Re: [9fans] A probably stupid question on portability

[Pietro Gagliardi <pietro10@mac.com>]

The following

#if defined(_INCLUDED_GASNET_INTERNAL_H) && !defined 
(_IN_GASNET_INTERNAL_H)

is equivalent to

#ifdef _INCLUDED_GASNET_INTERNAL_H
#ifndef _IN_GASNET_INTERNAL_H

for the standard C compilers in Plan 9.  A goal of the Plan 9 kernel  
was to drop #if/#ifdef code and have a single C source code base that  
did not use this construct.  The compilers were adapted to fit this  
requirement, so they allow #ifdef, but disallow #if.  That is why a  
Standard C preprocessor, cpp(1), is provided

On Oct 23, 2007, at 4:03 PM, Charles Forsyth wrote:

> #if and the defined stuff are in even the older c standards, but it's
> not defined to be part of the compiler (in plan 9, it's still in a  
> separate cpp,
> and usually that's not used, except with pcc, but see the -p option  
> in 2c(1))
>
> early on, cpp was fairly simple minded, part of the cc command(!), and
> a c file had to have # at the start to be macro-processed.
>
> the rot really set in with reiser
> 	This new version [of the preprocessor] was written by John F.  
> Reiser and is from 5 to 12
> 	times faster than the old.
> (but the input language was considerably more elaborate, and didn't  
> people use it!)
>
> From: "ron minnich" <rminnich@gmail.com>
> Date: October 23, 2007 3:10:31 PM EDT
> To: "Fans of the OS Plan 9 from Bell Labs" <9fans@cse.psu.edu>
> Subject: [9fans] A probably stupid question on portability
> Reply-To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
>
>
> Is this construct portable at this point? c99 or whatever? Or is it  
> gcc-centric?
>
> #if defined(_INCLUDED_GASNET_INTERNAL_H) && !defined 
> (_IN_GASNET_INTERNAL_H)
>
>
> ron
>