[Toybox] musl intentionally broke chrt

[Owen Shepherd]

Per POSIX, <sched.h> is in ths [PS] (Process Scheduling) option. You can
identify whether [PS] is implemented at compile time, by the value of
_POSIX_PRIORITY_SCHEDULING defined in <unistd.h>. This can be one of

* Undefined or -1, functionality never supported
* 0, functionally *maybe* supported (you can enquire with
sysconf(_SC_PRIORITY_SCHEDULING) at runtime). You can compile against it,
but it might not work.
* 200809L, supported per POSIX 2008 (Or potentially a different value for a
different version of POSIX)

(The sysconf call can return either -1 or 200809L)

musl doesn't define _POSIX_PRIORITY_SCHEDULING, so per POSIX is declaring
that it does not support that function grouping.

On Wed, Aug 30, 2017 at 9:42 AM Rob Landley <rob at landley.net> wrote:

> On 08/29/2017 10:32 AM, enh wrote:
> > On Tue, Aug 29, 2017 at 8:32 AM, enh <enh at google.com> wrote:
> >> can't you just infer musl from the relatively small
> >
> > ...number of c libraries out there...
>
> It would work, but I'm uncomfortable with it.
>
> People keep threatening to port toybox to to BSD and MacOS, there is an
> active uClibc fork buildroot's using, it's posible newlib, klibc, or
> dietlibc will grow legs someday, far down on my todo list is maybe
> porting toybox to xv6, what library is fuchsia using, musl itself didn't
> publicly exist ~5 years ago...
>
> The posix API is insufficient so I'm using Linux as my API, but
> freebsd's Linux emulation layer is a viable target too, and I wanted the
> rest of it to be as generic as I could with target-specific stuff hidden
> in portability.h. That means C library, compiler, processor architecture...
>
> I'm not sure that's _achievable_ with musl refusing to identify itself
> because its' experience is universal and everyone else is wrong...
>
> Sigh. If I'm going to have the "else case" apply workarounds, I might as
> well make the workarounds apply to everybody. Calling the syscalls
> directly isn't that big a deal.
>
> But having musl stay broken because it broke itself seems pretty
> reasonable too. The fact is, Linux has a system call and the man page
> says we have a certain behavior, and musl isn't supporting that. If you
> build against a uClibc where you switched off regex support, grep won't
> work. If you build against a musl you haven't fixed, chrt won't work...
>
> (This is one of those "the choices are close enough that there's no
> obvious winner" things that's harder to make than a more important
> decision would be. :)
>
> Right now I've thrown it back on the todo list, which means "musl stays
> broken" is the default for now. Probably acceptable. Lemme finish this
> utf8 plumbing and then I need to fix ps again, then get back to... was
> lsof or dd next?
>
> Rob
>
> (Taking a break from endless GPS. For some reason it takes me about a
> day to switch mental contexts after doing serious GPS stuff, and I keep
> getting sucked back into "5 more minutes of GPS, just this one quick
> thing" that turns into 8 hours, so I'm saying no a bit because the
> toybox todo heap is teetering dangerously September 19th is the 3 month
> anniversary of last release which means time for a new one...)
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