/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2021 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 "checkexceptionsafety.h"
#include "settings.h"
#include "symboldatabase.h"
#include <set>
#include <utility>
//---------------------------------------------------------------------------
// Register CheckExceptionSafety..
namespace {
CheckExceptionSafety instance;
}
//---------------------------------------------------------------------------
void CheckExceptionSafety::destructors()
{
if (!mSettings->severity.isEnabled(Severity::warning))
return;
const SymbolDatabase* const symbolDatabase = mTokenizer->getSymbolDatabase();
// Perform check..
for (const Scope * scope : symbolDatabase->functionScopes) {
const Function * function = scope->function;
if (!function)
continue;
// only looking for destructors
if (function->type == Function::eDestructor) {
// Inspect this destructor.
for (const Token *tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) {
// Skip try blocks
if (Token::simpleMatch(tok, "try {")) {
tok = tok->next()->link();
}
// Skip uncaught exceptions
else if (Token::simpleMatch(tok, "if ( ! std :: uncaught_exception ( ) ) {")) {
tok = tok->next()->link(); // end of if ( ... )
tok = tok->next()->link(); // end of { ... }
}
// throw found within a destructor
else if (tok->str() == "throw") {
destructorsError(tok, scope->className);
break;
}
}
}
}
}
void CheckExceptionSafety::destructorsError(const Token * const tok, const std::string &className)
{
reportError(tok, Severity::warning, "exceptThrowInDestructor",
"Class " + className + " is not safe, destructor throws exception\n"
"The class " + className + " is not safe because its destructor "
"throws an exception. If " + className + " is used and an exception "
"is thrown that is caught in an outer scope the program will terminate.", CWE398, Certainty::normal);
}
void CheckExceptionSafety::deallocThrow()
{
if (!mSettings->severity.isEnabled(Severity::warning))
return;
const bool printInconclusive = mSettings->certainty.isEnabled(Certainty::inconclusive);
const SymbolDatabase* const symbolDatabase = mTokenizer->getSymbolDatabase();
// Deallocate a global/member pointer and then throw exception
// the pointer will be a dead pointer
for (const Scope * scope : symbolDatabase->functionScopes) {
for (const Token *tok = scope->bodyStart->next(); tok != scope->bodyEnd; tok = tok->next()) {
// only looking for delete now
if (tok->str() != "delete")
continue;
// Check if this is something similar with: "delete p;"
tok = tok->next();
if (Token::simpleMatch(tok, "[ ]"))
tok = tok->tokAt(2);
if (!tok || tok == scope->bodyEnd)
break;
if (!Token::Match(tok, "%var% ;"))
continue;
// we only look for global variables
const Variable *var = tok->variable();
if (!var || !(var->isGlobal() || var->isStatic()))
continue;
const unsigned int varid(tok->varId());
// Token where throw occurs
const Token *throwToken = nullptr;
// is there a throw after the deallocation?
const Token* const end2 = tok->scope()->bodyEnd;
for (const Token *tok2 = tok; tok2 != end2; tok2 = tok2->next()) {
// Throw after delete -> Dead pointer
if (tok2->str() == "throw") {
if (printInconclusive) { // For inconclusive checking, throw directly.
deallocThrowError(tok2, tok->str());
break;
}
throwToken = tok2;
}
// Variable is assigned -> Bail out
else if (Token::Match(tok2, "%varid% =", varid)) {
if (throwToken) // For non-inconclusive checking, wait until we find an assignment to it. Otherwise we assume it is safe to leave a dead pointer.
deallocThrowError(throwToken, tok2->str());
break;
}
// Variable passed to function. Assume it becomes assigned -> Bail out
else if (Token::Match(tok2, "[,(] &| %varid% [,)]", varid)) // TODO: No bailout if passed by value or as const reference
break;
}
}
}
}
void CheckExceptionSafety::deallocThrowError(const Token * const tok, const std::string &varname)
{
reportError(tok, Severity::warning, "exceptDeallocThrow", "Exception thrown in invalid state, '" +
varname + "' points at deallocated memory.", CWE398, Certainty::normal);
}
//---------------------------------------------------------------------------
// catch(const exception & err)
// {
// throw err; // <- should be just "throw;"
// }
//---------------------------------------------------------------------------
void CheckExceptionSafety::checkRethrowCopy()
{
if (!mSettings->severity.isEnabled(Severity::style))
return;
const SymbolDatabase* const symbolDatabase = mTokenizer->getSymbolDatabase();
for (const Scope &scope : symbolDatabase->scopeList) {
if (scope.type != Scope::eCatch)
continue;
const unsigned int varid = scope.bodyStart->tokAt(-2)->varId();
if (varid) {
for (const Token* tok = scope.bodyStart->next(); tok && tok != scope.bodyEnd; tok = tok->next()) {
if (Token::simpleMatch(tok, "catch (") && tok->next()->link() && tok->next()->link()->next()) { // Don't check inner catch - it is handled in another iteration of outer loop.
tok = tok->next()->link()->next()->link();
if (!tok)
break;
} else if (Token::Match(tok, "%varid% .", varid)) {
const Token *parent = tok->astParent();
while (Token::simpleMatch(parent->astParent(), "."))
parent = parent->astParent();
if (Token::Match(parent->astParent(), "%assign%|++|--|(") && parent == parent->astParent()->astOperand1())
break;
} else if (Token::Match(tok, "throw %varid% ;", varid))
rethrowCopyError(tok, tok->strAt(1));
}
}
}
}
void CheckExceptionSafety::rethrowCopyError(const Token * const tok, const std::string &varname)
{
reportError(tok, Severity::style, "exceptRethrowCopy",
"Throwing a copy of the caught exception instead of rethrowing the original exception.\n"
"Rethrowing an exception with 'throw " + varname + ";' creates an unnecessary copy of '" + varname + "'. "
"To rethrow the caught exception without unnecessary copying or slicing, use a bare 'throw;'.", CWE398, Certainty::normal);
}
//---------------------------------------------------------------------------
// try {} catch (std::exception err) {} <- Should be "std::exception& err"
//---------------------------------------------------------------------------
void CheckExceptionSafety::checkCatchExceptionByValue()
{
if (!mSettings->severity.isEnabled(Severity::style))
return;
const SymbolDatabase* const symbolDatabase = mTokenizer->getSymbolDatabase();
for (const Scope &scope : symbolDatabase->scopeList) {
if (scope.type != Scope::eCatch)
continue;
// Find a pass-by-value declaration in the catch(), excluding basic types
// e.g. catch (std::exception err)
const Variable *var = scope.bodyStart->tokAt(-2)->variable();
if (var && var->isClass() && !var->isPointer() && !var->isReference())
catchExceptionByValueError(scope.classDef);
}
}
void CheckExceptionSafety::catchExceptionByValueError(const Token *tok)
{
reportError(tok, Severity::style,
"catchExceptionByValue", "Exception should be caught by reference.\n"
"The exception is caught by value. It could be caught "
"as a (const) reference which is usually recommended in C++.", CWE398, Certainty::normal);
}
static const Token * functionThrowsRecursive(const Function * function, std::set<const Function *> & recursive)
{
// check for recursion and bail if found
if (!recursive.insert(function).second)
return nullptr;
if (!function->functionScope)
return nullptr;
for (const Token *tok = function->functionScope->bodyStart->next();
tok != function->functionScope->bodyEnd; tok = tok->next()) {
if (Token::simpleMatch(tok, "try {"))
tok = tok->linkAt(1); // skip till start of catch clauses
if (tok->str() == "throw") {
return tok;
} else if (tok->function()) {
const Function * called = tok->function();
// check if called function has an exception specification
if (called->isThrow() && called->throwArg) {
return tok;
} else if (called->isNoExcept() && called->noexceptArg &&
called->noexceptArg->str() != "true") {
return tok;
} else if (functionThrowsRecursive(called, recursive)) {
return tok;
}
}
}
return nullptr;
}
static const Token * functionThrows(const Function * function)
{
std::set<const Function *> recursive;
return functionThrowsRecursive(function, recursive);
}
//--------------------------------------------------------------------------
// void func() noexcept { throw x; }
// void func() throw() { throw x; }
// void func() __attribute__((nothrow)); void func() { throw x; }
//--------------------------------------------------------------------------
void CheckExceptionSafety::nothrowThrows()
{
const SymbolDatabase* const symbolDatabase = mTokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
const Function* function = scope->function;
if (!function)
continue;
// check noexcept and noexcept(true) functions
if (function->isNoExcept() &&
(!function->noexceptArg || function->noexceptArg->str() == "true")) {
const Token *throws = functionThrows(function);
if (throws)
noexceptThrowError(throws);
}
// check throw() functions
else if (function->isThrow() && !function->throwArg) {
const Token *throws = functionThrows(function);
if (throws)
noexceptThrowError(throws);
}
// check __attribute__((nothrow)) or __declspec(nothrow) functions
else if (function->isAttributeNothrow()) {
const Token *throws = functionThrows(function);
if (throws)
noexceptThrowError(throws);
}
}
}
void CheckExceptionSafety::noexceptThrowError(const Token * const tok)
{
reportError(tok, Severity::error, "throwInNoexceptFunction", "Exception thrown in function declared not to throw exceptions.", CWE398, Certainty::normal);
}
//--------------------------------------------------------------------------
// void func() { functionWithExceptionSpecification(); }
//--------------------------------------------------------------------------
void CheckExceptionSafety::unhandledExceptionSpecification()
{
if (!mSettings->severity.isEnabled(Severity::style) || !mSettings->certainty.isEnabled(Certainty::inconclusive))
return;
const SymbolDatabase* const symbolDatabase = mTokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
// only check functions without exception epecification
if (scope->function && !scope->function->isThrow() &&
scope->className != "main" && scope->className != "wmain" &&
scope->className != "_tmain" && scope->className != "WinMain") {
for (const Token *tok = scope->function->functionScope->bodyStart->next();
tok != scope->function->functionScope->bodyEnd; tok = tok->next()) {
if (tok->str() == "try") {
break;
} else if (tok->function()) {
const Function * called = tok->function();
// check if called function has an exception specification
if (called->isThrow() && called->throwArg) {
unhandledExceptionSpecificationError(tok, called->tokenDef, scope->function->name());
break;
}
}
}
}
}
}
void CheckExceptionSafety::unhandledExceptionSpecificationError(const Token * const tok1, const Token * const tok2, const std::string & funcname)
{
const std::string str1(tok1 ? tok1->str() : "foo");
const std::list<const Token*> locationList = { tok1, tok2 };
reportError(locationList, Severity::style, "unhandledExceptionSpecification",
"Unhandled exception specification when calling function " + str1 + "().\n"
"Unhandled exception specification when calling function " + str1 + "(). "
"Either use a try/catch around the function call, or add a exception specification for " + funcname + "() also.", CWE703, Certainty::inconclusive);
}
//--------------------------------------------------------------------------
// 7.6.18.4 If no exception is presently being handled, evaluating a throw-expression with no operand calls std::terminate().
//--------------------------------------------------------------------------
void CheckExceptionSafety::rethrowNoCurrentException()
{
const SymbolDatabase* const symbolDatabase = mTokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
const Function* function = scope->function;
if (!function)
continue;
// Rethrow can be used in 'exception dispatcher' idiom which is FP in such case
// https://isocpp.org/wiki/faq/exceptions#throw-without-an-object
// We check the beginning of the function with idiom pattern
if (Token::simpleMatch(function->functionScope->bodyStart->next(), "try { throw ; } catch ("))
continue;
for (const Token *tok = function->functionScope->bodyStart->next();
tok != function->functionScope->bodyEnd; tok = tok->next()) {
if (Token::simpleMatch(tok, "catch (")) {
tok = tok->linkAt(1); // skip catch argument
if (Token::simpleMatch(tok, ") {"))
tok = tok->linkAt(1); // skip catch scope
else
break;
}
if (Token::simpleMatch(tok, "throw ;")) {
rethrowNoCurrentExceptionError(tok);
}
}
}
}
void CheckExceptionSafety::rethrowNoCurrentExceptionError(const Token *tok)
{
reportError(tok, Severity::error, "rethrowNoCurrentException",
"Rethrowing current exception with 'throw;', it seems there is no current exception to rethrow."
" If there is no current exception this calls std::terminate()."
" More: https://isocpp.org/wiki/faq/exceptions#throw-without-an-object",
CWE480, Certainty::normal);
}