To:                                                              07-137
From: Aleksandar Donev
Subject: Definition of "compile time contiguous"
Date: 2007 January 26
References: 06-311r1, 07-007, UTI 101

A straw vote was taken as proposed in 06-311 and it was recommended
that pointer rank remapping for contiguous targets only be allowed
when the target can be determined to be contiguous at compile-time
(see UTI 101). A reasonable definition of this was already crafted
at an earlier meeting and can be found at [319:7-16]. All that is
needed is to name it and move it some place else. I propose the phrase
"always-contiguous" and will use that as a placeholder. We also need
to change rank-remapping restrictions.

I also propose that we use this constraint in certain places where we
currently have restrictions to ensure there is no copy in/out of dummy
arguments. For example, restrictions on co-array passing, VOLATILE
and ASYNCHRONOUS. Specifically, if the actual is always-contiguous,
copy in/out does not need to be used. We already did this for
co-arrays...this paper adds the rest of the edits.

In this paper I do not propose to change anything about TARGETs and
pointer-association accross argument passing as this is complex and
should first be subjected to a technical discussion.

QUESTION:
I do not remember whether the straw vote discussion also included
regular (non rank-remapping) pointer assignment. If it did, we also
need to replace "contiguous" with "always-contiguous" at [165:9]. How
about arguments to C_LOC (see [471:10])? I recommend that we do not
require always-contiguous variables in those cases since in some
cases the definition of always contiguous might be too restrictive.

Edits:
----------

[165:10] Replace "<data-target> shall be contiguous (5.3.6)" with:
"<data-target> shall be always contiguous (5.3.6)"

[90:22-] Before section 5.3.7, add a new paragraph:
"An object is <<always-contiguous>> if it satisfies the following
conditions."
Then copy [319:7-16+] here including Note 12.30. Add a final sentence
to the Note:
"An always-contiguous object is a contiguous object."

[316:30] In C1235 replace
"If an actual argument is an array section or an assumed-shape
array," with
"If an actual argument is not a pointer array and is not
always-contiguous,"

[317:1] In C1236 replace:
"If an actual argument is a pointer array," with
"If an actual argument is a pointer array that does not have the
CONTIGUOUS attribute,"

[319:6] Replace the end of the paragraph "shall satisfy the following
conditions." with:
"shall be always-contiguous."

[320:2] Replace "compile-time contiguous" with "always-contiguous"

# EOF