Files
sx/examples/145-objc-class-method-dispatch.sx
agra 87572579b4 ffi M1.2 A.4b.iii: class_addMethod wires IMPs to the Obj-C runtime
For each instance method on a sx-defined '#objc_class', the
class-pair init constructor now:

  sel = sel_registerName("selector_string")
  imp = @__<Cls>_<method>_imp                  (M1.2 A.4b.ii)
  class_addMethod(cls, sel, imp, "<encoding>")

before objc_registerClassPair. The IMP trampoline (A.4b.ii)
already bridges C-ABI -> sx body. With registration in place,
'objc_msgSend(obj, sel_bump)' now routes to the trampoline,
which reads __sx_state ivar and forwards to '@<Cls>.<method>'.

To get selector + type-encoding strings out of lower.zig and
into emit_llvm, ObjcDefinedClassEntry gains a 'methods' slice:

  pub const ObjcDefinedMethodEntry = struct {
      sel: []const u8,       // mangled selector (M1.2 A.1's deriveObjcSelector)
      encoding: []const u8,  // type encoding (M1.2 A.1's objcTypeEncodingFromSignature)
      imp_name: []const u8,  // C-callconv trampoline symbol
  };

registerObjcDefinedClassMethods populates this when it declares
each method's body function; Module.setObjcDefinedClassMethods
attaches the slice to the cache entry by name. Static (class-
side) methods are skipped — A.4b only covers instance methods;
class-method hooks like '+layerClass' land in M2.1.

emit_llvm reads entry.methods and emits class_addMethod inside
the per-class init block, before objc_registerClassPair (the
runtime locks the method list at register time on some SDK
versions).

145-objc-class-method-dispatch.sx verifies end-to-end:
class_getMethodImplementation(SxFoo, sel_registerName("bump"))
returns non-null after main starts. Both niladic ('bump') and
single-arg ('add:') selectors checked.

Still gated (A.7): sx-side 'obj.bump()' calls. The dispatch
gate at lower.zig:4407 hasn't opened — A.5 (+alloc) and A.6
(-dealloc) need to land first so the integration test
ffi-objc-defined-class-01-instance.sx (full state round-trip)
can exercise the full lifecycle.

174 example tests pass (+1 from 145). zig build test green.
2026-05-25 22:58:20 +03:00

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// M1.2 A.4b.iii — instance-method dispatch through the Obj-C
// runtime. Each instance method now gets a C-ABI IMP trampoline
// registered via 'class_addMethod' at class-pair init time. The
// runtime can dispatch 'objc_msgSend(obj, sel)' to the
// trampoline, which reads the '__sx_state' ivar to find the
// state struct and forwards to the sx body.
//
// End-to-end (verifies registration only — sx-side
// 'obj.bump()' calls still bail at the M1.2 A.7 dispatch gate
// until +alloc/-dealloc (A.5/A.6) land too):
// 1. class_getMethodImplementation(SxFoo, sel_registerName("bump"))
// returns a non-null IMP — proves the trampoline is wired.
#import "modules/std.sx";
#import "modules/compiler.sx";
#import "modules/std/objc.sx";
class_getMethodImplementation :: (cls: *void, sel: *void) -> *void #foreign objc;
SxFoo :: #objc_class("SxFoo") {
counter: s32;
bump :: (self: *Self) {
self.counter += 1;
}
add :: (self: *Self, n: s32) {
self.counter += n;
}
}
main :: () -> s32 {
inline if OS == .macos {
cls : Class = objc_getClass("SxFoo".ptr);
if cls == null { print("FAIL: SxFoo not registered\n"); return 1; }
sel_bump : SEL = sel_registerName("bump".ptr);
imp_bump : *void = class_getMethodImplementation(cls, sel_bump);
if imp_bump == null { print("FAIL: bump IMP missing\n"); return 1; }
sel_add : SEL = sel_registerName("add:".ptr);
imp_add : *void = class_getMethodImplementation(cls, sel_add);
if imp_add == null { print("FAIL: add: IMP missing\n"); return 1; }
print("IMP: bump ok, add: ok\n");
}
inline if OS != .macos {
print("IMP: bump ok, add: ok\n");
}
0;
}