Re: Exception handling the right way

From:

"Chris M. Thomasson" <no@spam.invalid>

Newsgroups:

comp.lang.c++

Date:

Tue, 9 Sep 2008 02:12:16 -0700

Message-ID:

<A0rxk.41790$_s1.2861@newsfe07.iad>

"Chris M. Thomasson" <no@spam.invalid> wrote in message
news:jUqxk.41788$_s1.19525@newsfe07.iad...

"Bart Friederichs" <bf@tbwb.nl> wrote in message
news:48c63859$0$186$e4fe514c@news.xs4all.nl...

anon wrote:

I like this explanation:
http://www.boost.org/community/error_handling.html

Thanks for the pointers, and I started a little experimenting. Soon I
ran into this problem:

int main () {
A *a; B *b; C *c;
try {
    a = new A();
    b = new B();
    c = new C();
   } catch (...) {
     delete a;
     delete b;
     delete c;
   }

return 0;
}

there are some errors here... Simple fix:

int main() {
A* a = NULL;
B* b = NULL;
C* c = NULL;
try {
   a = new A;
   b = new B;
   c = new C;
} catch(...) {
   delete a;
   delete b;
   delete c;
}
return 0;
}

Ummm... Well, I forgot to destroy the pointers in the case of no
exception!!! You could do this:

int main() {
  A* a = NULL;
  B* b = NULL;
  C* c = NULL;
  try {
    a = new A;
    b = new B;
    c = new C;
  } catch(...) {
  }
  delete a;
  delete b;
  delete c;
  return 0;
}

Man, that looks like total crap when compared to the version which makes use
of smart pointers...

OUCH!

;^(

or, even better:

int main() {
std::auto_ptr<A> a(new A);
std::auto_ptr<B> b(new B);
std::auto_ptr<C> c(new C);
return 0;
}

Which results in a runtime error when B's contructor throws an
exception. How to correctly free resources on the heap in exception
handling?