> q.c:1: warning: ISO C forbids forward references to `enum' types
> If we use it elsewhere, we should stop.

Humpf, sorry about that. I have reverted this part of my patch
as follow:

2007-12-17  Joel Brobecker  <brobecker@adacore.com>

        * language.h (enum exp_opcode): Comment out this declaration,
        undoing the previous change.

Re-tested on x86-linux with a full rebuild. The situation is not
completely fixed yet, but we can discuss our options.

In terms of other places where it is used, I thought there were
several but a quick grep revealed only two:
  - language.h (our case, enum exp_opcode)
  - symtab.h (enum language)

Unless my egrep command is wrong, I must have some delusional episodes:
        % grep -E -e 'enum +[_0-9a-zA-Z]+;' **/*.h

I will send some patches ASAP.

-- 
Joel (UTC+4 for the next 5 weeks :-).