Re: [musl] [BUG] sysconf implementing _SC_NPROCESSORS_(CONF|ONLN) incorrectly

[Rich Felker <dalias@libc.org>]

On Wed, Apr 15, 2020 at 12:04:43PM +0200, Szabolcs Nagy wrote:
> * Norbert Lange <nolange79@gmail.com> [2020-04-15 11:57:16 +0200]:
> > I can't comment on whether glibc should be emulated. The point I am trying
> > to make is that it might be better to let the compilation fail by default,
> > or not provide the function at all.
> > 
> > The implementation right now doesn't seem sufficient (to put it midly) and
> > it prevents detection and automatic fallbacks. For example trace-cmd would
> > do this, and would work nicely - but instead it will gets musls
> > implementation that's defeated by setting an affinity mask.
> 
> the point is that the glibc implementation is not sufficient either.
> 
> you don't get what you think you get as a result so you better off
> to just always do the fallback.
> 
> identifying musl via a macro would be extremely bad in this case
> since we are discussing to change the implementation and the
> macro would not reflect that so a wrong default would be baked
> into the source (which shows why it is a good idea not to provide
> such a macro at all: most developers dont understand how to use
> such macros and by now there would be a lot of broken musl
> workarounds that are not relevant to the latest musl version).

Note that this could be represented by the sort of macro exposure I
want to propose on libc-coord: not __MUSL__ but something like
_EXT_SC_...NPROC_REFLECTS_RESOURCE_CONSTRAINTS. Of course then it
would document a specific permanent (without redefining the _SC_*
macros to different values for a new one) behavior, so this may not be
a good choice. As a worst case the behavior could be documented to the
application via another sysconf variable. :-P

Rich