To: J3                                                     J3/18-189
From: Malcolm Cohen
Subject: Country comment GB-050
Date: 2018-June-12

1. Introduction

The second paragraph of subclause 17.1 "Overview of IEEE arithmetic
support" contains several mistakes and unnecessary verbiage.
These should be fixed/deleted.

2. Response to GB-050

Accepted with modification.

3. Discussion of the comment

The problems are as follows:
(a) IEEE_SUPPORT_FLAG, and IEEE_SUPPORT_HALTING are incorrectly described
    as inquiry functions.  There is no need to even mention their
    classification here.
(b) In most places p2 is careful to say that support is within a scoping
    unit.  For "Which other exceptions" that qualification is missing.
(c) Three times, after saying something "shall be supported", it goes on
    to say that the corresponding support function "shall return true".
    This is unnecessary since that is what the function is already
    described as doing.

4. Additional changes

(A)
The word "may" is incorrect.
Either "might" or "can" would be acceptable.

(B)
We variously say that a flag "is accessible", or "has access to".
The wording "is accessible" is to be preferred.

(C)
The trailing "for the flag" on the last sentence conveys no information.
It is unclear whether accessibility of IEEE_SUPPORT_HALTING requires that
halting be supported
    a) for at least one flag,
    b) for all flags,
    c) for all supported exception flags.
Option (c) is the most plausible, but this question would be better
handled by defect processing.  In the meantime, deleting the phrase that
conveys no information is right.

5. Outstanding issues

The very first sentence of p2 is complete nonsense (modules themselves are
never "accessible", only entities within them).  There are a number of
plausible stories about what we intended.
This has to be left to defect processing.

6. Edits to N2146

Page 443, 17.1 "Overview of IEEE arithmetic support", paragraph 2,

After "Which other exceptions are supported"
insert "in the scoping unit".

Delete the first two instances of "inquiry"
(in "the inquiry function IEEE_SUPPORT_FLAG"
 and "the inquiry function IEEE_SUPPORT_HALTING").

Change "may be influenced" to "can be influenced".

Change
  "If a scoping unit has access to IEEE_UNDERFLOW_FLAG of IEEE_FEATURES"
to
  "If IEEE_UNDERFLOW_FLAG is accessible"
(we don't need to say "of IEEE_FEATURES" because we said this in the
 immediately-preceding sentence).

Delete "and return true from IEEE_SUPPORT_FLAG(IEEE_UNDERFLOW, X)".
Delete "and return true from the corresponding inquiry function".
Delete "and return true from IEEE_SUPPORT_HALTING(FLAG) for the flag".

This will make the whole paragraph read:
  "If IEEE_EXCEPTIONS or IEEE_ARITHMETIC is accessible in a scoping unit,
   the exceptions IEEE_OVERFLOW and IEEE_DIVIDE_BY_ZERO are supported in
   the scoping unit for all kinds of real and complex IEEE floating-point
   data.  Which other exceptions are supported in the scoping unit can be
   determined by the function IEEE_SUPPORT_FLAG (17.11.51); whether
   control of halting is supported can be determined by the function
   IEEE_SUPPORT_HALTING.  The extent of support of the other exceptions
   can be influenced by the accessibility of the named constants
   IEEE_INEXACT_FLAG, IEEE_INVALID_FLAG, and IEEE_UNDERFLOW_FLAG of the
   module IEEE_FEATURES.  If IEEE_UNDERFLOW_FLAG is accessible, within the
   scoping unit the processor shall support underflow for at least one
   kind of real.  Similarly, if IEEE_INEXACT_FLAG or IEEE_INVALID_FLAG is
   accessible, within the scoping unit the processor shall support the
   exception for at least one kind of real.  If IEEE_HALTING is
   accessible, within the scoping unit the processor shall support control
   of halting."

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