objc: use the stack class for new block templates (#518)

Initialize block templates with __NSStackBlock__ to match their
state before copying. Block_copy selects its behavior from the flags
and assigns __NSMallocBlock__ to the heap copy, so this corrects the
class without changing the copy behavior.

Closes #523

commit: 656af01456b2cd7a761884de06ccd88b31c30032
author: Hiroki KUMAZAKI · 32d ago · 2026-09-20 17:33 UTC
committer: GitHub · 32d ago · 2026-09-20 17:33 UTC
parent: 19b4768
signature: GPG UnverifiedB5690EEEBB952194 The key is unknown

1 file · +4 -1

M objc/objc_block_darwin.go +4 -1


@@ -19,7 +19,10 @@ const (
19	19		// when the reference count drops to zero, so the associated function is also unreferenced.
20	20
21	21		// blockBaseClass is the name of the class that block objects will be initialized with.
22		-	blockBaseClass = "__NSMallocBlock__"
	22	+	// A new block is a template that Block_copy always relocates to the
	23	+	// Objective-C heap, so the stack-block class is the accurate name here,
	24	+	// as the isa of the copied block becomes __NSMallocBlock__ anyway.
	25	+	blockBaseClass = "__NSStackBlock__"
23	26		// blockFlags is the set of flags that block objects will be initialized with.
24	27		blockFlags = blockHasCopyDispose \| blockHasSignature
25	28

 	// when the reference count drops to zero, so the associated function is also unreferenced.
 	// blockBaseClass is the name of the class that block objects will be initialized with.
-	blockBaseClass = "__NSMallocBlock__"
+	// A new block is a template that Block_copy always relocates to the
+	// Objective-C heap, so the stack-block class is the accurate name here,
+	// as the isa of the copied block becomes __NSMallocBlock__ anyway.
+	blockBaseClass = "__NSStackBlock__"
 	// blockFlags is the set of flags that block objects will be initialized with.
 	blockFlags = blockHasCopyDispose | blockHasSignature