Re: BUG #15525: Build failures when compiling Postgres with Make parallelization

On Thu, Nov 29, 2018 at 4:25 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Thomas Munro <thomas.munro@enterprisedb.com> writes:
> > Nice detective work.  Possibly because libtool/ranlib whacks it with
> > utime(), which only knows about time_t, here:
> > https://github.com/opensource-apple/cctools/blob/master/misc/libtool.c#L2779
>
> I suspected as much, but hadn't gone looking for the code.  I wonder
> why it bothers with any of that... it's certainly not documented
> behavior per the man page.

As for why Apple make doesn't have the problem, I think it's simply
that high resolution timestamp support for Darwin came along ~5 years
after Apple forked/froze their make due to the license change.  Here's
the commit:

https://github.com/mirror/make/commit/bfc3e1ca7c0c1504c9873ee1baacce73330b037e

As for what could be done about it, it seems like we (or the Nix
project, in a local patch) could declare individual targets to have
.LOW_RESOLUTION_TIME:

https://www.gnu.org/software/make/manual/html_node/Special-Targets.html

That doesn't seem any better than using "touch" to make a better mtime
though.  I'm kinda surprised that the Nix project doesn't have this
problem on other projects, though, if they're always using a modern
GNU make.  What are they doing differently?

-- 
Thomas Munro
http://www.enterprisedb.com