bug#68808: subsecond mtime discovery code insufficient

[Zack Weinberg]

On Tue, Jan 30, 2024, at 7:46 AM, Erik A Johnson wrote:
> I found the problem!  The default GNU make on macOS (even Sonoma) is
> 3.81 from 2006!  The configure script for GNU make versions <4.0 did
> not have the right test for subsecond resolution in the macOS stat()
> function, so 3.81 was built with resolution only to the second, not
> subsecond, thus needing at least one second sleep.

Okay, so that means the filesystem timestamp resolution test needs to
probe the behavior of `make` as well as all the other things it tests. I
will work on a patch for that as soon as I have a usable workstation
again, which will probably not be until next week at the earliest; if
anyone wants to beat me to it, feel free.

> (Why, then, does Apple continue to include 3.81 in the software 18
> years later? Beyond me.)

3.81 was the last version distributed under GPLv2; Apple won't touch
anything that's distributed under GPLv3.  Their copy of GNU M4 is also
vintage 2006, for the same reason.  I don't claim to understand why
their legal department thinks GPLv2 is fine but v3 has to be avoided,
but (like many other proprietary Unix vendors) they probably keep
shipping the old GNU tools instead of, like, switching to current BSD
tools, for the sake of compatibility with old scripts.

zw