From a4e287a85b77e3718ad25827b15ebdc877e81876 Mon Sep 17 00:00:00 2001
From: t-miller <tyler.rw.miller@protonmail.com>
Date: Mon, 12 Oct 2026 18:46:40 -0400
Subject: [PATCH] Make OSM wrapper construction exception-safe

---
 lib/osm_base_objects.h           |  2 +-
 test/test_object_construction.py | 53 ++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100644 test/test_object_construction.py

diff --git a/lib/osm_base_objects.h b/lib/osm_base_objects.h
index 50e3a6be..1ac3a268 100644
--- a/lib/osm_base_objects.h
+++ b/lib/osm_base_objects.h
@@ -73,7 +73,6 @@ class PyOSMObject
     pybind11::object get_or_create_python_object()
     {
         if (!m_valid) {
-            m_valid = true;
             if constexpr (std::is_same_v<T, osmium::Node>) {
                 m_pyobj = pybind11::module_::import("osmium.osm.types").attr("Node")(COSMNode{m_obj});
             } else if constexpr (std::is_same_v<T, osmium::Way>) {
@@ -87,6 +86,7 @@ class PyOSMObject
             }
         }
 
+        m_valid = true;
         return m_pyobj;
     }
 
diff --git a/test/test_object_construction.py b/test/test_object_construction.py
new file mode 100644
index 00000000..406055db
--- /dev/null
+++ b/test/test_object_construction.py
@@ -0,0 +1,53 @@
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# This file is part of pyosmium. (https://osmcode.org/pyosmium/)
+import subprocess
+import sys
+
+import pytest
+
+
+@pytest.mark.parametrize('object_type, data', [
+    ('Node', 'n1 x5 y5'),
+    ('Way', 'w1 Nn1,n2'),
+    ('Relation', 'r1 Mn1@'),
+])
+@pytest.mark.parametrize('exception', ['KeyboardInterrupt', 'MemoryError', 'RuntimeError'])
+def test_constructor_exception_does_not_crash_cleanup(object_type, data, exception):
+    # Keep native destruction in a child: a regression must not kill pytest.
+    # Tracing raises at the constructor entry without replacing wrapper classes.
+    code = '''
+import builtins
+import sys
+
+import osmium
+
+object_type, data, exception_name = sys.argv[1:]
+constructor = getattr(osmium.osm, object_type).__init__.__code__
+exception_type = getattr(builtins, exception_name)
+
+
+def fail_constructor(frame, event, arg):
+    if event == 'call' and frame.f_code is constructor:
+        sys.settrace(None)
+        raise exception_type('injected constructor failure')
+    return fail_constructor
+
+
+source = osmium.io.FileBuffer(data.encode(), 'opl')
+sys.settrace(fail_constructor)
+try:
+    list(osmium.FileProcessor(source))
+except exception_type:
+    sys.settrace(None)
+    print('caught ' + exception_name, flush=True)
+else:
+    raise AssertionError('constructor was not reached')
+'''
+    result = subprocess.run(
+        [sys.executable, '-X', 'faulthandler', '-c', code,
+         object_type, data, exception],
+        capture_output=True, text=True, timeout=30,
+    )
+    assert result.returncode == 0, result.stderr
+    assert result.stdout.strip() == 'caught ' + exception