Fix segfault with -W error on macOS (built with swig 4.3.1)

src/__init__.py

@@ -13,6 +13,7 @@
 import atexit
 import binascii
 import collections
+import contextlib
 import glob
 import importlib.util
 import inspect
@@ -30,7 +31,30 @@
 import weakref
 import zipfile
 
-from . import extra
+
+@contextlib.contextmanager
+def _swig_import():
+    '''
+    Context manager for importing our SWIG modules `extra` and `mupdf`.
+
+    With swig<4.4, module initialisation gives `DeprecationWarning: builtin
+    type SwigPyPacked has no __module__ attribute` (also for SwigPyObject and
+    swigvarlink). If warnings are errors (for example `python -W error` or
+    `pytest -W error`), swig's init code ignores the resulting exception and
+    then crashes with SEGV. So we ignore these warnings while importing. See
+    #4392 and https://github.com/swig/swig/issues/3061.
+    '''
+    with warnings.catch_warnings():
+        warnings.filterwarnings(
+                'ignore',
+                'builtin type .+ has no __module__ attribute',
+                DeprecationWarning,
+                )
+        yield
+
+
+with _swig_import():
+    from . import extra
 
 # Set up g_out_log and g_out_message from environment variables.
 #
@@ -396,10 +420,11 @@ def _warn_layout_once():
     # directory for conventional wheel installs, or from separate place in case
     # we are using a separately-installed system installation of mupdf.
     #
-    try:
-        from . import mupdf
-    except Exception:
-        import mupdf
+    with _swig_import():
+        try:
+            from . import mupdf
+        except Exception:
+            import mupdf
     if hasattr(mupdf, 'internal_check_ndebug'):
         mupdf.internal_check_ndebug()
     mupdf.reinit_singlethreaded()

src/extra.i

@@ -13,6 +13,13 @@ otherwise compilation can fail because free() and malloc() are not declared. */
 
 %init
 %{
+    /* With swig<4.4, if we have not created swig's globals object by the time
+    we are unloaded at exit, swig creates it then, which gives `DeprecationWarning:
+    builtin type swigvarlink has no __module__ attribute` and a SEGV if warnings
+    are errors. So we create it now, while src/__init__.py is ignoring these
+    warnings. See #4392. */
+    SWIG_globals();
+
     /* Initialise some globals that require Python functions.
 
     [Prior to 2023-08-18 we initialised these global variables inline,

tests/test_general.py

@@ -2037,7 +2037,22 @@ def test_4392():
     e3 = subprocess.run(command, shell=1, check=0).returncode
     print(f'{e3=}')
 
-    print(f'{e1=} {e2=} {e3=}', flush=1)
+    # With swig<4.4 an unclosed file used to give a SEGV at exit, because
+    # swig created a new type when unloading `extra`.
+    command = f'{sys.executable} -Werror -c "import pymupdf; open({path!r})"'
+    print(f'Running: {command}', flush=1)
+    e4 = subprocess.run(command, shell=1, check=0).returncode
+    print(f'{e4=}')
+
+    # Check that we don't get swig's `DeprecationWarning: builtin type
+    # SwigPyPacked has no __module__ attribute` etc.
+    command = f'{sys.executable} -W default -c "import pymupdf"'
+    print(f'Running: {command}', flush=1)
+    cp = subprocess.run(command, shell=1, check=0, capture_output=1, text=1)
+    print(f'{cp.returncode=}')
+    print(f'{cp.stderr=}')
+
+    print(f'{e1=} {e2=} {e3=} {e4=}', flush=1)
 
     print(f'{pymupdf.swig_version=}', flush=1)
     print(f'{pymupdf.swig_version_tuple=}', flush=1)
@@ -2052,30 +2067,20 @@ def test_4392():
     # Exit code 4: pytest command line usage error
     # Exit code 5: No tests were collected
 
+    # With swig<4.4 we used to get SEGV's here, but now we ignore swig's
+    # warnings when importing.
     assert e1 == 5
-    if pymupdf.swig_version_tuple >= (4, 4):
-        if sysconfig.get_config_var('Py_GIL_DISABLED') == 1 and sys._is_gil_enabled():
-            assert e2 == 4
-        else:
-            assert e2 == 5
-        if sysconfig.get_config_var('Py_GIL_DISABLED') == 1 and sys._is_gil_enabled():
-            # GIL warning results in failure because of -Werror.
-            assert e3 == 1
-        else:
-            assert e3 == 0
+    if sysconfig.get_config_var('Py_GIL_DISABLED') == 1 and sys._is_gil_enabled():
+        # GIL warning results in failure because of -Werror.
+        assert e2 == 4
+        assert e3 == 1
+        assert e4 == 1
     else:
-        # We get SEGV's etc with older swig.
-        if platform.system() == 'Windows':
-            assert (e2, e3) == (0xc0000005, 0xc0000005)
-        elif platform.system() == 'Linux':
-            # On plain linux we get (139, 139). On manylinux we get (-11,
-            # -11). On MacOS we get (-11, -11).
-            assert (e2, e3) == (139, 139) or (e2, e3) == (-11, -11)
-        elif platform.system() == 'Darwin':
-            # python3.14t gives (4, -11)?
-            assert (e2, e3) == (-11, -11) or (e2, e3) == (4, -11)
-        else:
-            assert e2 and e3
+        assert e2 == 5
+        assert e3 == 0
+        assert e4 == 0
+    assert cp.returncode == 0
+    assert 'has no __module__ attribute' not in cp.stderr
 
 
 def test_4639():