cppcheck/lib/checkautovariables.cpp

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/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2011 Daniel Marjamäki and Cppcheck team.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
//---------------------------------------------------------------------------
// Auto variables checks
//---------------------------------------------------------------------------
#include "checkautovariables.h"
#include "symboldatabase.h"
#include <sstream>
#include <iostream>
#include <string>
//---------------------------------------------------------------------------
// Register this check class into cppcheck by creating a static instance of it..
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namespace {
static CheckAutoVariables instance;
}
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bool CheckAutoVariables::errorAv(const Token* left, const Token* right)
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(left->varId());
if (!var || !var->isArgument() ||
(!var->isArray() && !Token::Match(var->nameToken()->tokAt(-3), "%type% * *")) ||
(var->isArray() && !Token::Match(var->nameToken()->tokAt(-2), "%type% *")))
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return false;
return isAutoVar(right->varId());
}
bool CheckAutoVariables::isAutoVar(unsigned int varId)
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(varId);
if (!var || !var->isLocal() || var->isStatic() || var->isArray() || var->typeEndToken()->str() == "*")
return false;
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if (Token::simpleMatch(var->nameToken()->previous(), "&")) {
// address of reference variable can be taken if the address
// of the variable it points at is not a auto-var
// TODO: check what the reference variable references.
return false;
}
return true;
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}
bool CheckAutoVariables::isAutoVarArray(unsigned int varId)
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(varId);
if (!var || !var->isLocal() || var->isStatic() || !var->isArray())
return false;
return true;
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}
void CheckAutoVariables::autoVariables()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
std::list<Scope>::const_iterator scope;
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for (scope = symbolDatabase->scopeList.begin(); scope != symbolDatabase->scopeList.end(); ++scope) {
// only check functions
if (scope->type != Scope::eFunction)
continue;
unsigned int indentlevel = 0;
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for (const Token *tok = scope->classDef->next()->link(); tok; tok = tok->next()) {
// indentlevel..
if (tok->str() == "{")
++indentlevel;
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else if (tok->str() == "}") {
if (indentlevel <= 1)
break;
--indentlevel;
}
//Critical assignment
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if (Token::Match(tok, "[;{}] * %var% = & %var%") && errorAv(tok->tokAt(2), tok->tokAt(5))) {
const Variable * var = symbolDatabase->getVariableFromVarId(tok->tokAt(5)->varId());
if (var && (!var->isClass() || var->type()))
errorAutoVariableAssignment(tok->next(), false);
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} else if (Token::Match(tok, "[;{}] %var% . %var% = & %var%")) {
// TODO: check if the parameter is only changed temporarily (#2969)
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if (_settings->inconclusive) {
const Variable * var1 = symbolDatabase->getVariableFromVarId(tok->tokAt(1)->varId());
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if (var1 && var1->isArgument() && Token::Match(var1->nameToken()->tokAt(-2), "%type% *")) {
const Variable * var2 = symbolDatabase->getVariableFromVarId(tok->tokAt(6)->varId());
if (var2 && var2->isLocal() && !var2->isStatic() && !Token::simpleMatch(var2->typeEndToken(), "*"))
errorAutoVariableAssignment(tok->next(), _settings->inconclusive);
}
}
tok = tok->tokAt(6);
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} else if (Token::Match(tok, "[;{}] %var% . %var% = %var% ;")) {
// TODO: check if the parameter is only changed temporarily (#2969)
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if (_settings->inconclusive) {
const Variable * var1 = symbolDatabase->getVariableFromVarId(tok->tokAt(1)->varId());
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if (var1 && var1->isArgument() && Token::Match(var1->nameToken()->tokAt(-2), "%type% *")) {
const Variable * var2 = symbolDatabase->getVariableFromVarId(tok->tokAt(5)->varId());
if (var2 && var2->isLocal() && var2->isArray() && !var2->isStatic())
errorAutoVariableAssignment(tok->next(), _settings->inconclusive);
}
}
tok = tok->tokAt(5);
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} else if (Token::Match(tok, "[;{}] * %var% = %var% ;")) {
const Variable * var1 = symbolDatabase->getVariableFromVarId(tok->tokAt(2)->varId());
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if (var1 && var1->isArgument() && Token::Match(var1->nameToken()->tokAt(-3), "%type% * *")) {
const Variable * var2 = symbolDatabase->getVariableFromVarId(tok->tokAt(4)->varId());
if (var2 && var2->isLocal() && var2->isArray() && !var2->isStatic())
errorAutoVariableAssignment(tok->next(), false);
}
tok = tok->tokAt(4);
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} else if (Token::Match(tok, "[;{}] %var% [ %any% ] = & %var%") && errorAv(tok->tokAt(1), tok->tokAt(7))) {
errorAutoVariableAssignment(tok->next(), false);
}
// Critical return
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else if (Token::Match(tok, "return & %var% ;") && isAutoVar(tok->tokAt(2)->varId())) {
errorReturnAddressToAutoVariable(tok);
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} else if (Token::Match(tok, "return & %var% [") &&
Token::simpleMatch(tok->tokAt(3)->link(), "] ;") &&
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isAutoVarArray(tok->tokAt(2)->varId())) {
errorReturnAddressToAutoVariable(tok);
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} else if (Token::Match(tok, "return & %var% ;") && tok->tokAt(2)->varId()) {
const Variable * var1 = symbolDatabase->getVariableFromVarId(tok->tokAt(2)->varId());
if (var1 && var1->isArgument() && var1->typeEndToken()->str() != "&")
errorReturnAddressOfFunctionParameter(tok, tok->strAt(2));
}
// Invalid pointer deallocation
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else if (Token::Match(tok, "free ( %var% ) ;") && isAutoVarArray(tok->tokAt(2)->varId())) {
errorInvalidDeallocation(tok);
}
}
}
}
//---------------------------------------------------------------------------
void CheckAutoVariables::returnPointerToLocalArray()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
std::list<Scope>::const_iterator scope;
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for (scope = symbolDatabase->scopeList.begin(); scope != symbolDatabase->scopeList.end(); ++scope) {
// only check functions
if (scope->type != Scope::eFunction)
continue;
const Token *tok = scope->classDef;
// skip any qualification
while (Token::Match(tok->tokAt(-2), "%type% ::"))
tok = tok->tokAt(-2);
// have we reached a function that returns a pointer
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if (Token::Match(tok->tokAt(-2), "%type% *")) {
// go to the '('
const Token *tok2 = scope->classDef->next();
// go to the ')'
tok2 = tok2->next()->link();
unsigned int indentlevel = 0;
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for (; tok2; tok2 = tok2->next()) {
// indentlevel..
if (tok2->str() == "{")
++indentlevel;
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else if (tok2->str() == "}") {
if (indentlevel <= 1)
break;
--indentlevel;
}
// Return pointer to local array variable..
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if (Token::Match(tok2, "return %var% ;")) {
const unsigned int varid = tok2->next()->varId();
const Variable *var = symbolDatabase->getVariableFromVarId(varid);
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if (var && var->isLocal() && !var->isStatic() && var->isArray()) {
errorReturnPointerToLocalArray(tok2);
}
}
}
}
}
}
void CheckAutoVariables::errorReturnAddressToAutoVariable(const Token *tok)
{
reportError(tok, Severity::error, "returnAddressOfAutoVariable", "Return of the address of an auto-variable");
}
void CheckAutoVariables::errorReturnPointerToLocalArray(const Token *tok)
{
reportError(tok, Severity::error, "returnLocalVariable", "Returning pointer to local array variable");
}
void CheckAutoVariables::errorAutoVariableAssignment(const Token *tok, bool inconclusive)
{
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if (!inconclusive) {
reportError(tok, Severity::error, "autoVariables",
"Assigning address of local auto-variable to a function parameter.\n"
"Dangerous assignment - function parameter takes the address of a local "
"auto-variable. Local auto-variables are reserved from the stack. And the "
"stack is freed when the function ends. So the pointer to a local variable "
"is invalid after the function ends.");
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} else {
reportInconclusiveError(tok, Severity::error, "autoVariables",
"Inconclusive: Assigning address of local auto-variable to a function parameter.\n"
"Inconclusive: function parameter takes the address of a local auto-variable. "
"Local auto-variables are reserved from the stack. And the stack is freed when "
"the function ends. The address is invalid after the function ends and it "
"might 'leak' from the function through the parameter.");
}
}
void CheckAutoVariables::errorReturnAddressOfFunctionParameter(const Token *tok, const std::string &varname)
{
reportError(tok, Severity::error, "returnAddressOfFunctionParameter",
"Return the address of function parameter '" + varname + "'\n"
"Address of the function parameter '" + varname + "' is invalid after the function exits. "
"Function parameters are created into the stack. When the function exits the stack is deleted.");
}
//---------------------------------------------------------------------------
// return temporary?
bool CheckAutoVariables::returnTemporary(const Token *tok) const
{
if (!Token::Match(tok, "return %var% ("))
return false;
return bool(0 != Token::findmatch(_tokenizer->tokens(), ("std :: string " + tok->next()->str() + " (").c_str()));
}
//---------------------------------------------------------------------------
void CheckAutoVariables::returnReference()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
std::list<Scope>::const_iterator scope;
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for (scope = symbolDatabase->scopeList.begin(); scope != symbolDatabase->scopeList.end(); ++scope) {
// only check functions
if (scope->type != Scope::eFunction)
continue;
const Token *tok = scope->classDef;
// skip any qualification
while (Token::Match(tok->tokAt(-2), "%type% ::"))
tok = tok->tokAt(-2);
// have we reached a function that returns a reference?
if (Token::Match(tok->tokAt(-2), "%type% &") ||
Token::simpleMatch(tok->tokAt(-2), "> &")) {
// go to the '('
const Token *tok2 = scope->classDef->next();
// go to the ')'
tok2 = tok2->link();
unsigned int indentlevel = 0;
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for (; tok2; tok2 = tok2->next()) {
// indentlevel..
if (tok2->str() == "{")
++indentlevel;
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else if (tok2->str() == "}") {
if (indentlevel <= 1)
break;
--indentlevel;
}
// return..
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if (Token::Match(tok2, "return %var% ;")) {
// is the returned variable a local variable?
const unsigned int varid = tok2->next()->varId();
const Variable *var = symbolDatabase->getVariableFromVarId(varid);
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if (var && var->isLocal() && !var->isStatic()) {
// report error..
errorReturnReference(tok2);
}
}
// return reference to temporary..
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else if (returnTemporary(tok2)) {
// report error..
errorReturnTempReference(tok2);
}
}
}
}
}
void CheckAutoVariables::errorReturnReference(const Token *tok)
{
reportError(tok, Severity::error, "returnReference", "Returning reference to auto variable");
}
void CheckAutoVariables::errorReturnTempReference(const Token *tok)
{
reportError(tok, Severity::error, "returnTempReference", "Returning reference to temporary");
}
void CheckAutoVariables::errorInvalidDeallocation(const Token *tok)
{
reportError(tok, Severity::error, "autovarInvalidDeallocation", "Invalid deallocation");
}
//---------------------------------------------------------------------------
// Return c_str
void CheckAutoVariables::returncstr()
{
// locate function that returns a const char *..
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
std::list<Scope>::const_iterator scope;
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for (scope = symbolDatabase->scopeList.begin(); scope != symbolDatabase->scopeList.end(); ++scope) {
// only check functions
if (scope->type != Scope::eFunction)
continue;
const Token *tok = scope->classDef;
// skip any qualification
while (Token::Match(tok->tokAt(-2), "%type% ::"))
tok = tok->tokAt(-2);
// have we reached a function that returns a const char *
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if (Token::simpleMatch(tok->tokAt(-3), "const char *")) {
// go to the '('
const Token *tok2 = scope->classDef->next();
// go to the ')'
tok2 = tok2->next()->link();
unsigned int indentlevel = 0;
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for (; tok2; tok2 = tok2->next()) {
// indentlevel..
if (tok2->str() == "{")
++indentlevel;
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else if (tok2->str() == "}") {
if (indentlevel <= 1)
break;
--indentlevel;
}
// return..
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if (Token::Match(tok2, "return %var% . c_str ( ) ;")) {
// is the returned variable a local variable?
const unsigned int varid = tok2->next()->varId();
const Variable *var = symbolDatabase->getVariableFromVarId(varid);
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if (var && var->isLocal() && !var->isStatic()) {
// report error..
errorReturnAutocstr(tok2);
}
}
// return pointer to temporary..
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else if (returnTemporary(tok2)) {
// report error..
errorReturnTempPointer(tok2);
}
}
}
}
}
void CheckAutoVariables::errorReturnAutocstr(const Token *tok)
{
reportError(tok, Severity::error, "returnAutocstr", "Returning pointer to auto variable");
}
void CheckAutoVariables::errorReturnTempPointer(const Token *tok)
{
reportError(tok, Severity::error, "returnTempPointer", "Returning pointer to temporary");
}