RE: [Boost-users] Re: Guidelines for effective exception usage

From: Mark Storer (MStorer_at_[hidden])
Date: 2004-08-23 18:51:14

> No it is not.  Even if you aren't throwing due to memory starvation,
> you could run out of memory during unwinding, when the exception is
> copied.  That leads you directly to terminate().  Do not pass Go; do
> not collect $200.

Venturing a little far afield, but one technique I've heard of is to grab a block, so you can release it in low-memory situations (or just every time you throw).  This ensures (in theory) that you'll have enough memory to copy your exception, create your strings, and so on.  If you manage to recover, you just grab another block ("prime the pump") and soldier bravely forward.

Given STL's habit of allowing people to specify an allocator, you could even go so far as to build a custom allocator that worked on some pre-allocated block of memory for your exceptions (strings, vectors, whatever you deem necessary).

Either way, you'll run out of memory a little earlier (not a big issue in many environments), but you _will_ get to pocket the $200.  It's not hard to imagine an environment where grabbing a couple extra Kb would be a Bad Thing, but I'd think this trick would be fine on PCs and the like.

--Mark Storer
  Senior Software Engineer
  Verity, Inc.