Module natives 

Standard native (FFI) table shipped with the facade.

Why Message make/unpack lives here (not as new opcodes)

crate::Value::Message is already a first-class wire/register value (ABI v2). Building and tearing it apart in bytecode could be ISA ops (MakeMessage, MsgSender, …), but that would burn opcode space and force every embedder that never does request-reply to carry the dispatch cost. Natives keep the envelope generic in the core while the std table opts into the helpers — same pattern as print / now_ms (design notes §30-31): host Rust owns the operation, bytecode only picks a slot.

Stable indices are an embed contract

Flash / separately-built .bf modules hard-code CallNative indices. Renumbering an existing slot is a breaking change. Keep std_native_map and std_native_table in lockstep; append only.

Index	Name	Role
0	print	host stdout log line (flow-visible)
1	now_ms	wall-clock millis as Value::Int
2	make_msg	build crate::Message from four scalars (untrusted sender)
3	msg_sender	extract sender → Value::Pid (authenticated after delivery)
4	msg_request_id	extract request_id → Value::Int
5	msg_tag	extract tag → Value::Int
6	msg_payload	extract payload → Value::Int
7	msg_reply_cap	extract reply_cap → Value::Cap (SEND grant)

CallNative argument layout

CallNative ra, fb, nc takes args from r[a .. a+nc] and writes the result back into r[a] — so a call destroys the first argument register. Samples that need to keep a Message while unpacking must Move it into the dest register first (see crate::samples::atomic_request_reply).

Functions

std_native_map

Name → CallNative index for documentation / host-side lookups.

std_native_table

Default FFI table: print, clock, and Message make/unpack.

std_natives

Build the default native table and its matching name map together.