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

[Po Lu <luangruo@yahoo.com>]

Gregory Heytings <gregory@heytings.org> writes:

> You did not, otherwise you would not have explained the build failure
> with something that had no relationship whatsoever with it.

Your build failure is one which we have _fixed_, and holds absolutely no
bearing on our expectations of C compilers.

> All that is irrelevant in the matter at hand.

You don't decide what is relevant or irrelevant.

> That's wrong.  Again you are just ignoring the information I gave
> you. So I'll say it again: alignas, a C11 feature, was introduced
> unconditionally in Emacs by e32a579975 in July 2012, and it was made
> conditional only ten years later, by 1e2bc1bbf4 in December 2021 (to
> support builds with older version of TCC).  Without the "# define
> alignas(a)" line in lisp.h, which was added by 1e2bc1bbf4 and was
> therefore not present in Emacs 25-28, Sun C 5.8 fails to compile Emacs
> 29 in the same way it fails to compile Emacs 25-28.

In e32a579975's lisp.h:

#ifndef alignas
# define alignas(alignment) /* empty */
# if USE_LSB_TAG

This definition was lost unintentionally to a succession of changes, and
promptly restored when its absence was brought to our attention.

I'm sorry to be blunt, but if in decision-making you consider and cite
only historical factors to your liking, or in argument you cannot make
the distinction between errors arising from some fundamental limitation
of a compiler and those caused by operator error, to wit, the failure to
provide several required compiler flags and install patches firmly
recommended by the supplier, whether a compiler can and should compile
Emacs is not for you to decide.  So believe what you want--you don't use
Solaris, or TCC, so the subject of your assertions cannot affect you to
any extent.