Date: Wed, 15 Apr 2020 12:01:39 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com, Florian Weimer <fw@...eb.enyo.de>, Norbert Lange <nolange79@...il.com> Subject: Re: [BUG] sysconf implementing _SC_NPROCESSORS_(CONF|ONLN) incorrectly On Wed, Apr 15, 2020 at 12:04:43PM +0200, Szabolcs Nagy wrote: > * Norbert Lange <nolange79@...il.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
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