C struct garbage collection not run frequently enough

[fatteneder]

@mattsignorelli

2. If it is unaware, then how can I tell the GC at object creation in a performant way how much memory is actually being used? If it is aware, then how can I fix this?

You have to allocate the memory in Julia and pass a pointer to it to C.
E.g.

mutable struct TheCtype
   x::Cint
end

function do_something(ct::TheCtype)
   p = pointer_from_objref(ct)
   GC.@preserve ct begin
      @ccall my_c_function(p::Ptr{Cvoid})::Cvoid
   end
end