gh-151422: Don't link libffi into _ctypes_test.so (#151423)

_ctypes_test doesn't use libffi directly, and linking it into the module 
causes emscripten tests to fail.

Author: hoodmane

Lib/test/test_ctypes/test_as_parameter.py

@@ -5,7 +5,7 @@
                     c_short, c_int, c_long, c_longlong,
                     c_byte, c_wchar, c_float, c_double,
                     ArgumentError)
-from test.support import import_helper, skip_if_sanitizer
+from test.support import import_helper, skip_if_sanitizer, skip_emscripten_stack_overflow
 _ctypes_test = import_helper.import_module("_ctypes_test")
 
 
@@ -193,6 +193,7 @@ class S8I(Structure):
                              (9*2, 8*3, 7*4, 6*5, 5*6, 4*7, 3*8, 2*9))
 
     @skip_if_sanitizer('requires deep stack', thread=True)
+    @skip_emscripten_stack_overflow()
     def test_recursive_as_param(self):
         class A:
             pass

Lib/test/test_ctypes/test_structures.py

@@ -299,9 +299,16 @@ class X(Structure):
         self.assertEqual(s.first, got.first)
         self.assertEqual(s.second, got.second)
 
+    @unittest.skipIf(support.is_wasm32, "wasm ABI is incompatible with test expectations")
     def _test_issue18060(self, Vector):
         # Regression tests for gh-62260
 
+        # This test passes a struct of two doubles by value to atan2(), whose C
+        # signature is atan2(double, double), so it only works on platforms
+        # where the abi of a function that takes a struct with two doubles
+        # matches the abi of a function that takes two doubles. The wasm32 ABI
+        # does not satisfy this condition and the test breaks.
+
         # The call to atan2() should succeed if the
         # class fields were correctly cloned in the
         # subclasses. Otherwise, it will segfault.

configure

@@ -8447,9 +8447,11 @@ PY_STDLIB_MOD([_testmultiphase], [test "$TEST_MODULES" = yes], [test "$ac_cv_fun
 PY_STDLIB_MOD([_testsinglephase], [test "$TEST_MODULES" = yes], [test "$ac_cv_func_dlopen" = yes])
 PY_STDLIB_MOD([xxsubtype], [test "$TEST_MODULES" = yes])
 PY_STDLIB_MOD([_xxtestfuzz], [test "$TEST_MODULES" = yes])
+dnl Check have_libffi so _ctypes_test is only built if _ctypes is built.
+dnl _ctypes_test doesn't use libffi directly.
 PY_STDLIB_MOD([_ctypes_test],
   [test "$TEST_MODULES" = yes], [test "$have_libffi" = yes -a "$ac_cv_func_dlopen" = yes],
-  [$LIBFFI_CFLAGS], [$LIBFFI_LIBS $LIBM])
+  [], [$LIBM])
 
 dnl Limited API template modules.
 dnl Emscripten does not support shared libraries yet.