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ffi M1.2 A.4b.i: __sx_state ivar registration

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Class-pair init constructor now registers a single hidden ivar
on each sx-defined class:

  class_addIvar(cls, "__sx_state", 8, 3, "^v")

before objc_registerClassPair. After the class is registered,
the constructor calls class_getInstanceVariable to fetch the
runtime Ivar handle and stores it in a per-class global
'__<ClassName>_state_ivar : *void'. Trampolines (A.4b.ii) will
read this global to 'object_getIvar' the state struct pointer.

lower.zig declares the per-class global at scan time
(declareObjcDefinedStateIvarGlobal) so emit_llvm finds it by
name when populating. Encoding '^v' = void* (a generic pointer
— the runtime treats it as opaque storage). log2 alignment = 3
for 8-byte pointer alignment on 64-bit.

144-objc-class-ivar-registration.sx exercises the round-trip:
after main starts, class_getInstanceVariable(SxFoo, "__sx_state")
returns non-null. Runs against the real Obj-C runtime on macOS.

142's IR snapshot refreshed to include the new constructor body
(class_addIvar + class_getInstanceVariable + ivar-global store).

173 example tests pass (+1 from 144). zig build test green.
This commit is contained in:
agra
2026-05-25 22:23:59 +03:00
parent b98a22e3f9
commit c2178c062b
6 changed files with 124 additions and 4 deletions
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20
src/ir/lower.zig
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@@ -9617,11 +9617,31 @@ pub const Lowering = struct {
if (!fcd.is_foreign and fcd.runtime == .objc_class) {
if (self.module.lookupObjcDefinedClass(fcd.name) == null) {
self.module.appendObjcDefinedClass(fcd.name, fcd);
// M1.2 A.4b.i: per-class ivar handle global. The class-pair
// init constructor (emit_llvm) populates it via
// class_getInstanceVariable after the class is registered;
// IMP trampolines read it to find the __sx_state ivar.
self.declareObjcDefinedStateIvarGlobal(fcd.name);
}
self.registerObjcDefinedClassMethods(fcd);
}
}
/// Declare a per-class global `__<ClassName>_state_ivar : *void = null`.
/// emit_llvm's `emitObjcDefinedClassInit` constructor fills it in via
/// `class_getInstanceVariable(cls, "__sx_state")` once per module load.
fn declareObjcDefinedStateIvarGlobal(self: *Lowering, class_name: []const u8) void {
const gname = std.fmt.allocPrint(self.alloc, "__{s}_state_ivar", .{class_name}) catch return;
const name_id = self.module.types.internString(gname);
_ = self.module.addGlobal(.{
.name = name_id,
.ty = self.module.types.ptrTo(.void),
.init_val = .null_val,
.is_extern = false,
.is_const = false,
});
}
/// For each bodied instance method on an sx-defined `#objc_class`,
/// synthesize an `FnDecl` from the `ForeignMethodDecl`, register it
/// in `fn_ast_map` under `<ClassName>.<methodName>`, and declare