Why a try/catch in priority_queue::push/pop?!?

[Paolo Carlini]

Hi,

today I noticed by chance these strange things: for example, push 
(likewise pop):

      void
      push(const value_type& __x)
      {
    try
        {
          c.push_back(__x);
          std::push_heap(c.begin(), c.end(), comp);
        }
    catch(...)
        {
          c.clear();
          __throw_exception_again;
        }
      }

why that try/catch? Certainly I cannot find support in the Standard for 
its presence and, AFAICS, can also run against reasonable user 
expectations: i.e., if c.push_back throws (e.g., bad_alloc) the user may 
reasonably expect that c remains unchanged! The case of push_heap is 
different, more complex, but again, I don't think the user, basing on 
the letter of the Standard can generally (i.e., portably) expect that a 
clear() will be invoked (supposedly to do him the "favor" of a 
"consistent", read, empty! , container)

I think the try/catch is very old, coming from the HP/SGI STL, maybe I 
missing historical facts which I'd like to know... Anyone helping?

Thanks,
Paolo.