What is the point of `void func() throw(type)`?

Question

I know this is a valid c++ program. What is the point of the throw in the function declarement? AFAIK it does nothing and isnt used for anything.

#include &l         


        

Answer 1

Basically this:

void func() throw(std::exception,B) {  /* Do Stuff */}

Is just shorthand fro this:

void func()
{
    try
    {
        /* Do Stuff */ 
    }
    catch(std::exception const& e)
    {
        throw;
    }
    catch(B const& e)
    {
        throw;
    }
    catch(...)
    {
        unexpected();  // This calls terminate
                       // i.e. It never returns.
    }
}

Calling terminate() is rarely what you want, as the stack is not unwound and thus all your efforts in RAII is wasted. The only exception to the rule is declaring an empty throw list and this is mainly for documentation purposes to show that you are supporting the no-throw exception gurantee (you should still manually catch all exceptions in this situation).

Some important (imho) places that should be no-throw are destructors and swap() methods. Destructors are rarely explicitly marked no-throw but swap() are quite often marked no-throw.

void myNoThrowFunc() throws()  // No-Throw (Mainlly for doc purposes).
{
    try
    {
        /* Do Stuff */
    }
    catch(...)  // Make sure it does not throw.
    {
        /* Log and/or do cleanup */
    }
}