[A21.5R21.4] [PATCH 21.5] #'featurep byte-optimisation

[Aidan Kehoe]

 Ar an ceathrú lá de mí Méan Fómhair, scríobh Steve Youngs: 

 > * Aidan Kehoe <kehoea at parhasard.net> writes:
 > 
 >   >  Ar an dara lá de mí Méan Fómhair, scríobh Steve Youngs: 
 >   >> APPROVE 21.5 RECOMMEND 21.4
 >   >> 
 >   >> This patch optimises #'featurep for the cases...
 >   >> 
 >   >> (featurep 'xemacs) and (featurep 'sxemacs)
 >   >> 
 >   >> ...making the former be always t and the latter be nil. 
 > 
 >   > The latter behaviour is inappropriate, isn’t it?
 > 
 > Not at all.  You don't want (featurep 'sxemacs) returning t on XEmacs do
 > you?

Nope. But it shouldn’t be optimised away to nil if the code is to run on
SXEmacs, though! Test case, with your patch applied to XEmacs:

$ echo "(if (featurep 'sxemacs) (message \"in SXEmacs\") (message \"not\"))" > /tmp/whatever.el
$ ~/xemacs-21.5/src/xemacs -batch -f batch-byte-compile /tmp/whatever.el

Compiling /tmp/whatever.el...
Wrote /tmp/whatever.elc
Done
$ ~/sxemacs-22.1.6/src/sxemacs -batch -l /tmp/whatever.elc
not
$

 > This same code in SXEmacs give t for both.  The intention is so that you
 > _can_ write SXEmacs only code if you want to and not have problems with
 > it on XEmacs.

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