pkg/53826: devel/m4 fails to build on Linux distributions using glibc >= 2.27

[david%gutteridge.ca@localhost]

>Number:         53826
>Category:       pkg
>Synopsis:       devel/m4 fails to build on Linux distributions using glibc >= 2.27
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jan 01 22:15:00 +0000 2019
>Originator:     David H. Gutteridge
>Release:        HEAD
>Organization:
>Environment:
Linux arcusix.nonus-porta.net 4.19.12-300.fc29.x86_64 #1 SMP Sat Dec 22 22:03:59 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
>Description:
During the glibc 2.27 development cycle, they removed features that
gnulib used to detect certain capabilities. This has broken devel/m4
on various Linux distributions, e.g. Fedora 28 and 29, Ubuntu 18.10,
Debian Sid, and probably others. (I came across this because I was
testing pkgsrc on Fedora 29.)

This was reported upstream back in March[1], and the m4 maintainers are
aware they need to update to reflect this, but there hasn't been a
release made yet. There are patches to adjust m4 provided in that email
thread, and they were taken as-is downstream by Fedora[2].

I've tested the patches in pkgsrc on Fedora 29, and I also tested them
on Debian Jessie (which has glibc 2.19) to confirm they were backwards
compatible, and there were no issues there. I presume if they work on
Jessie, there shouldn't be any older Linux LTS release where there'd be
an issue.

Before applying these patches, I'd like input from the pkgsrc Linux
people, to ensure there aren't any potential problems on other
distributions. (E.g., it appears Arch is a popular choice amongst
pkgsrc users. I don't have a testing setup for it.) I can provide the
patches in pkgsrc format if anyone wants them.

1. https://lists.gnu.org/r/bug-gnulib/2018-03/msg00002.html
2. https://src.fedoraproject.org/rpms/m4/blob/master/f/m4-1.4.18-glibc-change-work-around.patch

>How-To-Repeat:
Try to build devel/m4 on a Linux distribution using glibc >=2.27.

It will result in an error such as:

freadahead.c: In function 'freadahead':
freadahead.c:92:3: error: #error "Please port gnulib freadahead.c to your platform! Look at the definition of fflush, fread, ungetc on your system, then report this to bug-gnulib."
  #error "Please port gnulib freadahead.c to your platform! Look at the definition of fflush, fread, ungetc on your system, then report this to bug-gnulib."


>Fix:
(Patches referenced above, and I can provide pkgsrc formatted
versions.)