bug#55294: Configure failure on Solaris 11.4

[Eli Zaretskii]

> Resent-From: Paul Eggert <eggert@cs.ucla.edu>
> Original-Sender: "Debbugs-submit" <debbugs-submit-bounces@debbugs.gnu.org>
> Resent-CC: bug-gnu-emacs@gnu.org
> Resent-Sender: help-debbugs@gnu.org
> Cc: 55294@debbugs.gnu.org
> Date: Mon, 9 May 2022 12:07:51 -0700
> From: Paul Eggert <eggert@cs.ucla.edu>
> 
> Thanks for the bug report. The patch looks safe, since Emacs calls atan 
> as well as sqrt. And it looks like an improvement, since I can imagine 
> all sorts of reasons why sqrt would not need libm whereas atan would, 
> starting with the fact that typical hardware nowadays has sqrt 
> instructions but not atan instructions. (The 'configure' test itself 
> relies on undefined behavior, so it's not strictly portable anyway.)
> 
> Although it would be helpful to know how to reproduce the problem (which 
> compiler? how configured? etc.) and which symbols were not found in 
> temacs on Solaris 11.4, we don't need to know that to install the patch.

As I explained earlier, I'd like to understand it better, and would
not want to blindly move to another function.