> In Plan 9's C compiler, USED is known to the compiler.
> It makes the compiler insert a use of the variable right
> there to silence used and not set warnings.
>
> In the ports, it's a clumsy macro trying to have the same
> effect.
>
> > perhaps it could use if(&x) instead of if(x)
> > to cope with structures as well
>
> I tried this once, but then some (too smart for their
> own good) compilers complain that the value is never used.
Thanks.
BTW, I'm trying to build plan9port on Ubuntu 5.10. Some problems
encountered:
1) X headers are in /usr/include/X11 only. No 'include' in $X11, not
even a link. So, $PLAN9/src/libdraw/mkwsysrules.sh could not find them;
and set $WSYSTYPE to 'nowsys'. As a result nowsys-*.c get compiled, and
I noticed USED() there.
2) install(1) says:
> If LOCAL.config contains a line WSYS=nowsys then the system is built
> without using X11.
I guess it might be WSYSTYPE=nowsys?
3) 9c uses gcc, but USED() is still defined as if(x){}else{}, not the
version with __attribute__ ((unused)). When I added -D__GNUC__ in 9c, it
complained for redefinition. Why not
#ifdef __GNUC__
# if __GNUC__ >= 3
# undef USED
# define USED(x) { ulong __y __attribute__ ((unused));
__y =
(ulong)(x); }
# endif
#endif
functioning correctly?
Well, after all, those are all trivial. Few people will set
WSYSTYPE=nowsys.
