Re: [Libguestfs] [libnbd PATCH v5 01/12] rust: create basic Rust bindings
On Thu, Aug 03, 2023 at 03:36:05PM +0000, Tage Johansson wrote:
This commit creates basic Rust bindings in the rust directory.
The bindings are generated by generator/Rust.ml and
generator/RustSys.ml.
---
--- /dev/null
+++ b/generator/RustSys.ml
+(** Print the struct for a closure. *)
+let print_closure_struct { cbname; cbargs } =
+ pr "#[repr(C)]\n";
+ pr "#[derive(Debug, Clone, Copy)]\n";
+ pr "pub struct nbd_%s_callback {\n" cbname;
+ pr " pub callback: \n";
+ pr " Option<unsafe extern \"C\" fn(*mut c_void, %s) ->
c_int>,\n"
+ (cbargs |> List.map cbarg_types |> List.flatten |> String.concat ",
");
+ pr " pub user_data: *mut c_void,\n";
+ pr " pub free: Option<unsafe extern \"C\" fn(*mut
c_void)>,\n";
+ pr "}\n"
Why is 'callback' an Option<> rather than a mandatory argument? I get
that 'free' must be an Option<> (because it corresponds to an
OClosure, which is an optional callback), but 'callback' is a
mandatory function pointer in the C API; why would it ever be
acceptable to pass None instead of Some<function>?
--
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization: qemu.org | libguestfs.org