bug#48228: json-serialize should signal error when dll is not found [MS Windows]

[Nikolay Kudryavtsev]

06.05.2021 20:11, Dmitry Gutov wrote:
> If that ever happens, the workaround will only be needed in the new 
> version of Emacs (right?), so the same version could introduce the 
> predicate, and whoever needs it would just test it with fboundp first. 

You should not assume that the predicate would be introduced by the same 
version in which the incompatibility first happens. Let's say the new 
GMP got released 5 minutes ago, and my package that relies on it is 
already broken and I have to code the workaround, but I can't properly 
dispatch it since 27.2 does not have that gmp-available-p, so I have to 
write my own explicit test.

Eli is probably correct in that this would never happen in practice for 
GMP, but what I'm saying is that it's a good idea to have a single 
unified convention for testing every single dynamic library feature, so 
that if someone codes library X support we could expect it to follow the 
same convention and this would give us some protection from such 
problems in addition to giving you a quick way to see if whatever 
distro's Emacs binary you're currently using is properly configured.