[cairo] Atomic reference counting

[Behdad Esfahbod]

On Sun, 2007-09-23 at 22:14 +0100, Chris Wilson wrote:
> 
> +AC_ARG_ENABLE(atomics,
> +  AS_HELP_STRING([--disable-atomics],
> +                [Do not use atomic operations]),

Humm, what do you see as the usecase for this?  If we want to do
something like this it should be like --disable-mt and imply NO_MUTEX
too.


> +  [use_atomic=$enableval], [use_atomic=auto])
> +if test "x$use_atomic" != "xno"; then
> +    AC_TRY_COMPILE([int atomic_add(int i) { return __sync_fetch_and_add (&i, 1); }], [],
> +      AC_DEFINE(CAIRO_HAS_ATOMIC_OPS, 1, [Enable if your platform has native atomic operations])
> +      AC_DEFINE(CAIRO_HAS_INTEL_ATOMIC_PRIMITIVES, 1, [Enable if your compiler supports the Intel __sync_* atomic primitives])

I was thinking about defining CAIRO_HAS_ATOMIC_OPS automatically in the
header file based on whether any concrete implementation was found.  As
in:

#define CAIRO_HAS_ATOMIC_OPS 1
#if CAIRO_HAS_INTEL_ATOMIC_PRIMITIVES
...
#elif CAIRO_HAS_SOMEOTHER_ATOMIC_PRIMITIES
...
#else
...
# undef CAIRO_HAS_ATOMIC_OPS
#end

> +      )
> +fi
> + 


The rest looks good.  Thanks.  Feel free to push.
-- 
behdad
http://behdad.org/

"Those who would give up Essential Liberty to purchase a little
 Temporary Safety, deserve neither Liberty nor Safety."
        -- Benjamin Franklin, 1759