gh-156112: Load the ObjC runtime by name when find_library() cannot resolve it (#156113)

Provides a fallback name for the ObjC runtime library on iOS, and improved error 
handling when that library cannot be loaded.

Author: clementperon

Lib/_ios_support.py

@@ -10,12 +10,15 @@
 else:
     # ctypes is available. Load the ObjC library, and wrap the objc_getClass,
     # sel_registerName methods
-    lib = util.find_library("objc")
-    if lib is None:
-        # Failed to load the objc library
-        raise ImportError("ObjC runtime library couldn't be loaded")
+    # find_library() resolves a system library through the dyld shared cache,
+    # which needs _dyld_shared_cache_contains_path(); that is unavailable before
+    # iOS 14, so fall back to the bare name, which dyld resolves by itself.
+    lib = util.find_library("objc") or "libobjc.dylib"
 
-    objc = cdll.LoadLibrary(lib)
+    try:
+        objc = cdll.LoadLibrary(lib)
+    except OSError:
+        raise ImportError("ObjC runtime library couldn't be loaded")
     objc.objc_getClass.restype = c_void_p
     objc.objc_getClass.argtypes = [c_char_p]
     objc.sel_registerName.restype = c_void_p

Misc/NEWS.d/next/Library/2026-08-20-13-50-49.gh-issue-156112.yEcma8.rst

@@ -0,0 +1,4 @@
+:mod:`!_ios_support` no longer fails to import when
+:func:`ctypes.util.find_library` cannot resolve the ObjC runtime through the
+dyld shared cache, as is the case on iOS 13. The runtime is now loaded by name,
+which dyld resolves against the cache directly.