Re: [boost] Re: [Libcwd-devel] libcwd and Boost

From: Rob Stewart (stewart_at_[hidden])
Date: 2002-09-03 12:03:07

From: Carlo Wood <carlo_at_[hidden]>
> 
> It would be pretty hard to only use stack allocated memory,
> I think.  Let me give some internal details.
> 
> What is needed are three vectors:
[snip]
> What is according to you the maximum number of
> template arguments, substitutions and qualifiers in a type?
> 
> The code also uses about 25 internal strings.
> Each of these strings might need an arbitrary size,
[snip]
> The point is that the actual size of memory needed
> is not related to the demangler code, but to the
> application and its circumstances.  And so is the
> needed memory model.
> 
> By simply allowing the user to pass an Allocator
> parameter for the most general interface, they can
> deal with this issue themself (pre-allocation, seperate
> memory pool or whatever) and adjust the load on their
> resources according to their need.
> 
> Stack allocation could be implemented through a
> "pre-allocated" memory pool in the first call (a wrapper).

Yes, the user could provide the allocator that does whatever is appropriate for
the application, and that's not a bad approach.  However, using preallocated
memory is easier than you're making it out to be.  All (!) you need to do is
create an allocator that assigns memory from a large pool that it preallocates.
IOW, instead of calling a heap function which carves memory out of a large
chunk, the allocator manages its own (smaller) large chunk. (Note that I'm not
saying this is easy, but you don't need to decide how much memory to allocate
for each data structure.)

> Actually, I think that allocators like this should
> be part of boost too, and NOT as a part of my demangler
> library, but provided seperately.

That is certainly a valid point.  Of course, you could implement it first within
your library, then submit it for a separate review later.  Then, when accepted,
you could change demangle() to use that new allocator.  (Isn't it good that I'm
here to suggest work for you?)  Seriously, if you were to do the work to
implement your library, it could be the start of a set of commonly needed
allocators.

-- 
Rob Stewart                           stewart_at_[hidden]
Software Engineer                     http://www.sig.com
Susquehanna International Group, LLP  using std::disclaimer;