On Wed, 12 Apr 2006 13:10:06 -0700
Ben Greear <[email protected]> wrote:
> What is the reasoning for this change? Is the compiler
> able to optomize the right-hand-side to a constant with your
> change in place?
>
> > - if (veth->h_vlan_proto != __constant_htons(ETH_P_8021Q)) {
> > + if (veth->h_vlan_proto != htons(ETH_P_8021Q)) {
> > return -EINVAL;
> > }
Read the source, the macro handles it.
For i386:
htons maps to __cpu_to_be16
cpu_to_be16 maps to swab16 which is defined in swab.h
# define __swab16(x) \
(__builtin_constant_p((__u16)(x)) ? \
___swab16((x)) : \
__fswab16((x)))
-
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