Re: codecvt problem

From:
Seungbeom Kim <musiphil@bawi.org>
Newsgroups:
comp.lang.c++.moderated
Date:
Thu, 23 Jun 2011 14:42:07 CST
Message-ID:
<itu1vo$q84$1@usenet.stanford.edu>
On 2011-06-20 12:16, Ulrich Eckhardt wrote:

Seungbeom Kim wrote:

On 2011-06-17 05:42, Ulrich Eckhardt wrote:

This means that all "clean" initialisations
mentioned in this thread (e.g. "mbstate_t s = {};" or "mbstate_t s =
mbstate_t();") are actually not guaranteed to work.


I cannot understand why not. Can you explain it further?


1. a null pointer doesn't have to have all its bits zero
2. memset(&ptr, 0, sizeof ptr) only guarantees that all bits are zero, but
not that 'ptr' becomes a null pointer
3. above mentioned "clean" initialisations of pointers yield null pointers

With that, assuming the spec requires an initialisation with memset(),

other

initialisations where a pointer might become a null pointer are actually

not

portable, because they give a different result.


I see your point. I highly doubt that such implementations that ask
users to use memset will not work with real null pointers produced by
"clean" initialisations; i.e. I expect that they are based on the
assumption, or guarantee, that memset does produce a real null pointer;
i.e. that a null pointer is all-bits-zero.

--
Seungbeom Kim

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