Re: State of AVX512 support in NetBSD?

On Mon, 29 Jul 2024, Thomas Klausner wrote:

> For my recent build trouble of lang/ghc98 that only I can see but pho@
> can't[1], upstream has suggested it might be a problem with AVX512
> support[2] in NetBSD. (My CPU supports AVX512, pho's doesn't.)
>
> I'll give their suggestion (using -D__STDC_NO_ATOMICS__) a try, but
> does anyone know the actual state of AVX512 support on NetBSD?
>

I don't think this is AVX-512-related. The programs would've crashed with
an `Illegal instruction' like my test progs (attached) did on OpenBSD.

I think it may due to how the *BSDs handle conversions of multi-byte
chars. in non-UTF-8 locales:

In my test program, glibc's mbstowcs(3) returns -1 when fed UTF-8 chars
and the locale is C/POSIX.

*BSDs treat the same string as a byte sequence--ie. mbstowcs() == strlen()
if LC_ALL=C/POSIX.

If, however, the locale is some UTF-8 one (say, C.UTF-8), then both Linux
and the BSDs behave the same.

Try the attached like so on NetBSD and Linux:

```
$ make clean; LC_ALL=C.UTF-8 make
$ make clean; LC_ALL=C make
```

compare the hs*.txt files on Linux and NetBSD and notice that when LC_ALL=C
_hs_text_measure_off() returns a negative number (as it says it will in the
code when the buffer is short) for LC_ALL=C.

HTH,

-RVP