🚀 go-pugleaf

(clamage@Eng.Sun.COM (Steve Clamage))

|   In article 460@news.bridge.net, David Byrden <100101.2547@compuserve.com>
|   writes:
|   >Why, in the Septenber draft standard, is an allocator-specific verrion
|   >of 'new' provided;
|   >
|   >20.1.4.4
|   >
|   >           new(x) T    
|   >
|   >    returns an X::types<T>::pointer, where x is of an 
|   >    allocator type X

|   You are actually referring to the "placement new" syntax not having a
|   corresponding "placement delete" syntax.

Yes, and this is very annoying.  The lack of a placement-delete makes
placement-new nearly useless.  I can't, in fact, think of a single way that
placement-new could be used properly.


|   No good syntax was found for such. The obvious syntax
|   	delete (x) p;
|   leads to too many ambiguities. More importantly, it means that the
|   point of deletion would somehow have to know what placement version
|   of "new" was used and what the parameters were. Needing that knowledge
|   would make "placement delete" unsafe and hard to use. (Consider the
|   general case where the "new" and "delete" expressions are in different
|   compilation units, and the parameters to "new" affect how "delete"
|   should be called.)


The caller of 'delete' already has to know the allocation policy of the
object -- otherwise it would not know that it was safe to delete.  Further,
we already do this sort of thing all the time -- but we have to code it
explicitly, i.e., remove object from collection, delete object.

The lack of a placement-delete is on of the many factors in C++ conspiring
to make it absolutely impossible to make generic collections that hold
actual objects (with constructors) instead of just pointers.


</Matt>

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Matt Timmermans               | Phone:  +1 613 596-2233
Microstar Software Ltd.       | Fax:    +1 613 596-5934
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