Re: Emacs' C: static inline considered useless nowadays?

[Matt Armstrong <matt@rfc20.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Matt Armstrong <matt@rfc20.org>
>> Date: Sun, 16 Oct 2022 15:08:51 -0700
>> 
>> For Emacs, I would think:
>> 
>> a) In header files, use Emacs' INLINE and NO_INLINE macros.
>> 
>> b) In .c files, use static, EXTERN_INLINE, but never 'inline' since it
>> does nothing.
>> 
>> I'm seeking confirmation (or refutation) of (a) and (b).  I'm not asking
>> generally, but for Emacs' C code.
>
> See conf_post.h, around line 395: it explains the issue and the
> expected usage of these in our sources.

conf_post.h didn't answer my question since it seems to pertain to code
in header files.

I realize now that the conclusion of this thread so far is unclear:

a) "static inline" in .c files is okay.  No need for macros.

b) Criteria for when to use "static inline" is not clear.  Do we do this
   ad hoc as -Og builds are discovered to be slow?  Do it for all static
   functions?  Don't care?  I can see cases for any of these.

c) Neither (a) nor (b) are written down, and as Eli points out,
   conf_post.h suggests that at least sometimes you've got to use
   macros for inline functions in Emacs code, but that header is about
   how to do things in header files.