Re: C++... is it dying?
On 2008-07-22 11:53:56 -0400, shablool <ssnail@gmail.com> said:
On Jul 21, 11:10??pm, rpbg...@yahoo.com (Roland Pibinger) wrote:
Moreover, you don't need user-defined allocators when the
library merely uses value semantics (values and copies of
values). ??Even if there were a need for allocators they
wouldn't have to be template parameters.
Allocators are a misfeature. ??, Stepanov introduced them to
support different pointer models (small, medium, large, etc.).
Why they lived on after this need died, I can't fathom myself.
AFAIK, allocators were not part of the original STL. According to this
paper Stroustrup introduced them into STL:www.research.att.com/~bs/DnE200
5.pdf
STL allocators does not enable the user to associate a container
instance with specific memory-pool. As a matter of fact, multiple
instances of various STL containers would typically use the same
memory-storage (i.e., malloc/new).
First, let's be clear about the origin: they were, indeed, originally
used to mask the differences between different pointer types under
Windows, which had near (DS-relative) and far (absolute, loosely
speaking) pointers and references.
Second, the reason that STL allocators do not support specifying
per-container memory pools is only the design compromise that allows
but doesn't require containers to treat allocators of the same type as
equal. Several STL implementations don't rely on this assumption, and
you can, in fact, have per-instance allocators. This support will be
required in C++0x.
--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)