Bug 30625

Confirmed.

Is this related to PR 29606?

Wasn't there a bug for byte-sized strides in array descriptors?  This bug should depend on it, and PR29606 as well.

(In reply to comment #2)
> Wasn't there a bug for byte-sized strides in array descriptors?  This bug
> should depend on it, and PR29606 as well.
> 
Both of you are right about PR29606.  The byte-sized strides I do not remember.  It is one way to go but I do not think that it is the correct one.  I think that we need a new field in the descriptor or, maybe, a new species of descriptor. This field could serve two functions:
(i) If present for an intrinsic type, it carries the base stride in bytes; and
(ii) If present for a derived type it carries the size in bytes.
The present size subfield should be used to carry a unique code for the type, so that classes can be implemented, including abstract classes.

Paul

As I came across this once more: is it possible to issue a compile-time warning that "array pointers to components of derived type arrays" are allowed by the standard but are not yet implemented in gfortran (gfc_todo, maybe)? 

This would prevent some users (e.g. me) from using it right now. If otherwise the code compiles fine, one silently gets unusable results ...

Subject: Re:  Array pointers to components of derived type
 arrays do not work

dfranke at gcc dot gnu dot org wrote:
> ------- Comment #4 from dfranke at gcc dot gnu dot org  2007-02-01 11:28 -------
> As I came across this once more: is it possible to issue a compile-time warning
> that "array pointers to components of derived type arrays" are allowed by the
> standard but are not yet implemented in gfortran (gfc_todo, maybe)? 
>
> This would prevent some users (e.g. me) from using it right now. If otherwise
> the code compiles fine, one silently gets unusable results ...
>
>
>   
Daniel,

I'll see what I can come up with  - I have also been feeling round the
edges of how this might be cured.  Implementation of F2003 classes will
require another field in the descriptor.  I am trying to figure out how
best to do this without completely breaking the library API but I
am attempting to design this field to fulfill both functions.

Best regards

Paul

Paul, I take it you are aware of PR21881 ("Array descriptors limit derived type sizes")... I don't fully grasp the way array descriptor work for derived types, but I wanted to mention that PR to you... just in case.

(In reply to comment #6)
> Paul, I take it you are aware of PR21881 ("Array descriptors limit derived type
> sizes")... I don't fully grasp the way array descriptor work for derived types,
> but I wanted to mention that PR to you... just in case.
> 
FX, I was aware of the problem but not of the PR; I'll be honest if I say tha I am not sure that the size limit on derived types is an issue.  After all, pointers or allocatable components can be used to keep the size of the derived type down.

I think that I need to sketch out a design and post it on the list; it'll have to be CC'd to Paul Brooks and Steven Bosscher because they are responsible for the present layout of descriptors.  They maybe have opinions about how to proceed.

Paul 

target milestone 4.3.0 ?

Some discussion is here:

http://gcc.gnu.org/ml/fortran/2007-04/msg00115.html

Subject: Bug 30625

Author: pault
Date: Sun Sep 16 09:17:49 2007
New Revision: 128523

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=128523
Log:
2007-09-16  Paul Thomas  <pault@gcc.gnu.org>

	PR fortran/29396
	PR fortran/29606
	PR fortran/30625
	PR fortran/30871
	* trans.h : Add extra argument to gfc_build_array_ref. Rename
	gfc_conv_aliased_arg to gfc_conv_subref_array_arg.  Move
	prototype of is_aliased_array to gfortran.h and rename it
	gfc_is_subref_array.  Add field span to lang_decl, add a new
	decl lang specific flag accessed by GFC_DECL_SUBREF_ARRAY_P
	and a new type flag GFC_DECL_SUBREF_ARRAY_P.
	* trans.c (gfc_build_array_ref): Add the new argument, decl.
	If this is a subreference array pointer, use the lang_decl
	field 'span' to calculate the offset in bytes and use pointer
	arithmetic to address the element.
	* trans-array.c (gfc_conv_scalarized_array_ref,
	gfc_conv_array_ref): Add the backend declaration as the third
	field, if it is likely to be a subreference array pointer.
	(gfc_conv_descriptor_dimension, gfc_trans_array_ctor_element,
	gfc_trans_array_constructor_element, structure_alloc_comps,
	gfc_conv_array_index_offset): For all other references to
	gfc_build_array_ref, set the third argument to NULL.
	(gfc_get_dataptr_offset): New function.
	(gfc_conv_expr_descriptor): If the rhs of a pointer assignment
	is a subreference array, then calculate the offset to the
	subreference of the first element and set the descriptor data
	pointer to this, using gfc_get_dataptr_offset.
	trans-expr.c (gfc_get_expr_charlen): Use the expression for the
	character length for a character subreference.
	(gfc_conv_substring, gfc_conv_subref_array_arg): Add NULL for
	third argument in call to gfc_build_array_ref.
	(gfc_conv_aliased_arg): Rename to gfc_conv_subref_array_arg.
	(is_aliased_array): Remove.
	(gfc_conv_function_call): Change reference to is_aliased_array
	to gfc_is_subref_array and reference to gfc_conv_aliased_arg to
	gfc_conv_subref_array_arg.
	(gfc_trans_pointer_assignment): Add the array element length to
	the lang_decl 'span' field.
	* gfortran.h : Add subref_array_pointer to symbol_attribute and
	add the prototype for gfc_is_subref_array.
	* trans-stmt.c : Add NULL for third argument in all references
	to gfc_build_array_ref.
	* expr.c (gfc_is_subref_array): Renamed is_aliased_array.
	If this is a subreference array pointer, return true.
	(gfc_check_pointer_assign): If the rhs is a subreference array,
	set the lhs subreference_array_pointer attribute.
	* trans-decl.c (gfc_get_symbol_decl): Allocate the lang_decl
	field if the symbol is a subreference array pointer and set an
	initial value of zero for the 'span' field.
	* trans-io.c (set_internal_unit): Refer to is_subref_array and
	gfc_conv_subref_array_arg.
	(nml_get_addr_expr): Add NULL third argument to
	gfc_build_array_ref. 
	(gfc_trans_transfer): Use the scalarizer for a subreference
	array.

2007-09-16  Paul Thomas  <pault@gcc.gnu.org>

	PR fortran/29396
	PR fortran/29606
	PR fortran/30625
	PR fortran/30871
	* gfortran.dg/subref_array_pointer_1.f90: New test.
	* gfortran.dg/subref_array_pointer_2.f90: New test.


Added:
    trunk/gcc/testsuite/gfortran.dg/subref_array_pointer_1.f90
    trunk/gcc/testsuite/gfortran.dg/subref_array_pointer_2.f90
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/expr.c
    trunk/gcc/fortran/gfortran.h
    trunk/gcc/fortran/trans-array.c
    trunk/gcc/fortran/trans-decl.c
    trunk/gcc/fortran/trans-expr.c
    trunk/gcc/fortran/trans-io.c
    trunk/gcc/fortran/trans-stmt.c
    trunk/gcc/fortran/trans.c
    trunk/gcc/fortran/trans.h
    trunk/gcc/testsuite/ChangeLog

Fixed on trunk

Paul