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::isRefPtrArg(unsigned int varId)
{
const Variable *var = _tokenizer->getSymbolDatabase()->getVariableFromVarId(varId);
return(var && var->isArgument() && var->isReference() && var->isPointer());
}
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();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token *tok = scope->classStart; tok && tok != scope->classEnd; tok = tok->next()) {
// Critical assignment
if (Token::Match(tok, "[;{}] %var% = & %var%") && isRefPtrArg(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();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
if (!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->next(); 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();
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if (isAutoVarArray(varid)) {
errorReturnPointerToLocalArray(tok2);
}
}
}
}
}
}
void CheckAutoVariables::errorReturnAddressToAutoVariable(const Token *tok)
{
reportError(tok, Severity::error, "returnAddressOfAutoVariable", "Address of an auto-variable returned.");
}
void CheckAutoVariables::errorReturnPointerToLocalArray(const Token *tok)
{
reportError(tok, Severity::error, "returnLocalVariable", "Pointer to local array variable returned.");
}
void CheckAutoVariables::errorAutoVariableAssignment(const Token *tok, bool inconclusive)
{
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if (!inconclusive) {
reportError(tok, Severity::error, "autoVariables",
"Address of local auto-variable assigned to a function parameter.\n"
"Dangerous assignment - the function parameter is assigned the address of a local "
"auto-variable. Local auto-variables are reserved from the stack which "
"is freed when the function ends. So the pointer to a local variable "
"is invalid after the function ends.");
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} else {
reportError(tok, Severity::error, "autoVariables",
"Address of local auto-variable assigned to a function parameter.\n"
"Function parameter is assigned the address of a local auto-variable. "
"Local auto-variables are reserved from the stack which is freed when "
"the function ends. The address is invalid after the function ends and it "
"might 'leak' from the function through the parameter.", true);
}
}
void CheckAutoVariables::errorReturnAddressOfFunctionParameter(const Token *tok, const std::string &varname)
{
reportError(tok, Severity::error, "returnAddressOfFunctionParameter",
"Address of function parameter '" + varname + "' returned.\n"
"Address of the function parameter '" + varname + "' becomes invalid after the function exits because "
"function parameters are stored on the stack which is freed when the function exits. Thus the returned "
"value is invalid.");
}
//---------------------------------------------------------------------------
// return temporary?
bool CheckAutoVariables::returnTemporary(const Token *tok) const
{
if (!Token::Match(tok, "return %var% (") || !Token::simpleMatch(tok->linkAt(2), ") ;"))
return false;
const std::string &funcname(tok->next()->str());
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
std::list<Scope>::const_iterator scope;
bool func = false; // Might it be a function call?
bool retref = false; // is there such a function that returns a reference?
bool retvalue = false; // is there such a function that returns a value?
for (scope = symbolDatabase->scopeList.begin(); !retref && scope != symbolDatabase->scopeList.end(); ++scope) {
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if (scope->type == Scope::eFunction && scope->function && scope->function->type != Function::eConstructor && scope->function->type != Function::eCopyConstructor) {
if (scope->className == funcname) {
retref = scope->classDef->strAt(-1) == "&";
if (!retref) {
const Token* start = scope->classDef;
while (start->previous() && !Token::Match(start->previous(), ";|}|{|public:|private:|protected:")) {
if ((start->str() == ")" || start->str() == ">") && start->link())
start = start->link();
start = start->previous();
}
if (start->str() == "const")
start = start->next();
if (start->str() == "::")
start = start->next();
if (Token::simpleMatch(start, "std ::")) {
if (start->strAt(3) != "<" || !Token::simpleMatch(start->linkAt(3), "> ::"))
retvalue = true;
else
retref = true; // Assume that a reference is returned
} else {
if (symbolDatabase->isClassOrStruct(start->str()))
retvalue = true;
else
retref = true;
}
}
func = true;
}
}
}
if (!func && symbolDatabase->isClassOrStruct(funcname))
return true;
return bool(!retref && retvalue);
}
//---------------------------------------------------------------------------
void CheckAutoVariables::returnReference()
{
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
if (!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->next(); 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);
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if (isAutoVar(varid1)) {
// 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
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if (!isAutoVar(tok3->varId()))
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", "Reference to auto variable returned.");
}
void CheckAutoVariables::errorReturnTempReference(const Token *tok)
{
reportError(tok, Severity::error, "returnTempReference", "Reference to temporary returned.");
}
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.");
}