cppcheck/lib/checkautovariables.cpp

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/*
* Cppcheck - A tool for static C/C++ code analysis
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* Copyright (C) 2007-2012 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 <list>
#include <string>
//---------------------------------------------------------------------------
// Register this check class into cppcheck by creating a static instance of it..
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namespace {
static CheckAutoVariables instance;
}
bool CheckAutoVariables::isRefArg(unsigned int varId)
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(varId);
return(var && var->isArgument() && var->isReference());
}
bool CheckAutoVariables::isPtrArg(unsigned int varId)
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(varId);
return(var && var->isArgument() && var->isPointer());
}
bool CheckAutoVariables::isAutoVar(unsigned int varId)
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(varId);
if (!var || !var->isLocal() || var->isStatic())
return false;
if (var->isReference()) {
// 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);
return (var && var->isLocal() && !var->isStatic() && var->isArray());
}
// Verification that we really take the address of a local variable
static bool checkRvalueExpression(const Variable* var, const Token* next)
{
return((next->str() != "." || (!var->isPointer() && (!var->isClass() || var->type()))) && next->strAt(2) != ".");
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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;
for (const Token *tok = scope->classStart; tok && tok != scope->classEnd; tok = tok->next()) {
// Critical assignment
if (Token::Match(tok, "[;{}] %var% = & %var%") && isRefArg(tok->next()->varId()) && isAutoVar(tok->tokAt(4)->varId())) {
const Variable * var = symbolDatabase->getVariableFromVarId(tok->tokAt(4)->varId());
if (checkRvalueExpression(var, tok->tokAt(5)))
errorAutoVariableAssignment(tok->next(), false);
} else if (Token::Match(tok, "[;{}] * %var% = & %var%") && isPtrArg(tok->tokAt(2)->varId()) && isAutoVar(tok->tokAt(5)->varId())) {
const Variable * var = symbolDatabase->getVariableFromVarId(tok->tokAt(5)->varId());
if (checkRvalueExpression(var, tok->tokAt(6)))
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->next()->varId());
if (var1 && var1->isArgument() && var1->isPointer()) {
const Variable * var2 = symbolDatabase->getVariableFromVarId(tok->tokAt(6)->varId());
if (isAutoVar(tok->tokAt(6)->varId()) && checkRvalueExpression(var2, tok->tokAt(7)))
errorAutoVariableAssignment(tok->next(), true);
}
}
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->next()->varId());
if (var1 && var1->isArgument() && var1->isPointer()) {
if (isAutoVarArray(tok->tokAt(5)->varId()))
errorAutoVariableAssignment(tok->next(), true);
}
}
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% * *")) {
if (isAutoVarArray(tok->tokAt(4)->varId()))
errorAutoVariableAssignment(tok->next(), false);
}
tok = tok->tokAt(4);
} else if (Token::Match(tok, "[;{}] %var% [") && Token::Match(tok->linkAt(2), "] = & %var%") && isPtrArg(tok->next()->varId()) && isAutoVar(tok->linkAt(2)->tokAt(3)->varId())) {
const Token* const varTok = tok->linkAt(2)->tokAt(3);
const Variable * var = symbolDatabase->getVariableFromVarId(varTok->varId());
if (checkRvalueExpression(var, varTok->next()))
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->linkAt(3), "] ;") &&
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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
else if (Token::Match(tok, "free ( %var% ) ;") || Token::Match(tok, "delete [| ]| (| %var% !![")) {
tok = Token::findmatch(tok->next(), "%var%");
if (isAutoVarArray(tok->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 || !scope->function)
continue;
const Token *tok = scope->function->tokenDef;
// have we reached a function that returns a pointer
if (tok->previous() && tok->previous()->str() == "*") {
for (const Token *tok2 = scope->classStart; tok2 && tok2 != scope->classEnd; tok2 = tok2->next()) {
// 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;
// TODO: Find all functions that return objects by value
return bool(NULL != 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 || !scope->function)
continue;
const Token *tok = scope->function->tokenDef;
// have we reached a function that returns a reference?
if (tok->previous() && tok->previous()->str() == "&") {
for (const Token *tok2 = scope->classStart; tok2 && tok2 != scope->classEnd; tok2 = tok2->next()) {
// return..
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if (Token::Match(tok2, "return %var% ;")) {
// is the returned variable a local variable?
const unsigned int varid1 = tok2->next()->varId();
const Variable *var1 = symbolDatabase->getVariableFromVarId(varid1);
if (var1 && var1->isLocal() && !var1->isStatic()) {
// 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
const Variable *var2 = symbolDatabase->getVariableFromVarId(tok3->varId());
if (!var2 || !var2->isLocal() || var2->isStatic() || (var2->isPointer() && tok3->strAt(1) == "."))
continue;
}
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// 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",
"Deallocating auto-variable is invalid\n"
"Deallocating an auto-variable is invalid. You should only free memory "
"that has been allocated dynamically.");
}
//---------------------------------------------------------------------------
// Return c_str
void CheckAutoVariables::returncstr()
{
// TODO: Move this to CheckStl::string_c_str
// 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 || !scope->function)
continue;
const Token *tok = scope->function->tokenDef;
// have we reached a function that returns a const char *
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if (Token::simpleMatch(tok->tokAt(-3), "const char *")) {
for (const Token *tok2 = scope->classStart; tok2 && tok2 != scope->classEnd; tok2 = tok2->next()) {
// return pointer to temporary..
if (returnTemporary(tok2)) {
// report error..
errorReturnTempPointer(tok2);
}
}
}
}
}
void CheckAutoVariables::errorReturnTempPointer(const Token *tok)
{
reportError(tok, Severity::error, "returnTempPointer", "Returning pointer to temporary");
}