J3/13-256
From:    Van Snyder
To:      J3
Date:    2013 May 21
Subject: Editorial stuff concerning CRITICAL and CONCURRENT constructs

1. The problems
---------------

The constraints against using EXIT or CYCLE to leave CRITICAL or DO
CONCURRENT constructs are on the EXIT and CYCLE statements (C821 and
C845).

The constraints against using RETURN and branch to leave CRITICAL and DO
CONCURRENT constructs, and image control, are on the constructs (C810,
C811, C822-C824).

It would be more consistent, and more efficient, i.e., one constraint
each on EXIT, CYCLE, RETURN, branching and image control instead of one
constraint in each construct for each of these relationships, if the
constraints were on the EXIT, CYCLE, and RETURN statements, and on
branching and image control.

The same arguments apply to the description of the CHANGE TEAM construct
and collective subroutines in 13-251/N1967 (TS 18508 draft).

The edits to 12-007 are intended not to have technical effect.  One
corresponding edit to 13-251/N1967 has the technical effect of addressing an
oversight in 13-251/N1967: Failure to prohibit returning from a CHANGE TEAM
construct.

2. Edits to 12-007
------------------

Some of these are amended below to apply to 13-251/N1967, to encompass CHANGE
TEAM constructs in TS 18508.

[12-007:173:12-14 C810-C811] Delete the constraints.  Their effect will
reappear below in C845a, C850a, and C1269a.

[12-007:173:15-16 8.1.5p2] Delete the paragraph.  The first sentence is
covered by 8.1.2.2p2.  The second will reappear below at 188:29+.

[12-007:177:36-39 C822-C824] Delete the constraints.  Their effect will
reappear below in C845a, C850a, and C1269a.

[12-007:187:7+ 8.2.1p1+] Insert a constraint:

"C845a A branch within a CRITICAL or DO CONCURRENT construct shall not
       have a branch target that is outside the construct."

[12-007:188:29+ 8.5.1p4+] Insert a paragraph and constraint:

"A procedure invoked, directly or indirectly, from within a CRITICAL or
DO CONCURRENT construct, shall not execute an image control statement."

{The part about DO CONCURRENT could be in a note, since it is covered by
a conspiracy of C825 and C1288.}

"C850a An image control statement shall not appear within a CRITICAL or
       DO CONCURRENT construct."

[12-007:310:39+ C1269+] Insert a constraint:

"C1269a A <return-stmt> shall not appear within a CRITICAL or DO
        CONCURRENT construct."

3. For integration of TS 18508
------------------------------

[13-251/N1967:9:31-32 C501] Delete the constraint.  Its effect reappears
as C845a, a constraint on branching rather than on the CHANGE TEAM
construct.

[13-251/N1967:27:3+] Insert edits to 12-007:

"{After 8.2.1 Branch concepts paragraph 1, insert a constraint.}

"C845a A branch within a CHANGE TEAM, CRITICAL, or DO CONCURRENT
       construct shall not have a branch target that is outside the
       construct."

[13-251/N1967:28:4+] Insert a subclause and edits to 12-007:

"8.5a Edits to clause 12

"{After constraint C1269 in subclause 12.6.2.7 RETURN statement, insert
a constraint.}

"C1269a A <return-stmt> shall not appear within a CHANGE TEAM, CRITICAL,
        or DO CONCURRENT construct."