Re: CVS commit: src/sbin/newfs

[Greg Troxel <gdt%lexort.com@localhost>]

Taylor R Campbell <campbell+netbsd-source-changes-d%mumble.net@localhost> writes:

> Well, what happened is:
>
> 1. I was drafting posix_memalign and aligned_alloc for libbsdmalloc in
>    response to the thread about static program size yesterday, and
>    carefully reading the specs -- POSIX 2018, C11 -- to make sure I
>    got all the details right.
>
> 2. I saw a silly restriction in C11, that aligned_alloc(A, S) requires
>    A to divide S.
>
> 3. For the sake of encouraging portable code, I figured we should
>    enforce that restriction, so I went ahead and did that in both the
>    libbsdmalloc front end I was writing and in jemalloc.  (This caused
>    a bunch of tests to start failing.)
>
> 4. I audited all the uses of aligned_alloc in tree to make sury they
>    meet the restriction (which fixed the tests).
>
> 5. Someone pointed out that the silly restriction that was imposed in
>    C11 had actually been lifted in C17:
>
>         (C11) The value of alignment shall be a valid alignment
>         supported by the implementation and the value of size shall be
>         an integral multiple of alignment.
>
>         (C17) If the value of alignment is not a valid alignment
>         supported by the implementation the function shall fail by
>         returning a null pointer.
>
> 6. So I reverted the jemalloc enforcement of the C11 restriction, and
>    reverted the fixes made to conform to it, and removed the
>    restriction in the new libbsdmalloc code, and we're more or less
>    back to where we started.
>
> Except I am now reminded that I updated t_posix_memalign.c to verify
> this silly restriction of aligned_alloc, so I'd better go fix that
> before a bunch of tests start failing again!

Thanks for taking the time to explain so thoroughly.  So we are back to
status quo ante-fixum, which is by definition always ok :-)