From 6ef0eb29c6579db58e2cf3407b41d58c687ee742 Mon Sep 17 00:00:00 2001
From: Augustin Gottlieb <33221555+aguspe@users.noreply.github.com>
Date: Fri, 23 Jan 2026 03:00:37 +0100
Subject: Add early type validation for ObjectSpace.memsize_of_all klass
 argument

---
 ext/objspace/objspace.c        | 1 +
 test/objspace/test_objspace.rb | 6 +++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/ext/objspace/objspace.c b/ext/objspace/objspace.c
index 457ffc2789..1143e4801d 100644
--- a/ext/objspace/objspace.c
+++ b/ext/objspace/objspace.c
@@ -137,6 +137,7 @@ memsize_of_all_m(int argc, VALUE *argv, VALUE self)
 
     if (argc > 0) {
         rb_scan_args(argc, argv, "01", &data.klass);
+        if (!NIL_P(data.klass)) rb_obj_is_kind_of(Qnil, data.klass);
     }
 
     each_object_with_flags(total_i, &data);
diff --git a/test/objspace/test_objspace.rb b/test/objspace/test_objspace.rb
index 78947a095b..8b369c3894 100644
--- a/test/objspace/test_objspace.rb
+++ b/test/objspace/test_objspace.rb
@@ -54,7 +54,11 @@ class TestObjSpace < Test::Unit::TestCase
     assert_operator(a, :>, b)
     assert_operator(a, :>, 0)
     assert_operator(b, :>, 0)
-    assert_raise(TypeError) {ObjectSpace.memsize_of_all('error')}
+    assert_kind_of(Integer, ObjectSpace.memsize_of_all(Enumerable))
+  end
+
+  def test_memsize_of_all_with_wrong_type
+    assert_raise(TypeError) { ObjectSpace.memsize_of_all(Object.new) }
   end
 
   def test_count_objects_size
-- 
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