Enable some ctypes tests (#1407)

* Enable CPython.ctypes.test_structures

* Enable CPython.ctypes.test_values

* Enable Src/IronPythonTest/Cases/CPythonCasesManifest.ini

Author: slozier

Src/IronPython.Modules/_ctypes/ArrayType.cs

@@ -243,7 +243,7 @@ object INativeType.SetValue(MemoryHolder address, int offset, object value) {
 
                             return null;
                         }
-                        throw PythonOps.TypeError("bytes expected instead of {0} instance", PythonOps.GetPythonTypeName(value));
+                        throw PythonOps.TypeError("expected bytes, {0} found", PythonOps.GetPythonTypeName(value));
                     }
                     if (st._type == SimpleTypeKind.WChar) {
                         if (value is string str) {

Src/IronPython.Modules/_ctypes/MemoryHolder.cs

@@ -216,6 +216,8 @@ internal static Bytes ReadBytes(IntPtr addr, int offset, int length) {
         }
 
         internal static Bytes ReadBytes(IntPtr addr, int offset) {
+            if (addr == IntPtr.Zero && offset == 0) return null;
+
             // instead of Marshal.PtrToStringAnsi we do this because
             // ptrToStringAnsi gives special treatment to values >= 128.
             MemoryStream res = new MemoryStream();

Src/IronPython.Modules/_ctypes/StructType.cs

@@ -168,11 +168,11 @@ object INativeType.SetValue(MemoryHolder/*!*/ address, int offset, object value)
                 try {
                     return SetValueInternal(address, offset, value);
                 } catch (ArgumentTypeException e) {
-                    throw PythonOps.RuntimeError("({0}) <type 'exceptions.TypeError'>: {1}",
+                    throw PythonOps.RuntimeError("({0}) <class 'TypeError'>: {1}",
                         Name,
                         e.Message);
                 } catch (ArgumentException e) {
-                    throw PythonOps.RuntimeError("({0}) <type 'exceptions.ValueError'>: {1}",
+                    throw PythonOps.RuntimeError("({0}) <class 'ValueError'>: {1}",
                         Name,
                         e.Message);
                 }

Src/IronPythonTest/Cases/CPythonCasesManifest.ini

@@ -55,19 +55,10 @@ Ignore=true
 [CPython.ctypes.test_slicing]
 Ignore=true # https://github.com/IronLanguages/ironpython3/issues/1299
 
-[CPython.ctypes.test_stringptr]
-Ignore=true
-
-[CPython.ctypes.test_structures]
-Ignore=true
-
 [CPython.ctypes.test_unicode]
 Ignore=true
 Reason=https://github.com/IronLanguages/ironpython2/issues/405
 
-[CPython.ctypes.test_values]
-Ignore=true
-
 [CPython.ctypes.test_win32]
 Ignore=true
 

Src/StdLib/Lib/ctypes/test/test_structures.py

@@ -2,7 +2,10 @@
 from ctypes import *
 from ctypes.test import need_symbol
 from struct import calcsize
-import _testcapi
+try:
+    import _testcapi
+except ImportError:
+    _testcapi = None
 
 class SubclassesTest(unittest.TestCase):
     def test_subclass(self):
@@ -201,13 +204,14 @@ class X(Structure):
              "_pack_": -1}
         self.assertRaises(ValueError, type(Structure), "X", (Structure,), d)
 
-        # Issue 15989
-        d = {"_fields_": [("a", c_byte)],
-             "_pack_": _testcapi.INT_MAX + 1}
-        self.assertRaises(ValueError, type(Structure), "X", (Structure,), d)
-        d = {"_fields_": [("a", c_byte)],
-             "_pack_": _testcapi.UINT_MAX + 2}
-        self.assertRaises(ValueError, type(Structure), "X", (Structure,), d)
+        if _testcapi:
+            # Issue 15989
+            d = {"_fields_": [("a", c_byte)],
+                 "_pack_": _testcapi.INT_MAX + 1}
+            self.assertRaises(ValueError, type(Structure), "X", (Structure,), d)
+            d = {"_fields_": [("a", c_byte)],
+                 "_pack_": _testcapi.UINT_MAX + 2}
+            self.assertRaises(ValueError, type(Structure), "X", (Structure,), d)
 
     def test_initializers(self):
         class Person(Structure):

Src/StdLib/Lib/ctypes/test/test_values.py

@@ -4,6 +4,7 @@
 
 import unittest
 import sys
+from test import support
 from ctypes import *
 
 import _ctypes_test
@@ -28,6 +29,7 @@ def test_undefined(self):
         ctdll = CDLL(_ctypes_test.__file__)
         self.assertRaises(ValueError, c_int.in_dll, ctdll, "Undefined_Symbol")
 
+@support.cpython_only
 class PythonValuesTestCase(unittest.TestCase):
     """This test only works when python itself is a dll/shared library"""