsage.empty())
|
|
return nullptr;
|
|
|
|
MyFileInfo *fileInfo = new MyFileInfo;
|
|
fileInfo->unsafeUsage = unsafeUsage;
|
|
return fileInfo;
|
|
}
|
|
|
|
Check::FileInfo * CheckNullPointer::loadFileInfoFromXml(const tinyxml2::XMLElement *xmlElement) const
|
|
{
|
|
const std::list<CTU::FileInfo::UnsafeUsage> &unsafeUsage = CTU::loadUnsafeUsageListFromXml(xmlElement);
|
|
if (unsafeUsage.empty())
|
|
return nullptr;
|
|
|
|
MyFileInfo *fileInfo = new MyFileInfo;
|
|
fileInfo->unsafeUsage = unsafeUsage;
|
|
return fileInfo;
|
|
}
|
|
|
|
bool CheckNullPointer::analyseWholeProgram(const CTU::FileInfo *ctu, const std::list<Check::FileInfo*> &fileInfo, const Settings& settings, ErrorLogger &errorLogger)
|
|
{
|
|
if (!ctu)
|
|
return false;
|
|
bool foundErrors = false;
|
|
(void)settings; // This argument is unused
|
|
|
|
const std::map<std::string, std::list<const CTU::FileInfo::CallBase *>> callsMap = ctu->getCallsMap();
|
|
|
|
for (Check::FileInfo *fi1 : fileInfo) {
|
|
const MyFileInfo *fi = dynamic_cast<const MyFileInfo*>(fi1);
|
|
if (!fi)
|
|
continue;
|
|
for (const CTU::FileInfo::UnsafeUsage &unsafeUsage : fi->unsafeUsage) {
|
|
for (int warning = 0; warning <= 1; warning++) {
|
|
if (warning == 1 && !settings.severity.isEnabled(Severity::warning))
|
|
break;
|
|
|
|
const std::list<ErrorMessage::FileLocation> &locationList =
|
|
CTU::FileInfo::getErrorPath(CTU::FileInfo::InvalidValueType::null,
|
|
unsafeUsage,
|
|
callsMap,
|
|
"Dereferencing argument ARG that is null",
|
|
nullptr,
|
|
warning);
|
|
if (locationList.empty())
|
|
continue;
|
|
|
|
const ErrorMessage errmsg(locationList,
|
|
emptyString,
|
|
warning ? Severity::warning : Severity::error,
|
|
"Null pointer dereference: " + unsafeUsage.myArgumentName,
|
|
"ctunullpointer",
|
|
CWE_NULL_POINTER_DEREFERENCE, Certainty::normal);
|
|
errorLogger.reportErr(errmsg);
|
|
|
|
foundErrors = true;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
return foundErrors;
|
|
}
|