Re: ac_cv_sys_largefile_opts undocumented?

[Paul Eggert]

On 2024-04-27 15:39, dmitrii.pasechnik@cs.ox.ac.uk wrote:
> It's for nauty, a well-known program to deal with graph isomorphisms
> etc. I've made a Gentoo patch herehttps://bugs.gentoo.org/921138
> and I wanted to upstream it.

Oh my, that is indeed in an undocumented/hacky part of autoconf, one 
that I just changed in the master development sources a few days ago; see:

https://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=b71143738516017f0e0d347a4025301c06c40254

From your patch, it appears that nauty isn't using config.h and instead 
has its own file nauty-h.in that it maintains itself. Perhaps you could 
lessen this sort of problem by having it use config.h instead, at least 
for some things. Failing that, you could instead assume that 
ac_cv_sys_largefile_opts's value is a compiler option if and only if it 
begins with "-"; that's easy to say in a shell case statement and though 
still hacky would be a bit less brittle than what you've got.