Re: __builtin_va_arg rfc

[Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>]

Am Sun, 25 Apr 1999 schrieb Richard Henderson:
>On Sat, Apr 24, 1999 at 07:23:58PM -0600, Jeffrey A Law wrote:
>> An FYI, I don't think we should try to deal with this for egcs-1.2, even
>> though the primary motivation is to fix a ppc varargs/stdarg problem.
>
>Ok. 
>
>There is another way to solve the problem for PPC -- Alpha, which
>also uses a struct with weird initializations, builds the whole thing
>internally and passes it out like so
>
>/* Call __builtin_next_arg even though we aren't using its value, so that
>   we can verify that firstarg is correct.  */
>
>#define va_start(pvar, firstarg)                                \
>  (__builtin_next_arg (firstarg),                               \
>   (pvar) = *(__gnuc_va_list *) __builtin_saveregs ())
>
>All that's needed is for ppc to hide quite a lot of magic in
>expand_builtin_saveregs and suffer the cost of a structure copy.

Damned, I just started writing the PPC backend for Richards patch :-).

I'm willing to implement anything as long as it will go into 1.2. But from my
point of view it would make more sense to include Richards patch for 1.2 but
not to use it, except on PPC. This would make it possible for me to
easily backport any fixes in the mainline and possibly this stuff might be
enabled in 1.2.1 or later for other platforms too?

Franz.