Re: Redundant type checking in window.c and w32menu.c

[Ken Raeburn <raeburn@gnu.org>]

On Jun 19, 2007, at 10:44, Dmitry Antipov wrote:
> If we pass CHECK_CONS(), we don't need CONSP()s in Fcar() and Fcdr 
> () and may use XCAR()
> and XCDR() instead.

Makes sense.

> P.S. Is code size the only reason to call Fcar(), Fcdr() and their  
> safe versions directly
> from C code ? Replacing these dumb proxies with an appropriate  
> macros eliminates a lot of
> function calls at the cost of ~28K increment in code size (for a  
> stripped binary on x86).
> Note if someone needs smaller emacs executable (what a strange  
> requirement, but why not ?),
> just replacing -O2 with -Os saves ~235K.

You could make Fcar a static inline function in lisp.h (conditional  
on GCC, or maybe C99).  If the optimizer's good at its job, it should  
eliminate the redundant CONSP checks.  Using an inline function  
avoids having to check all Fcar uses for arguments that have function  
calls or side effects.  (A quick grep shows several of those.  In  
fact, if your test used the simple macro version, inline functions  
may result in less code size expansion because of this.)  And  
personally, I think inline functions are often more readable than  
macros, if they're not very simple macros.

Ken