383 lines
16 KiB
C++
383 lines
16 KiB
C++
/*
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* Cppcheck - A tool for static C/C++ code analysis
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* Copyright (C) 2007-2013 Daniel Marjamäki and 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 "checkuninitvar.h"
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#include <list>
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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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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::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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return true;
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}
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bool CheckAutoVariables::isAutoVarArray(const Token *tok)
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{
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const Variable *var = tok->variable();
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return (var && var->isLocal() && !var->isStatic() && var->isArray());
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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 == NULL)
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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, "%var% . %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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for (const Token *tok = start; tok != scope->classEnd; tok = tok->next()) {
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if (tok->varId() == varId)
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return true;
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if (tok->scope()->type == Scope::eFor || tok->scope()->type == Scope::eDo || tok->scope()->type == 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::autoVariables()
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{
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const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
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const bool reportWarnings(_settings->isEnabled("warning"));
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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 (reportWarnings &&
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Token::Match(tok, "[;{}] %var% =") &&
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isNonReferenceArg(tok->next()) &&
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!variableIsUsedInScope(Token::findsimplematch(tok->tokAt(2), ";"), tok->next()->varId(), scope)) {
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errorUselessAssignmentPtrArg(tok->next());
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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 (_settings->inconclusive) {
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const Variable * var1 = tok->next()->variable();
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if (var1 && var1->isArgument() && var1->isPointer()) {
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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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}
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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 (_settings->inconclusive) {
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const Variable * var1 = tok->next()->variable();
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if (var1 && var1->isArgument() && var1->isPointer()) {
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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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}
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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%") && isPtrArg(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% ;") && isAutoVar(tok->tokAt(2))) {
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errorReturnAddressToAutoVariable(tok);
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} else if (Token::Match(tok, "return & %var% [") &&
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Token::simpleMatch(tok->linkAt(3), "] ;") &&
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isAutoVarArray(tok->tokAt(2))) {
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errorReturnAddressToAutoVariable(tok);
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} else if (Token::Match(tok, "return & %var% ;") && tok->tokAt(2)->varId()) {
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const Variable * var1 = tok->tokAt(2)->variable();
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if (var1 && var1->isArgument() && var1->typeEndToken()->str() != "&")
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errorReturnAddressOfFunctionParameter(tok, tok->strAt(2));
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}
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// Invalid pointer deallocation
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else if (Token::Match(tok, "free ( %var% ) ;") || 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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}
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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 (Token::Match(tok2, "return %var% ;")) {
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if (isAutoVarArray(tok2->next())) {
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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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}
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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.");
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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.");
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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.");
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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.", 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.");
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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.");
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}
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//---------------------------------------------------------------------------
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// return temporary?
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bool CheckAutoVariables::returnTemporary(const Token *tok) const
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{
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const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
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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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retref = function->tokenDef->strAt(-1) == "&";
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if (!retref) {
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const Token *start = function->tokenDef;
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while (start->previous() && !Token::Match(start->previous(), ";|}|{|public:|private:|protected:")) {
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if ((start->str() == ")" || start->str() == ">") && start->link())
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start = start->link();
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start = start->previous();
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}
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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 (symbolDatabase->isClassOrStruct(start->str()))
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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 && symbolDatabase->isClassOrStruct(tok->str()))
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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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void CheckAutoVariables::returnReference()
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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 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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// return..
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if (Token::Match(tok2, "return %var% ;")) {
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// is the returned variable a local variable?
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if (isAutoVar(tok2->next())) {
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const Variable *var1 = tok2->next()->variable();
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// If reference variable is used, check what it references
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if (Token::Match(var1->nameToken(), "%var% [=(]")) {
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const Token *tok3 = var1->nameToken()->tokAt(2);
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if (!Token::Match(tok3, "%var% [);.]"))
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continue;
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// Only report error if variable that is referenced is
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// a auto variable
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if (!isAutoVar(tok3))
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continue;
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}
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// report error..
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errorReturnReference(tok2);
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}
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}
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// return reference to temporary..
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else if (Token::Match(tok2, "return %var% (") &&
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Token::simpleMatch(tok2->linkAt(2), ") ;")) {
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if (returnTemporary(tok2->next())) {
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// report error..
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errorReturnTempReference(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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}
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void CheckAutoVariables::errorReturnReference(const Token *tok)
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{
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reportError(tok, Severity::error, "returnReference", "Reference to auto variable returned.");
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}
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void CheckAutoVariables::errorReturnTempReference(const Token *tok)
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{
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reportError(tok, Severity::error, "returnTempReference", "Reference to temporary returned.");
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}
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void CheckAutoVariables::errorInvalidDeallocation(const Token *tok)
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{
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reportError(tok,
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Severity::error,
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"autovarInvalidDeallocation",
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"Deallocation of an auto-variable results in undefined behaviour.\n"
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"The deallocation of an auto-variable results in undefined behaviour. You should only free memory "
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"that has been allocated dynamically.");
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}
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