[FFmpeg-cvslog] r11889 - trunk/libavutil/mem.h

[Reimar Döffinger]

Hello,
On Sun, Feb 10, 2008 at 10:50:35PM +0100, Diego Biurrun wrote:
> On Sun, Feb 10, 2008 at 11:47:01PM +0200, Uoti Urpala wrote:
> > On Sun, 2008-02-10 at 22:16 +0100, Diego Biurrun wrote:
> > > On Sun, Feb 10, 2008 at 10:11:52PM +0100, Diego Biurrun wrote:
> > > > Wait, icc defines __GNUC__?!?
> > > 
> > > I suggest the following, which is farm more readable IMO even if -
> > > strictly speaking - it duplicates one line:
> > > 
> > > #ifdef __GNUC__
> > >   #define DECLARE_ALIGNED(n,t,v)       t v __attribute__ ((aligned (n)))
> > >   #define DECLARE_ASM_CONST(n,t,v)     static const t v attribute_used __attribute__ ((aligned (n)))
> > > #elif __ICC
> > 
> > icc does define __GNUC__ as it tries to support the same extensions. So
> > if there is a test for __GNUC__, any icc-specific code must be on the
> > __GNUC__ side, not the non-__GNUC__ side like in your suggestion.
> 
> Then it can be done the other way around:
> 
> #ifdef __ICC
>   #define DECLARE_ALIGNED(n,t,v)       t v __attribute__ ((aligned (n)))
>   #define DECLARE_ASM_CONST(n,t,v)     const t __attribute__ ((aligned (n))) v
> #elif __GNUC__
>   #define DECLARE_ALIGNED(n,t,v)       t v __attribute__ ((aligned (n)))
>   #define DECLARE_ASM_CONST(n,t,v)     static const t v attribute_used __attribute__ ((aligned (n)))
> #else
>   #define DECLARE_ALIGNED(n,t,v)       __declspec(align(n)) t v
>   #define DECLARE_ASM_CONST(n,t,v)     __declspec(align(n)) static const t v
> #endif

I'd still suggest something along the lines

#ifdef __ICC
  #define DECLARE_ALIGNED(n,t,v)       t v __attribute__ ((aligned (n)))
  #define DECLARE_ASM_CONST(n,t,v)     const t __attribute__ ((aligned (n))) v
#elif HAVE_DECLSPEC
  #define DECLARE_ALIGNED(n,t,v)       __declspec(align(n)) t v
  #define DECLARE_ASM_CONST(n,t,v)     __declspec(align(n)) static const t v
#elif HAVE_GENERIC_C
  #define DECLARE_ALIGNED(n,t,v)       t v
  #define DECLARE_ASM_CONST(n,t,v)     static const t v
#else
  #define DECLARE_ALIGNED(n,t,v)       t v __attribute__ ((aligned (n)))
  #define DECLARE_ASM_CONST(n,t,v)     static const t v attribute_used __attribute__ ((aligned (n)))
#endif

Where HAVE_GENERIC_C would/should only be used for a compile without any
asm at all (I don't mind if you leave that section out completely, I
just think it would be better to have. I would not like to have this
case the default though, since it could create hard-to-debug problems
while gaining little if anything in terms of supported compilers).

Greetings,
Reimar D?ffinger