Attribute Macro func 

#[func]

func is used export Rust functions to OCaml, performing the necessary wrapping/unwrapping automatically.

• Wraps the function body using ocaml::body
• Automatic type conversion for arguments/return value (including Result types)
• Defines a bytecode function automatically for functions that take more than 5 arguments. The bytecode function for my_func would be my_func_bytecode
• Allows for an optional ident argument specifying the name of the gc handle parameter