Is there a way to determine if an exception is occurring?

Question

In a destructor, is there a way to determine if an exception is currently being processed?

Answer 1

You can use std::uncaught_exception(), but it might not do what you think it does: see GoTW#47 for more information.

Answer 2

As Luc said, you can use std::uncaught_exception(). But why do you want to know? In any case, destructors should never throw exceptions!

Answer 3

You can use the Boost Test Library. Look here for a small example:

struct my_exception1
{
    explicit    my_exception1( int res_code ) : m_res_code( res_code ) {}
    int         m_res_code;
};


struct my_exception2
{
    explicit    my_exception2( int res_code ) : m_res_code( res_code ) {}
    int         m_res_code;
};

class dangerous_call {
public:
    dangerous_call( int argc ) : m_argc( argc ) {}
    int operator()()
    {
        if( m_argc < 2 )
            throw my_exception1( 23 );
        if( m_argc > 3 )
            throw my_exception2( 45 );
        else if( m_argc > 2 )
            throw "too many args";

        return 1;
    }

private:
    int     m_argc;
};


void translate_my_exception1( my_exception1 const& ex )
{
    std::cout << "Caught my_exception1(" << ex.m_res_code << ")"<< std::endl;
}


void translate_my_exception2( my_exception2 const& ex )
{
    std::cout << "Caught my_exception2(" << ex.m_res_code << ")"<< std::endl;
}



int 
cpp_main( int argc , char *[] )
{ 
    ::boost::execution_monitor ex_mon;
    ex_mon.register_exception_translator<my_exception1>(
        &translate_my_exception1);
    ex_mon.register_exception_translator<my_exception2>(
        &translate_my_exception2);
    try{
     // ex_mon.detect_memory_leak( true);
      ex_mon.execute( ::boost::unit_test::callback0<int>( 
          dangerous_call( argc ) ) );
    }   
    catch ( boost::execution_exception const& ex ) {
        std::cout << "Caught exception: " << ex.what() << std::endl;
    }
    return 0;
}

You have to dig in the documentation. It is a very powerful library to test your software! Anyway with the help of Boost you can catch any kind of exception trigerred anywhere in your function test!