From 203962945733c9420200b299d7bd7672b871f481 Mon Sep 17 00:00:00 2001
From: Yuxuan Jiang <jyx24@connect.hku.hk>
Date: Wed, 26 Feb 2025 10:25:55 +0800
Subject: [PATCH] Expose MjSpec raw pointer via `_address`

---
 python/mujoco/specs.cc      |  3 +++
 python/mujoco/specs_test.py | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/python/mujoco/specs.cc b/python/mujoco/specs.cc
index 0f7a4c2a..8853430e 100644
--- a/python/mujoco/specs.cc
+++ b/python/mujoco/specs.cc
@@ -393,6 +393,9 @@ PYBIND11_MODULE(_specs, m) {
   mjSpec.def("copy", [](const MjSpec& self) -> MjSpec {
     return MjSpec(self);
   });
+  mjSpec.def_property_readonly("_address", [](const MjSpec& self) {
+    return reinterpret_cast<uintptr_t>(self.ptr);
+  });
   mjSpec.def_property(
       "copy_during_attach",
       [](MjSpec& self) {
diff --git a/python/mujoco/specs_test.py b/python/mujoco/specs_test.py
index a958e595..e400347e 100644
--- a/python/mujoco/specs_test.py
+++ b/python/mujoco/specs_test.py
@@ -1159,5 +1159,15 @@ class SpecsTest(absltest.TestCase):
     ):
       model_spec.compile()
 
+  def test_address(self):
+    spec1 = mujoco.MjSpec()
+    spec2 = mujoco.MjSpec()
+    spec3 = spec1.copy()
+
+    self.assertGreater(spec1._address, 0)
+    self.assertGreater(spec2._address, 0)
+    self.assertGreater(spec3._address, 0)
+    self.assertLen({spec1._address, spec2._address, spec3._address}, 3)
+
 if __name__ == '__main__':
   absltest.main()