Subject: Re: bug#63850: cp fails for files > 2 GB if copy offload is unsupported

From: Paul Eggert <[email-masked]>
Date: Thu, 8 Jun 2023 10:44:25 -0700

On 6/8/23 04:28, Arsen Arsenović wrote:
> Please reconsider dropping the configure-time version check.

I already dropped it, so this discussion is more about the general 
principle than this particular case.

> It is entirely reasonable to expect that a user will roll back a kernel
> update, as there are many reasons one might have to do so.

Sure, but if they do so, and if programs use configure-time checks whose 
results depend on the kernel version, users will have to rebuild and 
reconfigure these programs.

That's just a fact of life. This is not just a Gnulib issue. Many 
programs do lots of configure-time checks. Nobody that I know of has 
time to audit them all.

*Usually* rolling back the kernel will work, because *usually* it's a 
small rollback and programs built for a newer kernel won't exercise the 
small area where the kernels differ in a way that will cause 
user-visible symptoms.

But in general it does not work, and cannot reasonably be expected to
work.

So: when in doubt, rebuild. Of course if you've carefully audited the 
program and know that its configure-time tests are valid for the older 
kernel, you can skip the rebuild. Or if building speed is more important 
to you than reliable applications, you can also skip the rebuild.