On Thu, Jun 07, 2012 at 01:27:56PM +0200, Alexander Graf wrote:
>
> On 07.06.2012, at 01:45, David Gibson wrote:
>
> > [snip]
> >>> You mean internally? Yeah, probably. Externally? The point of these
> >>> helpers is to make the code look less cluttered. We can already pass in
> >>> an array just fine, but C is quite annoying about generating those on
> >>> the fly, while it's easy to pass in ints as parameters :)
> >>
> >> Varargs?
> >
> > Ugly and risky with standard C varargs (because an explicit length
> > would be needed). Could be done neatly with gcc macro varargs.
>
> Could a combination of both like this work?
>
> #include <stdio.h>
> #include <stdarg.h>
>
> #define __VA_NARG__(...) \
> (__VA_NARG_(_0, ## __VA_ARGS__, __RSEQ_N()) - 1)
> #define __VA_NARG_(...) \
> __VA_ARG_N(__VA_ARGS__)
> #define __VA_ARG_N( \
> _1, _2, _3, _4, _5, _6, _7, _8, _9,_10, \
> _11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \
> _21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \
> _31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \
> _41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \
> _51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \
> _61,_62,_63,N,...) N
> #define __RSEQ_N() \
> 63, 62, 61, 60, \
> 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, \
> 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, \
> 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, \
> 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, \
> 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, \
> 9, 8, 7, 6, 5, 4, 3, 2, 1, 0
>
> #define PRINT_ELEMS(fdt, ...) print_elems(fdt, __VA_NARG__(__VA_ARGS__),
> __VA_ARGS__)
Um.. that might work, but it's ludicrously complicated. If we're
prepared to use the gcc statement expression extension and we're just
going to abort on errors like findnode_nofail, it can be done much
more easily using c99 variadic macros:
#define setprop_ints(fdt, path, prop, ...) \
do { \
uint32_t tmp[] = {__VA_ARGS__}; \
if (fdt_setprop(findnode_nofail(fdt, path), prop, \
tmp, sizeof(tmp)) != 0) { \
/* error message */ \
abort(); \
} \
} while (0)
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
