548 lines
21 KiB
C++
548 lines
21 KiB
C++
/*
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* Cppcheck - A tool for static C/C++ code analysis
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* Copyright (C) 2007-2016 Cppcheck team.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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//---------------------------------------------------------------------------
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// Auto variables checks
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//---------------------------------------------------------------------------
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#include "checkautovariables.h"
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#include "symboldatabase.h"
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#include <string>
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//---------------------------------------------------------------------------
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// Register this check class into cppcheck by creating a static instance of it..
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namespace {
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static CheckAutoVariables instance;
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}
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static const CWE CWE398(398U); // Indicator of Poor Code Quality
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static const CWE CWE562(562U); // Return of Stack Variable Address
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static const CWE CWE590(590U); // Free of Memory not on the Heap
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bool CheckAutoVariables::isPtrArg(const Token *tok)
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{
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const Variable *var = tok->variable();
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return (var && var->isArgument() && var->isPointer());
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}
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bool CheckAutoVariables::isArrayArg(const Token *tok)
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{
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const Variable *var = tok->variable();
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return (var && var->isArgument() && var->isArray());
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}
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bool CheckAutoVariables::isRefPtrArg(const Token *tok)
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{
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const Variable *var = tok->variable();
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return (var && var->isArgument() && var->isReference() && var->isPointer());
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}
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bool CheckAutoVariables::isNonReferenceArg(const Token *tok)
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{
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const Variable *var = tok->variable();
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return (var && var->isArgument() && !var->isReference() && (var->isPointer() || var->typeStartToken()->isStandardType() || var->type()));
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}
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bool CheckAutoVariables::isAutoVar(const Token *tok)
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{
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const Variable *var = tok->variable();
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if (!var || !var->isLocal() || var->isStatic())
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return false;
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if (var->isReference()) {
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// address of reference variable can be taken if the address
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// of the variable it points at is not a auto-var
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// TODO: check what the reference variable references.
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return false;
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}
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if (Token::Match(tok, "%name% .|::")) {
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do {
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tok = tok->tokAt(2);
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} while (Token::Match(tok, "%name% .|::"));
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if (Token::Match(tok, "%name% ("))
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return false;
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}
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return true;
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}
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bool CheckAutoVariables::isAutoVarArray(const Token *tok)
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{
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if (!tok)
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return false;
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// &x[..]
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if (tok->str() == "&" && Token::simpleMatch(tok->astOperand1(), "[") && !tok->astOperand2())
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return isAutoVarArray(tok->astOperand1()->astOperand1());
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// x+y
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if (tok->str() == "+")
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return isAutoVarArray(tok->astOperand1()) || isAutoVarArray(tok->astOperand2());
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// x-intexpr
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if (tok->str() == "-")
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return isAutoVarArray(tok->astOperand1()) &&
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tok->astOperand2() &&
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tok->astOperand2()->valueType() &&
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tok->astOperand2()->valueType()->isIntegral();
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const Variable *var = tok->variable();
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if (!var)
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return false;
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// Variable
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if (var->isLocal() && !var->isStatic() && var->isArray() && !var->isPointer())
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return true;
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// ValueFlow
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if (var->isPointer() && !var->isArgument()) {
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for (std::list<ValueFlow::Value>::const_iterator it = tok->values.begin(); it != tok->values.end(); ++it) {
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const ValueFlow::Value &val = *it;
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if (val.isTokValue() && isAutoVarArray(val.tokvalue))
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return true;
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}
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}
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return false;
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}
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// Verification that we really take the address of a local variable
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static bool checkRvalueExpression(const Token * const vartok)
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{
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const Variable * const var = vartok->variable();
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if (var == nullptr)
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return false;
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if (Token::Match(vartok->previous(), "& %name% [") && var->isPointer())
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return false;
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const Token * const next = vartok->next();
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// &a.b[0]
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if (Token::Match(vartok, "%name% . %var% [") && !var->isPointer()) {
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const Variable *var2 = next->next()->variable();
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return var2 && !var2->isPointer();
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}
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return ((next->str() != "." || (!var->isPointer() && (!var->isClass() || var->type()))) && next->strAt(2) != ".");
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}
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static bool variableIsUsedInScope(const Token* start, unsigned int varId, const Scope *scope)
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{
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if (!start) // Ticket #5024
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return false;
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for (const Token *tok = start; tok && tok != scope->classEnd; tok = tok->next()) {
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if (tok->varId() == varId)
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return true;
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const Scope::ScopeType scopeType = tok->scope()->type;
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if (scopeType == Scope::eFor || scopeType == Scope::eDo || scopeType == Scope::eWhile) // In case of loops, better checking would be necessary
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return true;
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if (Token::simpleMatch(tok, "asm ("))
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return true;
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}
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return false;
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}
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void CheckAutoVariables::assignFunctionArg()
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{
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const bool printStyle = _settings->isEnabled("style");
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const bool printWarning = _settings->isEnabled("warning");
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if (!printStyle && !printWarning)
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return;
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const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
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const std::size_t functions = symbolDatabase->functionScopes.size();
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for (std::size_t i = 0; i < functions; ++i) {
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const Scope * scope = symbolDatabase->functionScopes[i];
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for (const Token *tok = scope->classStart; tok && tok != scope->classEnd; tok = tok->next()) {
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// TODO: What happens if this is removed?
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if (tok->astParent())
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continue;
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if (!Token::Match(tok, "=|++|--") || !Token::Match(tok->astOperand1(), "%var%"))
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continue;
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const Token* const vartok = tok->astOperand1();
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if (isNonReferenceArg(vartok) &&
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!Token::Match(vartok->next(), "= %varid% ;", vartok->varId()) &&
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!variableIsUsedInScope(Token::findsimplematch(vartok->next(), ";"), vartok->varId(), scope) &&
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!Token::findsimplematch(vartok, "goto", scope->classEnd)) {
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if (vartok->variable()->isPointer() && printWarning)
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errorUselessAssignmentPtrArg(vartok);
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else if (printStyle)
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errorUselessAssignmentArg(vartok);
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}
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}
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}
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}
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void CheckAutoVariables::autoVariables()
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{
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const bool printInconclusive = _settings->inconclusive;
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const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
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const std::size_t functions = symbolDatabase->functionScopes.size();
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for (std::size_t i = 0; i < functions; ++i) {
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const Scope * scope = symbolDatabase->functionScopes[i];
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for (const Token *tok = scope->classStart; tok && tok != scope->classEnd; tok = tok->next()) {
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// Critical assignment
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if (Token::Match(tok, "[;{}] %var% = & %var%") && isRefPtrArg(tok->next()) && isAutoVar(tok->tokAt(4))) {
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if (checkRvalueExpression(tok->tokAt(4)))
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errorAutoVariableAssignment(tok->next(), false);
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} else if (Token::Match(tok, "[;{}] * %var% = & %var%") && isPtrArg(tok->tokAt(2)) && isAutoVar(tok->tokAt(5))) {
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if (checkRvalueExpression(tok->tokAt(5)))
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errorAutoVariableAssignment(tok->next(), false);
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} else if (Token::Match(tok, "[;{}] %var% . %var% = & %var%")) {
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// TODO: check if the parameter is only changed temporarily (#2969)
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if (printInconclusive && isPtrArg(tok->next())) {
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const Token * const var2tok = tok->tokAt(6);
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if (isAutoVar(var2tok) && checkRvalueExpression(var2tok))
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errorAutoVariableAssignment(tok->next(), true);
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}
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tok = tok->tokAt(6);
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} else if (Token::Match(tok, "[;{}] %var% . %var% = %var% ;")) {
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// TODO: check if the parameter is only changed temporarily (#2969)
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if (printInconclusive && isPtrArg(tok->next())) {
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if (isAutoVarArray(tok->tokAt(5)))
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errorAutoVariableAssignment(tok->next(), true);
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}
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tok = tok->tokAt(5);
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} else if (Token::Match(tok, "[;{}] * %var% = %var% ;")) {
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const Variable * var1 = tok->tokAt(2)->variable();
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if (var1 && var1->isArgument() && Token::Match(var1->nameToken()->tokAt(-3), "%type% * *")) {
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if (isAutoVarArray(tok->tokAt(4)))
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errorAutoVariableAssignment(tok->next(), false);
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}
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tok = tok->tokAt(4);
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} else if (Token::Match(tok, "[;{}] %var% [") && Token::Match(tok->linkAt(2), "] = & %var%") &&
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(isPtrArg(tok->next()) || isArrayArg(tok->next())) && isAutoVar(tok->linkAt(2)->tokAt(3))) {
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const Token* const varTok = tok->linkAt(2)->tokAt(3);
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if (checkRvalueExpression(varTok))
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errorAutoVariableAssignment(tok->next(), false);
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}
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// Critical return
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else if (Token::Match(tok, "return & %var% ;")) {
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const Token* varTok = tok->tokAt(2);
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if (isAutoVar(varTok))
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errorReturnAddressToAutoVariable(tok);
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else if (varTok->varId()) {
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const Variable * var1 = varTok->variable();
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if (var1 && var1->isArgument() && var1->typeEndToken()->str() != "&")
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errorReturnAddressOfFunctionParameter(tok, varTok->str());
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}
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}
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// Invalid pointer deallocation
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else if ((Token::Match(tok, "%name% ( %var% ) ;") && _settings->library.dealloc(tok)) ||
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(_tokenizer->isCPP() && Token::Match(tok, "delete [| ]| (| %var% !!["))) {
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tok = Token::findmatch(tok->next(), "%var%");
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if (isAutoVarArray(tok))
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errorInvalidDeallocation(tok);
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} else if ((Token::Match(tok, "%name% ( & %var% ) ;") && _settings->library.dealloc(tok)) ||
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(_tokenizer->isCPP() && Token::Match(tok, "delete [| ]| (| & %var% !!["))) {
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tok = Token::findmatch(tok->next(), "%var%");
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if (isAutoVar(tok))
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errorInvalidDeallocation(tok);
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}
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}
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}
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}
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//---------------------------------------------------------------------------
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void CheckAutoVariables::returnPointerToLocalArray()
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{
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const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
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const std::size_t functions = symbolDatabase->functionScopes.size();
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for (std::size_t i = 0; i < functions; ++i) {
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const Scope * scope = symbolDatabase->functionScopes[i];
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if (!scope->function)
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continue;
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const Token *tok = scope->function->tokenDef;
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// have we reached a function that returns a pointer
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if (tok->previous() && tok->previous()->str() == "*") {
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for (const Token *tok2 = scope->classStart->next(); tok2 && tok2 != scope->classEnd; tok2 = tok2->next()) {
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// Return pointer to local array variable..
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if (tok2 ->str() == "return" && isAutoVarArray(tok2->astOperand1())) {
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errorReturnPointerToLocalArray(tok2);
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}
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}
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}
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}
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}
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void CheckAutoVariables::errorReturnAddressToAutoVariable(const Token *tok)
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{
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reportError(tok, Severity::error, "returnAddressOfAutoVariable", "Address of an auto-variable returned.", CWE562, false);
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}
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void CheckAutoVariables::errorReturnPointerToLocalArray(const Token *tok)
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{
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reportError(tok, Severity::error, "returnLocalVariable", "Pointer to local array variable returned.", CWE562, false);
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}
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void CheckAutoVariables::errorAutoVariableAssignment(const Token *tok, bool inconclusive)
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{
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if (!inconclusive) {
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reportError(tok, Severity::error, "autoVariables",
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"Address of local auto-variable assigned to a function parameter.\n"
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"Dangerous assignment - the function parameter is assigned the address of a local "
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"auto-variable. Local auto-variables are reserved from the stack which "
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"is freed when the function ends. So the pointer to a local variable "
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"is invalid after the function ends.", CWE562, false);
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} else {
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reportError(tok, Severity::error, "autoVariables",
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"Address of local auto-variable assigned to a function parameter.\n"
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"Function parameter is assigned the address of a local auto-variable. "
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"Local auto-variables are reserved from the stack which is freed when "
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"the function ends. The address is invalid after the function ends and it "
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"might 'leak' from the function through the parameter.",
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CWE562,
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true);
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}
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}
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void CheckAutoVariables::errorReturnAddressOfFunctionParameter(const Token *tok, const std::string &varname)
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{
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reportError(tok, Severity::error, "returnAddressOfFunctionParameter",
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"Address of function parameter '" + varname + "' returned.\n"
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"Address of the function parameter '" + varname + "' becomes invalid after the function exits because "
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"function parameters are stored on the stack which is freed when the function exits. Thus the returned "
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"value is invalid.", CWE562, false);
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}
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void CheckAutoVariables::errorUselessAssignmentArg(const Token *tok)
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{
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reportError(tok,
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Severity::style,
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"uselessAssignmentArg",
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"Assignment of function parameter has no effect outside the function.", CWE398, false);
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}
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void CheckAutoVariables::errorUselessAssignmentPtrArg(const Token *tok)
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{
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reportError(tok,
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Severity::warning,
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"uselessAssignmentPtrArg",
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"Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?", CWE398, false);
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}
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//---------------------------------------------------------------------------
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// return temporary?
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bool CheckAutoVariables::returnTemporary(const Token *tok)
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{
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bool func = false; // Might it be a function call?
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bool retref = false; // is there such a function that returns a reference?
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bool retvalue = false; // is there such a function that returns a value?
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const Function *function = tok->function();
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if (function) {
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// Ticket #5478: Only functions or operator equal might return a temporary
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if (function->type != Function::eOperatorEqual && function->type != Function::eFunction)
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return false;
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retref = function->tokenDef->strAt(-1) == "&";
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if (!retref) {
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const Token *start = function->retDef;
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if (start->str() == "const")
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start = start->next();
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if (start->str() == "::")
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start = start->next();
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if (Token::simpleMatch(start, "std ::")) {
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if (start->strAt(3) != "<" || !Token::simpleMatch(start->linkAt(3), "> ::"))
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retvalue = true;
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else
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retref = true; // Assume that a reference is returned
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} else {
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if (start->type())
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retvalue = true;
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else
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retref = true;
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}
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}
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func = true;
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}
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if (!func && tok->type())
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return true;
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return bool(!retref && retvalue);
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}
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//---------------------------------------------------------------------------
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static bool astHasAutoResult(const Token *tok)
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{
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if (tok->astOperand1() && !astHasAutoResult(tok->astOperand1()))
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return false;
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if (tok->astOperand2() && !astHasAutoResult(tok->astOperand2()))
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return false;
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if (tok->isOp()) {
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if (tok->tokType() == Token::eIncDecOp)
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return false;
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if ((tok->str() == "<<" || tok->str() == ">>") && tok->astOperand1()) {
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const Token* tok2 = tok->astOperand1();
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while (tok2 && tok2->str() == "*" && !tok2->astOperand2())
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tok2 = tok2->astOperand1();
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return tok2 && tok2->variable() && !tok2->variable()->isClass() && !tok2->variable()->isStlType(); // Class or unknown type on LHS: Assume it is a stream
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}
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return true;
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}
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if (tok->isLiteral())
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return true;
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if (tok->isName()) {
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// TODO: check function calls, struct members, arrays, etc also
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if (!tok->variable())
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return false;
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if (tok->variable()->isStlType())
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return true;
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if (tok->variable()->isClass() || tok->variable()->isPointer() || tok->variable()->isReference()) // TODO: Properly handle pointers/references to classes in symbol database
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return false;
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return true;
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}
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return false;
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}
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/*!
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* Skip over a lambda expression
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* \return next token - or next token beyond lambda
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* \todo handle explicit return type
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*/
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static const Token* skipLambda(const Token* first)
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{
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if (!first)
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return nullptr;
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if (first->str() != "[")
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return first;
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const Token* tok = first->link()->next();
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if (!tok)
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return nullptr;
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if (tok->str() == "(") {
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tok = tok->link()->next();
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}
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if (tok->str() == "constexpr")
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tok = tok->next();
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if (tok->str() == "mutable")
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tok = tok->next();
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if (tok->str() == "{") {
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tok = tok->link()->next();
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}
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return tok;
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}
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void CheckAutoVariables::returnReference()
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{
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if (_tokenizer->isC())
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return;
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const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
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const std::size_t functions = symbolDatabase->functionScopes.size();
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for (std::size_t i = 0; i < functions; ++i) {
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const Scope * scope = symbolDatabase->functionScopes[i];
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if (!scope->function)
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continue;
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const Token *tok = scope->function->tokenDef;
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// have we reached a function that returns a reference?
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if (tok->previous() && tok->previous()->str() == "&") {
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for (const Token *tok2 = scope->classStart->next(); tok2 && tok2 != scope->classEnd; tok2 = tok2->next()) {
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if (!tok2->scope()->isExecutable()) {
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tok2 = tok2->scope()->classEnd;
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continue;
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}
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// Skip over lambdas
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tok2 = skipLambda(tok2);
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if (!tok2 || tok2->str() != "return")
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|
continue;
|
|
|
|
// return..
|
|
if (Token::Match(tok2, "return %var% ;")) {
|
|
// is the returned variable a local variable?
|
|
if (isAutoVar(tok2->next())) {
|
|
const Variable *var1 = tok2->next()->variable();
|
|
// If reference variable is used, check what it references
|
|
if (Token::Match(var1->nameToken(), "%var% [=(]")) {
|
|
const Token *tok3 = var1->nameToken()->tokAt(2);
|
|
if (!Token::Match(tok3, "%var% [);.]"))
|
|
continue;
|
|
|
|
// Only report error if variable that is referenced is
|
|
// a auto variable
|
|
if (!isAutoVar(tok3))
|
|
continue;
|
|
}
|
|
|
|
// report error..
|
|
errorReturnReference(tok2);
|
|
}
|
|
}
|
|
|
|
// return reference to temporary..
|
|
else if (Token::Match(tok2, "return %name% (") &&
|
|
Token::simpleMatch(tok2->linkAt(2), ") ;")) {
|
|
if (returnTemporary(tok2->next())) {
|
|
// report error..
|
|
errorReturnTempReference(tok2);
|
|
}
|
|
}
|
|
|
|
// Return reference to a literal or the result of a calculation
|
|
else if (tok2->astOperand1() && (tok2->astOperand1()->isCalculation() || tok2->next()->isLiteral()) && astHasAutoResult(tok2->astOperand1())) {
|
|
errorReturnTempReference(tok2);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void CheckAutoVariables::errorReturnReference(const Token *tok)
|
|
{
|
|
reportError(tok, Severity::error, "returnReference", "Reference to auto variable returned.", CWE562, false);
|
|
}
|
|
|
|
void CheckAutoVariables::errorReturnTempReference(const Token *tok)
|
|
{
|
|
reportError(tok, Severity::error, "returnTempReference", "Reference to temporary returned.", CWE562, false);
|
|
}
|
|
|
|
void CheckAutoVariables::errorInvalidDeallocation(const Token *tok)
|
|
{
|
|
reportError(tok,
|
|
Severity::error,
|
|
"autovarInvalidDeallocation",
|
|
"Deallocation of an auto-variable results in undefined behaviour.\n"
|
|
"The deallocation of an auto-variable results in undefined behaviour. You should only free memory "
|
|
"that has been allocated dynamically.", CWE590, false);
|
|
}
|