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From: mev@hpfcso.HP.COM (Mike Vermeulen)
Newsgroups: comp.sys.hp
Subject: Re: _HPUX_SOURCE Defintion and ANSI C
Message-ID: <7370271@hpfcso.HP.COM>
Date: 21 Dec 90 15:25:43 GMT
References: <136@bwilab3.UUCP>
Organization: Hewlett-Packard, Fort Collins, CO, USA
Lines: 33

> I was told to resolve this problem by #defining _HPUX_SOURCE. This solves
> the problem of the compiler not finding the prototypes but raises some
> questions about what it does. I was also told, by someone else, that the
> _HPUX_SOURCE tells the compiler that I am compiling kernel code. Is this
> true? Is there a better way to get access to the routines than _HPUX_SOURCE?
> What problems am I opening up by using this? (i.e. am I allowing access to
> kernel routines that I am not supposed to?)

_HPUX_SOURCE tells the compiler to use the same namespace as when compiling
in compatability mode (-Ac).  It has nothing to do with whether the code is
kernel code or not.  For background, here is the reason for needing
_HPUX_SOURCE:

   The ANSI C standard specifies exactly which symbols are reserved by the
   implementation and which ones are available for the user.  For example,
   while the symbol "open" is a UNIX* system call, this name is not reserved
   by the standard.  Thus programs compiling with ANSI C should have the
   ability to define their own routine named "open" and not have it conflict
   with the library/system routine.  When compiling with -Aa you get a complete
   ANSI C conformant compile including namespace.

   There are additional standards that specify additional names.  There are
   predefines that may be used to get these symbols.  For example, the POSIX
   standard specifies that the namespace for the POSIX namespace can be gotten
   by placing a #define _POSIX_SOURCE prior to including any headers.  The
   names for XOPEN can be gotten with the symbol _XOPEN_SOURCE.

   Thus _HPUX_SOURCE gets you the complete polluted namespace that is 
   available in compatability mode.

--mev

disclaimer: not an official response.