multilib flexibility snag; configure breaks in presence of any $prefix/lib64

[NatUni]

This was on FreeBSD; i have not tried elsewhere.

from FreeBSD PR #287043:

# mkdir /usr/local/lib64
# make clean configure >/dev/null || echo woe
configure: error: cannot find usable SQLite v3 library
woe
# rmdir /usr/local/lib64
# make clean configure >/dev/null && echo joy
joy

yes i realize its odd to have all three lib32, lib64 & lib

might should multilib only affect the order in which they're tried, rather than eliminate any from eligibility?

low prio (i found but a single piece of esoteric software hiding out in lib64 on a system with 6000 packages)

[Julien-Elie]

Thanks for the report!
I have forwarded it to rra/rra-c-util#20 where the logics about multilib comes from (https://github.com/rra/rra-c-util/blob/main/m4/lib-pathname.m4).

[rra]

Ugh, this is unfortunately either rather obnoxious or rather risky to fix. Ideally we would probe for the library twice, once with the detected multilib directory and then again with lib if that didn't work, but the macros are not structured that way so it will require a lot of rather complex and somewhat risky changes. It's hard to make any modifications to Autoconf machinery since it's so difficult to test them thoroughly.

The simple but risky fix is to do as you suggest and always add -L$2/lib in addition to -L$2/$rra_lib_arch_name even if the latter exists. Then hopefully the correct multilib directory will always be first in the search path and any 32-bit libraries in the /lib directory will be ignored. I can't see any obvious reason why that wouldn't work after thinking about it for a moment, but it may increase the risk that we incorrectly link with the 32-bit version of the library because the Fedora-style multilib layout unfortunately used /lib for 32-bit libraries on 64-bit systems.

I am not sure I have the enthusiasm for adding loops on the two multilib possibilities to all the macros, so I think I'm going to try that second approach, and I guess we'll see if anything breaks?