J3/10-245
To: J3
From: Malcolm Cohen
Subject:
Date: 2010 October 12

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NUMBER: F03/0124
TITLE: definition is poorly defined
KEYWORDS: definition
DEFECT TYPE: Interpretation
STATUS: J3 consideration in progress

QUESTION:

Consider the program:

       PROGRAM MAIN
         TYPE T1
           SEQUENCE
           INTEGER I, J
         END TYPE
         TYPE T2
           SEQUENCE
           INTEGER I, J
         END TYPE
         TYPE(T1) X
         TYPE(T2) Y
         EQUIVALENCE (X, Y)
         X%I = 1
         X%J = 2
         PRINT *, X, Y
       END

Is this program standard-conforming, and if so, what does it print?

According to items (1) and (12) of 16.6.5, the assignment to X%I
causes both X%I and Y%I to become defined.

Similarly, the assignment to X%J causes both X%J and Y%J to become
defined.

Then, according to item (15) of 16.6.5, both X and Y become defined.

However, according to 4.5.2.4, X and Y are types with different names,
and therefore are of different type, thus according to 16.6.6 item (1)
when X becomes defined Y becomes undefined, and vice versa.  This
appears to be a contradiction.

ANSWER:

The program was intended to be standard-conforming.
An edit is supplied to remove the apparent contradiction.

The program should print something like " 1 2 1 2".

EDITS:

[455:14+] In 16.6.6 item (1), insert new sub-list item
  "(c) When all components of a structure of a numeric sequence type
       or character sequence type become defined as a result of
       partially associated objects becoming defined, an associated
       variable of a different type does not become undefined."

SUBMITTED BY: Robert Corbett (via Van Snyder via Dan Nagle)

HISTORY: 08-269    m185  F03/0124 submitted
         10-nnn    m193  Draft answer

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