Re: 3.[234] PATCH: Update predefines for Tru64 UNIX

[Dave Love <d dot love at dl dot ac dot uk>]

Rainer Orth <ro at TechFak dot Uni-Bielefeld dot DE> writes:

> * cc defines SYSTYPE_BSD with -std0 and _SYSTYPE_BSD unconditionally.  gcc
>   also defines __SYSTYPE_BSD and __SYSTYPE_BSD__.  I've left this alone for
>   the moment.

I must have missed that.  I think gcc should define them too.

> * cc defines __ALPHA and __Alpha_AXP.  The former is not documented in
>   cc(1) and only used as an alternative to __alpha__ in the system
>   headers.  The latter is neither documented nor used anywhere in the
>   system headers.  Therefore I chose to omit them for gcc.

But I think __ALPHA missing was actually the issue for what I tried to
compile.  I don't see any good reason to leave them out, and __ALPHA
is at least shown in an example in cc(1) in Compaq C V6.5-207.  The
fact that the system headers don't use things and they're not
documented doesn't mean that user code doesn't use them.

> * cc defines __PRAGMA_ENVIRONMENT and __IEEE_FLOAT.  Both are only used in
>   the vendor C++ headers and not documented.  Nothing to do for gcc.

I guess that __PRAGMA_ENVIRONMENT shouldn't be defined, but I now
think __IEEE_FLOAT should be.  I realize I used it in old code, still
in production, written for DEC C, to distinguish Alpha using IEEE and
VAX number formats.  As far as I know on OSF^WDU^WTru64 you can only
have IEEE, but __IEEE_FLOAT should be defined in case of code which
does something like this:

#ifdef __alpha
#  if __IEEE_FLOAT == 1
#    define NATIVEFT DFNTF_LEIEEE
#  else
#    define NATIVEFT DFNTF_VAX
#  endif

[I think it's beside the point whether or not it will work on other
Alpha systems.]