[Toybox] [PATCH 1/2] macOS: use getconf rather than nproc for portability.

[Rob Landley]

On 11/28/18 2:16 PM, enh via Toybox wrote:
> Needed to build for macOS.
> ---
>  scripts/make.sh | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/make.sh b/scripts/make.sh
> index 306a7cd..59b1fd2 100755
> --- a/scripts/make.sh
> +++ b/scripts/make.sh
> @@ -15,7 +15,7 @@ source ./configure
>  UNSTRIPPED="generated/unstripped/$(basename "$OUTNAME")"
> 
>  # Try to keep one more cc invocation going than we have processors
> -[ -z "$CPUS" ] && CPUS=$(($(nproc)+1))
> +[ -z "$CPUS" ] && CPUS=$(($(getconf _NPROCESSORS_ONLN)+1))

Hmmm, I did that because:

  $ taskset 1 nproc
  1
  $ taskset 1 getconf _NPROCESSORS_ONLN
  8

Is there another...

  $ taskset 1 getconf -a | grep NPROC
  _NPROCESSORS_CONF                  8
  _NPROCESSORS_ONLN                  8

Sigh.

The theory was if nproc doesn't exist then $(nproc) resolves to an empty string
and $((+1)) becomes 1 (not an error, I checked), so it should still work, just
single-threaded? And then you could "CPUS=1 make" to set it manually if necessary...

Is this an _optimization_ for macos, or is it a build break? (I used to have a
mac laptop but sent it to a college student on twitter who wore out her computer.)

Would this work instead?

if [ -z "$CPUS" ]
then
  # nproc respects taskset, fall back to getconf for macos
  [ ! -z "$(type -P nproc)" ] && CPUS=$(($(nproc)+1)) ||
    CPUS=$(($(getconf _NPROCESSORS_ONLN))
fi

(I just dug up an aboriginal linux image and confirmed that type -P exists in
bash 2.05b from the dawn of time. Now with extra shellshock! I used to use which
but Red Hat broke it so their version prints out crap when it _doesn't_ find
stuff. The <strike>aristocrats</strike> people behind systemd!)

>  if [ -z "$SED" ]
>  then

That was put in for macos previously. I _thought_ this worked...

Hmmm... Toybox has a bootstrap issue where it provides tools that can build
toybox but sometimes has to run in environments that don't have those tools. I
keep thinking there should be some kind of build script that builds _just_ the
tools needed to build toybox, without requiring a configure step. Unfortunately,
$CFLAGS and library probes and such remain fiddly enough I haven't done it yet,
although I should be able to come up with a "no frills" hardwired build that's
portable-ish, for _just_ the build tools? (Yeah, which tools are the build
tools? That's mkroot territoy...)

And this wouldn't help macos because the resulting nproc (calling
sched_getaffinity()) wouldn't _run_ on macos. (Sed probably would, unless its
libc's regex was crazy...)

Rob