TITLE: new and sizes of zero

(Newsgroups: comp.lang.c++.moderated, 29 Jan 97)


GENTER: Rick Genter

> Is
> p = new void*[ 0 ];

> guaranteed to set p to a non-NULL value 


OLIVA: Alexandre Oliva <oliva@dcc.unicamp.br>

The Dec'96 DWP states in [expr.new, paragraph 8] that a new expression
involving a zero-sized array creates an array of no elements, and it
returns a pointer whose value is different from any other pointer.

GENTER:

> ... (barring being out of memory, of course)?


OLIVA:

new expressions are no longer allowed to result [in] NULL.  If no memory
can be allocated, operator new should throw a bad_alloc exception.


GENTER:

> Reading Stroustrup it says that ::operator new(0) is guaranteed to return a
> non-NULL value, but it says nothing about zero-dimensioned dynamic arrays.
> Thanks in advance.


OLIVA:

::operator new(size_t) is not used for arrays, although AFAIK, when
Stroustrup wrote the book, ::operator new[](size_t) did not exist yet.
Anyway, even for an array of no elements, the number of bytes
requested to the allocation function may be non-zero.  Anyway, even if
the requested size is zero, a pointer that is different from any other
pointer must be returned.

[ Netspeak decoder ring:

	AFAIK = as far as i know
	BTW   = by the way
	OTHO  = on the other hand
	IMHO  = in my humble opinion
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