va_arg *, and why not.

[Geoff Keating]

Hi Gabriel,

at lines 910, 1425, and 1488, diagnostic.c does things like:

static void
output_do_verbatim (buffer, msg, args)
     output_buffer *buffer;
     const char *msg;
     va_list args;
{
...
  output_buffer_ptr_to_format_args (buffer) = &args;
}

This is not portable.  It doesn't do what you want on machines where
va_list is an array type.  Instead of a pointer to a va_list, you get
a pointer to a pointer to a va_list[0], which is not the same thing.

Normally, you would use va_copy to work around this, by writing

  va_list tmp_args;
  va_copy (tmp_args, args);
  output_buffer_ptr_to_format_args (buffer) = &tmp_args;

or better would make output_buffer contain a real va_list, but you
can't do this in gcc, because it's not portable to old compilers.
You'll have to either:

1. implement va_copy, by using an autoconf test to determine whether
   or not va_list is an array type; or
2. only pass around va_list *.

This breaks the bootstrap on powerpc-linux.

-- 
- Geoffrey Keating <geoffk@cygnus.com>