[julia-users] Need Ref on UInt32 but not Float64

[Bryan Rivera]

For some reason I need to specify Ref{UInt32} instead of just UInt32. 
 Float64 does not seem to require the same. 

Can anyone explain this behavior?

function callbackfun(a::UInt32, b::Float64, c::UInt32)
    ...
end

cfunction(callbackfun, Void, (Ref{UInt32},Float64,Ref{UInt32}))  


typedef void (*CALLBACKFUN)(unsigned int z, double b, unsigned int c);