0000543: Missing C99 text about undeserved underflow

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Category

Severity

Type

Date Submitted

Last Update

0000543

[1003.1(2008)/Issue 7] Base Definitions and Headers

Objection

Omission

2012-02-17 10:25

2019-06-10 08:55

Reporter

geoffclare

View Status

public

Assigned To

ajosey

Priority

normal

Resolution

Accepted

Status

Closed

Name

Geoff Clare

Organization

The Open Group

User Reference

Section

4.19

Page Number

117

Line Number

3205

Interp Status

---

Final Accepted Text

Summary

0000543: Missing C99 text about undeserved underflow

Description

Section 4.19 Treatment of Error Conditions for Mathematical Functions
and its corresponding rationale are missing an equivalent for the
following text from C99 F.9 para 9 and footnote 321 (as amended by a
technical corrigendum):

    Whether or when library functions raise an undeserved "underflow"
    floating-point exception is unspecified.321) Otherwise, as
    implied by F.7.6, the <math.h> functions do not raise spurious
    floating-point exceptions (detectable by the user), other than the
    "inexact" floating-point exception.

    321) It is intended that undeserved "underflow" and "inexact"
    floating-point exceptions are raised only if avoiding them would
    be too costly.

Also, the feraiseexcept() page is missing an equivalent of the text
in F.7.6 referred to above, which is:

    If the argument to the feraiseexcept function in <fenv.h>
    represents IEC 60559 valid coincident floating-point exceptions
    for atomic operations (namely "overflow" and "inexact", or
    "underflow" and "inexact"), then "overflow" or "underflow" is
    raised before "inexact".

Since POSIX.1 defers to C99, implementations are already required to
behave in this way and no interpretation is needed when adding the
missing text.

Note that the added text in 4.19 should not be shaded MX because the
introduction to chapter 4 says "No shading to denote extensions or
options occurs in this chapter".

Desired Action

Add a new paragraph in 4.19 before the last paragraph:

    On implementations that support the IEC 60559 Floating-Point
    option, whether or when functions in the <math.h> header raise
    an undeserved underflow floating-point exception is unspecified.
    Otherwise, as implied by [xref to XSH feraiseexcept()] the
    <math.h> functions do not raise spurious floating-point exceptions
    (detectable by the user), other than the inexact floating-point
    exception.

Cross-volume change to XSH...
On page 834 line 27835 section feraiseexcept() change:

    The order in which these floating-point exceptions are raised is
    unspecified.

to:

    The order in which these floating-point exceptions are raised is
    unspecified, [MX]except that if the excepts argument represents
    IEC 60559 valid coincident floating-point exceptions for atomic
    operations (namely overflow and inexact, or underflow and inexact),
    then overflow or underflow shall be raised before inexact.[/MX]

Cross-volume change to XRAT...
On page 3452 line 115876 section A.4.19 change:

    There is no additional rationale provided for this section.

to:

    It is intended that undeserved underflow and inexact floating-point
    exceptions are raised only if avoiding them would be too costly.

Issue History
Date Modified	Username	Field	Change
2012-02-17 10:25	geoffclare	New Issue
2012-02-17 10:25	geoffclare	Status	New => Under Review
2012-02-17 10:25	geoffclare	Assigned To	=> ajosey
2012-02-17 10:25	geoffclare	Name	=> Geoff Clare
2012-02-17 10:25	geoffclare	Organization	=> The Open Group
2012-02-17 10:25	geoffclare	Section	=> 4.19
2012-02-17 10:25	geoffclare	Page Number	=> 117
2012-02-17 10:25	geoffclare	Line Number	=> 3205
2012-02-17 10:25	geoffclare	Interp Status	=> ---
2012-02-23 16:53	eblake	Status	Under Review => Resolved
2012-02-23 16:53	eblake	Resolution	Open => Accepted
2012-02-23 16:53	eblake	Description Updated
2012-02-23 16:53	eblake	Desired Action Updated
2012-02-23 16:53	eblake	Tag Attached: tc2-2008
2019-06-10 08:55	agadmin	Status	Resolved => Closed

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