Constant byteorder macros.

[Oliver Xymoron]

On Thu, 20 Jan 2000, H. Peter Anvin wrote:

> >  switch (status) {
> > 	case cpu_to_le16(CONSTANT_XYZ):
> > 
> > ... I need to define new macros __constant_cpu_to_le16(), etc.
> 
> Given that gcc has a __builtin_constant_p(x), you ought to be able to
> do:
> 
> #define cpu_to_le16(x) ( __builtin_constant_p(x) ? __constant_cpu_to_le16(x) : __cpu_to_le16(x) )

This is ugly and potentially means changing tons of macros. Couldn't you
just do the appropriate byteswap on the switch variable instead? There
aren't many (any?) other places in C aside from the preprocessor and array
sizing that insist on constant expressions.

--
 "Love the dolphins," she advised him. "Write by W.A.S.T.E.." 


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