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From: urlichs@smurf.sub.org (Matthias Urlichs)
Newsgroups: comp.unix.aux
Subject: Re: Here are some useful patches to rn for A/UX
Keywords: rn patches
Message-ID: <#-1qg2.0-5@smurf.sub.org>
Date: 3 Dec 90 18:53:54 GMT
References: <1990Nov30.015100.6211@wiskit.pdx.com> <ge^ng2.%k2@smurf.sub.org> <1990Dec2.014221.12113@panix.uucp>
Organization: University of Karlsruhe, FRG
Lines: 62

In comp.unix.aux, article <1990Dec2.014221.12113@panix.uucp>,
  alexis@panix.uucp (Alexis Rosen) writes:
< 
< Also, I did not know anything about the compatibility libraries (my knowledge
< of A/UX coding is basically non-existent yet...), although I know about the
< compiler define switches like _SYSV_SOURCE. Is there a brief and concise
< description of stuff like this in one place, or do I need to fish through
< the man pages for a year in order to discover everything?
< 
Man pages?

There are basically four "compatibility modes" or whatever Apple chooses to
call them:
- A/UX standard stuff (no additional library)
- SysV (use -lsysv)
- BSD (use -lbsd)
- POSIX (use  -lposix)

This is the environment which programs expect when you run them. Obviously,
it doesn't make sense to use more than one of the above. If you need anything
weird, include the appropriate setcompat() call in your program.
(There are some other minor differences, e.g. when enumerating directories.)

Distinguished from this are the various defining flags for cc which make
your C code compile in the first place:

-D_SYSV_SOURCE
-D_BSD_SOURCE
-D_POSIX_SOURCE
-D_AUX_SOURCE

if your program uses any special features from System V, BSD, Posix, or A/UX,
respectively. These can be combined freely.
There are some bugs in the include files; you can't include some of the
Streams stuff without using -D_SYSV_SOURCE or some of the networking code
without -D_POSIX_SOURCE because Apple forgot to replace some of the standard
typedef'd names in the Streams/networking-specific .h files.

Incidentally, Apple seems to have licensing problems with AT&T because Apple
modified all these include files. (AT&T doesn't seem to like that at all.)
These -D_XXX_SOURCE flags are somewhat awkward at first, but very easy to
work with if / as soon as you know what you want to do and what kind of
compile- and runtime environment the programs you're trying to compile expect
-- lots easier than mucking around with "universe" stuff like some other
vendors' Unix.

NB: None of the above applies to the TTY interface, which is System Five
throughout. The odd code which still doesn't have SysV terminal support will
have to be rewritten.
The biggest hassle are programs which don't use "feature flags" but expect
that there's either a -DBSD or a -DSYSV (or -DUSG) in the Makefile which
switches everything around. This is a problem because the A/UX terminal
handling is SysV while the signal handling is BSD. (Mostly.) Fortunately,
programmers learn, and the percentage of new code which does this sort of
thing is decreasing fast.

Disclaimer: All of the above is gross conjecture and should not be taken
seriously.

-- 
Matthias Urlichs -- urlichs@smurf.sub.org -- urlichs@smurf.ira.uka.de     /(o\
Humboldtstrasse 7 - 7500 Karlsruhe 1 - FRG -- +49+721+621127(0700-2330)   \o)/