Defect in XBD unistd.h

[Geoff Clare <yyy@xxxxxxxxxxxxx>]

@ page 398 lines 14023-14034 section unistd.h comment [gwc option constants 2]

Problem:

Defect code :  3. Clarification required

The descriptions on the <unistd.h> page under the heading "Constants
for Options and Option Groups" of the "undefined" case and the "defined
with value zero" case are separate and slightly different.  This can
mislead some readers into thinking that there must be some subtle
difference between the two cases, when in fact the intention was for
the requirements to be exactly the same.  (This intention is clear
from the explanation of the new options mechanism in the rationale on
the <unistd.h> page.)

I think the text ended up the way it is purely by historical accident.
The text for the "undefined" case was carried over from SUSv2 with some
minor adjustment, and the text describing the -1, >0 and 0 cases was
added after it.  The descriptions of the "undefined" case and the
"defined with value zero" case need to be merged in order to remove
any doubt about their equivalence.

Action:

On lines 14023-14025 delete:

    "If these are undefined, the fpathconf(), pathconf(), or sysconf()
    functions can be used to determine whether the option is provided
    for a particular invocation of the application."

On line 14033 change "is defined with the value zero" to "is undefined
or is defined with the value zero".

On line 14034 change "whether the option is supported" to "whether the
option is supported for a particular invocation of the application".