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cppcheck/lib/checknullpointer.cpp

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/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2012 Daniel Marjamäki and Cppcheck team.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
//---------------------------------------------------------------------------
#include "checknullpointer.h"
#include "executionpath.h"
#include "mathlib.h"
#include "symboldatabase.h"
#include <cctype>
//---------------------------------------------------------------------------
// Register this check class (by creating a static instance of it)
namespace {
CheckNullPointer instance;
}
//---------------------------------------------------------------------------
/**
* @brief parse a function call and extract information about variable usage
* @param tok first token
* @param var variables that the function read / write.
* @param value 0 => invalid with null pointers as parameter.
* 1-.. => invalid with uninitialized data.
*/
void CheckNullPointer::parseFunctionCall(const Token &tok, std::list<const Token *> &var, unsigned char value)
{
// standard functions that dereference first parameter..
static std::set<std::string> functionNames1_all;
static std::set<std::string> functionNames1_nullptr;
static std::set<std::string> functionNames1_uninit;
if (functionNames1_all.empty()) {
// cstdlib
functionNames1_all.insert("atoi");
functionNames1_all.insert("atof");
functionNames1_all.insert("atol");
functionNames1_all.insert("qsort");
functionNames1_all.insert("strtod");
functionNames1_all.insert("strtol");
functionNames1_all.insert("strtoul");
// cstring
functionNames1_all.insert("memchr");
functionNames1_all.insert("memcmp");
functionNames1_all.insert("strcat");
functionNames1_all.insert("strncat");
functionNames1_all.insert("strcoll");
functionNames1_all.insert("strchr");
functionNames1_all.insert("strrchr");
functionNames1_all.insert("strcmp");
functionNames1_all.insert("strncmp");
functionNames1_all.insert("strcspn");
functionNames1_all.insert("strdup");
functionNames1_all.insert("strndup");
functionNames1_all.insert("strpbrk");
functionNames1_all.insert("strlen");
functionNames1_all.insert("strspn");
functionNames1_all.insert("strstr");
// cstdio
functionNames1_all.insert("fclose");
functionNames1_all.insert("feof");
functionNames1_all.insert("fwrite");
functionNames1_all.insert("fseek");
functionNames1_all.insert("ftell");
functionNames1_all.insert("fputs");
functionNames1_all.insert("ferror");
functionNames1_all.insert("fgetc");
functionNames1_all.insert("fgetpos");
functionNames1_all.insert("fsetpos");
functionNames1_all.insert("freopen");
functionNames1_all.insert("fscanf");
functionNames1_all.insert("fprintf");
functionNames1_all.insert("fopen");
functionNames1_all.insert("rewind");
functionNames1_all.insert("printf");
functionNames1_all.insert("scanf");
functionNames1_all.insert("fscanf");
functionNames1_all.insert("sscanf");
functionNames1_all.insert("setbuf");
functionNames1_all.insert("setvbuf");
functionNames1_all.insert("rename");
functionNames1_all.insert("remove");
functionNames1_all.insert("puts");
functionNames1_all.insert("getc");
functionNames1_all.insert("clearerr");
// ctime
functionNames1_all.insert("asctime");
functionNames1_all.insert("ctime");
functionNames1_all.insert("mktime");
functionNames1_nullptr.insert("itoa");
functionNames1_nullptr.insert("memcpy");
functionNames1_nullptr.insert("memmove");
functionNames1_nullptr.insert("memset");
functionNames1_nullptr.insert("strcpy");
functionNames1_nullptr.insert("sprintf");
functionNames1_nullptr.insert("vsprintf");
functionNames1_nullptr.insert("vprintf");
functionNames1_nullptr.insert("fprintf");
functionNames1_nullptr.insert("vfprintf");
functionNames1_nullptr.insert("fread");
functionNames1_nullptr.insert("gets");
functionNames1_nullptr.insert("gmtime");
functionNames1_nullptr.insert("localtime");
functionNames1_nullptr.insert("strftime");
functionNames1_uninit.insert("perror");
functionNames1_uninit.insert("fflush");
}
// standard functions that dereference second parameter..
static std::set<std::string> functionNames2_all;
static std::set<std::string> functionNames2_nullptr;
if (functionNames2_all.empty()) {
functionNames2_all.insert("mbstowcs");
functionNames2_all.insert("wcstombs");
functionNames2_all.insert("memcmp");
functionNames2_all.insert("memcpy");
functionNames2_all.insert("memmove");
functionNames2_all.insert("strcat");
functionNames2_all.insert("strncat");
functionNames2_all.insert("strcmp");
functionNames2_all.insert("strncmp");
functionNames2_all.insert("strcoll");
functionNames2_all.insert("strcpy");
functionNames2_all.insert("strcspn");
functionNames2_all.insert("strncpy");
functionNames2_all.insert("strpbrk");
functionNames2_all.insert("strspn");
functionNames2_all.insert("strstr");
functionNames2_all.insert("strxfrm");
functionNames2_all.insert("sprintf");
functionNames2_all.insert("fprintf");
functionNames2_all.insert("fscanf");
functionNames2_all.insert("sscanf");
functionNames2_all.insert("fputs");
functionNames2_all.insert("fputc");
functionNames2_all.insert("ungetc");
functionNames2_all.insert("rename");
functionNames2_all.insert("putc");
functionNames2_all.insert("freopen");
functionNames2_nullptr.insert("frexp");
functionNames2_nullptr.insert("modf");
functionNames2_nullptr.insert("fgetpos");
}
if (Token::Match(&tok, "%var% ( )") || !tok.tokAt(2))
return;
const Token* firstParam = tok.tokAt(2);
const Token* secondParam = firstParam->nextArgument();
// 1st parameter..
if ((Token::Match(firstParam, "%var% ,|)") && firstParam->varId() > 0) ||
(value == 0 && Token::Match(firstParam, "0 ,|)"))) {
if (functionNames1_all.find(tok.str()) != functionNames1_all.end())
var.push_back(firstParam);
else if (value == 0 && functionNames1_nullptr.find(tok.str()) != functionNames1_nullptr.end())
var.push_back(firstParam);
else if (value != 0 && functionNames1_uninit.find(tok.str()) != functionNames1_uninit.end())
var.push_back(firstParam);
else if (value == 0 && Token::Match(&tok, "snprintf|vsnprintf|fnprintf|vfnprintf") && secondParam && secondParam->str() != "0") // Only if length (second parameter) is not zero
var.push_back(firstParam);
}
// 2nd parameter..
if (secondParam && ((value == 0 && secondParam->str() == "0") || (Token::Match(secondParam, "%var%") && secondParam->varId() > 0))) {
if (functionNames2_all.find(tok.str()) != functionNames2_all.end())
var.push_back(secondParam);
else if (value == 0 && functionNames2_nullptr.find(tok.str()) != functionNames2_nullptr.end())
var.push_back(secondParam);
}
if (Token::Match(&tok, "printf|sprintf|snprintf|fprintf|fnprintf|scanf|sscanf|fscanf")) {
const Token* argListTok = 0; // Points to first va_list argument
std::string formatString;
bool scan = Token::Match(&tok, "scanf|sscanf|fscanf");
if (Token::Match(&tok, "printf|scanf ( %str%")) {
formatString = firstParam->strValue();
argListTok = secondParam;
} else if (Token::Match(&tok, "sprintf|fprintf|sscanf|fscanf")) {
const Token* formatStringTok = secondParam; // Find second parameter (format string)
if (formatStringTok && formatStringTok->type() == Token::eString) {
argListTok = formatStringTok->nextArgument(); // Find third parameter (first argument of va_args)
formatString = formatStringTok->strValue();
}
} else if (Token::Match(&tok, "snprintf|fnprintf") && secondParam) {
const Token* formatStringTok = secondParam->nextArgument(); // Find third parameter (format string)
if (formatStringTok && formatStringTok->type() == Token::eString) {
argListTok = formatStringTok->nextArgument(); // Find fourth parameter (first argument of va_args)
formatString = formatStringTok->strValue();
}
}
if (argListTok) {
bool percent = false;
for (std::string::iterator i = formatString.begin(); i != formatString.end(); ++i) {
if (*i == '%') {
percent = !percent;
} else if (percent) {
percent = false;
bool _continue = false;
while (!std::isalpha(*i)) {
if (*i == '*') {
if (scan)
_continue = true;
else
argListTok = argListTok->nextArgument();
}
++i;
if (!argListTok || i == formatString.end())
return;
}
if (_continue)
continue;
if ((*i == 'n' || *i == 's' || scan) && (!scan || value == 0)) {
if ((value == 0 && argListTok->str() == "0") || (argListTok->varId() > 0)) {
var.push_back(argListTok);
}
}
if (*i != 'm') // %m is a non-standard glibc extension that requires no parameter
argListTok = argListTok->nextArgument(); // Find next argument
if (!argListTok)
break;
}
}
}
}
}
/**
* Is there a pointer dereference? Everything that should result in
* a nullpointer dereference error message will result in a true
* return value. If it's unknown if the pointer is dereferenced false
* is returned.
* @param tok token for the pointer
* @param unknown it is not known if there is a pointer dereference (could be reported as a debug message)
* @return true => there is a dereference
*/
bool CheckNullPointer::isPointerDeRef(const Token *tok, bool &unknown, const SymbolDatabase* symbolDatabase)
{
const bool inconclusive = unknown;
unknown = false;
// Dereferencing pointer..
if (tok->strAt(-1) == "*" && (Token::Match(tok->tokAt(-2), "return|throw|;|{|}|:|[|(|,") || tok->tokAt(-2)->isOp() || tok->tokAt(-2)->isAssignmentOp()) && !Token::Match(tok->tokAt(-3), "sizeof|decltype"))
return true;
// read/write member variable
if (!Token::simpleMatch(tok->tokAt(-2), "& (") && !Token::Match(tok->tokAt(-2), "sizeof|decltype (") && tok->strAt(-1) != "&" && Token::Match(tok->next(), ". %var%")) {
if (tok->strAt(3) != "(")
return true;
unknown = true;
return false;
}
if (Token::Match(tok, "%var% [") && (tok->previous()->str() != "&" || Token::Match(tok->next()->link()->next(), "[.(]")))
return true;
if (Token::Match(tok, "%var% ("))
return true;
if (Token::Match(tok, "%var% = %var% .") &&
tok->varId() > 0 &&
tok->varId() == tok->tokAt(2)->varId())
return true;
// std::string dereferences nullpointers
if (Token::Match(tok->tokAt(-4), "std :: string ( %var% )"))
return true;
if (Token::Match(tok->tokAt(-2), "%var% ( %var% )")) {
const Variable* var = symbolDatabase->getVariableFromVarId(tok->tokAt(-2)->varId());
if (var && !var->isPointer() && !var->isArray() && Token::Match(var->typeStartToken(), "std :: string !!::"))
return true;
}
// streams dereference nullpointers
if (Token::Match(tok->previous(), "<<|>> %var%")) {
const Variable* var = symbolDatabase->getVariableFromVarId(tok->varId());
if (var && var->isPointer() && var->typeStartToken()->str() == "char") { // Only outputing or reading to char* can cause problems
const Token* tok2 = tok->previous(); // Find start of statement
for (; tok2; tok2 = tok2->previous()) {
if (Token::Match(tok2->previous(), ";|{|}|:"))
break;
}
if (Token::Match(tok2, "std :: cout|cin|cerr"))
return true;
if (tok2 && tok2->varId() != 0) {
const Variable* var2 = symbolDatabase->getVariableFromVarId(tok2->varId());
if (var2 && Token::Match(var2->typeStartToken(), "std :: istream|ifstream|istringstream|ostream|ofstream|ostringstream|stringstream|fstream|iostream"))
return true;
}
}
}
unsigned int ovarid = 0;
if (Token::Match(tok, "%var% ==|!= %var%"))
ovarid = tok->tokAt(2)->varId();
else if (Token::Match(tok->tokAt(-2), "%var% ==|!= %var%"))
ovarid = tok->tokAt(-2)->varId();
else if (Token::Match(tok->tokAt(-2), "%var% =|+=|+ %var% )|]|,|;|+"))
ovarid = tok->tokAt(-2)->varId();
if (ovarid) {
const Variable* var = symbolDatabase->getVariableFromVarId(ovarid);
if (var && !var->isPointer() && !var->isArray() && Token::Match(var->typeStartToken(), "std :: string !!::"))
return true;
}
// Check if it's NOT a pointer dereference.
// This is most useful in inconclusive checking
if (inconclusive) {
// Not a dereference..
if (Token::Match(tok, "%var% ="))
return false;
// OK to delete a null
if (Token::Match(tok->previous(), "delete %var%") || Token::Match(tok->tokAt(-3), "delete [ ] %var%"))
return false;
// OK to check if pointer is null
// OK to take address of pointer
if (Token::Match(tok->previous(), "!|& %var%"))
return false;
// OK to pass pointer to function
if (Token::Match(tok->previous(), "[(,] %var% [,)]"))
return false;
// Compare pointer
if (Token::Match(tok->previous(), "(|&&|%oror%|==|!= %var%"))
return false;
if (Token::Match(tok, "%var% &&|%oror%|==|!=|)"))
return false;
// Taking address
if (Token::Match(tok->previous(), "return|= %var% ;"))
return false;
// (void)var
if (Token::Match(tok->previous(), "[{;}] %var% ;"))
return false;
// unknown if it's a dereference
unknown = true;
}
// assume that it's not a dereference (no false positives)
return false;
}
// check if function can assign pointer
bool CheckNullPointer::CanFunctionAssignPointer(const Token *functiontoken, unsigned int varid, bool& unknown) const
{
if (Token::Match(functiontoken, "if|while|for|switch|sizeof|catch"))
return false;
int argumentNumber = 0;
for (const Token *arg = functiontoken->tokAt(2); arg; arg = arg->nextArgument()) {
if (Token::Match(arg, "%varid% [,)]", varid)) {
const Token *ftok = _tokenizer->getFunctionTokenByName(functiontoken->str().c_str());
const Function* func = _tokenizer->getSymbolDatabase()->findFunctionByToken(ftok);
if (!func) { // Unknown function
unknown = true;
return true; // assume that the function might assign the pointer
}
const Variable* var = func->getArgumentVar(argumentNumber);
if (!var) { // Unknown variable
unknown = true;
return true;
} else if (var->isReference()) // Assume every pointer passed by reference is assigned
return true;
else
return false;
}
++argumentNumber;
}
// pointer is not passed
return false;
}
void CheckNullPointer::nullPointerLinkedList()
{
const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
// looping through items in a linked list in a inner loop.
// Here is an example:
// for (const Token *tok = tokens; tok; tok = tok->next) {
// if (tok->str() == "hello")
// tok = tok->next; // <- tok might become a null pointer!
// }
for (std::list<Scope>::const_iterator i = symbolDatabase->scopeList.begin(); i != symbolDatabase->scopeList.end(); ++i) {
const Token* const tok1 = i->classDef;
// search for a "for" scope..
if (i->type != Scope::eFor || !tok1)
continue;
// is there any dereferencing occurring in the for statement
const Token* end2 = tok1->linkAt(1);
for (const Token *tok2 = tok1->tokAt(2); tok2 != end2; tok2 = tok2->next()) {
// Dereferencing a variable inside the "for" parentheses..
if (Token::Match(tok2, "%var% . %var%")) {
// Variable id for dereferenced variable
const unsigned int varid(tok2->varId());
if (varid == 0)
continue;
// Is this variable a pointer?
const Variable* var = symbolDatabase->getVariableFromVarId(varid);
if (!var || !var->isPointer())
continue;
if (Token::Match(tok2->tokAt(-2), "%varid% ?", varid))
continue;
// Check usage of dereferenced variable in the loop..
for (std::list<Scope*>::const_iterator j = i->nestedList.begin(); j != i->nestedList.end(); ++j) {
Scope* scope = *j;
if (scope->type != Scope::eWhile)
continue;
// TODO: are there false negatives for "while ( %varid% ||"
if (Token::Match(scope->classDef->next(), "( %varid% &&|)", varid)) {
// Make sure there is a "break" or "return" inside the loop.
// Without the "break" a null pointer could be dereferenced in the
// for statement.
for (const Token *tok4 = scope->classStart; tok4; tok4 = tok4->next()) {
if (tok4 == i->classEnd) {
nullPointerError(tok1, var->name(), scope->classDef);
break;
}
// There is a "break" or "return" inside the loop.
// TODO: there can be false negatives. There could still be
// execution paths that are not properly terminated
else if (tok4->str() == "break" || tok4->str() == "return")
break;
}
}
}
}
}
}
}
void CheckNullPointer::nullPointerStructByDeRefAndChec()
{
// Dereferencing a struct pointer and then checking if it's NULL..
// skipvar: don't check vars that has been tested against null already
std::set<unsigned int> skipvar;
skipvar.insert(0);
// Scan through all tokens
for (const Token *tok1 = _tokenizer->tokens(); tok1; tok1 = tok1->next()) {
// Checking if some pointer is null.
// then add the pointer to skipvar => is it known that it isn't NULL
if (Token::Match(tok1, "if|while ( !| %var% )")) {
tok1 = tok1->tokAt(2);
if (tok1->str() == "!")
tok1 = tok1->next();
skipvar.insert(tok1->varId());
continue;
} else if (Token::Match(tok1, "( ! %var% %oror%") ||
Token::Match(tok1, "( %var% &&")) {
// TODO: there are false negatives caused by this. The
// variable should be removed from skipvar after the
// condition
tok1 = tok1->next();
if (tok1->str() == "!")
tok1 = tok1->next();
skipvar.insert(tok1->varId());
continue;
}
bool inconclusive = false;
/**
* @todo There are lots of false negatives here. A dereference
* is only investigated if a few specific conditions are met.
*/
// dereference in assignment
if (Token::Match(tok1, "[;{}] %var% . %var%")) {
tok1 = tok1->next();
if (tok1->strAt(3) == "(") {
if (!_settings->inconclusive)
continue;
inconclusive = true;
}
}
// dereference in assignment
else if (Token::Match(tok1, "[{};] %var% = %var% . %var%")) {
if (tok1->strAt(1) == tok1->strAt(3))
continue;
tok1 = tok1->tokAt(3);
}
// dereference in condition
else if (Token::Match(tok1, "if ( !| %var% .")) {
tok1 = tok1->tokAt(2);
if (tok1->str() == "!")
tok1 = tok1->next();
}
// dereference in function call (but not sizeof|decltype)
else if ((Token::Match(tok1->tokAt(-2), "%var% ( %var% . %var%") && !Token::Match(tok1->tokAt(-2), "sizeof|decltype ( %var% . %var%")) ||
Token::Match(tok1->previous(), ", %var% . %var%")) {
// Is the function return value taken by the pointer?
bool assignment = false;
const unsigned int varid1(tok1->varId());
if (varid1 == 0)
continue;
const Token *tok2 = tok1->previous();
while (tok2 && !Token::Match(tok2, "[;{}]")) {
if (Token::Match(tok2, "%varid% =", varid1)) {
assignment = true;
break;
}
tok2 = tok2->previous();
}
if (assignment)
continue;
// Is the dereference checked with a previous &&
bool checked = false;
for (tok2 = tok1->tokAt(-2); tok2; tok2 = tok2->previous()) {
if (Token::Match(tok2, "[,(;{}]"))
break;
else if (tok2->str() == ")")
tok2 = tok2->link();
else if (Token::Match(tok2, "%varid% &&", varid1)) {
checked = true;
break;
}
}
if (checked)
continue;
}
// Goto next token
else {
continue;
}
// struct dereference was found - investigate if it is later
// checked that it is not NULL
const unsigned int varid1(tok1->varId());
if (skipvar.find(varid1) != skipvar.end())
continue;
// name of struct pointer
const std::string& varname(tok1->str());
// is pointer local?
bool isLocal = false;
const Variable * var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(tok1->varId());
if (!var)
continue;
if (var->isLocal() || var->isArgument())
isLocal = true;
// member function may or may not nullify the pointer if it's global (#2647)
if (!isLocal) {
const Token *tok2 = tok1;
while (Token::Match(tok2, "%var% ."))
tok2 = tok2->tokAt(2);
if (Token::Match(tok2,"%var% ("))
continue;
}
// count { and } using tok2
const Token* const end2 = tok1->scope()->classEnd;
for (const Token *tok2 = tok1->tokAt(3); tok2 != end2; tok2 = tok2->next()) {
bool unknown = false;
// label / ?:
if (tok2->str() == ":")
break;
// function call..
else if (Token::Match(tok2, "[;{}] %var% (") && CanFunctionAssignPointer(tok2->next(), varid1, unknown)) {
if (!_settings->inconclusive || !unknown)
break;
inconclusive = true;
}
// Reassignment of the struct
else if (tok2->varId() == varid1) {
if (tok2->next()->str() == "=") {
// Avoid false positives when there is 'else if'
// TODO: can this be handled better?
if (tok1->strAt(-2) == "if")
skipvar.insert(varid1);
break;
}
if (Token::Match(tok2->tokAt(-2), "[,(] &"))
break;
}
// Loop..
/** @todo don't bail out if the variable is not used in the loop */
else if (tok2->str() == "do")
break;
// return/break at base level => stop checking
else if (tok2->scope()->classEnd == end2 && (tok2->str() == "return" || tok2->str() == "break"))
break;
// Function call: If the pointer is not a local variable it
// might be changed by the call.
else if (Token::Match(tok2, "[;{}] %var% (") &&
Token::simpleMatch(tok2->linkAt(2), ") ;") && !isLocal) {
break;
}
// Check if pointer is null.
// TODO: false negatives for "if (!p || .."
else if (!tok2->isExpandedMacro() && Token::Match(tok2, "if ( !| %varid% )|&&", varid1)) {
// Is this variable a pointer?
if (var->isPointer())
nullPointerError(tok1, varname, tok2, inconclusive);
break;
}
}
}
}
void CheckNullPointer::nullPointerByDeRefAndChec()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
// Dereferencing a pointer and then checking if it's NULL..
// This check will first scan for the check. And then scan backwards
// from the check, searching for dereferencing.
for (std::list<Scope>::const_iterator i = symbolDatabase->scopeList.begin(); i != symbolDatabase->scopeList.end(); ++i) {
// TODO: false negatives.
// - logical operators
const Token* tok = i->classDef;
if ((i->type == Scope::eIf || i->type == Scope::eElseIf || i->type == Scope::eWhile) &&
tok && Token::Match(tok, "else| %var% ( !| %var% )|%oror%|&&") && !tok->next()->isExpandedMacro()) {
if (tok->str() == "else")
tok = tok->next();
const Token * vartok = tok->tokAt(2);
if (vartok->str() == "!")
vartok = vartok->next();
// Variable id for pointer
const unsigned int varid(vartok->varId());
if (varid == 0)
continue;
// Name of pointer
const std::string& varname(vartok->str());
const Variable* var = symbolDatabase->getVariableFromVarId(varid);
// Check that variable is a pointer..
if (!var || !var->isPointer())
continue;
const Token * const decltok = var->nameToken();
bool inconclusive = false;
for (const Token *tok1 = tok->previous(); tok1 && tok1 != decltok; tok1 = tok1->previous()) {
if (tok1->str() == ")" && Token::Match(tok1->link()->previous(), "%var% (")) {
const Token *tok2 = tok1->link();
while (tok2 && !Token::Match(tok2, "[;{}?:]"))
tok2 = tok2->previous();
if (Token::Match(tok2, "[?:]"))
break;
if (Token::Match(tok2->next(), "%varid% = %var%", varid))
break;
if (Token::Match(tok2->next(), "while ( %varid%", varid))
break;
if (Token::Match(tok1->link(), "( ! %varid% %oror%", varid) ||
Token::Match(tok1->link(), "( %varid% &&", varid)) {
tok1 = tok1->link();
continue;
}
if (Token::simpleMatch(tok1->link()->previous(), "sizeof (")) {
tok1 = tok1->link()->previous();
continue;
}
if (Token::Match(tok2->next(), "%var% ( %varid% ,", varid)) {
std::list<const Token *> varlist;
parseFunctionCall(*(tok2->next()), varlist, 0);
if (!varlist.empty() && varlist.front() == tok2->tokAt(3)) {
nullPointerError(tok2->tokAt(3), varname, tok, inconclusive);
break;
}
}
// Passing pointer as parameter..
if (Token::Match(tok2->next(), "%type% (")) {
bool unknown = false;
if (CanFunctionAssignPointer(tok2->next(), varid, unknown)) {
if (!_settings->inconclusive || !unknown)
break;
inconclusive = true;
}
}
// calling unknown function => it might initialize the pointer
if (!(var->isLocal() || var->isArgument()))
break;
}
if (tok1->str() == "break")
break;
if (tok1->varId() == varid) {
// Don't write warning if the dereferencing is
// guarded by ?: or &&
const Token *tok2 = tok1->previous();
if (tok2 && (tok2->isArithmeticalOp() || tok2->str() == "(")) {
while (tok2 && !Token::Match(tok2, "[;{}?:]")) {
if (tok2->str() == ")") {
tok2 = tok2->link();
if (Token::Match(tok2, "( %varid% =", varid)) {
tok2 = tok2->next();
break;
}
}
// guarded by &&
if (tok2->varId() == varid && tok2->next()->str() == "&&")
break;
tok2 = tok2->previous();
}
}
if (Token::Match(tok2, "[?:]") || tok2->varId() == varid)
continue;
// unknown : this is set by isPointerDeRef if it is
// uncertain
bool unknown = _settings->inconclusive;
// reassign : is the pointer reassigned like this:
// tok = tok->next();
bool reassign = false;
if (Token::Match(tok1->previous(), "= %varid% .", varid)) {
const Token *back = tok1->tokAt(-2);
while (back) {
if (back->varId() == varid) {
reassign = true;
break;
}
if (Token::Match(back, "[{};,(]")) {
break;
}
back = back->previous();
}
}
if (reassign) {
break;
} else if (Token::simpleMatch(tok1->tokAt(-2), "* )") &&
Token::Match(tok1->linkAt(-1)->tokAt(-2), "%varid% = (", tok1->varId())) {
break;
} else if (Token::simpleMatch(tok1->tokAt(-3), "* ) (") &&
Token::Match(tok1->linkAt(-2)->tokAt(-2), "%varid% = (", tok1->varId())) {
break;
} else if (Token::Match(tok1->previous(), "&&|%oror%")) {
break;
} else if (Token::Match(tok1->tokAt(-2), "&&|%oror% !")) {
break;
} else if (CheckNullPointer::isPointerDeRef(tok1, unknown, symbolDatabase)) {
nullPointerError(tok1, varname, tok, inconclusive);
break;
} else if (tok1->strAt(-1) == "&") {
break;
} else if (tok1->strAt(1) == "=") {
break;
}
}
else if (tok1->str() == "{" ||
tok1->str() == "}")
break;
// label..
else if (Token::Match(tok1, "%type% :"))
break;
}
}
}
}
void CheckNullPointer::nullPointerByCheckAndDeRef()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
// Check if pointer is NULL and then dereference it..
for (std::list<Scope>::const_iterator i = symbolDatabase->scopeList.begin(); i != symbolDatabase->scopeList.end(); ++i) {
if (i->type != Scope::eIf && i->type != Scope::eElseIf && i->type != Scope::eWhile)
continue;
if (!i->classDef || i->classDef->isExpandedMacro())
continue;
const Token* const tok = i->type != Scope::eElseIf ? i->classDef->next() : i->classDef->tokAt(2);
// TODO: investigate false negatives:
// - handle "while"?
// - if there are logical operators
// - if (x) { } else { ... }
// If the if-body ends with a unknown macro then bailout
if (Token::Match(i->classEnd->tokAt(-3), "[;{}] %var% ;") && i->classEnd->tokAt(-2)->isUpperCaseName())
continue;
// vartok : token for the variable
const Token *vartok = 0;
const Token *checkConditionStart = 0;
if (Token::Match(tok, "( ! %var% )|&&")) {
vartok = tok->tokAt(2);
checkConditionStart = vartok->next();
} else if (Token::Match(tok, "( %var% )|&&")) {
vartok = tok->next();
} else if (Token::Match(tok, "( ! ( %var% =")) {
vartok = tok->tokAt(3);
if (Token::simpleMatch(tok->tokAt(2)->link(), ") &&"))
checkConditionStart = tok->tokAt(2)->link();
} else
continue;
// variable id for pointer
const unsigned int varid(vartok->varId());
if (varid == 0)
continue;
// Check if variable is a pointer
const Variable* var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(varid);
if (!var || !var->isPointer())
continue;
const Scope* declScope = &*i;
while (declScope->nestedIn && var->scope() != declScope && declScope->type != Scope::eFunction)
declScope = declScope->nestedIn;
if (Token::Match(vartok->next(), "&& ( %varid% =", varid))
continue;
// Name and line of the pointer
const std::string &pointerName = vartok->str();
// Check the condition (eg. ( !x && x->i )
if (checkConditionStart) {
const Token * const conditionEnd = tok->link();
for (const Token *tok2 = checkConditionStart; tok2 != conditionEnd; tok2 = tok2->next()) {
// If we hit a || operator, abort
if (tok2->str() == "||")
break;
// Pointer is used
bool unknown = _settings->inconclusive;
if (tok2->varId() == varid && (isPointerDeRef(tok2, unknown, symbolDatabase) || unknown)) {
nullPointerError(tok2, pointerName, vartok, unknown);
break;
}
}
}
// start token = inside the if-body
const Token *tok1 = i->classStart;
if (Token::Match(tok, "( %var% )|&&")) {
// start token = first token after the if/while body
tok1 = i->classEnd->next();
if (!tok1)
continue;
}
int indentlevel = 0;
// Set to true if we would normally bail out the check.
bool inconclusive = false;
// Count { and } for tok2
for (const Token *tok2 = tok1; tok2 != declScope->classEnd; tok2 = tok2->next()) {
if (tok2->str() == "{")
++indentlevel;
else if (tok2->str() == "}") {
if (indentlevel == 0) {
if (_settings->inconclusive)
inconclusive = true;
else
break;
}
--indentlevel;
// calling exit function?
bool unknown = false;
if (_tokenizer->IsScopeNoReturn(tok2, &unknown)) {
if (_settings->inconclusive && unknown)
inconclusive = true;
else
break;
}
if (indentlevel <= 0) {
// skip all "else" blocks because they are not executed in this execution path
while (Token::simpleMatch(tok2, "} else if ("))
tok2 = tok2->linkAt(3)->linkAt(1);
if (Token::simpleMatch(tok2, "} else {"))
tok2 = tok2->linkAt(2);
}
}
if (tok2->str() == "return" || tok2->str() == "throw") {
bool unknown = _settings->inconclusive;
for (; tok2 && tok2->str() != ";"; tok2 = tok2->next()) {
if (tok2->varId() == varid) {
if (CheckNullPointer::isPointerDeRef(tok2, unknown, symbolDatabase))
nullPointerError(tok2, pointerName, vartok, inconclusive);
else if (unknown)
nullPointerError(tok2, pointerName, vartok, true);
}
}
break;
}
if (Token::Match(tok2, "goto|continue|break|switch|for"))
break;
// parameters to sizeof are not dereferenced
if (Token::Match(tok2, "decltype|sizeof")) {
if (tok2->strAt(1) != "(")
tok2 = tok2->next();
else
tok2 = tok2->next()->link();
continue;
}
// function call, check if pointer is dereferenced
if (Token::Match(tok2, "%var% (") && !Token::Match(tok2, "if|while")) {
std::list<const Token *> vars;
parseFunctionCall(*tok2, vars, 0);
for (std::list<const Token *>::const_iterator it = vars.begin(); it != vars.end(); ++it) {
if (Token::Match(*it, "%varid% [,)]", varid)) {
nullPointerError(*it, pointerName, vartok, inconclusive);
break;
}
}
}
// calling unknown function (abort/init)..
else if (Token::simpleMatch(tok2, ") ;") &&
(Token::Match(tok2->link()->tokAt(-2), "[;{}.] %var% (") ||
Token::Match(tok2->link()->tokAt(-5), "[;{}] ( * %var% ) ("))) {
// noreturn function?
bool unknown = false;
if (_tokenizer->IsScopeNoReturn(tok2->tokAt(2), &unknown)) {
if (!unknown || !_settings->inconclusive) {
break;
}
inconclusive = _settings->inconclusive;
}
// init function (global variables)
if (!var || !(var->isLocal() || var->isArgument()))
break;
}
if (tok2->varId() == varid) {
// unknown: this is set to true by isPointerDeRef if
// the function fails to determine if there
// is a dereference or not
bool unknown = _settings->inconclusive;
if (Token::Match(tok2->previous(), "[;{}=] %var% = 0 ;"))
;
else if (CheckNullPointer::isPointerDeRef(tok2, unknown, symbolDatabase))
nullPointerError(tok2, pointerName, vartok, inconclusive);
else if (unknown && _settings->inconclusive)
nullPointerError(tok2, pointerName, vartok, true);
else
break;
}
}
}
}
void CheckNullPointer::nullPointer()
{
nullPointerLinkedList();
nullPointerStructByDeRefAndChec();
nullPointerByDeRefAndChec();
nullPointerByCheckAndDeRef();
}
/** Dereferencing null constant (simplified token list) */
void CheckNullPointer::nullConstantDereference()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
for (std::list<Scope>::const_iterator i = symbolDatabase->scopeList.begin(); i != symbolDatabase->scopeList.end(); ++i) {
if (i->type != Scope::eFunction || !i->classStart)
continue;
const Token *tok = i->classStart;
if (i->function && (i->function->type == Function::eConstructor || i->function->type == Function::eCopyConstructor))
tok = i->function->token; // Check initialization list
for (; tok != i->classEnd; tok = tok->next()) {
if (Token::Match(tok, "sizeof|decltype|typeid ("))
tok = tok->next()->link();
else if (Token::simpleMatch(tok, "* 0")) {
if (Token::Match(tok->previous(), "return|throw|;|{|}|:|[|(|,") || tok->previous()->isOp() || tok->previous()->isAssignmentOp()) {
nullPointerError(tok);
}
}
else if (Token::Match(tok, "0 [") && (tok->previous()->str() != "&" || !Token::Match(tok->next()->link()->next(), "[.(]")))
nullPointerError(tok);
else if (Token::Match(tok->previous(), "!!. %var% (") && (tok->previous()->str() != "::" || tok->strAt(-2) == "std")) {
if (Token::simpleMatch(tok->tokAt(2), "0 )") && tok->varId()) { // constructor call
const Variable* var = symbolDatabase->getVariableFromVarId(tok->varId());
if (var && !var->isPointer() && !var->isArray() && Token::Match(var->typeStartToken(), "std :: string !!::"))
nullPointerError(tok);
} else { // function call
std::list<const Token *> var;
parseFunctionCall(*tok, var, 0);
// is one of the var items a NULL pointer?
for (std::list<const Token *>::const_iterator it = var.begin(); it != var.end(); ++it) {
if (Token::Match(*it, "0 [,)]")) {
nullPointerError(*it);
}
}
}
} else if (Token::simpleMatch(tok, "std :: string ( 0 )"))
nullPointerError(tok);
else if (Token::simpleMatch(tok->previous(), ">> 0")) { // Only checking input stream operations is safe here, because otherwise 0 can be an integer as well
const Token* tok2 = tok->previous(); // Find start of statement
for (; tok2; tok2 = tok2->previous()) {
if (Token::Match(tok2->previous(), ";|{|}|:"))
break;
}
if (Token::simpleMatch(tok2, "std :: cin"))
nullPointerError(tok);
if (tok2 && tok2->varId() != 0) {
const Variable* var = symbolDatabase->getVariableFromVarId(tok2->varId());
if (var && Token::Match(var->typeStartToken(), "std :: istream|ifstream|istringstream|stringstream|fstream|iostream"))
nullPointerError(tok);
}
}
unsigned int ovarid = 0;
if (Token::Match(tok, "0 ==|!= %var%"))
ovarid = tok->tokAt(2)->varId();
else if (Token::Match(tok, "%var% ==|!= 0"))
ovarid = tok->varId();
else if (Token::Match(tok, "%var% =|+=|+ 0 )|]|,|;|+"))
ovarid = tok->varId();
if (ovarid) {
const Variable* var = symbolDatabase->getVariableFromVarId(ovarid);
if (var && !var->isPointer() && !var->isArray() && Token::Match(var->typeStartToken(), "std :: string !!::"))
nullPointerError(tok);
}
}
}
}
/// @addtogroup Checks
/// @{
/**
* @brief %Check for null pointer usage (using ExecutionPath)
*/
class Nullpointer : public ExecutionPath {
public:
/** Startup constructor */
Nullpointer(Check *c, const SymbolDatabase* symbolDatabase_) : ExecutionPath(c, 0), symbolDatabase(symbolDatabase_), null(false) {
}
private:
const SymbolDatabase* symbolDatabase;
/** Create checking of specific variable: */
Nullpointer(Check *c, const unsigned int id, const std::string &name, const SymbolDatabase* symbolDatabase_)
: ExecutionPath(c, id),
symbolDatabase(symbolDatabase_),
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) {
if ((Token::Match(tok->tokAt(-4), "[=[(,] %var% && * %var% ,|]|)|;|=|%op%") ||
Token::Match(tok->tokAt(-5), "[=[(,] ! %var% %oror% * %var% ,|]|)|;|=|%op%") ||
Token::Match(tok->tokAt(-4), "return|case %var% && * %var% ,|:|;|=|%op%") ||
Token::Match(tok->tokAt(-5), "return|case ! %var% %oror% * %var% ,|:|;|=|%op%")) &&
tok->tokAt(-3) && (tok->tokAt(-3)->varId() == tok->varId()))
return;
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 (tok.varId() != 0) {
// Pointer declaration declaration?
const Variable* var = symbolDatabase->getVariableFromVarId(tok.varId());
if (var && var->isPointer() && var->nameToken() == &tok)
checks.push_back(new Nullpointer(owner, var->varId(), var->name(), symbolDatabase));
}
if (Token::simpleMatch(&tok, "try {")) {
// Bail out all used variables
const Token* tok2 = &tok;
const Token* endtok = tok.linkAt(1);
for (; tok2 && tok2 != endtok; tok2 = tok2->next()) {
if (tok2->varId())
bailOutVar(checks,tok2->varId());
}
return tok2;
}
if (Token::Match(&tok, "%var% (")) {
if (tok.str() == "sizeof" || tok.str() == "typeid")
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);
}
else if (Token::simpleMatch(&tok, "( 0 &&"))
return tok.link();
if (tok.varId() != 0) {
// unknown: if isPointerDeRef fails to determine if there
// is a dereference this will be set to true.
bool unknown = owner->inconclusiveFlag();
bool deref = CheckNullPointer::isPointerDeRef(&tok, unknown, symbolDatabase);
if (deref)
dereference(checks, &tok);
else if (unknown && owner->inconclusiveFlag())
dereference(checks, &tok);
if (Token::Match(tok.previous(), "[;{}=] %var% = 0 ;"))
setnull(checks, tok.varId());
else if (!deref &&
(!tok.previous()->isOp() || tok.previous()->str() == "&") && !tok.previous()->isAssignmentOp() &&
(!tok.next()->isOp() || tok.next()->str() == ">>"))
bailOutVar(checks, tok.varId()); // If its possible that the pointers value changes, bail out.
}
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();
}
else if (tok.str() == "return") {
bool unknown = owner->inconclusiveFlag();
const Token* tok2 = &tok;
for (; tok2 && tok2->str() != ";"; tok2 = tok2->next()) {
if (tok2->varId()) {
if (CheckNullPointer::isPointerDeRef(tok2, unknown, symbolDatabase) || unknown)
dereference(checks, tok2);
}
// If return statement contains "?" then assume there
// is no dangours dereferencing later
if (tok2->str() == "?") {
while (tok2 && tok2->str() != ";")
tok2 = tok2->next();
return tok2;
}
}
return tok2;
}
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() == ")" || tok2->str() == "&&" || tok2->str() == "||" || tok2->str() == "?")
break;
bool unknown = owner->inconclusiveFlag();
if (tok2->varId() && (CheckNullPointer::isPointerDeRef(tok2, unknown, symbolDatabase) || unknown))
dereference(checks, tok2);
}
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, _tokenizer->getSymbolDatabase());
checkExecutionPaths(_tokenizer->getSymbolDatabase(), &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 Token* nullCheck, bool inconclusive)
{
std::list<const Token*> callstack;
callstack.push_back(tok);
callstack.push_back(nullCheck);
const std::string errmsg("Possible null pointer dereference: " + varname + " - otherwise it is redundant to check it against null.");
reportError(callstack, Severity::error, "nullPointer", errmsg, inconclusive);
}
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