Files
sx/examples/ffi-06-callback.sx
agra 92c6b47f12 mem: Step 3 — thread __sx_ctx through closure/fn-pointer/method dispatch
Continues the implicit-Context refactor. Bare-fn trampolines, lambda
trampolines, and protocol thunks now carry __sx_ctx at slot 0; call
sites for closures, fn-pointer variables, and method dispatch prepend
the caller's current ctx.

- emit_llvm.zig:1687 call_indirect treats `fp_ctx_slots` leading args
  as opaque ptr (the implicit ctx) when the fn-pointer is default-conv
  under has_implicit_ctx.
- lower.zig:fnPtrTypeWantsCtx predicate gates the prepend at both
  scope-local and global fn-pointer call sites.
- lower.zig:fixupMethodReceiver skips __sx_ctx when probing the
  receiver param's type.
- lower.zig:lowerLambda builds closure type from user-visible params
  only (skip ctx + env).
- lower.zig:closure(bare_fn) builds closure type from user-visible
  params only.
- module.zig: Module.has_implicit_ctx flag mirrors Lowering's switch
  so emit_llvm can read it without a back-pointer.

Tests updated:
- 5 ObjC-block/runtime tests get `callconv(.c)` on fn-ptr types
  cast from `objc_msgSend` / Block.invoke (C-side calls into sx).
- ffi-06-callback gets `callconv(.c)` on double_it/add_with_ctx —
  the registered C-side callbacks.
- 08-types snapshot regen (undefined-init drift from layout shift).
- 11 JNI/ObjC .ir snapshots regen for the ctx-prepended thunk
  signatures.

151/152 example tests pass. Remaining failure (05-run) is the
comptime/interp path that requires Step 7 (callWithDefaultContext).
2026-05-25 08:41:50 +03:00

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// Phase 0 baseline (PLAN-FFI.md step 0.6): sx function passed to C
// as a function pointer; C invokes it; sx-side observable effect.
// Mirrors the `app->onInputEvent` install pattern in
// library/modules/platform/android.sx.
//
// Two arities covered:
// 1. (s32) -> s32 — single-arg callback
// 2. (*void, s32) -> s32 — pointer + value (onInputEvent shape)
//
// Plus a side-effect via a global so we can confirm the callback
// actually fired (return value + state mutation both observable).
#import "modules/std.sx";
#import c {
#source "ffi-06-callback.c";
};
ffi_apply_callback :: (cb: (s32) -> s32, value: s32) -> s32 #foreign;
ffi_apply_callback2 :: (cb: (*void, s32) -> s32, ctx: *void, v: s32) -> s32 #foreign;
g_callback_hits : s32 = 0;
g_callback_sum : s32 = 0;
double_it :: (x: s32) -> s32 callconv(.c) {
g_callback_hits += 1;
g_callback_sum += x;
x * 2;
}
add_with_ctx :: (ctx: *void, v: s32) -> s32 callconv(.c) {
g_callback_hits += 1;
// Pass a sentinel via ctx to prove the pointer arg also survives the
// round-trip — read it back as an s32 through *s32.
p : *s32 = xx ctx;
p.* + v;
}
main :: () -> s32 {
// ── Single-arg callback ────────────────────────────────────────
r1 := ffi_apply_callback(double_it, 21);
print("callback returned = {}\n", r1);
print("hits after first call = {}\n", g_callback_hits);
print("sum after first call = {}\n", g_callback_sum);
// Two more calls confirm the same fn pointer keeps working.
ffi_apply_callback(double_it, 7);
ffi_apply_callback(double_it, 11);
print("hits after three calls = {}\n", g_callback_hits);
print("sum after three calls = {}\n", g_callback_sum);
// ── Two-arg callback with opaque ctx pointer ───────────────────
ctx_val : s32 = 100;
r2 := ffi_apply_callback2(add_with_ctx, xx @ctx_val, 42);
print("ctx + value = {}\n", r2);
print("hits after ctx callback = {}\n", g_callback_hits);
0;
}