Creating C structs with pointers to other structs

[stevengj]

@cshenton

What’s the idiomatic way to create a pointer to a Foo , since pointer_from_objref should not be called on immutables?

fooref = Ref(foo_object)
GC.@preserve fooref  begin
    ptr = Base.unsafe_convert(Ptr{Foo}, fooref)
    ....some code using ptr....
end

Here, I used GC.@preserve to make sure that the fooref object lives for as long as I need ptr. Other strategies can also be employed (e.g. stashing fooref in some persistent data structure) if you need ptr to be valid for a longer time.