3240ac0080
5a: record {.ffiHost.} procs in a compile-time registry (FFIHostMeta /
ffiHostRegistry), populated by the macro, so generators can see host fns.
5b: the Go generator emits an idiomatic wrapper over the host C ABI:
- a single //export cgo trampoline backs every host fn; a cgo.Handle in
userData selects the Go closure;
- the closure runs on a fresh GOROUTINE so the FFI thread is never blocked
(the non-blocking contract), then answers via <lib>_host_complete by token;
- a per-host `Set<Name>(func(string) (string, error))` method registers it.
Validated end to end with `go run` (examples/host_demo): Go UseToken -> Nim
{.ffi.} handler -> await fetchToken {.ffiHost.} -> Go trampoline -> goroutine
runs the closure -> host_complete -> future resolves on the loop thread ->
"token[TOK-session]" back in Go. Timer's Go output is unchanged (no host fns);
its regenerated .h just gains the always-exported host ABI decls.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Go (cgo) bindings — native (same-process) example
Generated cgo bindings for the timer library. The Go wrapper links the library
directly and calls the native C ABI, marshalling each {.ffi.} type from an
idiomatic Go struct into its flat C-POD form per call.
Files
| File | Description |
|---|---|
my_timer.go |
Generated cgo package. One Go struct per {.ffi.} type plus a toC() marshaller; one method per {.ffi.} proc. |
my_timer.h |
Native C header (emitted alongside the .go so cgo's #include resolves locally). |
go.mod |
Makes the package an importable module. |
example/ |
A runnable main.go that exercises the struct-param methods. |
Regenerate with nimble genbindings_go (from the repo root); the files here are
overwritten each time and gofmt-finalized.
Mapping
Nim ({.ffi.}) |
Go |
|---|---|
string |
string |
int / int64 … |
int64 … |
bool |
bool |
seq[T] |
[]T |
Option[T] / Maybe[T] |
*T (nil = none) |
nested {.ffi.} struct |
nested Go struct |
Each call deep-copies its arguments across the FFI thread, so the Go-side C
allocations are freed (via defer) as soon as the call returns. String-returning
methods give back a Go string; struct-returning methods give back a typed Go
struct — the C-POD return is read into Go inside the result callback (delivered
via a runtime/cgo.Handle), so the caller never touches C memory.
Build & run
cd examples/timer/go_bindings
make run
Expected output:
created timer
version: nim-timer v0.1.0
echo: echoed="hello from Go" timerName="go-native-demo"
complex: itemCount=2 hasNote=true summary="received 2 messages, note=a note, retries=3"
schedule: jobId="go-native-demo:nightly" willRunCount=12
done
Echo, Complex and Schedule take {.ffi.} structs, slices and optionals
directly and return typed Go structs — previously these procs were skipped by
the Go generator.
For the cross-process / cross-machine path (CBOR over a socket), see
../ipc; a Go client could speak the same wire protocol using any Go
CBOR library.