Re: unresolved: htonl(), htons(), __memcpy3d

[Mark McLoughlin <mark@csn.ul.ie>]

On Thu, 22 Feb 2001 aprasad@in.ibm.com wrote:

> just compile with -O2 options.

Yeah, this got me for a while very recently and although I found
out what was wrong I never looked too closely at what was going
on in that header file, but I have now.

It all seems a bit strange to me..... maybe somebody could explain
it to me?

in include/linux/byteorder/generic.h... (version 2.4.1)

protoypes defined for htonl, line 150
> extern __u32                    ntohl(__u32);

if __OPTIMIZE__ is defined the macros __htonl and htonl  are defined
> #if defined(__GNUC__) && (__GNUC__ >= 2) && defined(__OPTIMIZE__)
.
.
> #define ___htonl(x) __cpu_to_be32(x)
.
.
> #define htonl(x) ___htonl(x)

Now, the comment at the top of the file says

> * It seems that some programs (which? where? or perhaps a standard? POSIX?)
> * might like the above to be functions, not macros (why?).
> * if that's true, then detect them, and take measures.
> * Anyway, the measure is: define only ___ntohl as a macro instead,
> * and in a separate file, have
> * unsigned long inline ntohl(x){return ___ntohl(x);}

That inline function doesn't seem to exist, and even if it did, it
wouldn't be able to be used from a module(?)

Could someone explain the wisdom of all this to me and why __OPTIMIZE__
needs to be defined before these macros can be used?

Cheers,
Mark

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