To: J3                                                     10-203r2
From: Bill Long
Subject: Interop TR: typedefs for cdesc members
Date: 2010 October 11
Reference: 10-165r2.pdf

Discussion:

The present C descriptor contains multiple members that are expected
to have small integer values. The present specification is that each
of these is type int. It was proposed at meeting 192 that these should
instead have implementation-defined types, as to potentially save
space in the descriptor.  The current list of members is rank, type,
attribute, and state. Realistically, each of these could be as small
as an 8-bit byte, and hence could be packed into a single word if
desired.

The present structures CFI_dim_t and CFI_bounds_t contain members that
are typed as size_t. In some cases, these values could be negative
(bounds, for example), so size_t is not appropriate. The types need to
be signed integers large enough to hold the size of the address space
as an integer, such as ptrdiff_t. These specific size_t declarations
are replaced by a typedef that is defined in the module.

Edits are provided to add four new typedef names, one for each
of the current small integer members of the C descriptor, and also a
typedef name for the declarations of the members of CFI_dim_t
and CFI_bounds_t. The names correspond to standard integer
types.

If members are added to the C descriptor that have small integer
values, those should have corresponding typedef names.



Edits to 10-165r2:

[9:9] After "bounds_t, " add "typedef definitions for CFI_attribute_t,
CFI_index_t, CFI_rank_t, CFI_state_t, and CFI_type_t, ".

[9:9] Delete "with type int".

[9:27] Replace <<int>> with <<CFI_rank_t>>.

[9:28] At the end of the paragraph add a new sentence: "CFI_rank_t
shall be a typedef name for a standard integer type capable of
representing the largest supported rank."

[9:29] Replace <<int>> with <<CFI_type_t>>.

[9:31] At the end of the paragraph, add a new sentence: "CFI_type_t
shall be a typedef name for a standard integer type capable of
representing the values for the supported type specifiers."

[9:32] Replace <<int>> with <<CFI_attribute_t>>.

[9:34] At the end of the paragraph, add a new sentence:
"CFI_attribute_t shall be a typedef name for a standard integer
type capable of representing the values of the attribute codes."

[9:35] Replace <<int>> with <<CFI_state_t>>.

[9:36] At the end of the paragraph, add a new sentence: "CFI_state_t
shall be a typedef name for a standard integer type."

[10:7] After the second sentence of 5.2.3, para 1, add a new sentence:
"CFI_index_t is a typedef name for a standard signed integer
type capable of representing the result of subtracting two pointers."

[10:7] Replace "It is defined in the file ISO_Fortran_binding.h, and"
with "CFI_dim_t" {We already say that the struct is defined in the
header file in 5.2.1.}

[10:9] Replace <<size_t>> with <<CFI_index_t>>.

[10:10] Replace <<size_t>> with <<CFI_index_t>>.

[10:11] Replace <<size_t>> with <<CFI_index_t>>.

[10:15] Replace "It is defined in the file ISO_Fortran_binding.h, and"
with "CFI_bounds_t" {We already say that the struct is defined in the
header file in 5.2.1.}

[10:17] Replace <<size_t>> with <<CFI_index_t>>.

[10:18] Replace <<size_t>> with <<CFI_index_t>>.

[10:19] Replace <<size_t>> with <<CFI_index_t>>.