What namespaces are available?

[Doug Gwyn]

In article <543 at garcon.cso.uiuc.edu> mcdaniel at uicsrd.csrd.uiuc.edu (Tim McDaniel) writes:
>karl at haddock.ima.isc.com (Karl Heuer) writes (marked with ">"):
>>	_[a-z0-9][_A-Za-z0-9]*	what I called semi-reserved
>Am I missing something obvious?  If so, PLEASE let me know and I'll
>just shut up.

I don't understand why Karl wants to distinguish between "reserved"
identifiers (which is a notion in the pANS) and "semi-reserved"
identifiers (which is not).  Certain identifiers have semantics
specified by the pANS, and a large class of other identifiers (the
"underscore" names) are reserved for possible use by implementations.
There are several name spaces in C, and the exact class of reserved
names is different for different name spaces (unfortunately, in my
opinion), but a given identifier in a particular name space is either
reserved or it is not.  If an application uses a name that was reserved
for implementations, it is no longer standard conforming; whether or
not it gets away with it obviously depends on the implementation.

(There are also some names that are reserved for future standards,
but we don't seem to be talking about those.)