Re: [9fans] USED() macro

[Russ Cox <rsc@swtch.com>]

> 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.

Fixed.

> 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?

Fixed.

> 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?

It probably is functioning correctly.  You still can't do
    Rectangle r;
    USED(r);
with that definition because you can't cast a Rectangle
to a ulong.  I could change the definition for __GNUC__>=3
but then it would allow non-scalar USED but all the other
platforms would not, so then I'd be getting reports from
the non-gcc users.  I'd rather all the platforms be consistent.

If you're not seeing a warning about the variable never
being used or being set and not used, then it's functioning fine.

Russ