Re: master 37889523278: Add new `swap` macro and use it

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Stefan Kangas <stefankangas@gmail.com>
> Date: Sat, 06 Jan 2024 15:39:11 +0800
> 
> Stefan Kangas <stefankangas@gmail.com> writes:
> 
> > branch: master
> > commit 37889523278fe65733938fb11c3701898309961c
> > Author: Stefan Kangas <stefankangas@gmail.com>
> > Commit: Stefan Kangas <stefankangas@gmail.com>
> >
> >     Add new `swap` macro and use it
> >     
> >     A `swap` macro prevents programming errors and is more concise.
> >     It is a natural addition to our existing `min` and `max` macros.
> 
> It's well known that a generic "swap" macro is impossible to express in
> Standard C for lack of a standard "typeof"-like expression.  To
> compensate for this limitation, the macro must accept an argument
> identifying the type of the field where the temporary value is saved,
> which is more trouble than it's worth and reintroduces the type
> conversion problems such macros are intended to prevent.
> 
> Neither typeof nor __typeof__ are portable by our standards, the latter
> being an extension compatible with the Standard enabled when GCC is
> configured to obey the standard to the letter, while the former is a
> keyword enabled in other situations.

Regardless of portability issues, I think the macro should be called
SWAP, upper-case, to avoid clashes with functions.