Re: gcc 3.2.1 draft release notes, 3rd draft

[Zack Weinberg <zack@codesourcery.com>]

On Tue, Oct 15, 2002 at 10:08:46AM -0700, Mark Mitchell wrote:
> >Then how about adding a rule something like the following to the bison
> >grammar (yes, I know these are the wrong terminal names, but the idea
> >should be clear):
> >
> >       TYPEDEF ID '=' error ';'
> >	       { error("Please use __typeof() instead");}
> 
> Along these lines, one could perhaps even do the transformation at that
> point.
> 
>  TYPEDEF ID = expression ;
> 
>    { /* Do whatever you do for the typeof case. */ }

It's worth pointing out that the grammar does not distinguish between
typedef declarations and other declarations.  It's all handled by

datadef: declspecs declarator '=' init ';'

(simplified for clarity) The present error message comes from the
semantics layer, c-decl.c:start_decl():

  if (initialized)
    /* Is it valid for this decl to have an initializer at all?
       If not, set INITIALIZED to zero, which will indirectly
       tell `finish_decl' to ignore the initializer once it is parsed.  */
    switch (TREE_CODE (decl))
      {
      case TYPE_DECL:
        error ("typedef `%s' is initialized",
               IDENTIFIER_POINTER (DECL_NAME (decl)));
        initialized = 0;
        break;

It would be easy to insert in here

  advice ("Please use __typeof() instead");

("advice" is a diagnostic category I propose for helpful advice, such
as this, or the "Each undeclared identifier is reported only once"
message, which can be shut up with -fno-advice; right now, imagine
that it reads "error")

"Trying to do the above transformation" boils down to my original
patch that fixed the bug in the extension.

zw