Re: Changes in GC and in pure space (was: [Emacs-diffs] master 5d4dd55: Fix lifetime error in previous patch)

[Paul Eggert <eggert@cs.ucla.edu>]

Eli Zaretskii wrote:

> How portable is "INLINE"

Quite portable, as its portability issues were shaken out years ago. It's been 
used in Emacs since 2013, and it's designed for C99-and-later so future C 
compilers should support it well.

> (and if it's portable enough, why do we use a jmacro for it)?

First, for convenience so that it's easier to follow the C rule that exactly one 
compilation unit must declare a function to be 'extern inline' if any 
compilation unit declares the function to be plain 'inline'. Second, for 
portability to C compilers that still do not support C99-style 'extern inline' 
(are these still significant? I don't offhand know).

> I FWIW, personally find the issue of confusion about macro argument
> evaluation to be a very weak one as justification to get rid of macros

There are other reasons to avoid macros. Aside from the performance issue I 
mentioned in my buffer.h patch, debugging Emacs can be easier when C macros are 
avoided. On the Ubuntu 18.04.3 platform where I'm typing this message, when I'm 
using GDB to debug /usr/bin/emacs I can print expressions involving functions or 
constants but not expressions involving macros; this is because Ubuntu builds 
/usr/bin/emacs with -g instead of -g3. So avoiding macros helps make it easier 
to debug Emacs in my situation, which is common on GNUish platforms.

Of course functions and constants cannot replace some C macros, such as INLINE. 
But many of Emacs's C macros ought to be functions or constants now, and this is 
not simply to avoid confusion.