800 lines
26 KiB
C++
800 lines
26 KiB
C++
/*
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* Cppcheck - A tool for static C/C++ code analysis
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* Copyright (C) 2007-2010 Daniel Marjamäki and 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 "executionpath.h"
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#include "mathlib.h"
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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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{
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CheckNullPointer instance;
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}
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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 value 0 => invalid with null pointers as parameter.
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* 1-.. => invalid with uninitialized data.
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*/
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void CheckNullPointer::parseFunctionCall(const Token &tok, std::list<const Token *> &var, unsigned char value)
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{
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// standard functions that dereference first parameter..
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// both uninitialized data and null pointers are invalid.
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static std::set<std::string> functionNames1;
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if (functionNames1.empty())
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{
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functionNames1.insert("memchr");
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functionNames1.insert("memcmp");
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functionNames1.insert("strcat");
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functionNames1.insert("strncat");
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functionNames1.insert("strchr");
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functionNames1.insert("strrchr");
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functionNames1.insert("strcmp");
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functionNames1.insert("strncmp");
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functionNames1.insert("strdup");
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functionNames1.insert("strndup");
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functionNames1.insert("strlen");
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functionNames1.insert("strstr");
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}
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// standard functions that dereference second parameter..
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// both uninitialized data and null pointers are invalid.
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static std::set<std::string> functionNames2;
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if (functionNames2.empty())
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{
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functionNames2.insert("memcmp");
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functionNames2.insert("memcpy");
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functionNames2.insert("memmove");
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functionNames2.insert("strcat");
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functionNames2.insert("strncat");
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functionNames2.insert("strcmp");
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functionNames2.insert("strncmp");
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functionNames2.insert("strcpy");
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functionNames2.insert("strncpy");
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functionNames2.insert("strstr");
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}
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// 1st parameter..
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if (Token::Match(&tok, "%var% ( %var% ,|)") && tok.tokAt(2)->varId() > 0)
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{
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if (functionNames1.find(tok.str()) != functionNames1.end())
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var.push_back(tok.tokAt(2));
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else if (value == 0 && Token::Match(&tok, "memchr|memcmp|memcpy|memmove|memset|strcpy|printf|sprintf|snprintf"))
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var.push_back(tok.tokAt(2));
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else if (Token::simpleMatch(&tok, "fflush"))
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var.push_back(tok.tokAt(2));
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}
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// 2nd parameter..
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if (Token::Match(&tok, "%var% ( %any% , %var% ,|)") && tok.tokAt(4)->varId() > 0)
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{
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if (functionNames2.find(tok.str()) != functionNames2.end())
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var.push_back(tok.tokAt(4));
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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)
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{
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unknown = false;
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// Dereferencing pointer..
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if (Token::Match(tok->tokAt(-3), "!!sizeof [;{}=+-/(,] * %var%"))
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return true;
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if (!Token::simpleMatch(tok->tokAt(-2), "& (") && tok->strAt(-1) != "&&" && Token::Match(tok->next(), ". %var%"))
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return true;
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if (Token::Match(tok->previous(), "[;{}=+-/(,] %var% ["))
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return true;
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if (Token::Match(tok->previous(), "return %var% ["))
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return true;
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if (Token::Match(tok, "%var% ("))
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return true;
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if (Token::Match(tok, "%var% = %var% .") &&
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tok->varId() > 0 &&
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tok->varId() == tok->tokAt(2)->varId())
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return true;
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// Not a dereference..
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if (Token::Match(tok->previous(), "[;{}] %var% ="))
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return false;
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// unknown if it's a dereference
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unknown = 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::nullPointerAfterLoop()
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{
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// Locate insufficient null-pointer handling after loop
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for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next())
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{
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if (! Token::Match(tok, "while ( %var% )"))
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continue;
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const unsigned int varid(tok->tokAt(2)->varId());
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if (varid == 0)
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continue;
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const std::string varname(tok->strAt(2));
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// Locate the end of the while loop..
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const Token *tok2 = tok->tokAt(4);
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if (tok2->str() == "{")
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tok2 = tok2->link();
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else
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{
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while (tok2 && tok2->str() != ";")
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tok2 = tok2->next();
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}
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// Goto next token
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if (tok2)
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tok2 = tok2->next();
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// Check if the variable is dereferenced..
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while (tok2)
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{
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if (tok2->str() == "{" || tok2->str() == "}" || tok2->str() == "break")
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break;
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if (tok2->varId() == varid)
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{
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bool unknown = false;
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if (CheckNullPointer::isPointerDeRef(tok2, unknown))
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{
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// Is this variable a pointer?
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const Token *tok3 = Token::findmatch(_tokenizer->tokens(), "%type% * %varid% [;)=]", varid);
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if (!tok3)
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break;
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if (!tok3->previous() ||
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Token::Match(tok3->previous(), "[({};]") ||
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tok3->previous()->isName())
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{
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nullPointerError(tok2, varname);
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}
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}
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break;
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}
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tok2 = tok2->next();
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}
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}
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}
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void CheckNullPointer::nullPointerLinkedList()
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{
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// looping through items in a linked list in a inner loop..
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for (const Token *tok1 = _tokenizer->tokens(); tok1; tok1 = tok1->next())
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{
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// search for a "for" token..
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if (!Token::simpleMatch(tok1, "for ("))
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continue;
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if (!Token::simpleMatch(tok1->next()->link(), ") {"))
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continue;
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// is there any dereferencing occuring in the for statement..
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unsigned int parlevel2 = 1;
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for (const Token *tok2 = tok1->tokAt(2); tok2; tok2 = tok2->next())
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{
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// Parantheses..
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if (tok2->str() == "(")
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++parlevel2;
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else if (tok2->str() == ")")
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{
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if (parlevel2 <= 1)
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break;
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--parlevel2;
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}
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// Dereferencing a variable inside the "for" parantheses..
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else if (Token::Match(tok2, "%var% . %var%"))
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{
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const unsigned int varid(tok2->varId());
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if (varid == 0)
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continue;
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if (Token::Match(tok2->tokAt(-2), "%varid% ?", varid))
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continue;
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const std::string varname(tok2->str());
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// Check usage of dereferenced variable in the loop..
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unsigned int indentlevel3 = 0;
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for (const Token *tok3 = tok1->next()->link(); tok3; tok3 = tok3->next())
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{
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if (tok3->str() == "{")
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++indentlevel3;
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else if (tok3->str() == "}")
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{
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if (indentlevel3 <= 1)
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break;
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--indentlevel3;
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}
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else if (Token::Match(tok3, "while ( %varid% &&|)", varid))
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{
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// Make sure there is a "break" to prevent segmentation faults..
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unsigned int indentlevel4 = indentlevel3;
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for (const Token *tok4 = tok3->next()->link(); tok4; tok4 = tok4->next())
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{
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if (tok4->str() == "{")
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++indentlevel4;
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else if (tok4->str() == "}")
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{
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if (indentlevel4 <= 1)
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{
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// Is this variable a pointer?
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const Token *tempTok = Token::findmatch(_tokenizer->tokens(), "%type% * %varid% [;)=]", varid);
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if (tempTok)
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nullPointerError(tok1, varname, tok3->linenr());
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break;
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}
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--indentlevel4;
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}
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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::nullPointerStructByDeRefAndChec()
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{
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// don't check vars that has been tested against null already
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std::set<unsigned int> skipvar;
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skipvar.insert(0);
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// Dereferencing a struct pointer and then checking if it's NULL..
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for (const Token *tok1 = _tokenizer->tokens(); tok1; tok1 = tok1->next())
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{
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if (Token::Match(tok1, "if|while ( !| %var% )"))
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{
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tok1 = tok1->tokAt(2);
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if (tok1->str() == "!")
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tok1 = tok1->next();
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skipvar.insert(tok1->varId());
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continue;
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}
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// dereference in assignment
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if (Token::Match(tok1, "[{};] %var% = %var% . %var%"))
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{
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if (std::string(tok1->strAt(1)) == tok1->strAt(3))
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continue;
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tok1 = tok1->tokAt(3);
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}
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// dereference in function call
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else if (Token::Match(tok1->tokAt(-2), "%var% ( %var% . %var%") ||
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Token::Match(tok1->previous(), ", %var% . %var%"))
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{
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}
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// Goto next token
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else
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{
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continue;
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}
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// struct dereference was found - investigate if it is later
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// checked that it is not NULL
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const unsigned int varid1(tok1->varId());
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if (skipvar.find(varid1) != skipvar.end())
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continue;
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const std::string varname(tok1->str());
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unsigned int indentlevel2 = 0;
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for (const Token *tok2 = tok1->tokAt(3); tok2; tok2 = tok2->next())
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{
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if (tok2->str() == "{")
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++indentlevel2;
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else if (tok2->str() == "}")
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{
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if (indentlevel2 <= 1)
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break;
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--indentlevel2;
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}
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// goto destination..
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else if (tok2->isName() && Token::simpleMatch(tok2->next(), ":"))
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break;
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// Reassignment of the struct
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else if (tok2->varId() == varid1)
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{
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if (tok2->next()->str() == "=")
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break;
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if (Token::Match(tok2->tokAt(-2), "[,(] &"))
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break;
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}
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// Loop..
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/** @todo don't bail out if the variable is not used in the loop */
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else if (tok2->str() == "do")
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break;
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// return at base level => stop checking
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else if (indentlevel2 == 0 && tok2->str() == "return")
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break;
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else if (Token::Match(tok2, "if ( !| %varid% )", varid1))
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{
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// Is this variable a pointer?
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const Token *tempTok = Token::findmatch(_tokenizer->tokens(), "%type% * %varid% [;)=]", varid1);
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if (tempTok)
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nullPointerError(tok1, varname, tok2->linenr());
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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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void CheckNullPointer::nullPointerByDeRefAndChec()
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{
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// Dereferencing a pointer and then checking if it's NULL..
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for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next())
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{
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if (tok->str() == "if" && Token::Match(tok->previous(), "; if ( ! %var% )"))
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{
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const unsigned int varid(tok->tokAt(3)->varId());
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if (varid == 0)
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continue;
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const std::string varname(tok->strAt(3));
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// Check that variable is a pointer..
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const Token *decltok = Token::findmatch(_tokenizer->tokens(), "%varid%", varid);
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if (!Token::Match(decltok->tokAt(-3), "[{};,(] %type% *"))
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continue;
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for (const Token *tok1 = tok->previous(); tok1 && tok1 != decltok; tok1 = tok1->previous())
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{
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if (tok1->varId() == varid)
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{
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bool unknown = false;
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if (CheckNullPointer::isPointerDeRef(tok1, unknown))
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{
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nullPointerError(tok1, varname, tok->linenr());
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break;
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}
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else if (Token::simpleMatch(tok1->previous(), "&"))
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{
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break;
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}
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else if (Token::simpleMatch(tok1->next(), "="))
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{
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break;
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}
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}
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else if (tok1->str() == "{" ||
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tok1->str() == "}")
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break;
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// label..
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else if (Token::Match(tok1, "%type% :"))
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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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void CheckNullPointer::nullPointerByCheckAndDeRef()
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{
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// Check if pointer is NULL and then dereference it..
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for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next())
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{
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if (Token::Match(tok, "if ( ! %var% ) {"))
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{
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bool null = true;
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const unsigned int varid(tok->tokAt(3)->varId());
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if (varid == 0)
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continue;
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unsigned int indentlevel = 1;
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for (const Token *tok2 = tok->tokAt(6); tok2; tok2 = tok2->next())
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{
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if (tok2->str() == "{")
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++indentlevel;
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else if (tok2->str() == "}")
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{
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if (indentlevel == 0)
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break;
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--indentlevel;
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if (null && indentlevel == 0)
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{
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// skip all "else" blocks because they are not executed in this execution path
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while (Token::Match(tok2, "} else {"))
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tok2 = tok2->tokAt(2)->link();
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null = false;
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}
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}
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if (Token::Match(tok2, "goto|return|continue|break|throw|if"))
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{
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if (Token::Match(tok2, "return * %varid%", varid))
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nullPointerError(tok2, tok->strAt(3));
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break;
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}
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// abort function..
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if (Token::Match(tok2->previous(), "[;{}] %var% (") &&
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Token::simpleMatch(tok2->next()->link(), ") ; }"))
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{
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break;
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}
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if (tok2->varId() == varid)
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{
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bool unknown = false;
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if (Token::Match(tok2->previous(), "[;{}=] %var% = 0 ;"))
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;
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else if (CheckNullPointer::isPointerDeRef(tok2, unknown))
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nullPointerError(tok2, tok->strAt(3));
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else
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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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void CheckNullPointer::nullPointer()
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{
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nullPointerAfterLoop();
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nullPointerLinkedList();
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nullPointerStructByDeRefAndChec();
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nullPointerByDeRefAndChec();
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nullPointerByCheckAndDeRef();
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}
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/** Derefencing null constant (simplified token list) */
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void CheckNullPointer::nullConstantDereference()
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{
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// this is kept at 0 for all scopes that are not executing
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unsigned int indentlevel = 0;
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for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next())
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{
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// start of executable scope..
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if (indentlevel == 0 && Token::Match(tok, ") const| {"))
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indentlevel = 1;
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else if (indentlevel >= 1)
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{
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if (tok->str() == "{")
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++indentlevel;
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else if (tok->str() == "}")
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{
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if (indentlevel <= 2)
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indentlevel = 0;
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else
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--indentlevel;
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}
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if (tok->str() == "(" && Token::simpleMatch(tok->previous(), "sizeof"))
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tok = tok->link();
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else if (Token::simpleMatch(tok, "exit ( )"))
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{
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// Goto end of scope
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while (tok && tok->str() != "}")
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{
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if (tok->str() == "{")
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tok = tok->link();
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tok = tok->next();
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}
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if (!tok)
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break;
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}
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else if (Token::simpleMatch(tok, "* 0"))
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{
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if (Token::Match(tok->previous(), "[<>;{}=+-*/(,]") ||
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Token::Match(tok->previous(), "return|<<"))
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{
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nullPointerError(tok);
|
|
}
|
|
}
|
|
}
|
|
}
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|
}
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|
|
|
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/// @addtogroup Checks
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/// @{
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|
|
|
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/**
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* @brief %Check for null pointer usage (using ExecutionPath)
|
|
*/
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|
|
|
class Nullpointer : public ExecutionPath
|
|
{
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|
public:
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|
/** Startup constructor */
|
|
Nullpointer(Check *c) : ExecutionPath(c, 0), null(false)
|
|
{
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|
}
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|
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|
private:
|
|
/** Create checking of specific variable: */
|
|
Nullpointer(Check *c, const unsigned int id, const std::string &name)
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|
: ExecutionPath(c, id),
|
|
varname(name),
|
|
null(false)
|
|
{
|
|
}
|
|
|
|
/** Copy this check */
|
|
ExecutionPath *copy()
|
|
{
|
|
return new Nullpointer(*this);
|
|
}
|
|
|
|
/** no implementation => compiler error if used by accident */
|
|
void operator=(const Nullpointer &);
|
|
|
|
/** is other execution path equal? */
|
|
bool is_equal(const ExecutionPath *e) const
|
|
{
|
|
const Nullpointer *c = static_cast<const Nullpointer *>(e);
|
|
return (varname == c->varname && null == c->null);
|
|
}
|
|
|
|
/** variable name for this check (empty => dummy check) */
|
|
const std::string varname;
|
|
|
|
/** is this variable null? */
|
|
bool null;
|
|
|
|
/** variable is set to null */
|
|
static void setnull(std::list<ExecutionPath *> &checks, const unsigned int varid)
|
|
{
|
|
std::list<ExecutionPath *>::iterator it;
|
|
for (it = checks.begin(); it != checks.end(); ++it)
|
|
{
|
|
Nullpointer *c = dynamic_cast<Nullpointer *>(*it);
|
|
if (c && c->varId == varid)
|
|
c->null = true;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Dereferencing variable. Check if it is safe (if the variable is null there's an error)
|
|
* @param checks Checks
|
|
* @param tok token where dereferencing happens
|
|
*/
|
|
static void dereference(std::list<ExecutionPath *> &checks, const Token *tok)
|
|
{
|
|
const unsigned int varid(tok->varId());
|
|
|
|
std::list<ExecutionPath *>::iterator it;
|
|
for (it = checks.begin(); it != checks.end(); ++it)
|
|
{
|
|
Nullpointer *c = dynamic_cast<Nullpointer *>(*it);
|
|
if (c && c->varId == varid && c->null)
|
|
{
|
|
CheckNullPointer *checkNullPointer = dynamic_cast<CheckNullPointer *>(c->owner);
|
|
if (checkNullPointer)
|
|
{
|
|
checkNullPointer->nullPointerError(tok, c->varname);
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/** parse tokens */
|
|
const Token *parse(const Token &tok, std::list<ExecutionPath *> &checks) const
|
|
{
|
|
if (Token::Match(tok.previous(), "[;{}] const| %type% * %var% ;"))
|
|
{
|
|
const Token * vartok = tok.tokAt(2);
|
|
|
|
if (tok.str() == "const")
|
|
vartok = vartok->next();
|
|
|
|
if (vartok->varId() != 0)
|
|
checks.push_back(new Nullpointer(owner, vartok->varId(), vartok->str()));
|
|
return vartok->next();
|
|
}
|
|
|
|
// Template pointer variable..
|
|
if (Token::Match(tok.previous(), "[;{}] %type% ::|<"))
|
|
{
|
|
const Token * vartok = &tok;
|
|
while (Token::Match(vartok, "%type% ::"))
|
|
vartok = vartok->tokAt(2);
|
|
if (Token::Match(vartok, "%type% < %type%"))
|
|
{
|
|
vartok = vartok->tokAt(3);
|
|
while (vartok && (vartok->str() == "*" || vartok->isName()))
|
|
vartok = vartok->next();
|
|
}
|
|
if (vartok
|
|
&& (vartok->str() == ">" || vartok->isName())
|
|
&& Token::Match(vartok->next(), "* %var% ;|="))
|
|
{
|
|
vartok = vartok->tokAt(2);
|
|
checks.push_back(new Nullpointer(owner, vartok->varId(), vartok->str()));
|
|
if (Token::simpleMatch(vartok->next(), "= 0 ;"))
|
|
setnull(checks, vartok->varId());
|
|
return vartok->next();
|
|
}
|
|
}
|
|
|
|
if (Token::simpleMatch(&tok, "try {"))
|
|
{
|
|
// Bail out all used variables
|
|
unsigned int indentlevel = 0;
|
|
for (const Token *tok2 = &tok; tok2; tok2 = tok2->next())
|
|
{
|
|
if (tok2->str() == "{")
|
|
++indentlevel;
|
|
else if (tok2->str() == "}")
|
|
{
|
|
if (indentlevel == 0)
|
|
break;
|
|
if (indentlevel == 1 && !Token::simpleMatch(tok2,"} catch ("))
|
|
return tok2;
|
|
--indentlevel;
|
|
}
|
|
else if (tok2->varId())
|
|
bailOutVar(checks,tok2->varId());
|
|
}
|
|
}
|
|
|
|
if (Token::Match(&tok, "%var% ("))
|
|
{
|
|
if (tok.str() == "sizeof")
|
|
return tok.next()->link();
|
|
|
|
// parse usage..
|
|
std::list<const Token *> var;
|
|
CheckNullPointer::parseFunctionCall(tok, var, 0);
|
|
for (std::list<const Token *>::const_iterator it = var.begin(); it != var.end(); ++it)
|
|
dereference(checks, *it);
|
|
}
|
|
|
|
if (tok.varId() != 0)
|
|
{
|
|
bool unknown = false;
|
|
if (Token::Match(tok.previous(), "[;{}=] %var% = 0 ;"))
|
|
setnull(checks, tok.varId());
|
|
else if (CheckNullPointer::isPointerDeRef(&tok, unknown))
|
|
dereference(checks, &tok);
|
|
else
|
|
// TODO: Report debug warning that it's unknown if a
|
|
// pointer is dereferenced
|
|
bailOutVar(checks, tok.varId());
|
|
}
|
|
|
|
else if (tok.str() == "delete")
|
|
{
|
|
const Token *ret = tok.next();
|
|
if (Token::simpleMatch(ret, "[ ]"))
|
|
ret = ret->tokAt(2);
|
|
if (Token::Match(ret, "%var% ;"))
|
|
return ret->next();
|
|
}
|
|
|
|
return &tok;
|
|
}
|
|
|
|
/** parse condition. @sa ExecutionPath::parseCondition */
|
|
bool parseCondition(const Token &tok, std::list<ExecutionPath *> &checks)
|
|
{
|
|
for (const Token *tok2 = &tok; tok2; tok2 = tok2->next())
|
|
{
|
|
if (tok2->str() == "(" || tok2->str() == ")")
|
|
break;
|
|
if (Token::Match(tok2, "[<>=] * %var%"))
|
|
dereference(checks, tok2->tokAt(2));
|
|
}
|
|
|
|
if (Token::Match(&tok, "!| %var% ("))
|
|
{
|
|
std::list<const Token *> var;
|
|
CheckNullPointer::parseFunctionCall(tok.str() == "!" ? *tok.next() : tok, var, 0);
|
|
for (std::list<const Token *>::const_iterator it = var.begin(); it != var.end(); ++it)
|
|
dereference(checks, *it);
|
|
}
|
|
|
|
return ExecutionPath::parseCondition(tok, checks);
|
|
}
|
|
|
|
|
|
void parseLoopBody(const Token *tok, std::list<ExecutionPath *> &checks) const
|
|
{
|
|
while (tok)
|
|
{
|
|
if (Token::Match(tok, "{|}|return|goto|break|if"))
|
|
return;
|
|
const Token *next = parse(*tok, checks);
|
|
if (next)
|
|
tok = tok->next();
|
|
}
|
|
}
|
|
|
|
};
|
|
/// @}
|
|
|
|
|
|
void CheckNullPointer::executionPaths()
|
|
{
|
|
// Check for null pointer errors..
|
|
Nullpointer c(this);
|
|
checkExecutionPaths(_tokenizer->tokens(), &c);
|
|
}
|
|
|
|
void CheckNullPointer::nullPointerError(const Token *tok)
|
|
{
|
|
reportError(tok, Severity::error, "nullPointer", "Null pointer dereference");
|
|
}
|
|
|
|
void CheckNullPointer::nullPointerError(const Token *tok, const std::string &varname)
|
|
{
|
|
reportError(tok, Severity::error, "nullPointer", "Possible null pointer dereference: " + varname);
|
|
}
|
|
|
|
void CheckNullPointer::nullPointerError(const Token *tok, const std::string &varname, const unsigned int line)
|
|
{
|
|
reportError(tok, Severity::error, "nullPointer", "Possible null pointer dereference: " + varname + " - otherwise it is redundant to check if " + varname + " is null at line " + MathLib::toString<unsigned int>(line));
|
|
}
|
|
|