From: DJ Delorie <dj@redhat.com>
To: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>,
Paul Eggert <eggert@cs.ucla.edu>
Cc: libc-alpha@sourceware.org
Subject: Re: [patch] aligned_alloc: conform to C17
Date: Thu, 16 Mar 2023 20:00:56 -0400 [thread overview]
Message-ID: <xno7os2qmf.fsf@greed.delorie.com> (raw)
In-Reply-To: <3d314630-5ba2-65eb-06c1-50a4966516ca@linaro.org>
Adhemerval Zanella Netto via Libc-alpha <libc-alpha@sourceware.org>
writes:
> Hi D.J, this patch does not build correctly [1]. Maybe you send it too soon?
Sigh, fixing...
also, it's DJ not D.J.
>> + GLIBC_2.38 {
>> + __libc_aligned_alloc;
>> + }
> How is is actually used? There is no redirection in the header if -std=c17 is used,
> nor any abilist update.
aligned_alloc() used to be a weak alias to _libc_memalign but since they
now do different things, I changed it to a weak alias to
_libc_aligned_alloc. I put the new symbol in so that it's the same as
the old symbol.
Ug, I need to update all the .abilist files too...
Paul Eggert <eggert@cs.ucla.edu> writes:
> powerof2 (0) == 1, unfortunately. Does the C standard let aligned_alloc
_mid_memalign enforces a minimum alignment so this isn't an issue, other
than the pedantry of whether 0 is an iso-valid alignment.
I suspect fixing the macro might be more generally useful than fixing
this edge case, but I haven't looked for any potential side-effects.
As for "non-negative alignment" I assume they mean "passing a negative
number as `alignment' to aligned_alloc()", not referring to the power of
two itself.
"Every valid alignment value shall be a nonnegative integral power of
two."
but alignments are also to be represented by type size_t, which is
integral and unsigned, so no interpretation of "nonnegative integral
power of two" even makes sense, other than the pedantic align=zero.
The only other hint is this one:
"The types char, ... shall have the weakest alignment requirement."
That's align=1, implying that align=0 cannot be a valid alignment.
next prev parent reply other threads:[~2023-03-17 0:00 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-16 20:48 DJ Delorie
2023-03-16 21:00 ` Adhemerval Zanella Netto
2023-03-17 0:00 ` DJ Delorie [this message]
2023-03-17 6:33 ` Paul Eggert
2023-03-17 19:55 ` DJ Delorie
2023-03-16 22:00 ` Paul Eggert
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