Re: REG_STRUCT_HAS_ADDR

[Mark Kettenis <kettenis@chello.nl>]

   Date: Mon, 08 Sep 2003 14:43:41 -0400
   From: Andrew Cagney <ac131313@redhat.com>

   > Unfortunately this breaks debugging with stabs, since stabsread.c uses
   > the same REG_STRUCT_HAS_ADDR to see if a function argument is passed
   > by value or by reference.  I think we really want to get rid of the
   > broken code in infcall.c in the long run.  Therefore I looked for a
   > way to disable it for "modern" targets, i.e. targets that define
   > PUSH_DUMMY_CALL as opposed to the old PUSH_DUMMY_FRAME & friends.
   > Looking at the code I found that the following targets (besides SPARC)
   > are using REG_STRUCT_HAS_ADDR:

   Instead, add a new method:
	   STABS_REG_STRUCT_HAS_ADDR
   with a default of:
	   if (DEPRECATED_REG_STRUCT_HAS_ADDR_P ()
	     return REG_STRUCT ... ();
	   else
	     return 0;
   (no predicate) (I think I've got that right) (better name?) and 
   deprecate REG_STRUCT_HAS_ADDR{,_P}.  I think stabsread.c can then switch 
   to the STABS variant.

   That should let you safely disentangle the SPARC without breaking 
   "stabsread.c".

That's a good strategy.  However, making this stabs-specific seems
wrong to me.  The new method will simply indicate whether the ABI
silently uses pass by reference instead of pass by value for function
argument of a certain type.  Therefore I don't think we should put
STABS in the name.  What about PASS_ARGUMENT_BY_REFERENCE?  I'm going
to drop the GCC_P argument too, since nobody is using it.  I'll post a
patch later today.

   > -  if (REG_STRUCT_HAS_ADDR_P ())
   > +  if (REG_STRUCT_HAS_ADDR_P ()
   > +      && !gdbarch_push_dummy_call_p (current_gdbcarch))

   The switch to push_dummy_call_p shouldn't cause unexpected side effects 
   such as disabling REG_STRUCT_HAS_ADDR_P.  From memory, I've got the 
   current code down to just one and even that doesn't really need it.

I had doubts whether I could get away with this.  Anyway, this saves
me from building a MIPS cross-environment ;-).

Mark