Bug#406754: Bug #406754: portaudio19: FTBFS: #error Memory barriers are not defined on this system.

[Falk Hueffner]

Hi,

the correct solution is to use __sync_synchronize as fallback, which
is a full memory barrier defined by gcc (starting from 4.1) for all
platforms. It is also desirable to use this on all platforms that
don't differentiate read/write/full barriers, since it gives the
compiler better opportunities to optimize.

-- 
	Falk