Reserving Identifiers for future use

The POSIX standards reserve a number of identifiers for
future use.  By specifying a list of reserved identifiers
WG15 have given implementors of their standard plenty of
latitude to add to the existing namespace.  However, they
have failed to consider the impact on writers of applications.

In the last few years there has been a growing interest in
the testing of applications for conformance to standards.
Commercially applications are significantly more important
that POSIX implementations.

It is quite common for 50%, or more of the total number of
POSIX related conformance problems found in an applications
source code to directly relate to the definition of identifiers,
by the application, reserved by the POSIX standard.  In nearly
all cases, in my experience, the application vendor has seen no
benefit in spending substantial time in renaming identifiers
(which would usually also involve changes to published, company
wide, interfaces and changes to documentation).

By making it so easy for an application to define an identifier
that matches one given on the reserved list WG15 have
weakened the strength of their standard.  Vendors now actively
make decisions to ignore non-conforming constructs in their
source code.

What can WG15 do?

The simplest solution would be to remove all wording relating
to the use of reserved identifiers from the conformance model.
The list of reserved identifiers would be informative only.

If the WG15 felt that use of some identifier spellings ought
to be part of the conformance statement then they should consider
very carefully any additions to the existing list.  They
should also consider removing the following, existing reserved
spellings:

   1) All identifiers ending in _t

   2) All those cases where a short initial sequence of
      characters followed by any number of characters is
      reserved without the need to include a particular
      system header.

To prevent additional, unnecessary non-conformities the
following rules should be adopted:

   1) Where possible a spelling only becomes reserved when a
      specified system header is included.

   2) A spelling that does not require a specific header to be
      included should include at least four specific characters
      in its matchin pattern, preferably mixed case.