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cppcheck/lib/checkunusedvar.cpp

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/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2023 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/>.
*/
//---------------------------------------------------------------------------
#include "checkunusedvar.h"
#include "astutils.h"
#include "errortypes.h"
#include "fwdanalysis.h"
#include "library.h"
#include "preprocessor.h"
#include "settings.h"
#include "symboldatabase.h"
#include "token.h"
#include "tokenize.h"
#include "tokenlist.h"
#include "utils.h"
#include "valueflow.h"
#include <algorithm>
#include <list>
#include <set>
#include <utility>
#include <vector>
//---------------------------------------------------------------------------
// Register this check class (by creating a static instance of it)
namespace {
CheckUnusedVar instance;
}
static const CWE CWE563(563U); // Assignment to Variable without Use ('Unused Variable')
static const CWE CWE665(665U); // Improper Initialization
/** Is scope a raii class scope */
static bool isRaiiClassScope(const Scope *classScope)
{
return classScope && classScope->getDestructor() != nullptr;
}
/** Is ValueType a raii class? */
static bool isRaiiClass(const ValueType *valueType, bool cpp, bool defaultReturn = true)
{
if (!cpp)
return false;
if (!valueType)
return defaultReturn;
if ((valueType->smartPointerType && isRaiiClassScope(valueType->smartPointerType->classScope)) || (!valueType->smartPointerType && valueType->type == ValueType::Type::SMART_POINTER))
return true;
switch (valueType->type) {
case ValueType::Type::UNKNOWN_TYPE:
case ValueType::Type::NONSTD:
return defaultReturn;
case ValueType::Type::RECORD:
if (isRaiiClassScope(valueType->typeScope))
return true;
return defaultReturn;
case ValueType::Type::POD:
case ValueType::Type::SMART_POINTER:
case ValueType::Type::CONTAINER:
case ValueType::Type::ITERATOR:
case ValueType::Type::VOID:
case ValueType::Type::BOOL:
case ValueType::Type::CHAR:
case ValueType::Type::SHORT:
case ValueType::Type::WCHAR_T:
case ValueType::Type::INT:
case ValueType::Type::LONG:
case ValueType::Type::LONGLONG:
case ValueType::Type::UNKNOWN_INT:
case ValueType::Type::FLOAT:
case ValueType::Type::DOUBLE:
case ValueType::Type::LONGDOUBLE:
return false;
}
return defaultReturn;
}
/**
* @brief This class is used create a list of variables within a function.
*/
class Variables {
public:
enum VariableType { standard, array, pointer, reference, pointerArray, referenceArray, pointerPointer, none };
/** Store information about variable usage */
class VariableUsage {
public:
explicit VariableUsage(const Variable *var = nullptr,
VariableType type = standard,
bool read = false,
bool write = false,
bool modified = false,
bool allocateMemory = false) :
_var(var),
_lastAccess(var ? var->nameToken() : nullptr),
mType(type),
_read(read),
_write(write),
_modified(modified),
_allocateMemory(allocateMemory) {}
/** variable is used.. set both read+write */
void use() {
_read = true;
_write = true;
}
/** is variable unused? */
bool unused() const {
return (!_read && !_write);
}
std::set<nonneg int> _aliases;
std::set<const Scope*> _assignments;
const Variable* _var;
const Token* _lastAccess;
VariableType mType;
bool _read;
bool _write;
bool _modified; // read/modify/write
bool _allocateMemory;
};
void clear() {
mVarUsage.clear();
}
const std::map<nonneg int, VariableUsage> &varUsage() const {
return mVarUsage;
}
void addVar(const Variable *var, VariableType type, bool write_);
void allocateMemory(nonneg int varid, const Token* tok);
void read(nonneg int varid, const Token* tok);
void readAliases(nonneg int varid, const Token* tok);
void readAll(nonneg int varid, const Token* tok);
void write(nonneg int varid, const Token* tok);
void writeAliases(nonneg int varid, const Token* tok);
void writeAll(nonneg int varid, const Token* tok);
void use(nonneg int varid, const Token* tok);
void modified(nonneg int varid, const Token* tok);
VariableUsage *find(nonneg int varid);
void alias(nonneg int varid1, nonneg int varid2, bool replace);
void erase(nonneg int varid) {
mVarUsage.erase(varid);
}
void eraseAliases(nonneg int varid);
void eraseAll(nonneg int varid);
void clearAliases(nonneg int varid);
private:
std::map<nonneg int, VariableUsage> mVarUsage;
};
/**
* Alias the 2 given variables. Either replace the existing aliases if
* they exist or merge them. You would replace an existing alias when this
* assignment is in the same scope as the previous assignment. You might
* merge the aliases when this assignment is in a different scope from the
* previous assignment depending on the relationship of the 2 scopes.
*/
void Variables::alias(nonneg int varid1, nonneg int varid2, bool replace)
{
VariableUsage *var1 = find(varid1);
VariableUsage *var2 = find(varid2);
if (!var1 || !var2)
return;
// alias to self
if (varid1 == varid2) {
var1->use();
return;
}
if (replace) {
// remove var1 from all aliases
for (std::set<nonneg int>::const_iterator i = var1->_aliases.cbegin(); i != var1->_aliases.cend(); ++i) {
VariableUsage *temp = find(*i);
if (temp)
temp->_aliases.erase(var1->_var->declarationId());
}
// remove all aliases from var1
var1->_aliases.clear();
}
// var1 gets all var2s aliases
for (std::set<nonneg int>::const_iterator i = var2->_aliases.cbegin(); i != var2->_aliases.cend(); ++i) {
if (*i != varid1)
var1->_aliases.insert(*i);
}
// var2 is an alias of var1
var2->_aliases.insert(varid1);
var1->_aliases.insert(varid2);
if (var2->mType == Variables::pointer) {
var2->_read = true;
}
}
void Variables::clearAliases(nonneg int varid)
{
VariableUsage *usage = find(varid);
if (usage) {
// remove usage from all aliases
for (std::set<nonneg int>::const_iterator i = usage->_aliases.cbegin(); i != usage->_aliases.cend(); ++i) {
VariableUsage *temp = find(*i);
if (temp)
temp->_aliases.erase(usage->_var->declarationId());
}
// remove all aliases from usage
usage->_aliases.clear();
}
}
void Variables::eraseAliases(nonneg int varid)
{
VariableUsage *usage = find(varid);
if (usage) {
for (std::set<nonneg int>::const_iterator aliases = usage->_aliases.cbegin(); aliases != usage->_aliases.cend(); ++aliases)
erase(*aliases);
}
}
void Variables::eraseAll(nonneg int varid)
{
eraseAliases(varid);
erase(varid);
}
void Variables::addVar(const Variable *var,
VariableType type,
bool write_)
{
if (var->declarationId() > 0) {
mVarUsage.insert(std::make_pair(var->declarationId(), VariableUsage(var, type, false, write_, false)));
}
}
void Variables::allocateMemory(nonneg int varid, const Token* tok)
{
VariableUsage *usage = find(varid);
if (usage) {
usage->_allocateMemory = true;
usage->_lastAccess = tok;
}
}
void Variables::read(nonneg int varid, const Token* tok)
{
VariableUsage *usage = find(varid);
if (usage) {
usage->_read = true;
if (tok)
usage->_lastAccess = tok;
}
}
void Variables::readAliases(nonneg int varid, const Token* tok)
{
const VariableUsage *usage = find(varid);
if (usage) {
for (nonneg int const aliases : usage->_aliases) {
VariableUsage *aliased = find(aliases);
if (aliased) {
aliased->_read = true;
aliased->_lastAccess = tok;
}
}
}
}
void Variables::readAll(nonneg int varid, const Token* tok)
{
read(varid, tok);
readAliases(varid, tok);
}
void Variables::write(nonneg int varid, const Token* tok)
{
VariableUsage *usage = find(varid);
if (usage) {
usage->_write = true;
if (!usage->_var->isStatic() && !Token::simpleMatch(tok->next(), "= 0 ;"))
usage->_read = false;
usage->_lastAccess = tok;
}
}
void Variables::writeAliases(nonneg int varid, const Token* tok)
{
VariableUsage *usage = find(varid);
if (usage) {
for (std::set<nonneg int>::const_iterator aliases = usage->_aliases.cbegin(); aliases != usage->_aliases.cend(); ++aliases) {
VariableUsage *aliased = find(*aliases);
if (aliased) {
aliased->_write = true;
aliased->_lastAccess = tok;
}
}
}
}
void Variables::writeAll(nonneg int varid, const Token* tok)
{
write(varid, tok);
writeAliases(varid, tok);
}
void Variables::use(nonneg int varid, const Token* tok)
{
VariableUsage *usage = find(varid);
if (usage) {
usage->use();
usage->_lastAccess = tok;
for (std::set<nonneg int>::const_iterator aliases = usage->_aliases.cbegin(); aliases != usage->_aliases.cend(); ++aliases) {
VariableUsage *aliased = find(*aliases);
if (aliased) {
aliased->use();
aliased->_lastAccess = tok;
}
}
}
}
void Variables::modified(nonneg int varid, const Token* tok)
{
VariableUsage *usage = find(varid);
if (usage) {
if (!usage->_var->isStatic())
usage->_read = false;
usage->_modified = true;
usage->_lastAccess = tok;
for (std::set<nonneg int>::const_iterator aliases = usage->_aliases.cbegin(); aliases != usage->_aliases.cend(); ++aliases) {
VariableUsage *aliased = find(*aliases);
if (aliased) {
aliased->_modified = true;
aliased->_lastAccess = tok;
}
}
}
}
Variables::VariableUsage *Variables::find(nonneg int varid)
{
if (varid) {
const std::map<nonneg int, VariableUsage>::iterator i = mVarUsage.find(varid);
if (i != mVarUsage.end())
return &i->second;
}
return nullptr;
}
static const Token* doAssignment(Variables &variables, const Token *tok, bool dereference, const Scope *scope)
{
// a = a + b;
if (Token::Match(tok, "%var% = %var% !!;")) {
const Token* rhsVarTok = tok->tokAt(2);
if (tok->varId() == rhsVarTok->varId()) {
return rhsVarTok;
}
}
if (Token::Match(tok, "%var% %assign%") && tok->strAt(1) != "=")
return tok->next();
const Token* const tokOld = tok;
// check for aliased variable
const nonneg int varid1 = tok->varId();
Variables::VariableUsage *var1 = variables.find(varid1);
if (var1) {
// jump behind '='
tok = tok->next();
while (!tok->isAssignmentOp()) {
if (tok->varId())
variables.read(tok->varId(), tok);
tok = tok->next();
}
tok = tok->next();
if (Token::Match(tok, "( const| struct|union| %type% * ) ( ("))
tok = tok->link()->next();
if (Token::Match(tok, "( [(<] const| struct|union| %type% *| [>)]"))
tok = tok->next();
if (Token::Match(tok, "(| &| %name%") ||
(Token::Match(tok->next(), "< const| struct|union| %type% *| > ( &| %name%"))) {
bool addressOf = false;
if (Token::Match(tok, "%var% ."))
variables.use(tok->varId(), tok); // use = read + write
// check for C style cast
if (tok->str() == "(") {
tok = tok->next();
if (tok->str() == "const")
tok = tok->next();
if (Token::Match(tok, "struct|union"))
tok = tok->next();
while ((tok->isName() && tok->varId() == 0) || (tok->str() == "*") || (tok->str() == ")"))
tok = tok->next();
if (tok->str() == "&") {
addressOf = true;
tok = tok->next();
} else if (tok->str() == "(") {
tok = tok->next();
if (tok->str() == "&") {
addressOf = true;
tok = tok->next();
}
} else if (Token::Match(tok, "%cop% %var%")) {
variables.read(tok->next()->varId(), tok);
}
}
// check for C++ style cast
else if (tok->str().find("cast") != std::string::npos &&
tok->strAt(1) == "<") {
tok = tok->tokAt(2);
if (tok->str() == "const")
tok = tok->next();
if (Token::Match(tok, "struct|union"))
tok = tok->next();
tok = tok->next();
if (tok->str() == "*")
tok = tok->next();
tok = tok->tokAt(2);
if (!tok)
return tokOld;
if (tok->str() == "&") {
addressOf = true;
tok = tok->next();
}
}
// no cast, no ?
else if (!Token::Match(tok, "%name% ?")) {
if (tok->str() == "&") {
addressOf = true;
tok = tok->next();
} else if (tok->str() == "new")
return tokOld;
}
// check if variable is local
const nonneg int varid2 = tok->varId();
const Variables::VariableUsage* var2 = variables.find(varid2);
if (var2) { // local variable (alias or read it)
if (var1->mType == Variables::pointer || var1->mType == Variables::pointerArray) {
if (dereference)
variables.read(varid2, tok);
else {
if (addressOf ||
var2->mType == Variables::array ||
var2->mType == Variables::pointer) {
bool replace = true;
// pointerArray => don't replace
if (var1->mType == Variables::pointerArray)
replace = false;
// check if variable declared in same scope
else if (scope == var1->_var->scope())
replace = true;
// not in same scope as declaration
else {
// no other assignment in this scope
if (var1->_assignments.find(scope) == var1->_assignments.end() ||
scope->type == Scope::eSwitch) {
// nothing to replace
// cppcheck-suppress duplicateBranch - remove when TODO below is address
if (var1->_assignments.empty())
replace = false;
// this variable has previous assignments
else {
// TODO: determine if existing aliases should be replaced or merged
replace = false;
}
}
// assignment in this scope
else {
// replace when only one other assignment, merge them otherwise
replace = (var1->_assignments.size() == 1);
}
}
variables.alias(varid1, varid2, replace);
} else if (tok->strAt(1) == "?") {
if (var2->mType == Variables::reference)
variables.readAliases(varid2, tok);
else
variables.read(varid2, tok);
} else {
variables.readAll(varid2, tok);
}
}
} else if (var1->mType == Variables::reference) {
variables.alias(varid1, varid2, true);
} else if (var1->mType == Variables::standard && addressOf) {
variables.alias(varid1, varid2, true);
} else {
if ((var2->mType == Variables::pointer || var2->mType == Variables::pointerArray) && tok->strAt(1) == "[")
variables.readAliases(varid2, tok);
variables.read(varid2, tok);
}
} else { // not a local variable (or an unsupported local variable)
if (var1->mType == Variables::pointer && !dereference) {
// check if variable declaration is in this scope
if (var1->_var->scope() == scope) {
// If variable is used in RHS then "use" variable
for (const Token *rhs = tok; rhs && rhs->str() != ";"; rhs = rhs->next()) {
if (rhs->varId() == varid1) {
variables.use(varid1, tok);
break;
}
}
variables.clearAliases(varid1);
} else {
// no other assignment in this scope
if (var1->_assignments.find(scope) == var1->_assignments.end()) {
/**
* @todo determine if existing aliases should be discarded
*/
}
// this assignment replaces the last assignment in this scope
else {
// aliased variables in a larger scope are not supported
// remove all aliases
variables.clearAliases(varid1);
}
}
}
}
} else
tok = tokOld;
var1->_assignments.insert(scope);
}
// check for alias to struct member
// char c[10]; a.b = c;
else if (Token::Match(tok->tokAt(-2), "%name% .")) {
const Token *rhsVarTok = tok->tokAt(2);
if (rhsVarTok && rhsVarTok->varId()) {
const nonneg int varid2 = rhsVarTok->varId();
const Variables::VariableUsage *var2 = variables.find(varid2);
// struct member aliased to local variable
if (var2 && (var2->mType == Variables::array ||
var2->mType == Variables::pointer)) {
// erase aliased variable and all variables that alias it
// to prevent false positives
variables.eraseAll(varid2);
}
}
}
// Possible pointer alias
else if (Token::Match(tok, "%name% = %name% ;")) {
const nonneg int varid2 = tok->tokAt(2)->varId();
const Variables::VariableUsage *var2 = variables.find(varid2);
if (var2 && (var2->mType == Variables::array ||
var2->mType == Variables::pointer)) {
variables.use(varid2,tok);
}
}
return tok;
}
static bool isPartOfClassStructUnion(const Token* tok)
{
for (; tok; tok = tok->previous()) {
if (tok->str() == "}" || tok->str() == ")")
tok = tok->link();
else if (tok->str() == "(")
return false;
else if (tok->str() == "{") {
return (tok->strAt(-1) == "struct" || tok->strAt(-2) == "struct" || tok->strAt(-1) == "class" || tok->strAt(-2) == "class" || tok->strAt(-1) == "union" || tok->strAt(-2) == "union");
}
}
return false;
}
static bool isVarDecl(const Token *tok)
{
return tok && tok->variable() && tok->variable()->nameToken() == tok;
}
// Skip [ .. ]
static const Token * skipBrackets(const Token *tok)
{
while (tok && tok->str() == "[")
tok = tok->link()->next();
return tok;
}
// Skip [ .. ] . x
static const Token * skipBracketsAndMembers(const Token *tok)
{
while (tok) {
if (tok->str() == "[")
tok = tok->link()->next();
else if (Token::Match(tok, ". %name%"))
tok = tok->tokAt(2);
else
break;
}
return tok;
}
static void useFunctionArgs(const Token *tok, Variables& variables)
{
// TODO: Match function args to see if they are const or not. Assume that const data is not written.
if (!tok)
return;
if (tok->str() == ",") {
useFunctionArgs(tok->astOperand1(), variables);
useFunctionArgs(tok->astOperand2(), variables);
} else if (Token::Match(tok, "[+:]") && (!tok->valueType() || tok->valueType()->pointer)) {
useFunctionArgs(tok->astOperand1(), variables);
useFunctionArgs(tok->astOperand2(), variables);
} else if (tok->variable() && tok->variable()->isArray()) {
variables.use(tok->varId(), tok);
}
}
//---------------------------------------------------------------------------
// Usage of function variables
//---------------------------------------------------------------------------
void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const scope, Variables& variables)
{
// Find declarations if the scope is executable..
if (scope->isExecutable()) {
// Find declarations
for (std::list<Variable>::const_iterator i = scope->varlist.cbegin(); i != scope->varlist.cend(); ++i) {
if (i->isThrow() || i->isExtern())
continue;
Variables::VariableType type = Variables::none;
if (i->isArray() && (i->nameToken()->previous()->str() == "*" || i->nameToken()->strAt(-2) == "*"))
type = Variables::pointerArray;
else if (i->isArray() && i->nameToken()->previous()->str() == "&")
type = Variables::referenceArray;
else if (i->isArray())
type = Variables::array;
else if (i->isReference() && !(i->valueType() && i->valueType()->type == ValueType::UNKNOWN_TYPE && Token::simpleMatch(i->typeStartToken(), "auto")))
type = Variables::reference;
else if (i->nameToken()->previous()->str() == "*" && i->nameToken()->strAt(-2) == "*")
type = Variables::pointerPointer;
else if (i->isPointerToArray())
type = Variables::pointerPointer;
else if (i->isPointer())
type = Variables::pointer;
else if (mTokenizer->isC() ||
i->typeEndToken()->isStandardType() ||
isRecordTypeWithoutSideEffects(i->type()) ||
mSettings->library.detectContainer(i->typeStartToken()) ||
i->isStlType())
type = Variables::standard;
if (type == Variables::none || isPartOfClassStructUnion(i->typeStartToken()))
continue;
const Token* defValTok = i->nameToken()->next();
if (Token::Match(i->nameToken()->previous(), "* %var% ) (")) // function pointer. Jump behind parameter list.
defValTok = defValTok->linkAt(1)->next();
for (; defValTok; defValTok = defValTok->next()) {
if (defValTok->str() == "[")
defValTok = defValTok->link();
else if (defValTok->str() == "(" || defValTok->str() == "{" || defValTok->str() == "=" || defValTok->str() == ":") {
variables.addVar(&*i, type, true);
break;
} else if (defValTok->str() == ";" || defValTok->str() == "," || defValTok->str() == ")") {
variables.addVar(&*i, type, i->isStatic() && i->scope()->type != Scope::eFunction);
break;
}
}
if (i->isArray() && i->isClass() && // Array of class/struct members. Initialized by ctor except for std::array
!(i->isStlType() && i->valueType() && i->valueType()->containerTypeToken && i->valueType()->containerTypeToken->isStandardType()))
variables.write(i->declarationId(), i->nameToken());
if (i->isArray() && Token::Match(i->nameToken(), "%name% [ %var% ]")) // Array index variable read.
variables.read(i->nameToken()->tokAt(2)->varId(), i->nameToken());
if (defValTok && defValTok->next()) {
// simple assignment "var = 123"
if (defValTok->str() == "=" && defValTok->next()->str() != "{") {
doAssignment(variables, i->nameToken(), false, scope);
} else {
// could be "var = {...}" OR "var{...}" (since C++11)
const Token* tokBraceStart = nullptr;
if (Token::simpleMatch(defValTok, "= {")) {
// "var = {...}"
tokBraceStart = defValTok->next();
} else if (defValTok->str() == "{") {
// "var{...}"
tokBraceStart = defValTok;
}
if (tokBraceStart) {
for (const Token* tok = tokBraceStart->next(); tok && tok != tokBraceStart->link(); tok = tok->next()) {
if (tok->varId()) {
// Variables used to initialize the array read.
variables.read(tok->varId(), i->nameToken());
}
}
}
}
}
}
}
// Check variable usage
const Token *tok;
if (scope->type == Scope::eFunction)
tok = scope->bodyStart->next();
else
tok = scope->classDef->next();
for (; tok && tok != scope->bodyEnd; tok = tok->next()) {
if (tok->str() == "{" && tok != scope->bodyStart && !tok->previous()->varId()) {
if (std::any_of(scope->nestedList.cbegin(), scope->nestedList.cend(), [&](const Scope* s) {
return s->bodyStart == tok;
})) {
checkFunctionVariableUsage_iterateScopes(tok->scope(), variables); // Scan child scope
tok = tok->link();
}
if (!tok)
break;
}
if (Token::Match(tok, "asm ( %str% )")) {
variables.clear();
break;
}
// templates
if (tok->isName() && endsWith(tok->str(), '>')) {
// TODO: This is a quick fix to handle when constants are used
// as template parameters. Try to handle this better, perhaps
// only remove constants.
variables.clear();
}
else if (Token::Match(tok->previous(), "[;{}]")) {
for (const Token* tok2 = tok->next(); tok2; tok2 = tok2->next()) {
if (tok2->varId()) {
// Is this a variable declaration?
const Variable *var = tok2->variable();
if (!var || var->nameToken() != tok2)
continue;
// Mark template parameters used in declaration as use..
if (tok2->strAt(-1) == ">") {
for (const Token *tok3 = tok; tok3 != tok2; tok3 = tok3->next()) {
if (tok3->varId())
variables.use(tok3->varId(), tok3);
}
}
// Skip variable declaration..
tok = tok2->next();
if (Token::Match(tok, "( %name% )")) // Simple initialization through copy ctor
tok = tok->next();
else if (Token::Match(tok, "= %var% ;")) { // Simple initialization
tok = tok->next();
if (!var->isReference())
variables.read(tok->varId(), tok);
} else if (tok->str() == "[" && Token::simpleMatch(skipBrackets(tok),"= {")) {
const Token * const rhs1 = skipBrackets(tok)->next();
for (const Token *rhs = rhs1->link(); rhs != rhs1; rhs = rhs->previous()) {
if (rhs->varId())
variables.readAll(rhs->varId(), rhs);
}
} else if (var->typeEndToken()->str() == ">") // Be careful with types like std::vector
tok = tok->previous();
break;
}
if (Token::Match(tok2, "[;({=]"))
break;
}
}
// Freeing memory (not considered "using" the pointer if it was also allocated in this function)
if ((Token::Match(tok, "%name% ( %var% )") && mSettings->library.getDeallocFuncInfo(tok)) ||
(mTokenizer->isCPP() && (Token::Match(tok, "delete %var% ;") || Token::Match(tok, "delete [ ] %var% ;")))) {
nonneg int varid = 0;
if (tok->str() != "delete") {
const Token *varTok = tok->tokAt(2);
varid = varTok->varId();
tok = varTok->next();
} else if (tok->strAt(1) == "[") {
const Token *varTok = tok->tokAt(3);
varid = varTok->varId();
tok = varTok;
} else {
varid = tok->next()->varId();
tok = tok->next();
}
const Variables::VariableUsage *const var = variables.find(varid);
if (var) {
if (!var->_aliases.empty())
variables.use(varid, tok);
else if (!var->_allocateMemory)
variables.readAll(varid, tok);
}
}
else if (Token::Match(tok, "return|throw")) {
for (const Token *tok2 = tok->next(); tok2; tok2 = tok2->next()) {
if (tok2->varId())
variables.readAll(tok2->varId(), tok);
else if (tok2->str() == ";")
break;
}
}
// assignment
else if (Token::Match(tok, "*| ++|--| %name% ++|--| %assign%") ||
Token::Match(tok, "*| ( const| %type% *| ) %name% %assign%")) {
bool dereference = false;
bool pre = false;
bool post = false;
if (tok->str() == "*") {
dereference = true;
tok = tok->next();
}
if (Token::Match(tok, "( const| %type% *| ) %name% %assign%"))
tok = tok->link()->next();
else if (tok->str() == "(")
tok = tok->next();
if (tok->tokType() == Token::eIncDecOp) {
pre = true;
tok = tok->next();
}
if (tok->next()->tokType() == Token::eIncDecOp)
post = true;
const nonneg int varid1 = tok->varId();
const Token * const start = tok;
// assignment in while head..
bool inwhile = false;
{
const Token *parent = tok->astParent();
while (parent) {
if (Token::simpleMatch(parent->previous(), "while (")) {
inwhile = true;
break;
}
parent = parent->astParent();
}
}
tok = doAssignment(variables, tok, dereference, scope);
if (tok && tok->isAssignmentOp() && tok->str() != "=") {
variables.use(varid1, tok);
if (Token::Match(tok, "%assign% %name%")) {
tok = tok->next();
variables.read(tok->varId(), tok);
}
}
if (pre || post)
variables.use(varid1, tok);
if (dereference) {
const Variables::VariableUsage *const var = variables.find(varid1);
if (var && var->mType == Variables::array)
variables.write(varid1, tok);
variables.writeAliases(varid1, tok);
variables.read(varid1, tok);
} else {
const Variables::VariableUsage *const var = variables.find(varid1);
if (var && (inwhile || start->strAt(-1) == ",")) {
variables.use(varid1, tok);
} else if (var && var->mType == Variables::reference) {
variables.writeAliases(varid1, tok);
variables.read(varid1, tok);
}
// Consider allocating memory separately because allocating/freeing alone does not constitute using the variable
else if (var && var->mType == Variables::pointer &&
Token::Match(start, "%name% =") &&
findAllocFuncCallToken(start->next()->astOperand2(), mSettings->library)) {
const Token *allocFuncCallToken = findAllocFuncCallToken(start->next()->astOperand2(), mSettings->library);
const Library::AllocFunc *allocFunc = mSettings->library.getAllocFuncInfo(allocFuncCallToken);
bool allocateMemory = !allocFunc || Library::ismemory(allocFunc->groupId);
if (allocFuncCallToken->str() == "new") {
const Token *type = allocFuncCallToken->next();
// skip nothrow
if (mTokenizer->isCPP() && (Token::simpleMatch(type, "( nothrow )") ||
Token::simpleMatch(type, "( std :: nothrow )")))
type = type->link()->next();
// is it a user defined type?
if (!type->isStandardType()) {
const Variable *variable = start->variable();
if (!variable || !isRecordTypeWithoutSideEffects(variable->type()))
allocateMemory = false;
}
}
if (allocateMemory)
variables.allocateMemory(varid1, tok);
else
variables.write(varid1, tok);
} else if (varid1 && Token::Match(tok, "%varid% .", varid1)) {
variables.read(varid1, tok);
variables.write(varid1, start);
} else {
variables.write(varid1, tok);
}
}
const Variables::VariableUsage * const var2 = variables.find(tok->varId());
if (var2) {
if (var2->mType == Variables::reference) {
variables.writeAliases(tok->varId(), tok);
variables.read(tok->varId(), tok);
} else if (tok->varId() != varid1 && Token::Match(tok, "%name% .|["))
variables.read(tok->varId(), tok);
else if (tok->varId() != varid1 &&
var2->mType == Variables::standard &&
tok->strAt(-1) != "&")
variables.use(tok->varId(), tok);
}
const Token * const equal = skipBracketsAndMembers(tok->next());
// checked for chained assignments
if (tok != start && equal && equal->str() == "=") {
const nonneg int varId = tok->varId();
const Variables::VariableUsage * const var = variables.find(varId);
if (var && var->mType != Variables::reference) {
variables.read(varId,tok);
}
tok = tok->previous();
}
}
// assignment
else if ((Token::Match(tok, "%name% [") && Token::simpleMatch(skipBracketsAndMembers(tok->next()), "=")) ||
(tok->isUnaryOp("*") && Token::simpleMatch(tok->astParent(), "=") && Token::simpleMatch(tok->astOperand1(), "+"))) {
const Token *eq = tok;
while (eq && !eq->isAssignmentOp())
eq = eq->astParent();
const bool deref = eq && eq->astOperand1() && eq->astOperand1()->valueType() && eq->astOperand1()->valueType()->pointer == 0U;
if (tok->str() == "*") {
tok = tok->tokAt(2);
if (tok->str() == "(")
tok = tok->link()->next();
}
const nonneg int varid = tok->varId();
const Variables::VariableUsage *var = variables.find(varid);
if (var) {
// Consider allocating memory separately because allocating/freeing alone does not constitute using the variable
if (var->mType == Variables::pointer &&
((mTokenizer->isCPP() && Token::simpleMatch(skipBrackets(tok->next()), "= new")) ||
(Token::Match(skipBrackets(tok->next()), "= %name% (") && mSettings->library.getAllocFuncInfo(tok->tokAt(2))))) {
variables.allocateMemory(varid, tok);
} else if (var->mType == Variables::pointer || var->mType == Variables::reference) {
variables.read(varid, tok);
variables.writeAliases(varid, tok);
} else if (var->mType == Variables::pointerArray) {
tok = doAssignment(variables, tok, deref, scope);
} else
variables.writeAll(varid, tok);
}
}
else if (mTokenizer->isCPP() && Token::Match(tok, "[;{}] %var% <<")) {
variables.erase(tok->next()->varId());
}
else if (Token::Match(tok, "& %var%")) {
if (tok->astOperand2()) { // bitop
variables.read(tok->next()->varId(), tok);
} else // addressof
variables.use(tok->next()->varId(), tok); // use = read + write
} else if (Token::Match(tok, ">>|>>= %name%")) {
if (isLikelyStreamRead(mTokenizer->isCPP(), tok))
variables.use(tok->next()->varId(), tok); // use = read + write
else
variables.read(tok->next()->varId(), tok);
} else if (Token::Match(tok, "%var% >>|&") && Token::Match(tok->previous(), "[{};:]")) {
variables.read(tok->varId(), tok);
} else if (isLikelyStreamRead(mTokenizer->isCPP(),tok->previous())) {
variables.use(tok->varId(), tok);
}
// function parameter
else if (Token::Match(tok, "[(,] %var% [")) {
variables.use(tok->next()->varId(), tok); // use = read + write
} else if (Token::Match(tok, "[(,] %var% [,)]") && tok->previous()->str() != "*") {
variables.use(tok->next()->varId(), tok); // use = read + write
} else if (Token::Match(tok, "[(,] & %var% [,)]")) {
variables.eraseAll(tok->tokAt(2)->varId());
} else if (Token::Match(tok, "[(,] (") &&
Token::Match(tok->next()->link(), ") %var% [,)[]")) {
variables.use(tok->next()->link()->next()->varId(), tok); // use = read + write
} else if (Token::Match(tok, "[(,] *| *| %var%")) {
const Token* vartok = tok->next();
while (vartok->str() == "*")
vartok = vartok->next();
if (!(vartok->variable() && vartok == vartok->variable()->nameToken()) &&
!(tok->str() == "(" && !Token::Match(tok->previous(), "%name%")))
variables.use(vartok->varId(), vartok);
}
// function
else if (Token::Match(tok, "%name% (")) {
if (tok->varId() && !tok->function()) // operator()
variables.use(tok->varId(), tok);
else
variables.read(tok->varId(), tok);
useFunctionArgs(tok->next()->astOperand2(), variables);
} else if (Token::Match(tok, "std :: ref ( %var% )")) {
variables.eraseAll(tok->tokAt(4)->varId());
}
else if (Token::Match(tok->previous(), "[{,] %var% [,}]")) {
variables.use(tok->varId(), tok);
}
else if (tok->varId() && Token::Match(tok, "%var% .")) {
variables.use(tok->varId(), tok); // use = read + write
}
else if (tok->str() == ":" && (!tok->valueType() || tok->valueType()->pointer)) {
if (tok->astOperand1())
variables.use(tok->astOperand1()->varId(), tok->astOperand1());
if (tok->astOperand2())
variables.use(tok->astOperand2()->varId(), tok->astOperand2());
}
else if (tok->isExtendedOp() && tok->next() && tok->next()->varId() && tok->strAt(2) != "=" && !isVarDecl(tok->next())) {
variables.readAll(tok->next()->varId(), tok);
}
else if (tok->varId() && !isVarDecl(tok) && tok->next() && (tok->next()->str() == ")" || tok->next()->isExtendedOp())) {
if (Token::Match(tok->tokAt(-2), "%name% ( %var% [,)]") &&
!(tok->tokAt(-2)->variable() && tok->tokAt(-2)->variable()->isReference()))
variables.use(tok->varId(), tok);
else
variables.readAll(tok->varId(), tok);
}
else if (Token::Match(tok, "%var% ;") && Token::Match(tok->previous(), "[;{}:]")) {
variables.readAll(tok->varId(), tok);
}
// ++|--
else if (tok->next() && tok->next()->tokType() == Token::eIncDecOp && tok->next()->astOperand1() && tok->next()->astOperand1()->varId()) {
if (tok->next()->astParent())
variables.use(tok->next()->astOperand1()->varId(), tok);
else
variables.modified(tok->next()->astOperand1()->varId(), tok);
}
else if (tok->isAssignmentOp()) {
for (const Token *tok2 = tok->next(); tok2 && tok2->str() != ";"; tok2 = tok2->next()) {
if (tok2->varId()) {
if (tok2->strAt(1) == "=")
variables.write(tok2->varId(), tok);
else if (tok2->next() && tok2->next()->isAssignmentOp())
variables.use(tok2->varId(), tok);
else
variables.read(tok2->varId(), tok);
}
}
} else if (tok->variable() && tok->variable()->isClass() && tok->variable()->type() &&
(tok->variable()->type()->needInitialization == Type::NeedInitialization::False) &&
tok->next()->str() == ";") {
variables.write(tok->varId(), tok);
}
}
}
void CheckUnusedVar::checkFunctionVariableUsage()
{
if (!mSettings->severity.isEnabled(Severity::style) && !mSettings->checkLibrary)
return;
logChecker("CheckUnusedVar::checkFunctionVariableUsage"); // style
// Parse all executing scopes..
const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
auto reportLibraryCfgError = [this](const Token* tok, const std::string& typeName) {
if (mSettings->checkLibrary) {
reportError(tok,
Severity::information,
"checkLibraryCheckType",
"--check-library: Provide <type-checks><unusedvar> configuration for " + typeName);
}
};
// only check functions
for (const Scope * scope : symbolDatabase->functionScopes) {
// Bailout when there are lambdas or inline functions
// TODO: Handle lambdas and inline functions properly
if (scope->hasInlineOrLambdaFunction())
continue;
for (const Token *tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) {
if (findLambdaEndToken(tok))
// todo: handle lambdas
break;
if (Token::simpleMatch(tok, "try {"))
// todo: check try blocks
tok = tok->linkAt(1);
const Token *varDecl = nullptr;
if (tok->variable() && tok->variable()->nameToken() == tok) {
const Token * eq = tok->next();
while (Token::simpleMatch(eq, "["))
eq = eq->link()->next();
if (Token::simpleMatch(eq, ") (") && Token::simpleMatch(eq->linkAt(1), ") ="))
eq = eq->linkAt(1)->next();
if (Token::simpleMatch(eq, "=")) {
varDecl = tok;
tok = eq;
}
}
// not assignment/initialization/increment => continue
const bool isAssignment = tok->isAssignmentOp() && tok->astOperand1();
const bool isInitialization = (Token::Match(tok, "%var% (|{") && tok->variable() && tok->variable()->nameToken() == tok);
const bool isIncrementOrDecrement = (tok->tokType() == Token::Type::eIncDecOp);
if (!isAssignment && !isInitialization && !isIncrementOrDecrement)
continue;
if (isInitialization && Token::Match(tok, "%var% { }")) // don't warn for trivial initialization
continue;
if (isIncrementOrDecrement && tok->astParent() && precedes(tok, tok->astOperand1()))
continue;
if (tok->str() == "=" && !(tok->valueType() && tok->valueType()->pointer) && isRaiiClass(tok->valueType(), mTokenizer->isCPP(), false))
continue;
const bool isPointer = tok->valueType() && (tok->valueType()->pointer || tok->valueType()->type == ValueType::SMART_POINTER);
if (tok->isName()) {
if (isRaiiClass(tok->valueType(), mTokenizer->isCPP(), false))
continue;
tok = tok->next();
}
if (!isInitialization && tok->astParent() && !tok->astParent()->isAssignmentOp() && tok->str() != "(") {
const Token *parent = tok->astParent();
while (Token::Match(parent, "%oror%|%comp%|!|&&"))
parent = parent->astParent();
if (!parent)
continue;
if (!Token::simpleMatch(parent->previous(), "if ("))
continue;
}
// Do not warn about assignment with NULL
if (isPointer && isNullOperand(tok->astOperand2()))
continue;
if (!tok->astOperand1())
continue;
const Token *iteratorToken = tok->astOperand1();
while (Token::Match(iteratorToken, "[.*]"))
iteratorToken = iteratorToken->astOperand1();
if (iteratorToken && iteratorToken->variable() && iteratorToken->variable()->typeEndToken()->str().find("iterator") != std::string::npos)
continue;
const Token *op1tok = tok->astOperand1();
while (Token::Match(op1tok, ".|[|*"))
op1tok = op1tok->astOperand1();
// Assignment in macro => do not warn
if (isAssignment && tok->isExpandedMacro() && op1tok && op1tok->isExpandedMacro())
continue;
const Variable *op1Var = op1tok ? op1tok->variable() : nullptr;
if (!op1Var && Token::Match(tok, "(|{") && tok->previous() && tok->previous()->variable())
op1Var = tok->previous()->variable();
std::string bailoutTypeName;
if (op1Var) {
if (op1Var->isReference() && op1Var->nameToken() != tok->astOperand1())
// todo: check references
continue;
if (op1Var->isStatic())
// todo: check static variables
continue;
if (op1Var->nameToken()->isAttributeUnused())
continue;
// Avoid FP for union..
if (op1Var->type() && op1Var->type()->isUnionType())
continue;
// Bailout for unknown template classes, we have no idea what side effects such assignments have
if (mTokenizer->isCPP() &&
op1Var->isClass() &&
(!op1Var->valueType() || op1Var->valueType()->type == ValueType::Type::UNKNOWN_TYPE)) {
// Check in the library if we should bailout or not..
std::string typeName = op1Var->getTypeName();
if (startsWith(typeName, "::"))
typeName.erase(typeName.begin(), typeName.begin() + 2);
switch (mSettings->library.getTypeCheck("unusedvar", typeName)) {
case Library::TypeCheck::def:
bailoutTypeName = typeName;
break;
case Library::TypeCheck::check:
break;
case Library::TypeCheck::suppress:
case Library::TypeCheck::checkFiniteLifetime:
continue;
}
}
}
// Is there a redundant assignment?
const Token *start = tok->findExpressionStartEndTokens().second->next();
const Token *expr = varDecl ? varDecl : tok->astOperand1();
if (isInitialization)
expr = tok->previous();
// Is variable in lhs a union member?
if (tok->previous() && tok->previous()->variable() && tok->previous()->variable()->nameToken()->scope()->type == Scope::eUnion)
continue;
FwdAnalysis fwdAnalysis(mTokenizer->isCPP(), mSettings->library);
const Token* scopeEnd = ValueFlow::getEndOfExprScope(expr, scope, /*smallest*/ false);
if (fwdAnalysis.unusedValue(expr, start, scopeEnd)) {
if (!bailoutTypeName.empty()) {
if (bailoutTypeName != "auto")
reportLibraryCfgError(tok, bailoutTypeName);
continue;
}
// warn
if (!expr->variable() || !expr->variable()->isMaybeUnused())
unreadVariableError(tok, expr->expressionString(), false);
}
}
// varId, usage {read, write, modified}
Variables variables;
checkFunctionVariableUsage_iterateScopes(scope, variables);
// Check usage of all variables in the current scope..
for (std::map<nonneg int, Variables::VariableUsage>::const_iterator it = variables.varUsage().cbegin();
it != variables.varUsage().cend();
++it) {
const Variables::VariableUsage &usage = it->second;
// variable has been marked as unused so ignore it
if (usage._var->nameToken()->isAttributeUnused() || usage._var->nameToken()->isAttributeUsed())
continue;
// skip things that are only partially implemented to prevent false positives
if (usage.mType == Variables::pointerPointer ||
usage.mType == Variables::pointerArray ||
usage.mType == Variables::referenceArray)
continue;
const std::string &varname = usage._var->name();
const Variable* var = symbolDatabase->getVariableFromVarId(it->first);
// variable has had memory allocated for it, but hasn't done
// anything with that memory other than, perhaps, freeing it
if (usage.unused() && !usage._modified && usage._allocateMemory)
allocatedButUnusedVariableError(usage._lastAccess, varname);
// variable has not been written, read, or modified
else if (usage.unused() && !usage._modified) {
if (!usage._var->isMaybeUnused()) {
unusedVariableError(usage._var->nameToken(), varname);
}
}
// variable has not been written but has been modified
else if (usage._modified && !usage._write && !usage._allocateMemory && var && !var->isStlType()) {
if (var->isStatic()) // static variables are initialized by default
continue;
unassignedVariableError(usage._var->nameToken(), varname);
}
// variable has been read but not written
else if (!usage._write && !usage._allocateMemory && var && !var->isStlType() && !isEmptyType(var->type()) &&
!(var->type() && var->type()->needInitialization == Type::NeedInitialization::False))
unassignedVariableError(usage._var->nameToken(), varname);
else if (!usage._var->isMaybeUnused() && !usage._modified && !usage._read && var) {
const Token* vnt = var->nameToken();
bool error = false;
if (vnt->next()->isSplittedVarDeclEq() || (!var->isReference() && vnt->next()->str() == "=")) {
const Token* nextStmt = vnt->tokAt(2);
if (nextStmt->isExpandedMacro()) {
const Token* parent = nextStmt;
while (parent->astParent() && parent == parent->astParent()->astOperand1())
parent = parent->astParent();
if (parent->isAssignmentOp() && parent->isExpandedMacro())
continue;
}
while (nextStmt && nextStmt->str() != ";")
nextStmt = nextStmt->next();
error = precedes(usage._lastAccess, nextStmt);
}
if (error) {
if (mTokenizer->isCPP() && var->isClass() &&
(!var->valueType() || var->valueType()->type == ValueType::Type::UNKNOWN_TYPE)) {
const std::string typeName = var->getTypeName();
switch (mSettings->library.getTypeCheck("unusedvar", typeName)) {
case Library::TypeCheck::def:
reportLibraryCfgError(vnt, typeName);
break;
case Library::TypeCheck::check:
break;
case Library::TypeCheck::suppress:
case Library::TypeCheck::checkFiniteLifetime:
error = false;
}
}
if (error)
unreadVariableError(vnt, varname, false);
}
}
}
}
}
void CheckUnusedVar::unusedVariableError(const Token *tok, const std::string &varname)
{
if (!mSettings->severity.isEnabled(Severity::style))
return;
reportError(tok, Severity::style, "unusedVariable", "$symbol:" + varname + "\nUnused variable: $symbol", CWE563, Certainty::normal);
}
void CheckUnusedVar::allocatedButUnusedVariableError(const Token *tok, const std::string &varname)
{
if (!mSettings->severity.isEnabled(Severity::style))
return;
reportError(tok, Severity::style, "unusedAllocatedMemory", "$symbol:" + varname + "\nVariable '$symbol' is allocated memory that is never used.", CWE563, Certainty::normal);
}
void CheckUnusedVar::unreadVariableError(const Token *tok, const std::string &varname, bool modified)
{
if (!mSettings->severity.isEnabled(Severity::style))
return;
if (modified)
reportError(tok, Severity::style, "unreadVariable", "$symbol:" + varname + "\nVariable '$symbol' is modified but its new value is never used.", CWE563, Certainty::normal);
else
reportError(tok, Severity::style, "unreadVariable", "$symbol:" + varname + "\nVariable '$symbol' is assigned a value that is never used.", CWE563, Certainty::normal);
}
void CheckUnusedVar::unassignedVariableError(const Token *tok, const std::string &varname)
{
if (!mSettings->severity.isEnabled(Severity::style))
return;
reportError(tok, Severity::style, "unassignedVariable", "$symbol:" + varname + "\nVariable '$symbol' is not assigned a value.", CWE665, Certainty::normal);
}
//---------------------------------------------------------------------------
// Check that all struct members are used
//---------------------------------------------------------------------------
void CheckUnusedVar::checkStructMemberUsage()
{
if (!mSettings->severity.isEnabled(Severity::style))
return;
logChecker("CheckUnusedVar::checkStructMemberUsage"); // style
const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
for (const Scope &scope : symbolDatabase->scopeList) {
if (scope.type != Scope::eStruct && scope.type != Scope::eClass && scope.type != Scope::eUnion)
continue;
if (scope.bodyStart->fileIndex() != 0 || scope.className.empty())
continue;
if (scope.classDef->isExpandedMacro())
continue;
// Packed struct => possibly used by lowlevel code. Struct members might be required by hardware.
if (scope.bodyEnd->isAttributePacked())
continue;
if (const Preprocessor *preprocessor = mTokenizer->getPreprocessor()) {
const auto& directives = preprocessor->getDirectives();
const bool isPacked = std::any_of(directives.cbegin(), directives.cend(), [&](const Directive& d) {
return d.linenr < scope.bodyStart->linenr() && d.str == "#pragma pack(1)" && d.file == mTokenizer->list.getFiles().front();
});
if (isPacked)
continue;
}
// Bail out for template struct, members might be used in non-matching instantiations
if (scope.className.find('<') != std::string::npos)
continue;
// bail out if struct is inherited
const bool isInherited = std::any_of(symbolDatabase->scopeList.cbegin(), symbolDatabase->scopeList.cend(), [&](const Scope& derivedScope) {
const Type* dType = derivedScope.definedType;
return dType && std::any_of(dType->derivedFrom.cbegin(), dType->derivedFrom.cend(), [&](const Type::BaseInfo& derivedFrom) {
return derivedFrom.type == scope.definedType && derivedFrom.access != AccessControl::Private;
});
});
// bail out for extern/global struct
bool bailout = false;
for (const Variable* var : symbolDatabase->variableList()) {
if (var && (var->isExtern() || (var->isGlobal() && !var->isStatic())) && var->typeEndToken()->str() == scope.className) {
bailout = true;
break;
}
if (bailout)
break;
}
if (bailout)
continue;
// Bail out if some data is casted to struct..
const std::string castPattern("( struct| " + scope.className + " * ) &| %name%");
if (Token::findmatch(scope.bodyEnd, castPattern.c_str()))
continue;
// (struct S){..}
const std::string initPattern("( struct| " + scope.className + " ) {");
if (Token::findmatch(scope.bodyEnd, initPattern.c_str()))
continue;
// Bail out if struct is used in sizeof..
for (const Token *tok = scope.bodyEnd; nullptr != (tok = Token::findsimplematch(tok, "sizeof ("));) {
tok = tok->tokAt(2);
if (Token::Match(tok, ("struct| " + scope.className).c_str())) {
bailout = true;
break;
}
}
if (bailout)
continue;
for (const Variable &var : scope.varlist) {
// only warn for variables without side effects
if (!var.typeStartToken()->isStandardType() && !var.isPointer() && !astIsContainer(var.nameToken()) && !isRecordTypeWithoutSideEffects(var.type()))
continue;
if (isInherited && !var.isPrivate())
continue;
// Check if the struct member variable is used anywhere in the file
bool use = false;
for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
if (Token::Match(tok, ". %name%") && !tok->next()->variable() && !tok->next()->function() && tok->next()->str() == var.name()) {
// not known => assume variable is used
use = true;
break;
}
if (tok->variable() != &var)
continue;
if (tok != var.nameToken()) {
use = true;
break;
}
}
if (!use) {
std::string prefix = "struct";
if (scope.type == Scope::ScopeType::eClass)
prefix = "class";
else if (scope.type == Scope::ScopeType::eUnion)
prefix = "union";
unusedStructMemberError(var.nameToken(), scope.className, var.name(), prefix);
}
}
}
}
void CheckUnusedVar::unusedStructMemberError(const Token* tok, const std::string& structname, const std::string& varname, const std::string& prefix)
{
reportError(tok, Severity::style, "unusedStructMember", "$symbol:" + structname + "::" + varname + '\n' + prefix + " member '$symbol' is never used.", CWE563, Certainty::normal);
}
bool CheckUnusedVar::isRecordTypeWithoutSideEffects(const Type* type)
{
// a type that has no side effects (no constructors and no members with constructors)
/** @todo false negative: check constructors for side effects */
const std::pair<std::map<const Type *,bool>::iterator,bool> found=mIsRecordTypeWithoutSideEffectsMap.insert(
std::pair<const Type *,bool>(type,false)); //Initialize with side effects for possible recursions
bool & withoutSideEffects = found.first->second;
if (!found.second)
return withoutSideEffects;
// unknown types are assumed to have side effects
if (!type || !type->classScope)
return (withoutSideEffects = false);
// Non-empty constructors => possible side effects
for (const Function& f : type->classScope->functionList) {
if (!f.isConstructor() && !f.isDestructor())
continue;
if (f.argDef && Token::simpleMatch(f.argDef->link(), ") ="))
continue; // ignore default/deleted constructors
const bool emptyBody = (f.functionScope && Token::simpleMatch(f.functionScope->bodyStart, "{ }"));
const Token* nextToken = f.argDef->link();
if (Token::simpleMatch(nextToken, ") :")) {
// validating initialization list
nextToken = nextToken->next(); // goto ":"
for (const Token *initListToken = nextToken; Token::Match(initListToken, "[:,] %var% [({]"); initListToken = initListToken->linkAt(2)->next()) {
const Token* varToken = initListToken->next();
const Variable* variable = varToken->variable();
if (variable && !isVariableWithoutSideEffects(*variable)) {
return withoutSideEffects = false;
}
const Token* valueEnd = initListToken->linkAt(2);
for (const Token* valueToken = initListToken->tokAt(3); valueToken != valueEnd; valueToken = valueToken->next()) {
const Variable* initValueVar = valueToken->variable();
if (initValueVar && !isVariableWithoutSideEffects(*initValueVar)) {
return withoutSideEffects = false;
}
if ((valueToken->tokType() == Token::Type::eName) ||
(valueToken->tokType() == Token::Type::eLambda) ||
(valueToken->tokType() == Token::Type::eOther)) {
return withoutSideEffects = false;
}
const Function* initValueFunc = valueToken->function();
if (initValueFunc && !isFunctionWithoutSideEffects(*initValueFunc, valueToken,
std::list<const Function*> {})) {
return withoutSideEffects = false;
}
}
}
}
if (!emptyBody)
return (withoutSideEffects = false);
}
// Derived from type that has side effects?
if (std::any_of(type->derivedFrom.cbegin(), type->derivedFrom.cend(), [this](const Type::BaseInfo& derivedFrom) {
return !isRecordTypeWithoutSideEffects(derivedFrom.type);
}))
return (withoutSideEffects = false);
// Is there a member variable with possible side effects
for (const Variable& var : type->classScope->varlist) {
withoutSideEffects = isVariableWithoutSideEffects(var);
if (!withoutSideEffects) {
return withoutSideEffects;
}
}
return (withoutSideEffects = true);
}
bool CheckUnusedVar::isVariableWithoutSideEffects(const Variable& var)
{
const Type* variableType = var.type();
if (variableType) {
if (!isRecordTypeWithoutSideEffects(variableType))
return false;
} else {
if (WRONG_DATA(!var.valueType(), var.typeStartToken()))
return false;
const ValueType::Type valueType = var.valueType()->type;
if ((valueType == ValueType::Type::UNKNOWN_TYPE) || (valueType == ValueType::Type::NONSTD))
return false;
}
return true;
}
bool CheckUnusedVar::isEmptyType(const Type* type)
{
// a type that has no variables and no constructor
const std::pair<std::map<const Type *,bool>::iterator,bool> found=mIsEmptyTypeMap.insert(
std::pair<const Type *,bool>(type,false));
bool & emptyType=found.first->second;
if (!found.second)
return emptyType;
if (type && type->classScope && type->classScope->numConstructors == 0 &&
(type->classScope->varlist.empty())) {
return (emptyType = std::all_of(type->derivedFrom.cbegin(), type->derivedFrom.cend(), [this](const Type::BaseInfo& bi) {
return isEmptyType(bi.type);
}));
}
// unknown types are assumed to be nonempty
return (emptyType = false);
}
bool CheckUnusedVar::isFunctionWithoutSideEffects(const Function& func, const Token* functionUsageToken,
std::list<const Function*> checkedFuncs)
{
// no body to analyze
if (!func.hasBody()) {
return false;
}
for (const Token* argsToken = functionUsageToken->next(); !Token::simpleMatch(argsToken, ")"); argsToken = argsToken->next()) {
const Variable* argVar = argsToken->variable();
if (argVar && argVar->isGlobal()) {
return false; // TODO: analyze global variable usage
}
}
bool sideEffectReturnFound = false;
std::set<const Variable*> pointersToGlobals;
for (const Token* bodyToken = func.functionScope->bodyStart->next(); bodyToken != func.functionScope->bodyEnd;
bodyToken = bodyToken->next()) {
// check variable inside function body
const Variable* bodyVariable = bodyToken->variable();
if (bodyVariable) {
if (!isVariableWithoutSideEffects(*bodyVariable)) {
return false;
}
// check if global variable is changed
if (bodyVariable->isGlobal() || (pointersToGlobals.find(bodyVariable) != pointersToGlobals.end())) {
const int indirect = bodyVariable->isArray() ? bodyVariable->dimensions().size() : bodyVariable->isPointer();
if (isVariableChanged(bodyToken, indirect, mSettings, mTokenizer->isCPP())) {
return false;
}
// check if pointer to global variable assigned to another variable (another_var = &global_var)
if (Token::simpleMatch(bodyToken->tokAt(-1), "&") && Token::simpleMatch(bodyToken->tokAt(-2), "=")) {
const Token* assigned_var_token = bodyToken->tokAt(-3);
if (assigned_var_token && assigned_var_token->variable()) {
pointersToGlobals.insert(assigned_var_token->variable());
}
}
}
}
// check nested function
const Function* bodyFunction = bodyToken->function();
if (bodyFunction) {
if (std::find(checkedFuncs.cbegin(), checkedFuncs.cend(), bodyFunction) != checkedFuncs.cend()) { // recursion found
continue;
}
checkedFuncs.push_back(bodyFunction);
if (!isFunctionWithoutSideEffects(*bodyFunction, bodyToken, checkedFuncs)) {
return false;
}
}
// check returned value
if (Token::simpleMatch(bodyToken, "return")) {
const Token* returnValueToken = bodyToken->next();
// TODO: handle complex return expressions
if (!Token::simpleMatch(returnValueToken->next(), ";")) {
sideEffectReturnFound = true;
continue;
}
// simple one-token return
const Variable* returnVariable = returnValueToken->variable();
if (returnValueToken->isLiteral() ||
(returnVariable && isVariableWithoutSideEffects(*returnVariable))) {
continue;
}
sideEffectReturnFound = true;
}
// unknown name
if (bodyToken->isNameOnly()) {
return false;
}
}
return !sideEffectReturnFound;
}
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