bpo-41100: ctypes: check _dyld_shared_cache_contains_path in find_library

Lib/ctypes/macholib/dyld.py

@@ -7,6 +7,12 @@
 from ctypes.macholib.dylib import dylib_info
 from itertools import *
 
+try:
+    from _ctypes import _dyld_shared_cache_contains_path
+except ImportError:
+    def _dyld_shared_cache_contains_path(*args):
+        raise NotImplementedError
+
 __all__ = [
     'dyld_find', 'framework_find',
     'framework_info', 'dylib_info',
@@ -124,6 +130,12 @@ def dyld_find(name, executable_path=None, env=None):
             ), env):
         if os.path.isfile(path):
             return path
+        try:
+            if _dyld_shared_cache_contains_path(path):
+                return path
+        except NotImplementedError:
+            pass
+
     raise ValueError("dylib %s could not be found" % (name,))
 
 def framework_find(fn, executable_path=None, env=None):

Lib/ctypes/test/test_macholib.py

@@ -46,18 +46,23 @@ class MachOTest(unittest.TestCase):
     @unittest.skipUnless(sys.platform == "darwin", 'OSX-specific test')
     def test_find(self):
 
-        self.assertEqual(find_lib('pthread'),
-                             '/usr/lib/libSystem.B.dylib')
+        # On Mac OS 11, system dylibs are only present in the shared cache,
+        # so symlinks like libpthread.dylib -> libSystem.B.dylib will not
+        # be resolved by dyld_find
+
+        self.assertIn(find_lib('pthread'),
+                             ('/usr/lib/libSystem.B.dylib', '/usr/lib/libpthread.dylib'))
 
         result = find_lib('z')
         # Issue #21093: dyld default search path includes $HOME/lib and
         # /usr/local/lib before /usr/lib, which caused test failures if
         # a local copy of libz exists in one of them. Now ignore the head
         # of the path.
-        self.assertRegex(result, r".*/lib/libz\..*.*\.dylib")
+        self.assertRegex(result, r".*/lib/libz.*\.dylib")
 
-        self.assertEqual(find_lib('IOKit'),
-                             '/System/Library/Frameworks/IOKit.framework/Versions/A/IOKit')
+        self.assertIn(find_lib('IOKit'),
+                             ('/System/Library/Frameworks/IOKit.framework/Versions/A/IOKit',
+                             '/System/Library/Frameworks/IOKit.framework/IOKit'))
 
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Core and Builtins/2020-06-30-18-24-28.bpo-41100._QkcD_.rst

@@ -0,0 +1 @@
+ctypes: Mac OS 11: check for system libraries in the shared cache

Modules/_ctypes/callproc.c

@@ -64,6 +64,10 @@
 #include "ctypes_dlfcn.h"
 #endif
 
+#if __APPLE__ && HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH
+#include <mach-o/dyld.h>
+#endif
+
 #ifdef MS_WIN32
 #include <malloc.h>
 #endif
@@ -1398,6 +1402,36 @@ copy_com_pointer(PyObject *self, PyObject *args)
 }
 #else
 
+#if __APPLE__ && HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH
+static PyObject *py_dyld_shared_cache_contains_path(PyObject *self, PyObject *args)
+{
+    if (__builtin_available(macos 11, ios 14, watchos 7, tvos 14, *)) {
+        PyObject *name, *name2;
+        char *name_str;
+        if (!PyArg_ParseTuple(args, "O", &name))
+            return NULL;
+
+        if (name == Py_None)
+            Py_RETURN_FALSE;
+
+        if (PyUnicode_FSConverter(name, &name2) == 0)
+            return NULL;
+        if (PyBytes_Check(name2))
+            name_str = PyBytes_AS_STRING(name2);
+        else
+            name_str = PyByteArray_AS_STRING(name2);
+
+        if(_dyld_shared_cache_contains_path(name_str))
+            Py_RETURN_TRUE;
+        else
+            Py_RETURN_FALSE;
+    } else {
+        PyErr_SetString(PyExc_NotImplementedError, "_dyld_shared_cache_contains_path symbol is missing");
+        return NULL;
+    }
+}
+#endif
+
 static PyObject *py_dl_open(PyObject *self, PyObject *args)
 {
     PyObject *name, *name2;
@@ -1908,6 +1942,9 @@ PyMethodDef _ctypes_module_methods[] = {
      "dlopen(name, flag={RTLD_GLOBAL|RTLD_LOCAL}) open a shared library"},
     {"dlclose", py_dl_close, METH_VARARGS, "dlclose a library"},
     {"dlsym", py_dl_sym, METH_VARARGS, "find symbol in shared library"},
+#endif
+#if __APPLE__ && HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH
+    {"_dyld_shared_cache_contains_path", py_dyld_shared_cache_contains_path, METH_VARARGS, "check if path is in the shared cache"},
 #endif
     {"alignment", align_func, METH_O, alignment_doc},
     {"sizeof", sizeof_func, METH_O, sizeof_doc},

configure

@@ -11601,6 +11601,15 @@ fi
 done
 
 
+ac_fn_c_check_decl "$LINENO" "_dyld_shared_cache_contains_path" "ac_cv_have_decl__dyld_shared_cache_contains_path" "#include <mach-o/dyld.h>
+"
+if test "x$ac_cv_have_decl__dyld_shared_cache_contains_path" = xyes; then :
+
+$as_echo "#define HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH 1" >>confdefs.h
+
+fi
+
+
 # DYNLOADFILE specifies which dynload_*.o file we will use for dynamic
 # loading of modules.
 

configure.ac

@@ -3603,6 +3603,10 @@ DLINCLDIR=.
 # platforms, such as AIX, have dlopen(), but don't want to use it.
 AC_CHECK_FUNCS(dlopen)
 
+AC_CHECK_DECL(_dyld_shared_cache_contains_path,
+  AC_DEFINE(HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH, 1, Define if you have the '_dyld_shared_cache_contains_path' function),
+  [], [#include <mach-o/dyld.h>])
+
 # DYNLOADFILE specifies which dynload_*.o file we will use for dynamic
 # loading of modules.
 AC_SUBST(DYNLOADFILE)

pyconfig.h.in

@@ -284,6 +284,9 @@
 /* Define to 1 if you have the `dup3' function. */
 #undef HAVE_DUP3
 
+/* Define if you have the '_dyld_shared_cache_contains_path' function */
+#undef HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH
+
 /* Defined when any dynamic module loading is enabled. */
 #undef HAVE_DYNAMIC_LOADING