/* * 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 . */ //--------------------------------------------------------------------------- #include "checknullpointer.h" #include "executionpath.h" #include "mathlib.h" #include "symboldatabase.h" #include //--------------------------------------------------------------------------- // 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 &var, unsigned char value) { // standard functions that dereference first parameter.. static std::set functionNames1_all; static std::set functionNames1_nullptr; static std::set 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("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("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"); 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("freopen"); 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("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("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("perror"); functionNames1_uninit.insert("fflush"); } // standard functions that dereference second parameter.. static std::set functionNames2_all; static std::set 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("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("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") || (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|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)) { 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")) return true; // read/write member variable if (!Token::simpleMatch(prev->previous(), "& (") && !Token::Match(prev->previous(), "sizeof|decltype (") && 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::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()); if (Token::Match(tok2->tokAt(-2), "%varid% ?", varid)) continue; // Check usage of dereferenced variable in the loop.. for (std::list::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.. const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase(); // skipvar: don't check vars that has been tested against null already std::set skipvar; skipvar.insert(0); 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; for (const Token *tok1 = scope->classStart; tok1 != scope->classEnd; 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 = tok1->variable(); 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::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(); const Variable *var = vartok->variable(); // Check that variable is a pointer.. if (!var || !var->isPointer()) continue; // Variable id for pointer const unsigned int varid(vartok->varId()); // Name of pointer const std::string& varname(vartok->str()); 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 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 (!tok2 || 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(); } } else if (Token::Match(tok1->tokAt(-4), "%varid% = ( * %varid%", varid)) { reassign = true; } else if (Token::Match(tok1->tokAt(-3), "%varid% = * %varid%", varid)) { reassign = true; } 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)) { 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::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")) { 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 vars; parseFunctionCall(*tok2, vars, 0); for (std::list::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")) { nullPointerStructByDeRefAndChec(); 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->type == Function::eConstructor || scope->function->type == Function::eCopyConstructor)) tok = scope->function->token; // Check initialization list for (; tok != scope->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()) { 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 var; parseFunctionCall(*tok, var, 0); // is one of the var items a NULL pointer? for (std::list::const_iterator it = var.begin(); it != var.end(); ++it) { if (Token::Match(*it, "0 [,)]")) { 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 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 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()) { bool unknown = _settings->inconclusive; 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", endOfIf) != NULL; 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()); } continue; } } 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) && tok->strAt(-1) != "&&" && tok->strAt(-1) != "||" && tok->strAt(-2) != "&&" && tok->strAt(-2) != "||") nullPointerDefaultArgError(tok, tok->str()); } } } } /// @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(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 &checks, const unsigned int varid) { std::list::iterator it; for (it = checks.begin(); it != checks.end(); ++it) { Nullpointer *c = dynamic_cast(*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 &checks, const Token *tok) { const unsigned int varid(tok->varId()); std::list::iterator it; for (it = checks.begin(); it != checks.end(); ++it) { Nullpointer *c = dynamic_cast(*it); if (c && c->varId == varid && c->null) { for (const Token *tok2 = tok; tok2 && tok2->str() != ";"; tok2 = tok2->previous()) { // Checking that pointer is not NULL if (Token::Match(tok2, "return|=|[|(|,|&& %varid% )| &&", varid)) return; if (Token::Match(tok2, "return|=|[|(|,|%oror% ! %varid% )| %oror%", varid)) return; } CheckNullPointer *checkNullPointer = dynamic_cast(c->owner); if (checkNullPointer) { checkNullPointer->nullPointerError(tok, c->varname); return; } } } } /** parse tokens */ const Token *parse(const Token &tok, std::list &checks) const { if (tok.varId() != 0) { // Pointer declaration declaration? const Variable *var = tok.variable(); 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 var; CheckNullPointer::parseFunctionCall(tok, var, 0); for (std::list::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); 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.next()->isConstOp() || 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) || 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 &tok; } /** parse condition. @sa ExecutionPath::parseCondition */ bool parseCondition(const Token &tok, std::list &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) || unknown)) dereference(checks, tok2); } if (Token::Match(&tok, "!| %var% (")) { std::list var; CheckNullPointer::parseFunctionCall(tok.str() == "!" ? *tok.next() : tok, var, 0); for (std::list::const_iterator it = var.begin(); it != var.end(); ++it) dereference(checks, *it); } return ExecutionPath::parseCondition(tok, checks); } void parseLoopBody(const Token *tok, std::list &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 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); }