Public Comment Number PC-UK0141

ISO/IEC CD 9899 (SC22N2620) Public Comment

=========================================== 

Date: 1998-02-25
Author: N.M Maclaren
Author Affiliation: Self
Postal Address:
    University of Cambridge,
    Computer Laboratory,
    New Museums Site,
    Pembroke Street,
    Cambridge CB3 3QG,
    United Kingdom
E-mail Address: <nmm1@cam.ac.uk>
Telephone Number: +44 1223 334761
Fax Number:       +44 1223 334679
Number of individual comments: 1


Comment 1. 

Category: Normative change to existing feature retaining the original intent

Committee Draft subsection: 7.7.1

Title: Which <math.h> functions can set errno


Detailed description:

C89 was and C9X is unclear about whether tan() and similar functions are
allowed to set errno or not.  Its specification has no reference to a
domain error and therefore, by implication, it has no reference to errno.
By 7.1.4 paragraph 3, it is therefore allowed to set errno at whim.  But is
this so?  Furthermore, there are several implications in C9X that the
handling of IEEE exception flags and errno have similar properties, so this
becomes even more of a trap.  I suggest adding the following wording to the
end of paragraph 1:

    This section documents the use of errno by all the functions
    defined in the header <math.h>, which therefore will set errno only
    when an error is detected (see 7.1.4).