Re: Fix C23 compiler warning

Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> Ah, yeah. That was 2.71 actually:
> https://postgr.es/m/3838336.1657985206@sss.pgh.pa.us
> 1.72 seems to have been released with some fixes from that one. Per
> that thread, the related problem you noticed was with m4, and apparently
> it was because macOS ships a version from 2006 (1.4.7). Here on Debian
> bookworm I have m4 1.4.19; maybe macOS has updated its copy now?

macOS hasn't gotten better:

$ which m4
/usr/bin/m4
$ m4 --version
GNU M4 1.4.6
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

It does seem like you-need-a-newer-m4 will be an issue for some folks,
but given that you only need it to rebuild the configure script, maybe
that will be a small enough set of people that we can cope. (In
particular, the buildfarm wouldn't need updates.) On macOS, it's
already pretty difficult to do useful development without any packages
from MacPorts or Homebrew. MacPorts is shipping m4 1.4.19, and I'm
sure Homebrew has something modern as well, so it's not like people
would be forced to do their own builds on that platform.

So maybe we should revive that idea, though I'd definitely target
autoconf 2.72 not 2.71.

regards, tom lane