Re: On time64 and Large File Support

[Paul Eggert]

On 11/12/22 21:11, Zack Weinberg wrote:
> "A couple hours" more like eight, ugh.

I know the feeling. I didn't get time free until recently.

I reviewed your patch and had the following thoughts.

* Gnulib doesn't need AC_SYS_LARGEFILE_REQUIRED or 
AC_SYS_YEAR2038_REQUIRED and they're easy for users to do on their own 
with a simple AS_IF, so let's omit these variants for now, to keep 
things simpler.

* The documentation incorrectly implies that AC_SYS_LARGEFILE and 
AC_SYS_YEAR2038 are orthogonal, i.e., that one can request large-file 
support and year-2038 support independently. But AC_SYS_YEAR2038 
AC_REQUIREs AC_SYS_LARGEFILE, and one cannot configure with 
--disable-largefile --enable-year2038 and expect things to work. This is 
inherent to the underlying _TIME_BITS mechanism; it's not something 
Autoconf can fix with glibc, and since this year-2038 business only 
occurs with glibc it's not something Autoconf can (or is likely to be 
able to) fix anywhere.

To help things move forward I installed your patch into Autoconf master 
on Savannah, and followed up with the attached patch which tries to 
address the above issues. In particular, it notes that the difference 
between AC_SYS_LARGEFILE and AC_SYS_YEAR2038 is a temporary hack, in 
that eventually (hopefully well before the year 2038) AC_SYS_LARGEFILE 
will be an alias for what AC_SYS_YEAR2038 does now.

Comments welcome of course.

I tested this by migrating these Autoconf changes into my private copy 
of Gnulib and gzip, and building gzip on both 32- and 64-bit glibc. I 
plan to install those changes on Savannah soon, and to follow up with 
similar changes to GNU coreutils etc. This should help to test these 
Autoconf changes before the next Autoconf is released.

0001-Omit-just-added-_REQUIRED-macros.patch
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