To:         J3 Members                                       J3/16-124
From:       Van Snyder
Subject:    I/O on other units while defined I/O is active
Date: 2016 January 25

1. Introduction
===============

The prohibitions in 9.6.4.8.3p20-21 appear to be intended so as not to
require the runtime library to be reentrant.  But if the processor
supports asynchronous input/output, it is necessarily reentrant.  They
also appear to prohibit a previously-begun asynchronous input/output
statement to proceed once a defined input/output subroutine becomes
active.

The prohibitions should be removed.

If they're not removed, an interp is necessary to answer the question
whether a previously-begun asynchronous input/output statement is
allowed to proceed once a defined input/output subroutine becomes
active.

2. Edits
========

[xvi Introduction, under Input/output] Insert a sentence: "While a
parent input/output statement is active, an input/output statement may
read from or write to any external unit."

[233:1-7 9.6.4.8.3p20-22] Delete the three paragraphs beginning "While
a parent...."

{This is also the subject of an interp.}

{Another paper edits one of the deleted paragraphs.}