To: J3
From: interp
Subject: interp 66
Date:  May 31, 2000

Interp 66 failed the letter ballot, and interp has revised this interpretation based on comments from Henry and subgroup
discussion.

Changes to interp 66 are in BOLD.

NUMBER: 000066
TITLE: Errors in processing data transfer statements
KEYWORDS: ERR=; IOSTAT=; Data transfer statements
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

Consider the following program.

      INTEGER :: A(10), IDX, J
      OPEN(10, FORM='UNFORMATTED', ACCESS='SEQUENTIAL', STATUS='OLD',         &
     &         ACTION='READ')
      READ(10, IOSTAT=IOS) IDX, J, A(IDX)
      END

If an error occurs while processing the variable J in the data transfer
statement, does this program become non-standard conforming?

According to 9.4.3:

    "If an error condition or an end-of-file condition occurs during
     execution of an input/output statement, execution of the input/output
     statement terminates and if the input/output statement contains any
     implied-DOs, all of the implied-DO variables in the statement become
     undefined.  If an error condition occurs during execution of an
     input/output statement, the position of the file becomes
     indeterminate.

     If an error or end-of-file condition occurs on input, all input list
     items become undefined."

According to 9.4.4:

     "The effect of executing a data transfer input/output statement shall
      be as if the following operations were performed in the order
      specified:

      (1) Determine the direction of data transfer
      (2) Identify the unit
      (3) Establish the format if one is specified
      (4) Position the file prior to data transfer (9.2.1.3.2)
      (5) Transfer data between the file and the entities specified by the
          input/output list (if any) or namelist
      (6) Determine whether an error condition, an end-of-file condition,
          or an end-of-record condition has occurred
      (7) Position the file after data transfer (9.2.1.3.3)
      (8) Cause any variables specified in the IOSTAT= and SIZE= specifiers
          to become defined."

A simple reading of this seems to indicate that the point at which the error
occurs and is detected by a standard-conforming processor is unspecified.
Because IDX becomes undefined, the reference to IDX in the variable A(IDX) is
incorrect.  However, this is a very common style of coding I/O operations in
Fortran.

QUESTION 1:
Was it the committee's intent that such a program should not be standard-
conforming in the presence of an error condition?

QUESTION 2:
Does the fact that the error occurred before the item A(IDX) was processed
mean that there was no reference to IDX, and hence, that the program is
standard-conforming?

ANSWER 1: No.

ANSWER 2: Yes.

DISCUSSION:  The referenced paragraph (9.4.4) is misleading.  The entire
I/O list is not necessarily expected to be processed in the presence of an
error.

EDIT:
    For Fortran 95:
Section 9.4.4, list item 6  [150:33], delete "an error condition,", and change ", or" to "or"

Section 9.4.4, add the following after list item (8):
 "If an error condition occurs during any of the above operations, execution of the data transfer statement
terminates, any variable specified in an IOSTAT= specifier becomes defined, and the error condition is
processed as described in 9.4.3."



SUBMITTED BY:  Henry Zongaro
HISTORY:  J3/99-177   m150  submitted
          J3/99-212   m150  approved uc
                  May 2000  failed J3 letter ballot
          J3/00-213   m153  J3 consideration in progress

		J3/00-213
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