Re: How expensive are exceptions?

From:

Risto Lankinen <rlankine@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Wed, 6 Jun 2007 08:21:29 CST

Message-ID:

<1181108138.561386.227140@n4g2000hsb.googlegroups.com>

On 5 kes?, 22:45, Mathias Gaunard <loufo...@gmail.com> wrote:

Catching requires the type to be identified with RTTI.

This is a very common misconception about exceptions.
In fact, catch blocks can be resolved at compile time,
and RTTI _might_ be used but is not required at all.

Observe this program to print "Base" (the compile-time
type of the thrown object) whereas if RTTI were used it
would print "Derived" (the run-time type of the thrown
object):

  - - -

struct Base
{
     virtual ~Base()
     {
     }
};

struct Derived : public Base
{
};

int main()
{
     Base *p = new Derived;

     try
     {
         throw *p;
     }
     catch( const Derived & )
     {
         cout << "Derived" << endl;
     }
     catch( const Base & )
     {
         cout << "Base" << endl;
     }
     catch( ... )
     {
         cout << "<unknown>" << endl;
     }

     delete p;

     return 0;
}

  - - -

Cheers!

  - Risto -

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