[Media_api] Some #pragmas for Windows

[Peter Castine]

The only alternative to scattering compiler-dependent #ifdefs through  
the code that I am aware of is to conditionally #define some macros  
at the beginning of a header file that gets included in everything.  
I've seen things like

// At the top of some global .h file
#ifdef (__cplusplus)
  #define EXTERN_C_START		extern "C" {
  #define EXTERN_C_END		}
#else
  #define EXTERN_C_START
  #define EXTERN_C_END
#end

and then use EXTERN_C_START and EXTERN_C_END instead of conditional  
compile statements in header files using C conventions. Both Apple  
and MS use this technique extensively for pseudo-qualifiers and  
pseudo-types. On Windows __cdecl, __stdecl, ad inf., on Mac  
<CarbonCore/ConditionalMacros.h> does tons conditional #defines.

Dunno which alternative is better practice. Also, I don't think you  
can get this to work with #pragmas. I think something like the  
following won't work:

---------------------------------
#ifdef (_MSC_VER)
  #define PRAGMA_NOWARN(X)	#pragma warning(disable: X)
#else
  #define PRAGMA_NOWARN(X)
#endif

PRAGMA_NOWARN(4133)		// This ain't gonna do what I want, is it?
---------------------------------

Any preprocessor gurus out there who can prove me wrong? Some funky  
post-K&RII macro substitution?


-- P.

On 4-May-2007, at 14:19, Roger Dannenberg wrote:

> I didn't mean to imply your code was wrong, and in fact I don't  
> think I thought of using ifdefs to isolate pragmas when I was  
> trying to do something in the past. I was only wondering if it's  
> the best way -- I figure many have dealt with this, but I've never  
> seen any discussion of best practices. -Roger

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