I want to modify the data stored in an elementary julia object (e.g. Int64)
using external C code. I can do this if the type is wrapped in an array, but is
it possible to do something like `pointer(x::Float64) -> address of data in x`
with the memory being guaranteed by julia?
Here’s a short snippet to describe:
~~~
#C side
void myfunc(long* x) {
x[0] += 1;
}
#julia side, works
x = Int64[0]
ccall((:myfunc, lib), Void, (Ptr{Void}, ), convert(Ptr{Void}, pointer(x)))
println(x)
>> [1]
#julia side, desired
x = 0
ccall((:myfunc, lib), Void, (Ptr{Void}, ), pointer(x))
println(x)
>> 1
~~~
I tried pointer_from_objref but as I understand this gives me the pointer of
the whole julia type with meta-data etc. If I write to this address in C, I
fear I’ll have problems.
