Re: [PATCH] Enhance array types debug info. for Ada

[Jakub Jelinek <jakub@redhat.com>]

On Tue, Oct 07, 2014 at 10:08:23AM +0200, Pierre-Marie de Rodat wrote:
> >>gcc/fortran/
> >>	* trans-types.c (gfc_get_array_descr_info): Use PLACEHOLDER_EXPR nodes
> >>	instead of VAR_DECL ones in type-related expressions.  Remove base_decl
> >>	initialization.
> >
> >Ugh, I must say I don't like PLACEHOLDER_EXPRs at all.
> 
> Why so? I know that as far as supported front-ends are concerned,
> PLACEHOLDE_EXPR nodes are used only in GNAT, but it seems to me they
> describe the best what object the bound/stride/allocated/associated
> expressions (self-)reference.

But isn't there a risk that you will have PLACEHOLDER_EXPRs (likely for Ada
only) in some trees not constructed by the langhook?
I mean, DW_OP_push_object_address isn't meaningful in all DWARF contexts,
in some it is forbidden, in others there is really no object to push, and as
implemented, you emit DW_OP_push_object_address (which emits the address of
a context related particular object) for any kind of PLACEHOLDER_EXPR with
RECORD_TYPE.

Thus, I'd feel safer, even if you decide to use a PLACEHOLDER_EXPR, that
the translation of that to DW_OP_push_object_address would be done only
if the PLACEHOLDER_EXPR is equal to some global variable, normally NULL,
and only changed temporarily while emitting loc for the array descriptor.
But then IMHO a DEBUG_EXPR_DECL is better.

That said, if Jason is fine with the patchset as is, I can live with it,
as other FEs don't use PLACEHOLDER_EXPRs, worst case it will affect Ada
only.
Also, please verify that with your patch the generated debug info for some
Fortran arrays is the same.

	Jakub