/* * Cppcheck - A tool for static C/C++ code analysis * Copyright (C) 2007-2010 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 "checkuninitvar.h" #include "mathlib.h" #include "executionpath.h" #include "checknullpointer.h" // CheckNullPointer::parseFunctionCall #include //--------------------------------------------------------------------------- // Register this check class (by creating a static instance of it) namespace { CheckUninitVar instance; } //--------------------------------------------------------------------------- /// @addtogroup Checks /// @{ /** * @brief %Check that uninitialized variables aren't used (using ExecutionPath) * */ class UninitVar : public ExecutionPath { public: /** Startup constructor */ UninitVar(Check *c) : ExecutionPath(c, 0), pointer(false), array(false), alloc(false), strncpy_(false) { } private: /** Create a copy of this check */ ExecutionPath *copy() { return new UninitVar(*this); } /** no implementation => compiler error if used */ void operator=(const UninitVar &); /** internal constructor for creating extra checks */ UninitVar(Check *c, unsigned int v, const std::string &name, bool p, bool a) : ExecutionPath(c, v), varname(name), pointer(p), array(a), alloc(false), strncpy_(false) { } /** is other execution path equal? */ bool is_equal(const ExecutionPath *e) const { const UninitVar *c = static_cast(e); return (varname == c->varname && pointer == c->pointer && array == c->array && alloc == c->alloc && strncpy_ == c->strncpy_); } /** variable name for this check */ const std::string varname; /** is this variable a pointer? */ const bool pointer; /** is this variable an array? */ const bool array; /** is this variable allocated? */ bool alloc; /** is this variable initialized with strncpy (not always zero-terminated) */ bool strncpy_; /** allocating pointer. For example : p = malloc(10); */ static void alloc_pointer(std::list &checks, unsigned int varid) { std::list::const_iterator it; for (it = checks.begin(); it != checks.end(); ++it) { UninitVar *c = dynamic_cast(*it); if (c && c->varId == varid) c->alloc = true; } } /** Initializing a pointer value. For example: *p = 0; */ static void init_pointer(std::list &checks, const Token *tok) { const unsigned int varid(tok->varId()); if (!varid) return; std::list::iterator it = checks.begin(); while (it != checks.end()) { UninitVar *c = dynamic_cast(*it); if (c && c->varId == varid) { if (c->alloc || c->array) { delete c; checks.erase(it++); continue; } else { use_pointer(checks, tok); } } ++it; } } /** Deallocate a pointer. For example: free(p); */ static void dealloc_pointer(std::list &checks, const Token *tok) { const unsigned int varid(tok->varId()); if (!varid) return; std::list::const_iterator it; for (it = checks.begin(); it != checks.end(); ++it) { UninitVar *c = dynamic_cast(*it); if (c && c->varId == varid) { if (c->pointer && !c->alloc) { CheckUninitVar *checkUninitVar = dynamic_cast(c->owner); if (checkUninitVar) { checkUninitVar->uninitvarError(tok, c->varname); break; } } c->alloc = false; } } } /** * Pointer assignment: p = x; * if p is a pointer and x is an array/pointer then bail out * \param checks all available checks * \param tok1 the "p" token * \param tok2 the "x" token */ static void pointer_assignment(std::list &checks, const Token *tok1, const Token *tok2) { const unsigned int varid1(tok1->varId()); if (varid1 == 0) return; const unsigned int varid2(tok2->varId()); if (varid2 == 0) return; std::list::const_iterator it; // bail out if first variable is a pointer for (it = checks.begin(); it != checks.end(); ++it) { UninitVar *c = dynamic_cast(*it); if (c && c->varId == varid1 && c->pointer) { bailOutVar(checks, varid1); break; } } // bail out if second variable is a array/pointer for (it = checks.begin(); it != checks.end(); ++it) { UninitVar *c = dynamic_cast(*it); if (c && c->varId == varid2 && (c->pointer || c->array)) { bailOutVar(checks, varid2); break; } } } /** Initialize an array with strncpy. */ static void init_strncpy(std::list &checks, const Token *tok) { const unsigned int varid(tok->varId()); if (!varid) return; std::list::const_iterator it; for (it = checks.begin(); it != checks.end(); ++it) { UninitVar *c = dynamic_cast(*it); if (c && c->varId == varid) { c->strncpy_ = true; } } } /** * use - called from the use* functions below. * @param checks all available checks * @param tok variable token * @param mode specific behaviour * @return if error is found, true is returned */ static bool use(std::list &checks, const Token *tok, const int mode) { const unsigned int varid(tok->varId()); if (varid == 0) return false; std::list::const_iterator it; for (it = checks.begin(); it != checks.end(); ++it) { UninitVar *c = dynamic_cast(*it); if (c && c->varId == varid) { // mode 0 : the variable is used "directly" // example: .. = var; // it is ok to read the address of an uninitialized array. // it is ok to read the address of an allocated pointer if (mode == 0 && (c->array || (c->pointer && c->alloc))) continue; // mode 2 : bad usage of pointer. if it's not a pointer then the usage is ok. // example: ptr->foo(); if (mode == 2 && !c->pointer) continue; // mode 3 : using dead pointer is invalid. if (mode == 3 && (!c->pointer || c->alloc)) continue; // mode 4 : reading uninitialized array or pointer is invalid. if (mode == 4 && (!c->array && !c->pointer)) continue; CheckUninitVar *checkUninitVar = dynamic_cast(c->owner); if (checkUninitVar) { if (c->strncpy_) checkUninitVar->uninitstringError(tok, c->varname); else if (c->pointer && c->alloc) checkUninitVar->uninitdataError(tok, c->varname); else checkUninitVar->uninitvarError(tok, c->varname); return true; } } } // No error found return false; } /** * Reading variable. Use this function in situations when it is * invalid to read the data of the variable but not the address. * @param checks all available checks * @param tok variable token * @return if error is found, true is returned */ static bool use(std::list &checks, const Token *tok) { return use(checks, tok, 0); } /** * Reading array elements. If the variable is not an array then the usage is ok. * @param checks all available checks * @param tok variable token */ static void use_array(std::list &checks, const Token *tok) { use(checks, tok, 1); } /** * Bad pointer usage. If the variable is not a pointer then the usage is ok. * @param checks all available checks * @param tok variable token * @return if error is found, true is returned */ static bool use_pointer(std::list &checks, const Token *tok) { return use(checks, tok, 2); } /** * Using variable.. if it's a dead pointer the usage is invalid. * @param checks all available checks * @param tok variable token * @return if error is found, true is returned */ static bool use_dead_pointer(std::list &checks, const Token *tok) { return use(checks, tok, 3); } /** * Using variable.. reading from uninitialized array or pointer data is invalid. * Example: = x[0]; * @param checks all available checks * @param tok variable token * @return if error is found, true is returned */ static bool use_array_or_pointer_data(std::list &checks, const Token *tok) { return use(checks, tok, 4); } /** declaring a variable */ void declare(std::list &checks, const Token *vartok, const Token &tok, const bool p, const bool a) const { if (vartok->varId() == 0) return; // Suppress warnings if variable in inner scope has same name as variable in outer scope if (!tok.isStandardType()) { std::set dup; for (std::list::const_iterator it = checks.begin(); it != checks.end(); ++it) { UninitVar *c = dynamic_cast(*it); if (c && c->varname == vartok->str() && c->varId != vartok->varId()) dup.insert(c->varId); } if (!dup.empty()) { for (std::set::const_iterator it = dup.begin(); it != dup.end(); ++it) bailOutVar(checks, *it); return; } } if (a || p || tok.isStandardType()) checks.push_back(new UninitVar(owner, vartok->varId(), vartok->str(), p, a)); } /** * Parse right hand side expression in statement * @param tok2 start token of rhs * @param checks the execution paths */ void parserhs(const Token *tok2, std::list &checks) const { // check variable usages in rhs/index while (NULL != (tok2 = tok2->next())) { if (Token::Match(tok2, "[;)=?]")) break; if (Token::Match(tok2, "%var% (")) break; if (tok2->varId() && !Token::Match(tok2->previous(), "&|::") && !Token::simpleMatch(tok2->next(), "=")) { // Multiple assignments.. if (Token::simpleMatch(tok2->next(), "[")) { const Token * tok3 = tok2; while (Token::simpleMatch(tok3->next(), "[")) tok3 = tok3->next()->link(); if (Token::simpleMatch(tok3, "] =")) continue; } bool foundError; if (tok2->previous()->str() == "*" || tok2->next()->str() == "[") foundError = use_array_or_pointer_data(checks, tok2); else foundError = use(checks, tok2); // prevent duplicate error messages if (foundError) { bailOutVar(checks, tok2->varId()); } } } } /** parse tokens. @sa ExecutionPath::parse */ const Token *parse(const Token &tok, std::list &checks) const { // Variable declaration.. if (Token::Match(tok.previous(), "[;{}] %var%") && tok.str() != "return") { if (Token::Match(&tok, "enum %type% {")) return tok.tokAt(2)->link(); const Token * vartok = &tok; while (Token::Match(vartok, "const|struct")) vartok = vartok->next(); if (Token::Match(vartok, "%type% *| %var% ;")) { vartok = vartok->next(); const bool p(vartok->str() == "*"); if (p) vartok = vartok->next(); declare(checks, vartok, tok, p, false); return vartok; } // Variable declaration for array.. if (Token::Match(vartok, "%type% %var% [") && Token::simpleMatch(vartok->tokAt(2)->link(), "] ;")) { vartok = vartok->next(); declare(checks, vartok, tok, false, true); return vartok->next()->link(); } // Template pointer variable.. if (Token::Match(vartok, "%type% ::|<")) { while (Token::Match(vartok, "%type% ::")) vartok = vartok->tokAt(2); if (Token::Match(vartok, "%type% < %type%")) { vartok = vartok->tokAt(3); while (vartok && (vartok->str() == "*" || vartok->isName())) vartok = vartok->next(); if (Token::Match(vartok, "> * %var% ;")) { declare(checks, vartok->tokAt(2), tok, true, false); return vartok->tokAt(2); } } } } if (tok.varId()) { // array variable passed as function parameter.. if (Token::Match(tok.previous(), "[(,] %var% [+-,)]")) { use(checks, &tok); use_array(checks, &tok); return &tok; } // Used.. if (Token::Match(tok.previous(), "[[(,+-*/] %var% []),;+-*/]")) { use(checks, &tok); return &tok; } if (Token::Match(tok.previous(), "++|--") || Token::Match(tok.next(), "++|--")) { use(checks, &tok); return &tok; } if (Token::Match(tok.previous(), "[;{}] %var% [=[.]")) { if (tok.next()->str() == ".") { if (use_dead_pointer(checks, &tok)) { return &tok; } } else { const Token *tok2 = tok.next(); if (tok2->str() == "[" && Token::simpleMatch(tok2->link(), "] =")) { parserhs(tok2, checks); tok2 = tok2->link()->next(); } parserhs(tok2, checks); } // pointer aliasing? if (Token::Match(tok.tokAt(2), "%var% ;")) { pointer_assignment(checks, &tok, tok.tokAt(2)); } } if (Token::simpleMatch(tok.next(), "(")) { use_pointer(checks, &tok); } if (Token::Match(tok.tokAt(-2), "[;{}] *")) { if (Token::simpleMatch(tok.next(), "=")) { // is the pointer used in the rhs? bool used = false; for (const Token *tok2 = tok.tokAt(2); tok2; tok2 = tok2->next()) { if (Token::Match(tok2, "[,;=(]")) break; else if (Token::Match(tok2, "* %varid%", tok.varId())) { used = true; break; } } if (used) use_pointer(checks, &tok); else init_pointer(checks, &tok); } else { use_pointer(checks, &tok); } return &tok; } // += etc if (Token::Match(tok.previous(), "[;{}]") || Token::Match(tok.tokAt(-2), "[;{}] *")) { // goto the equal.. const Token *eq = tok.next(); if (eq && eq->str() == "[" && eq->link() && eq->link()->next()) eq = eq->link()->next(); // is it X= if (Token::Match(eq, "+=|-=|*=|/=|&=|^=") || eq->str() == "|=") { if (tok.previous()->str() == "*") use_pointer(checks, &tok); else if (tok.next()->str() == "[") use_array(checks, &tok); else use(checks, &tok); } } if (Token::Match(tok.next(), "= malloc|kmalloc") || Token::simpleMatch(tok.next(), "= new char [")) { alloc_pointer(checks, tok.varId()); if (tok.tokAt(3)->str() == "(") return tok.tokAt(3); } else if (Token::simpleMatch(tok.previous(), ">>") || Token::simpleMatch(tok.next(), "=")) { ExecutionPath::bailOutVar(checks, tok.varId()); return &tok; } if (Token::simpleMatch(tok.next(), "[")) { const Token *tok2 = tok.next()->link(); if (Token::simpleMatch(tok2 ? tok2->next() : 0, "=")) { ExecutionPath::bailOutVar(checks, tok.varId()); return &tok; } } if (Token::simpleMatch(tok.previous(), "delete") || Token::simpleMatch(tok.tokAt(-3), "delete [ ]")) { dealloc_pointer(checks, &tok); return &tok; } } if (Token::Match(&tok, "%var% (") && uvarFunctions.find(tok.str()) == uvarFunctions.end()) { if (Token::simpleMatch(&tok, "sizeof (")) return tok.next()->link(); // deallocate pointer if (Token::Match(&tok, "free|kfree|fclose ( %var% )")) { dealloc_pointer(checks, tok.tokAt(2)); return tok.tokAt(3); } // parse usage.. { std::list var; CheckNullPointer::parseFunctionCall(tok, var, 1); for (std::list::const_iterator it = var.begin(); it != var.end(); ++it) use_array(checks, *it); // Using uninitialized pointer is bad if using null pointer is bad std::list var2; CheckNullPointer::parseFunctionCall(tok, var2, 0); for (std::list::const_iterator it = var2.begin(); it != var2.end(); ++it) { if (std::find(var.begin(), var.end(), *it) == var.end()) use_dead_pointer(checks, *it); } } // strncpy doesn't 0-terminate first parameter if (Token::Match(&tok, "strncpy ( %var% ,")) { if (Token::Match(tok.tokAt(4), "%str% ,")) { if (Token::Match(tok.tokAt(6), "%num% )")) { const unsigned int len = Token::getStrLength(tok.tokAt(4)); const long sz = MathLib::toLongNumber(tok.strAt(6)); if (sz >= 0 && len >= static_cast(sz)) { init_strncpy(checks, tok.tokAt(2)); return tok.next()->link(); } } } else { init_strncpy(checks, tok.tokAt(2)); return tok.next()->link(); } } if (Token::simpleMatch(&tok, "asm ( )")) { ExecutionPath::bailOut(checks); return &tok; } // is the variable passed as a parameter to some function? unsigned int parlevel = 0; std::set bailouts; for (const Token *tok2 = tok.next(); tok2; tok2 = tok2->next()) { if (tok2->str() == "(") ++parlevel; else if (tok2->str() == ")") { if (parlevel <= 1) break; --parlevel; } else if (Token::simpleMatch(tok2, "sizeof (")) { tok2 = tok2->next()->link(); if (!tok2) break; } else if (tok2->varId()) { if (Token::Match(tok2->tokAt(-2), "[(,] *") || Token::Match(tok2->next(), ". %var%")) { if (use_dead_pointer(checks, tok2)) ExecutionPath::bailOutVar(checks, tok2->varId()); } // it is possible that the variable is initialized here if (Token::Match(tok2->previous(), "[(,] %var% [,)]")) bailouts.insert(tok2->varId()); // array initialization.. if (Token::Match(tok2->previous(), "[,(] %var% [+-]")) { // if var is array, bailout for (std::list::const_iterator it = checks.begin(); it != checks.end(); ++it) { if ((*it)->varId == tok2->varId()) { const UninitVar *c = dynamic_cast(*it); if (c && (c->array || (c->pointer && c->alloc))) bailouts.insert(tok2->varId()); break; } } } } } for (std::set::const_iterator it = bailouts.begin(); it != bailouts.end(); ++it) ExecutionPath::bailOutVar(checks, *it); } // function call via function pointer if (Token::Match(&tok, "( * %var% ) (")) { // is the variable passed as a parameter to some function? unsigned int parlevel = 0; for (const Token *tok2 = tok.link()->next(); tok2; tok2 = tok2->next()) { if (tok2->str() == "(") ++parlevel; else if (tok2->str() == ")") { if (parlevel <= 1) break; --parlevel; } else if (tok2->varId()) { // it is possible that the variable is initialized here ExecutionPath::bailOutVar(checks, tok2->varId()); } } } if (tok.str() == "return") { // Todo: if (!array && .. if (Token::Match(tok.next(), "%var% ;")) { use(checks, tok.next()); } else if (Token::Match(tok.next(), "%var% [")) { use_array_or_pointer_data(checks, tok.next()); } } if (tok.varId()) { if (Token::simpleMatch(tok.previous(), "=")) { if (Token::Match(tok.tokAt(-3), "& %var% =")) { bailOutVar(checks, tok.varId()); return &tok; } if (!Token::Match(tok.tokAt(-3), ". %var% =")) { if (!Token::Match(tok.tokAt(-3), "[;{}] %var% =")) { use(checks, &tok); return &tok; } const unsigned int varid2 = tok.tokAt(-2)->varId(); if (varid2) { { use(checks, &tok); return &tok; } } } } if (Token::simpleMatch(tok.next(), ".")) { const Token *tok2 = tok.next(); while (Token::Match(tok2, ". %var%")) tok2 = tok2->tokAt(2); if (tok2 && tok2->str() != "=" && tok.strAt(-1) != "&") use_pointer(checks, &tok); else bailOutVar(checks, tok.varId()); return &tok; } if (Token::simpleMatch(tok.next(), "[")) { ExecutionPath::bailOutVar(checks, tok.varId()); return &tok; } if (Token::Match(tok.tokAt(-2), "[,(=] *")) { use_pointer(checks, &tok); return &tok; } if (Token::simpleMatch(tok.previous(), "&")) { ExecutionPath::bailOutVar(checks, tok.varId()); } } // Parse "for" if (Token::Match(&tok, "[;{}] for (")) { // initialized variables std::set varid1; varid1.insert(0); // Parse token const Token *tok2; // parse setup for (tok2 = tok.tokAt(3); tok2; tok2 = tok2->next()) { if (tok2->str() == ";") break; if (tok2->varId()) varid1.insert(tok2->varId()); } // parse condition if (Token::Match(tok2, "; %var% <|<=|>=|> %num% ;")) { // If the variable hasn't been initialized then call "use" if (varid1.find(tok2->next()->varId()) == varid1.end()) use(checks, tok2->next()); } // goto stepcode tok2 = tok2->next(); while (tok2 && tok2->str() != ";") tok2 = tok2->next(); // parse the stepcode if (Token::Match(tok2, "; ++|-- %var% ) {") || Token::Match(tok2, "; %var% ++|-- ) {")) { // get id of variable.. unsigned int varid = tok2->next()->varId(); if (!varid) varid = tok2->tokAt(2)->varId(); // Check that the variable hasn't been initialized and // that it isn't initialized in the body.. if (varid1.find(varid) == varid1.end()) { unsigned int indentlevel = 0; for (const Token *tok3 = tok2->tokAt(5); tok3; tok3 = tok3->next()) { if (tok3->str() == "{") ++indentlevel; else if (tok3->str() == "}") { if (indentlevel == 0) break; --indentlevel; } if (tok3->varId() == varid) { varid = 0; // variable is used.. maybe it's initialized. clear the variable id. break; } } // If the variable isn't initialized in the body call "use" if (varid != 0) { // goto variable tok2 = tok2->next(); if (!tok2->varId()) tok2 = tok2->next(); // call "use" use(checks, tok2); } } } } return &tok; } bool parseCondition(const Token &tok, std::list &checks) { if (tok.varId() && Token::Match(&tok, "%var% <|<=|==|!=|)")) use(checks, &tok); else if (Token::Match(&tok, "!| %var% [")) use_array_or_pointer_data(checks, tok.str() == "!" ? tok.next() : &tok); else if (Token::Match(&tok, "!| %var% (")) { std::list var; CheckNullPointer::parseFunctionCall(tok.str() == "!" ? *tok.next() : tok, var, 1); for (std::list::const_iterator it = var.begin(); it != var.end(); ++it) use_array(checks, *it); } else if (Token::Match(&tok, "! %var% )")) { use(checks, &tok); return false; } return ExecutionPath::parseCondition(tok, checks); } void parseLoopBody(const Token *tok, std::list &checks) const { while (tok) { if (tok->str() == "{" || tok->str() == "}" || tok->str() == "for") return; const Token *next = parse(*tok, checks); tok = next->next(); } } public: /** Functions that don't handle uninitialized variables well */ static std::set uvarFunctions; static void analyseFunctions(const Token * const tokens, std::set &func) { for (const Token *tok = tokens; tok; tok = tok->next()) { if (tok->str() == "{") { tok = tok->link(); continue; } if (tok->str() != "::" && Token::Match(tok->next(), "%var% ( %type%")) { if (!Token::Match(tok->tokAt(2)->link(), ") [{;]")) continue; const Token *tok2 = tok->tokAt(3); while (tok2 && tok2->str() != ")") { if (tok2->str() == ",") tok2 = tok2->next(); if (Token::Match(tok2, "%type% %var% ,|)") && tok2->isStandardType()) { tok2 = tok2->tokAt(2); continue; } if (tok2->isStandardType() && Token::Match(tok2, "%type% & %var% ,|)")) { const unsigned int varid(tok2->tokAt(2)->varId()); // flags for read/write bool r = false, w = false; // check how the variable is used in the function unsigned int indentlevel = 0; for (const Token *tok3 = tok2; tok3; tok3 = tok3->next()) { if (tok3->str() == "{") ++indentlevel; else if (tok3->str() == "}") { if (indentlevel <= 1) break; --indentlevel; } else if (indentlevel == 0 && tok3->str() == ";") break; else if (indentlevel >= 1 && tok3->varId() == varid) { if (Token::Match(tok3->previous(), "++|--") || Token::Match(tok3->next(), "++|--")) { r = true; } else { w = true; break; } } } if (!r || w) break; tok2 = tok2->tokAt(3); continue; } if (Token::Match(tok2, "const %type% &|*| const| %var% ,|)") && tok2->next()->isStandardType()) { tok2 = tok2->tokAt(3); while (tok2->isName()) tok2 = tok2->next(); continue; } if (Token::Match(tok2, "const %type% %var% [ ] ,|)") && tok2->next()->isStandardType()) { tok2 = tok2->tokAt(5); continue; } break; } // found simple function.. if (tok2->link() == tok->tokAt(2)) func.insert(tok->next()->str()); } } } }; /** Functions that don't handle uninitialized variables well */ std::set UninitVar::uvarFunctions; /// @} void CheckUninitVar::analyse(const Token * const tokens, std::set &func) const { UninitVar::analyseFunctions(tokens, func); } void CheckUninitVar::saveAnalysisData(const std::set &data) const { UninitVar::uvarFunctions.insert(data.begin(), data.end()); } void CheckUninitVar::executionPaths() { // check if variable is accessed uninitialized.. { // no writing if multiple threads are used (TODO: thread safe analysis?) if (_settings->_jobs == 1) UninitVar::analyseFunctions(_tokenizer->tokens(), UninitVar::uvarFunctions); UninitVar c(this); checkExecutionPaths(_tokenizer->tokens(), &c); } } void CheckUninitVar::uninitstringError(const Token *tok, const std::string &varname) { reportError(tok, Severity::error, "uninitstring", "Dangerous usage of '" + varname + "' (strncpy doesn't always 0-terminate it)"); } void CheckUninitVar::uninitdataError(const Token *tok, const std::string &varname) { reportError(tok, Severity::error, "uninitdata", "Data is allocated but not initialized: " + varname); } void CheckUninitVar::uninitvarError(const Token *tok, const std::string &varname) { reportError(tok, Severity::error, "uninitvar", "Uninitialized variable: " + varname); }