🚀 go-pugleaf

Is there some reason why there cannot be ':' arguments to an asm
directive at the top level (outside any procedure)?

For instance, on the 386 I would like to declare a structure at a
particular virtual address.  I would like to do this without some
sort of horrible "genassym" program which first creates a header file
with sizes and offsets which I can then include in a .S file and use
to generate the proper .set directive.  Thus, I would like something
like this:

asm volatile (".set _u,%P0" :: "i" (USTACKTOP - sizeof (struct Uenv)));
extern struct Uenv u;

Unfortunately, gcc seems to dislike the presence of a colon in an asm
structure not in a function.  This works if I put it in a fuction, but
that seems must less appropriate and makes the code much less
readable.

Is there some other way to get what I want, or some reason why gcc is
limiting how I can use asm statements?

[I'm using gcc 2.7.2 on i386/OpenBSD]

Thanks,
David