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cppcheck/lib/checknullpointer.cpp

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/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2013 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 "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 library --library files data
* @param value 0 => invalid with null pointers as parameter.
* 1-.. => only invalid with uninitialized data.
*/
void CheckNullPointer::parseFunctionCall(const Token &tok, std::list<const Token *> &var, const Library *library, unsigned char value)
{
// standard functions that dereference first parameter..
static std::set<std::string> functionNames1_all; // used no matter what 'value' is
static std::set<std::string> functionNames1_nullptr; // used only when 'value' is 0
static std::set<std::string> functionNames1_uninit; // used only when 'value' is non-zero
if (functionNames1_all.empty()) {
// cstdlib
functionNames1_all.insert("atoi");
functionNames1_all.insert("atof");
functionNames1_all.insert("atol");
functionNames1_all.insert("qsort");
functionNames1_all.insert("strtof");
functionNames1_all.insert("strtod");
functionNames1_all.insert("strtol");
functionNames1_all.insert("strtoul");
functionNames1_all.insert("strtold");
functionNames1_all.insert("strtoll");
functionNames1_all.insert("strtoull");
functionNames1_all.insert("wcstof");
functionNames1_all.insert("wcstod");
functionNames1_all.insert("wcstol");
functionNames1_all.insert("wcstoul");
functionNames1_all.insert("wcstold");
functionNames1_all.insert("wcstoll");
functionNames1_all.insert("wcstoull");
// cstring
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");
functionNames1_all.insert("wcscat");
functionNames1_all.insert("wcsncat");
functionNames1_all.insert("wcscoll");
functionNames1_all.insert("wcschr");
functionNames1_all.insert("wcsrchr");
functionNames1_all.insert("wcscmp");
functionNames1_all.insert("wcsncmp");
functionNames1_all.insert("wcscspn");
functionNames1_all.insert("wcsdup");
functionNames1_all.insert("wcsndup");
functionNames1_all.insert("wcspbrk");
functionNames1_all.insert("wcslen");
functionNames1_all.insert("wcsspn");
functionNames1_all.insert("wcsstr");
// 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("fputws");
functionNames1_all.insert("ferror");
functionNames1_all.insert("fgetc");
functionNames1_all.insert("fgetwc");
functionNames1_all.insert("fgetpos");
functionNames1_all.insert("fsetpos");
functionNames1_all.insert("fscanf");
functionNames1_all.insert("fprintf");
functionNames1_all.insert("fwscanf");
functionNames1_all.insert("fwprintf");
functionNames1_all.insert("fopen");
functionNames1_all.insert("rewind");
functionNames1_all.insert("printf");
functionNames1_all.insert("wprintf");
functionNames1_all.insert("scanf");
functionNames1_all.insert("wscanf");
functionNames1_all.insert("fscanf");
functionNames1_all.insert("sscanf");
functionNames1_all.insert("fwscanf");
functionNames1_all.insert("swscanf");
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("strcpy");
functionNames1_nullptr.insert("sprintf");
functionNames1_nullptr.insert("vsprintf");
functionNames1_nullptr.insert("vprintf");
functionNames1_nullptr.insert("fprintf");
functionNames1_nullptr.insert("vfprintf");
functionNames1_nullptr.insert("wcscpy");
functionNames1_nullptr.insert("swprintf");
functionNames1_nullptr.insert("vswprintf");
functionNames1_nullptr.insert("vwprintf");
functionNames1_nullptr.insert("fwprintf");
functionNames1_nullptr.insert("vfwprintf");
functionNames1_nullptr.insert("fread");
functionNames1_nullptr.insert("gets");
functionNames1_nullptr.insert("gmtime");
functionNames1_nullptr.insert("localtime");
functionNames1_nullptr.insert("strftime");
functionNames1_uninit.insert("itoa"); // value to convert
functionNames1_uninit.insert("perror");
functionNames1_uninit.insert("fflush");
functionNames1_uninit.insert("freopen");
}
// standard functions that dereference second parameter..
static std::set<std::string> functionNames2_all; // used no matter what 'value' is
static std::set<std::string> functionNames2_nullptr; // used only if 'value' is 0
if (functionNames2_all.empty()) {
functionNames2_all.insert("mbstowcs");
functionNames2_all.insert("wcstombs");
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("wcscat");
functionNames2_all.insert("wcsncat");
functionNames2_all.insert("wcscmp");
functionNames2_all.insert("wcsncmp");
functionNames2_all.insert("wcscoll");
functionNames2_all.insert("wcscpy");
functionNames2_all.insert("wcscspn");
functionNames2_all.insert("wcsncpy");
functionNames2_all.insert("wcspbrk");
functionNames2_all.insert("wcsspn");
functionNames2_all.insert("wcsstr");
functionNames2_all.insert("wcsxfrm");
functionNames2_all.insert("sprintf");
functionNames2_all.insert("fprintf");
functionNames2_all.insert("fscanf");
functionNames2_all.insert("sscanf");
functionNames2_all.insert("swprintf");
functionNames2_all.insert("fwprintf");
functionNames2_all.insert("fwscanf");
functionNames2_all.insert("swscanf");
functionNames2_all.insert("fputs");
functionNames2_all.insert("fputc");
functionNames2_all.insert("ungetc");
functionNames2_all.insert("fputws");
functionNames2_all.insert("fputwc");
functionNames2_all.insert("ungetwc");
functionNames2_all.insert("rename");
functionNames2_all.insert("putc");
functionNames2_all.insert("putwc");
functionNames2_all.insert("freopen");
functionNames2_nullptr.insert("itoa"); // destination buffer
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|NULL ,|)"))) {
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);
else if (value == 0 && library != NULL && library->isnullargbad(tok.str(),1))
var.push_back(firstParam);
else if (value == 1 && library != NULL && library->isuninitargbad(tok.str(),1))
var.push_back(firstParam);
}
// 2nd parameter..
if ((value == 0 && Token::Match(secondParam, "0|NULL ,|)")) || (secondParam && secondParam->varId() > 0 && Token::Match(secondParam->next(),"[,)]"))) {
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);
else if (value == 0 && library != NULL && library->isnullargbad(tok.str(),2))
var.push_back(secondParam);
else if (value == 1 && library != NULL && library->isuninitargbad(tok.str(),2))
var.push_back(secondParam);
}
if (Token::Match(&tok, "printf|sprintf|snprintf|fprintf|fnprintf|scanf|sscanf|fscanf|wprintf|swprintf|fwprintf|wscanf|swscanf|fwscanf")) {
const Token* argListTok = 0; // Points to first va_list argument
std::string formatString;
bool scan = Token::Match(&tok, "scanf|sscanf|fscanf|wscanf|swscanf|fwscanf");
if (Token::Match(&tok, "printf|scanf|wprintf|wscanf ( %str%")) {
formatString = firstParam->strValue();
argListTok = secondParam;
} else if (Token::Match(&tok, "sprintf|fprintf|sscanf|fscanf|fwprintf|fwscanf|swscanf")) {
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|swprintf") && 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 && Token::Match(argListTok,"%var% [,)]"))) {
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 bool inconclusive = unknown;
unknown = false;
const Token* prev = tok->previous();
while (prev->str() == "." || prev->str() == "::") { // Skip over previous member dereferences
prev = prev->previous();
while (prev->link() && (prev->str() == "]" || prev->str() == ">"))
prev = prev->link()->previous();
prev = prev->previous();
}
while (prev->str() == ")") // Skip over casts
prev = prev->link()->previous();
// Dereferencing pointer..
if (prev->str() == "*" && (Token::Match(prev->previous(), "return|throw|;|{|}|:|[|(|,") || prev->previous()->isOp()) && !Token::Match(prev->tokAt(-2), "sizeof|decltype|typeof"))
return true;
// read/write member variable
if (!Token::simpleMatch(prev->previous(), "& (") && !Token::Match(prev->previous(), "sizeof|decltype|typeof (") && prev->str() != "&" && Token::Match(tok->next(), ". %var%")) {
if (tok->strAt(3) != "(")
return true;
unknown = true;
return false;
}
if (Token::Match(tok, "%var% [") && (prev->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(prev->tokAt(-3), "std :: string|wstring (") && tok->strAt(1) == ")")
return true;
if (Token::Match(prev->previous(), "%var% (") && tok->strAt(1) == ")") {
const Variable* var = tok->tokAt(-2)->variable();
if (var && !var->isPointer() && !var->isArray() && Token::Match(var->typeStartToken(), "std :: string|wstring !!::"))
return true;
}
// streams dereference nullpointers
if (Token::Match(prev, "<<|>>")) {
const Variable* var = tok->variable();
if (var && var->isPointer() && Token::Match(var->typeStartToken(), "char|wchar_t")) { // Only outputting or reading to char* can cause problems
const Token* tok2 = prev; // 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 = tok2->variable();
if (var2 && Token::Match(var2->typeStartToken(), "std :: istream|ifstream|istringstream|wistringstream|ostream|ofstream|ostringstream|wostringstream|stringstream|wstringstream|fstream|iostream"))
return true;
}
}
}
const Variable *ovar = NULL;
if (Token::Match(tok, "%var% ==|!= %var%"))
ovar = tok->tokAt(2)->variable();
else if (Token::Match(prev->previous(), "%var% ==|!="))
ovar = tok->tokAt(-2)->variable();
else if (Token::Match(prev->previous(), "%var% =|+") && Token::Match(tok->next(), ")|]|,|;|+"))
ovar = tok->tokAt(-2)->variable();
if (ovar && !ovar->isPointer() && !ovar->isArray() && Token::Match(ovar->typeStartToken(), "std :: string|wstring !!::"))
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(prev, "delete") || Token::Match(prev->tokAt(-2), "delete [ ]"))
return false;
// OK to check if pointer is null
// OK to take address of pointer
if (Token::Match(prev, "!|&"))
return false;
// OK to check pointer in "= p ? : "
if (tok->next()->str() == "?" &&
(Token::Match(prev, "return|throw|;|{|}|:|[|(|,") || prev->isAssignmentOp()))
return false;
// OK to pass pointer to function
if (Token::Match(prev, "[(,]") && Token::Match(tok->next(), "[,)]") &&
(prev->str() != "(" ||
Token::Match(prev->previous(), "%var% (")))
return false;
// Compare pointer
if (Token::Match(prev, "(|&&|%oror%|==|!="))
return false;
if (Token::Match(tok, "%var% &&|%oror%|==|!=|)"))
return false;
// Taking address
if (Token::Match(prev, "return|=") && tok->strAt(1) == ";")
return false;
// (void)var
if (Token::Match(prev, "[{;}]") && tok->strAt(1) == ";")
return false;
// Shift pointer (e.g. to cout, but its no char* (see above))
if (Token::Match(prev, "<<|>>"))
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)
{
if (Token::Match(functiontoken, "if|while|for|switch|sizeof|catch"))
return false;
unsigned int argumentNumber = 0;
for (const Token *arg = functiontoken->tokAt(2); arg; arg = arg->nextArgument()) {
if (Token::Match(arg, "%varid% [,)]", varid)) {
const Function* func = functiontoken->function();
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%")) {
// Is this variable a pointer?
const Variable *var = tok2->variable();
if (!var || !var->isPointer())
continue;
// Variable id for dereferenced variable
const unsigned int varid(tok2->varId());
// We don't support variables without a varid
if (varid == 0)
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::nullPointerByDeRefAndChec()
{
for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
const Variable *var = tok->variable();
if (!var || !var->isPointer() || tok == var->nameToken())
continue;
// Can pointer be NULL?
const ValueFlow::Value *value = tok->getValue(0);
if (!value)
continue;
// Is pointer used as function parameter?
if (Token::Match(tok->previous(), "[(,] %var% [,)]")) {
const Token *ftok = tok->previous();
while (ftok && ftok->str() != "(") {
if (ftok->str() == ")")
ftok = ftok->link();
ftok = ftok->previous();
}
if (!ftok || !ftok->previous())
continue;
std::list<const Token *> varlist;
parseFunctionCall(*ftok->previous(), varlist, &_settings->library, 0);
if (std::find(varlist.begin(), varlist.end(), tok) != varlist.end()) {
if (value->condition == NULL)
nullPointerError(tok, tok->str());
else if (_settings->isEnabled("warning"))
nullPointerError(tok, tok->str(), value->condition, value->inconclusive);
}
continue;
}
// Pointer dereference.
bool unknown = false;
if (!isPointerDeRef(tok,unknown)) {
if (_settings->inconclusive && unknown) {
if (value->condition == NULL)
nullPointerError(tok, tok->str(), true);
else
nullPointerError(tok, tok->str(), value->condition, true);
}
continue;
}
if (value->condition == NULL)
nullPointerError(tok, tok->str(), value->inconclusive);
else if (_settings->isEnabled("warning"))
nullPointerError(tok, tok->str(), value->condition, value->inconclusive);
}
}
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->linkAt(2), ") &&"))
checkConditionStart = tok->linkAt(2);
} else
continue;
// Check if variable is a pointer
const Variable *var = vartok->variable();
if (!var || !var->isPointer())
continue;
// variable id for pointer
const unsigned int varid(vartok->varId());
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) || 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))
nullPointerError(tok2, pointerName, vartok, inconclusive);
else if (unknown)
nullPointerError(tok2, pointerName, vartok, true);
if (Token::Match(tok2, "%var% ?"))
break;
}
}
break;
}
// Bailout for "if".
if (tok2->str() == "if") {
if (_settings->inconclusive)
inconclusive = true;
else
break;
}
if (Token::Match(tok2, "goto|continue|break|switch|for"))
break;
// parameters to sizeof are not dereferenced
if (Token::Match(tok2, "decltype|sizeof|typeof")) {
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, &_settings->library, 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))
nullPointerError(tok2, pointerName, vartok, inconclusive);
else if (unknown && _settings->inconclusive)
nullPointerError(tok2, pointerName, vartok, true);
else
break;
}
}
}
}
void CheckNullPointer::nullPointer()
{
nullPointerLinkedList();
if (_settings->isEnabled("warning")) {
nullPointerByDeRefAndChec();
nullPointerByCheckAndDeRef();
nullPointerDefaultArgument();
}
}
/** Dereferencing null constant (simplified token list) */
void CheckNullPointer::nullConstantDereference()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
if (scope->function == 0 || !scope->function->hasBody) // We only look for functions with a body
continue;
const Token *tok = scope->classStart;
if (scope->function && scope->function->isConstructor())
tok = scope->function->token; // Check initialization list
for (; tok != scope->classEnd; tok = tok->next()) {
if (Token::Match(tok, "sizeof|decltype|typeid|typeof ("))
tok = tok->next()->link();
else if (Token::simpleMatch(tok, "* 0")) {
if (Token::Match(tok->previous(), "return|throw|;|{|}|:|[|(|,") || tok->previous()->isOp()) {
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 = tok->variable();
if (var && !var->isPointer() && !var->isArray() && Token::Match(var->typeStartToken(), "std :: string|wstring !!::"))
nullPointerError(tok);
} else { // function call
std::list<const Token *> var;
parseFunctionCall(*tok, var, &_settings->library, 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|NULL [,)]")) {
nullPointerError(*it);
}
}
}
} else if (Token::Match(tok, "std :: string|wstring ( 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 = tok2->variable();
if (var && Token::Match(var->typeStartToken(), "std :: istream|ifstream|istringstream|wistringstream|stringstream|wstringstream|fstream|iostream"))
nullPointerError(tok);
}
}
const Variable *ovar = 0;
if (Token::Match(tok, "0 ==|!= %var% !!."))
ovar = tok->tokAt(2)->variable();
else if (Token::Match(tok, "%var% ==|!= 0"))
ovar = tok->variable();
else if (Token::Match(tok, "%var% =|+ 0 )|]|,|;|+"))
ovar = tok->variable();
if (ovar && !ovar->isPointer() && !ovar->isArray() && Token::Match(ovar->typeStartToken(), "std :: string|wstring !!::"))
nullPointerError(tok);
}
}
}
/**
* @brief If tok is a function call that passes in a pointer such that
* the pointer may be modified, this function will remove that
* pointer from pointerArgs.
*/
void CheckNullPointer::removeAssignedVarFromSet(const Token* tok, std::set<unsigned int>& pointerArgs)
{
// If a pointer's address is passed into a function, stop considering it
if (Token::Match(tok->previous(), "[;{}] %var% (")) {
// Common functions that are known NOT to modify their pointer argument
const char safeFunctions[] = "printf|sprintf|fprintf|vprintf";
const Token* endParen = tok->next()->link();
for (const Token* tok2 = tok->next(); tok2 != endParen; tok2 = tok2->next()) {
if (tok2->isName() && tok2->varId() > 0 && !Token::Match(tok, safeFunctions)) {
pointerArgs.erase(tok2->varId());
}
}
}
}
/**
* @brief Does one part of the check for nullPointer().
* -# default argument that sets a pointer to 0
* -# dereference pointer
*/
void CheckNullPointer::nullPointerDefaultArgument()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
if (scope->function == 0 || !scope->function->hasBody) // We only look for functions with a body
continue;
// Scan the argument list for default arguments that are pointers and
// which default to a NULL pointer if no argument is specified.
std::set<unsigned int> pointerArgs;
for (const Token *tok = scope->function->arg; tok != scope->function->arg->link(); tok = tok->next()) {
if (Token::Match(tok, "%var% = 0 ,|)") && tok->varId() != 0) {
const Variable *var = tok->variable();
if (var && var->isPointer())
pointerArgs.insert(tok->varId());
}
}
// Report an error if any of the default-NULL arguments are dereferenced
if (!pointerArgs.empty()) {
for (const Token *tok = scope->classStart; tok != scope->classEnd; tok = tok->next()) {
// If we encounter a possible NULL-pointer check, skip over its body
if (Token::simpleMatch(tok, "if ( ")) {
bool dependsOnPointer = false;
const Token *endOfCondition = tok->next()->link();
if (!endOfCondition)
continue;
const Token *startOfIfBlock =
Token::simpleMatch(endOfCondition, ") {") ? endOfCondition->next() : NULL;
if (!startOfIfBlock)
continue;
// If this if() statement may return, it may be a null
// pointer check for the pointers referenced in its condition
const Token *endOfIf = startOfIfBlock->link();
bool isExitOrReturn =
Token::findmatch(startOfIfBlock, "exit|return|throw", endOfIf) != NULL;
if (Token::Match(tok, "if ( %var% == 0 )")) {
const unsigned int var = tok->tokAt(2)->varId();
if (var > 0 && pointerArgs.count(var) > 0) {
if (isExitOrReturn)
pointerArgs.erase(var);
else
dependsOnPointer = true;
}
} else {
for (const Token *tok2 = tok->next(); tok2 != endOfCondition; tok2 = tok2->next()) {
if (tok2->isName() && tok2->varId() > 0 &&
pointerArgs.count(tok2->varId()) > 0) {
// If the if() depends on a pointer and may return, stop
// considering that pointer because it may be a NULL-pointer
// check that returns if the pointer is NULL.
if (isExitOrReturn)
pointerArgs.erase(tok2->varId());
else
dependsOnPointer = true;
}
}
}
if (dependsOnPointer && endOfIf) {
for (; tok != endOfIf; tok = tok->next()) {
// If a pointer is assigned a new value, stop considering it.
if (Token::Match(tok, "%var% ="))
pointerArgs.erase(tok->varId());
else
removeAssignedVarFromSet(tok, pointerArgs);
}
continue;
}
}
// If there is a noreturn function (e.g. exit()), stop considering the rest of
// this function.
bool unknown = false;
if (Token::Match(tok, "return|throw|exit") ||
(_tokenizer->IsScopeNoReturn(tok, &unknown) && !unknown))
break;
removeAssignedVarFromSet(tok, pointerArgs);
if (tok->varId() == 0 || pointerArgs.count(tok->varId()) == 0)
continue;
// If a pointer is assigned a new value, stop considering it.
if (Token::Match(tok, "%var% ="))
pointerArgs.erase(tok->varId());
// If a pointer dereference is preceded by an && or ||,
// they serve as a sequence point so the dereference
// may not be executed.
if (isPointerDeRef(tok, unknown) && !unknown &&
tok->strAt(-1) != "&&" && tok->strAt(-1) != "||" &&
tok->strAt(-2) != "&&" && tok->strAt(-2) != "||")
nullPointerDefaultArgError(tok, tok->str());
}
}
}
}
/// @addtogroup Checks
/// @{
void CheckNullPointer::nullPointerError(const Token *tok)
{
reportError(tok, Severity::error, "nullPointer", "Null pointer dereference");
}
void CheckNullPointer::nullPointerError(const Token *tok, const std::string &varname, bool inconclusive)
{
reportError(tok, Severity::error, "nullPointer", "Possible null pointer dereference: " + varname, inconclusive);
}
void CheckNullPointer::nullPointerError(const Token *tok, const std::string &varname, const Token* nullCheck, bool inconclusive)
{
std::list<const Token*> callstack;
callstack.push_back(tok);
callstack.push_back(nullCheck);
const std::string errmsg("Possible null pointer dereference: " + varname + " - otherwise it is redundant to check it against null.");
reportError(callstack, Severity::warning, "nullPointer", errmsg, inconclusive);
}
void CheckNullPointer::nullPointerDefaultArgError(const Token *tok, const std::string &varname)
{
reportError(tok, Severity::warning, "nullPointer", "Possible null pointer dereference if the default parameter value is used: " + varname);
}
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