Re: [Boost-Users] MacOS.hpp and PowerPlant incompatibility

From: John Maddock (john_maddock_at_[hidden])
Date: 2002-06-06 06:17:35

> I am trying to use the boost libraries with a PowerPlant project on the
> MacOS, and I ran into a small incompatibility between the headers.  I am
not
> sure which codebase is at fault here.
>
> The issue is with the __MACH__ symbol.  In the Boost code where it is
> checking for what platform I am using, it correctly identifies my platform
> as MacOS.  Then, in a file called MacOS.hpp, it uses the __MACH__ symbol
to
> determine if I am using the BSD standard C libraries or MSL.  (I am using
> MSL.)
>
> It does this by checking for the EXISTANCE of the __MACH__ symbol, not
> the value of it:
>
> // If __MACH__, we're using the BSD standard C library, not the MSL:
> #if defined(__MACH__)
>
> However, in the PowerPlant header PP_Macros.h, the __MACH__ symbol is
> defined and set to zero:
>
> #ifndef __dest_os                // For MSL
>
>    #ifndef __MACH__
>       #define __MACH__  0
>    #endif
>
>    #if __MACH__
>       #include <ansi_prefix.mach.h>
>    #else
>       #define __dest_os  __mac_os
>    #endif
> #endif
>
> I was able to work around the problem for now by making the Boost
libraries
> check for both the existance of __MACH__ and the value:
>
> #if defined(__MACH__) && __MACH__
>
> Seems to work.
>
> However, I am curious.  Which way is the right way?  Is the __MACH__
> symbol's existance or its value supposed to signal whether or not it is
> "turned on"?  The boost headers seem to think it is its existance, but the
> PowerPlant headers seem to think it is its value.
>
> I want to report the problem, but I am not sure whose code needs to
change,
> PowerPlant or Boost.  Ideas?

Is PowerPlant a third party lib? If so then I don't think it should be
setting a reserved symbol like __MACH__, however it's easy enough to change
the boost code to verify that __MACH__ is greater than zero, so I'll make
that change anyway unless there are objections (any Darwin experts out
there?).

John Maddock
http://ourworld.compuserve.com/homepages/john_maddock/index.htm