patch 9.0.1776: No support for stable Python 3 ABI

Problem: No support for stable Python 3 ABI Solution: Support Python 3 stable ABI Commits: 1) Support Python 3 stable ABI to allow mixed version interoperatbility Vim currently supports embedding Python for use with plugins, and the "dynamic" linking option allows the user to specify a locally installed version of Python by setting `pythonthreedll`. However, one caveat is that the Python 3 libs are not binary compatible across minor versions, and mixing versions can potentially be dangerous (e.g. let's say Vim was linked against the Python 3.10 SDK, but the user sets `pythonthreedll` to a 3.11 lib). Usually, nothing bad happens, but in theory this could lead to crashes, memory corruption, and other unpredictable behaviors. It's also difficult for the user to tell something is wrong because Vim has no way of reporting what Python 3 version Vim was linked with. For Vim installed via a package manager, this usually isn't an issue because all the dependencies would already be figured out. For prebuilt Vim binaries like MacVim (my motivation for working on this), AppImage, and Win32 installer this could potentially be an issue as usually a single binary is distributed. This is more tricky when a new Python version is released, as there's a chicken-and-egg issue with deciding what Python version to build against and hard to keep in sync when a new Python version just drops and we have a mix of users of different Python versions, and a user just blindly upgrading to a new Python could lead to bad interactions with Vim. Python 3 does have a solution for this problem: stable ABI / limited API (see https://docs.python.org/3/c-api/stable.html). The C SDK limits the API to a set of functions that are promised to be stable across versions. This pull request adds an ifdef config that allows us to turn it on when building Vim. Vim binaries built with this option should be safe to freely link with any Python 3 libraies without having the constraint of having to use the same minor version. Note: Python 2 has no such concept and this doesn't change how Python 2 integration works (not that there is going to be a new version of Python 2 that would cause compatibility issues in the future anyway). --- Technical details: ====== The stable ABI can be accessed when we compile with the Python 3 limited API (by defining `Py_LIMITED_API`). The Python 3 code (in `if_python3.c` and `if_py_both.h`) would now handle this and switch to limited API mode. Without it set, Vim will still use the full API as before so this is an opt-in change. The main difference is that `PyType_Object` is now an opaque struct that we can't directly create "static types" out of, and we have to create type objects as "heap types" instead. This is because the struct is not stable and changes from version to version (e.g. 3.8 added a `tp_vectorcall` field to it). I had to change all the types to be allocated on the heap instead with just a pointer to them. Other functions are also simply missing in limited API, or they are introduced too late (e.g. `PyUnicode_AsUTF8AndSize` in 3.10) to it that we need some other ways to do the same thing, so I had to abstract a few things into macros, and sometimes re-implement functions like `PyObject_NEW`. One caveat is that in limited API, `OutputType` (used for replacing `sys.stdout`) no longer inherits from `PyStdPrinter_Type` which I don't think has any real issue other than minor differences in how they convert to a string and missing a couple functions like `mode()` and `fileno()`. Also fixed an existing bug where `tp_basicsize` was set incorrectly for `BufferObject`, `TabListObject, `WinListObject`. Technically, there could be a small performance drop, there is a little more indirection with accessing type objects, and some APIs like `PyUnicode_AsUTF8AndSize` are missing, but in practice I didn't see any difference, and any well-written Python plugin should try to avoid excessing callbacks to the `vim` module in Python anyway. I only tested limited API mode down to Python 3.7, which seemes to compile and work fine. I haven't tried earlier Python versions. 2) Fix PyIter_Check on older Python vers / type##Ptr unused warning For PyIter_Check, older versions exposed them as either macros (used in full API), or a function (for use in limited API). A previous change exposed PyIter_Check to the dynamic build because Python just moved it to function-only in 3.10 anyway. Because of that, just make sure we always grab the function in dynamic builds in earlier versions since that's what Python eventually did anyway. 3) Move Py_LIMITED_API define to configure script Can now use --with-python-stable-abi flag to customize what stable ABI version to target. Can also use an env var to do so as well. 4) Show +python/dyn-stable in :version, and allow has() feature query Not sure if the "/dyn-stable" suffix would break things, or whether we should do it another way. Or just don't show it in version and rely on has() feature checking. 5) Documentation first draft. Still need to implement v:python3_version 6) Fix PyIter_Check build breaks when compiling against Python 3.8 7) Add CI coverage stable ABI on Linux/Windows / make configurable on Windows This adds configurable options for Windows make files (both MinGW and MSVC). CI will also now exercise both traditional full API and stable ABI for Linux and Windows in the matrix for coverage. Also added a "dynamic" option to Linux matrix as a drive-by change to make other scripting languages like Ruby / Perl testable under both static and dynamic builds. 8) Fix inaccuracy in Windows docs Python's own docs are confusing but you don't actually want to use `python3.dll` for the dynamic linkage. 9) Add generated autoconf file 10) Add v:python3_version support This variable indicates the version of Python3 that Vim was built against (PY_VERSION_HEX), and will be useful to check whether the Python library you are loading in dynamically actually fits it. When built with stable ABI, it will be the limited ABI version instead (`Py_LIMITED_API`), which indicates the minimum version of Python 3 the user should have, rather than the exact match. When stable ABI is used, we won't be exposing PY_VERSION_HEX in this var because it just doesn't seem necessary to do so (the whole point of stable ABI is the promise that it will work across versions), and I don't want to confuse the user with too many variables. Also, cleaned up some documentation, and added help tags. 11) Fix Python 3.7 compat issues Fix a couple issues when using limited API < 3.8 - Crash on exit: In Python 3.7, if a heap-allocated type is destroyed before all instances are, it would cause a crash later. This happens when we destroyed `OptionsType` before calling `Py_Finalize` when using the limited API. To make it worse, later versions changed the semantics and now each instance has a strong reference to its own type and the recommendation has changed to have each instance de-ref its own type and have its type in GC traversal. To avoid dealing with these cross-version variations, we just don't free the heap type. They are static types in non-limited-API anyway and are designed to last through the entirety of the app, and we also don't restart the Python runtime and therefore do not need it to have absolutely 0 leaks. See: - https://docs.python.org/3/whatsnew/3.8.html#changes-in-the-c-api - https://docs.python.org/3/whatsnew/3.9.html#changes-in-the-c-api - PyIter_Check: This function is not provided in limited APIs older than 3.8. Previously I was trying to mock it out using manual PyType_GetSlot() but it was brittle and also does not actually work properly for static types (it will generate a Python error). Just return false. It does mean using limited API < 3.8 is not recommended as you lose the functionality to handle iterators, but from playing with plugins I couldn't find it to be an issue. - Fix loading of PyIter_Check so it will be done when limited API < 3.8. Otherwise loading a 3.7 Python lib will fail even if limited API was specified to use it. 12) Make sure to only load `PyUnicode_AsUTF8AndSize` in needed in limited API We don't use this function unless limited API >= 3.10, but we were loading it regardless. Usually it's ok in Unix-like systems where Python just has a single lib that we load from, but in Windows where there is a separate python3.dll this would not work as the symbol would not have been exposed in this more limited DLL file. This makes it much clearer under what condition is this function needed. closes: #12032 Signed-off-by: Christian Brabandt <cb@256bit.org> Co-authored-by: Yee Cheng Chin <ychin.git@gmail.com>
2025-09-25 03:54:15 -04:00 · 2023-08-20 21:18:38 +02:00
parent 20cd8699ac
commit c13b3d1350
18 changed files with 769 additions and 153 deletions
--- a/src/if_python3.c
+++ b/src/if_python3.c
@@ -71,6 +71,10 @@
 #define PyLong_Type (*py3_PyLong_Type)
 #define PyBool_Type (*py3_PyBool_Type)

+#ifdef Py_LIMITED_API
+# define USE_LIMITED_API // Using Python 3 limited ABI
+#endif
+
 #include <Python.h>

 #undef main // Defined in python.h - aargh
@@ -203,7 +207,9 @@ static HINSTANCE hinstPy3 = 0; // Instance of python.dll
 # ifndef PyMapping_Keys
 #  define PyMapping_Keys py3_PyMapping_Keys
 # endif
-# if PY_VERSION_HEX >= 0x030a00b2
+# if (defined(USE_LIMITED_API) && Py_LIMITED_API >= 0x03080000) || \
+       (!defined(USE_LIMITED_API) && PY_VERSION_HEX >= 0x03080000)
+#  undef PyIter_Check
 #  define PyIter_Check py3_PyIter_Check
 # endif
 # define PyIter_Next py3_PyIter_Next
@@ -212,10 +218,15 @@ static HINSTANCE hinstPy3 = 0; // Instance of python.dll
 # define PyObject_GetItem py3_PyObject_GetItem
 # define PyObject_IsTrue py3_PyObject_IsTrue
 # define PyModule_GetDict py3_PyModule_GetDict
-#undef PyRun_SimpleString
-# define PyRun_SimpleString py3_PyRun_SimpleString
-#undef PyRun_String
-# define PyRun_String py3_PyRun_String
+# ifndef USE_LIMITED_API
+#  undef PyRun_SimpleString
+#  define PyRun_SimpleString py3_PyRun_SimpleString
+#  undef PyRun_String
+#  define PyRun_String py3_PyRun_String
+# else
+#  define Py_CompileString py3_Py_CompileString
+#  define PyEval_EvalCode py3_PyEval_EvalCode
+# endif
 # define PyObject_GetAttrString py3_PyObject_GetAttrString
 # define PyObject_HasAttrString py3_PyObject_HasAttrString
 # define PyObject_SetAttrString py3_PyObject_SetAttrString
@@ -228,7 +239,7 @@ static HINSTANCE hinstPy3 = 0; // Instance of python.dll
 # define PySys_GetObject py3_PySys_GetObject
 # define PySys_SetArgv py3_PySys_SetArgv
 # define PyType_Ready py3_PyType_Ready
-# if PY_VERSION_HEX >= 0x030900b0
+# if PY_VERSION_HEX >= 0x03040000
 #  define PyType_GetFlags py3_PyType_GetFlags
 # endif
 #undef Py_BuildValue
@@ -244,14 +255,23 @@ static HINSTANCE hinstPy3 = 0; // Instance of python.dll
 # define PyModule_AddObject py3_PyModule_AddObject
 # define PyImport_AppendInittab py3_PyImport_AppendInittab
 # define PyImport_AddModule py3_PyImport_AddModule
-# if PY_VERSION_HEX >= 0x030300f0
-#  undef _PyUnicode_AsString
-#  define _PyUnicode_AsString py3_PyUnicode_AsUTF8
+# ifdef USE_LIMITED_API
+#  if Py_LIMITED_API >= 0x030a0000
+#   define PyUnicode_AsUTF8AndSize py3_PyUnicode_AsUTF8AndSize
+#  endif
 # else
-#  define _PyUnicode_AsString py3__PyUnicode_AsString
+#  if PY_VERSION_HEX >= 0x030300f0
+#   define PyUnicode_AsUTF8AndSize py3_PyUnicode_AsUTF8AndSize
+#  else
+#   define _PyUnicode_AsString py3__PyUnicode_AsString
+#  endif
 # endif
+# undef PyUnicode_CompareWithASCIIString
+# define PyUnicode_CompareWithASCIIString py3_PyUnicode_CompareWithASCIIString
 # undef PyUnicode_AsEncodedString
 # define PyUnicode_AsEncodedString py3_PyUnicode_AsEncodedString
+# undef PyUnicode_AsUTF8String
+# define PyUnicode_AsUTF8String py3_PyUnicode_AsUTF8String
 # undef PyBytes_AsString
 # define PyBytes_AsString py3_PyBytes_AsString
 # ifndef PyBytes_AsStringAndSize
@@ -261,7 +281,7 @@ static HINSTANCE hinstPy3 = 0; // Instance of python.dll
 # define PyBytes_FromString py3_PyBytes_FromString
 # undef PyBytes_FromStringAndSize
 # define PyBytes_FromStringAndSize py3_PyBytes_FromStringAndSize
-# if defined(Py_DEBUG) || PY_VERSION_HEX >= 0x030900b0
+# if defined(Py_DEBUG) || PY_VERSION_HEX >= 0x030900b0 || defined(USE_LIMITED_API)
 #  define _Py_Dealloc py3__Py_Dealloc
 # endif
 # define PyFloat_FromDouble py3_PyFloat_FromDouble
@@ -310,6 +330,10 @@ static HINSTANCE hinstPy3 = 0; // Instance of python.dll
 # define PyType_IsSubtype py3_PyType_IsSubtype
 # define PyCapsule_New py3_PyCapsule_New
 # define PyCapsule_GetPointer py3_PyCapsule_GetPointer
+# ifdef USE_LIMITED_API
+#  define PyType_GetSlot py3_PyType_GetSlot
+#  define PyType_FromSpec py3_PyType_FromSpec
+# endif

 # if defined(Py_DEBUG) && !defined(Py_DEBUG_NO_PYMALLOC)
 #  undef PyObject_NEW
@@ -358,8 +382,13 @@ static void (*py3_Py_Finalize)(void);
 static void (*py3_PyErr_SetString)(PyObject *, const char *);
 static void (*py3_PyErr_SetObject)(PyObject *, PyObject *);
 static int (*py3_PyErr_ExceptionMatches)(PyObject *);
+# ifndef USE_LIMITED_API
 static int (*py3_PyRun_SimpleString)(char *);
 static PyObject* (*py3_PyRun_String)(char *, int, PyObject *, PyObject *);
+# else
+static PyObject* (*py3_Py_CompileString)(const char *, const char *, int);
+static PyObject* (*py3_PyEval_EvalCode)(PyObject *co, PyObject *globals, PyObject *locals);
+# endif
 static PyObject* (*py3_PyObject_GetAttrString)(PyObject *, const char *);
 static int (*py3_PyObject_HasAttrString)(PyObject *, const char *);
 static int (*py3_PyObject_SetAttrString)(PyObject *, const char *, PyObject *);
@@ -379,7 +408,8 @@ static PyObject* (*py3_PyDict_GetItemString)(PyObject *, const char *);
 static int (*py3_PyDict_Next)(PyObject *, Py_ssize_t *, PyObject **, PyObject **);
 static PyObject* (*py3_PyLong_FromLong)(long);
 static PyObject* (*py3_PyDict_New)(void);
-# if PY_VERSION_HEX >= 0x030a00b2
+# if (defined(USE_LIMITED_API) && Py_LIMITED_API >= 0x03080000) || \
+       (!defined(USE_LIMITED_API) && PY_VERSION_HEX >= 0x03080000)
 static int (*py3_PyIter_Check)(PyObject *o);
 # endif
 static PyObject* (*py3_PyIter_Next)(PyObject *);
@@ -388,7 +418,7 @@ static PyObject* (*py3_PyObject_Repr)(PyObject *);
 static PyObject* (*py3_PyObject_GetItem)(PyObject *, PyObject *);
 static int (*py3_PyObject_IsTrue)(PyObject *);
 static PyObject* (*py3_Py_BuildValue)(char *, ...);
-# if PY_VERSION_HEX >= 0x030900b0
+# if PY_VERSION_HEX >= 0x03040000
 static int (*py3_PyType_GetFlags)(PyTypeObject *o);
 # endif
 static int (*py3_PyType_Ready)(PyTypeObject *type);
@@ -425,17 +455,25 @@ static PyObject* py3__Py_FalseStruct;
 static PyObject* py3__Py_TrueStruct;
 static int (*py3_PyModule_AddObject)(PyObject *m, const char *name, PyObject *o);
 static int (*py3_PyImport_AppendInittab)(const char *name, PyObject* (*initfunc)(void));
-# if PY_VERSION_HEX >= 0x030300f0
-static char* (*py3_PyUnicode_AsUTF8)(PyObject *unicode);
+# ifdef USE_LIMITED_API
+#  if Py_LIMITED_API >= 0x030a0000
+static char* (*py3_PyUnicode_AsUTF8AndSize)(PyObject *unicode, Py_ssize_t *size);
+#  endif
 # else
+#  if PY_VERSION_HEX >= 0x030300f0
+static char* (*py3_PyUnicode_AsUTF8AndSize)(PyObject *unicode, Py_ssize_t *size);
+#  else
 static char* (*py3__PyUnicode_AsString)(PyObject *unicode);
+#  endif
 # endif
+static int (*py3_PyUnicode_CompareWithASCIIString)(PyObject *unicode, const char* string);
 static PyObject* (*py3_PyUnicode_AsEncodedString)(PyObject *unicode, const char* encoding, const char* errors);
+static PyObject* (*py3_PyUnicode_AsUTF8String)(PyObject *unicode);
 static char* (*py3_PyBytes_AsString)(PyObject *bytes);
 static int (*py3_PyBytes_AsStringAndSize)(PyObject *bytes, char **buffer, Py_ssize_t *length);
 static PyObject* (*py3_PyBytes_FromString)(char *str);
 static PyObject* (*py3_PyBytes_FromStringAndSize)(char *str, Py_ssize_t length);
-# if defined(Py_DEBUG) || PY_VERSION_HEX >= 0x030900b0
+# if defined(Py_DEBUG) || PY_VERSION_HEX >= 0x030900b0 || defined(USE_LIMITED_API)
 static void (*py3__Py_Dealloc)(PyObject *obj);
 # endif
 # if PY_VERSION_HEX >= 0x030900b0
@@ -477,6 +515,10 @@ static PyObject*(*py3__PyObject_GC_New)(PyTypeObject *);
 static void(*py3_PyObject_GC_Del)(void *);
 static void(*py3_PyObject_GC_UnTrack)(void *);
 static int (*py3_PyType_IsSubtype)(PyTypeObject *, PyTypeObject *);
+# ifdef USE_LIMITED_API
+static void* (*py3_PyType_GetSlot)(PyTypeObject *, int);
+static PyObject* (*py3_PyType_FromSpec)(PyType_Spec *);
+# endif

 // Imported exception objects
 static PyObject *p3imp_PyExc_AttributeError;
@@ -542,8 +584,13 @@ static struct
    {"PyErr_SetString", (PYTHON_PROC*)&py3_PyErr_SetString},
    {"PyErr_SetObject", (PYTHON_PROC*)&py3_PyErr_SetObject},
    {"PyErr_ExceptionMatches", (PYTHON_PROC*)&py3_PyErr_ExceptionMatches},
+# ifndef USE_LIMITED_API
    {"PyRun_SimpleString", (PYTHON_PROC*)&py3_PyRun_SimpleString},
    {"PyRun_String", (PYTHON_PROC*)&py3_PyRun_String},
+# else
+    {"Py_CompileString", (PYTHON_PROC*)&py3_Py_CompileString},
+    {"PyEval_EvalCode", (PYTHON_PROC*)&PyEval_EvalCode},
+# endif
    {"PyObject_GetAttrString", (PYTHON_PROC*)&py3_PyObject_GetAttrString},
    {"PyObject_HasAttrString", (PYTHON_PROC*)&py3_PyObject_HasAttrString},
    {"PyObject_SetAttrString", (PYTHON_PROC*)&py3_PyObject_SetAttrString},
@@ -563,7 +610,8 @@ static struct
    {"PyDict_Next", (PYTHON_PROC*)&py3_PyDict_Next},
    {"PyMapping_Check", (PYTHON_PROC*)&py3_PyMapping_Check},
    {"PyMapping_Keys", (PYTHON_PROC*)&py3_PyMapping_Keys},
-# if PY_VERSION_HEX >= 0x030a00b2
+# if (defined(USE_LIMITED_API) && Py_LIMITED_API >= 0x03080000) || \
+       (!defined(USE_LIMITED_API) && PY_VERSION_HEX >= 0x03080000)
    {"PyIter_Check", (PYTHON_PROC*)&py3_PyIter_Check},
 # endif
    {"PyIter_Next", (PYTHON_PROC*)&py3_PyIter_Next},
@@ -573,7 +621,7 @@ static struct
    {"PyObject_IsTrue", (PYTHON_PROC*)&py3_PyObject_IsTrue},
    {"PyLong_FromLong", (PYTHON_PROC*)&py3_PyLong_FromLong},
    {"PyDict_New", (PYTHON_PROC*)&py3_PyDict_New},
-# if PY_VERSION_HEX >= 0x030900b0
+# if PY_VERSION_HEX >= 0x03040000
    {"PyType_GetFlags", (PYTHON_PROC*)&py3_PyType_GetFlags},
 # endif
    {"PyType_Ready", (PYTHON_PROC*)&py3_PyType_Ready},
@@ -595,11 +643,19 @@ static struct
    {"PyObject_Init", (PYTHON_PROC*)&py3__PyObject_Init},
    {"PyModule_AddObject", (PYTHON_PROC*)&py3_PyModule_AddObject},
    {"PyImport_AppendInittab", (PYTHON_PROC*)&py3_PyImport_AppendInittab},
-# if PY_VERSION_HEX >= 0x030300f0
-    {"PyUnicode_AsUTF8", (PYTHON_PROC*)&py3_PyUnicode_AsUTF8},
+# ifdef USE_LIMITED_API
+#  if Py_LIMITED_API >= 0x030a0000
+    {"PyUnicode_AsUTF8AndSize", (PYTHON_PROC*)&py3_PyUnicode_AsUTF8AndSize},
+#  endif
 # else
+#  if PY_VERSION_HEX >= 0x030300f0
+    {"PyUnicode_AsUTF8AndSize", (PYTHON_PROC*)&py3_PyUnicode_AsUTF8AndSize},
+#  else
    {"_PyUnicode_AsString", (PYTHON_PROC*)&py3__PyUnicode_AsString},
+#  endif
 # endif
+    {"PyUnicode_CompareWithASCIIString", (PYTHON_PROC*)&py3_PyUnicode_CompareWithASCIIString},
+    {"PyUnicode_AsUTF8String", (PYTHON_PROC*)&py3_PyUnicode_AsUTF8String},
 # ifndef Py_UNICODE_USE_UCS_FUNCTIONS
    {"PyUnicode_FromFormat", (PYTHON_PROC*)&py3_PyUnicode_FromFormat},
 # else
@@ -613,7 +669,7 @@ static struct
    {"PyBytes_AsStringAndSize", (PYTHON_PROC*)&py3_PyBytes_AsStringAndSize},
    {"PyBytes_FromString", (PYTHON_PROC*)&py3_PyBytes_FromString},
    {"PyBytes_FromStringAndSize", (PYTHON_PROC*)&py3_PyBytes_FromStringAndSize},
-# if defined(Py_DEBUG) || PY_VERSION_HEX >= 0x030900b0
+# if defined(Py_DEBUG) || PY_VERSION_HEX >= 0x030900b0 || defined(USE_LIMITED_API)
    {"_Py_Dealloc", (PYTHON_PROC*)&py3__Py_Dealloc},
 # endif
 # if PY_VERSION_HEX >= 0x030900b0
@@ -654,6 +710,12 @@ static struct
    {"PyType_IsSubtype", (PYTHON_PROC*)&py3_PyType_IsSubtype},
    {"PyCapsule_New", (PYTHON_PROC*)&py3_PyCapsule_New},
    {"PyCapsule_GetPointer", (PYTHON_PROC*)&py3_PyCapsule_GetPointer},
+# ifdef USE_LIMITED_API
+#  if PY_VERSION_HEX >= 0x03040000
+    {"PyType_GetSlot", (PYTHON_PROC*)&py3_PyType_GetSlot},
+#  endif
+    {"PyType_FromSpec", (PYTHON_PROC*)&py3_PyType_FromSpec},
+# endif
    {"", NULL},
 };

@@ -922,7 +984,12 @@ static int py3initialised = 0;
 #define PYINITIALISED py3initialised
 static int python_end_called = FALSE;

-#define DESTRUCTOR_FINISH(self) Py_TYPE(self)->tp_free((PyObject*)self)
+#ifdef USE_LIMITED_API
+# define DESTRUCTOR_FINISH(self) \
+    ((freefunc)PyType_GetSlot(Py_TYPE(self), Py_tp_free))((PyObject*)self)
+#else
+# define DESTRUCTOR_FINISH(self) Py_TYPE(self)->tp_free((PyObject*)self)
+#endif

 #define WIN_PYTHON_REF(win) win->w_python3_ref
 #define BUF_PYTHON_REF(buf) buf->b_python3_ref
@@ -975,11 +1042,51 @@ static struct PyModuleDef vimmodule;
 */
 #include "if_py_both.h"

+#ifndef USE_LIMITED_API
+# if PY_VERSION_HEX >= 0x030300f0
+#  define PY_UNICODE_GET_UTF8_CHARS(obj) PyUnicode_AsUTF8AndSize(obj, NULL)
+# else
+#  define PY_UNICODE_GET_UTF8_CHARS _PyUnicode_AsString
+# endif
+#else
+# if Py_LIMITED_API >= 0x030A0000
+#  define PY_UNICODE_GET_UTF8_CHARS(obj) PyUnicode_AsUTF8AndSize(obj, NULL)
+# else
+// Python limited API before 3.10 lack easy ways to query the raw UTF-8 chars.
+// We need to first convert the string to bytes, and then extract the chars.
+// This function is only used for attribute string comparisons, which have
+// known short length. As such, just allocate a short static buffer to hold
+// the characters instead of having to allocate/deallcoate it.
+//
+// An alternative would be to convert all attribute string comparisons to use
+// PyUnicode_CompareWithASCIIString to skip having to extract the chars.
+static char py3_unicode_utf8_chars[20];
+char* PY_UNICODE_GET_UTF8_CHARS(PyObject* str)
+{
+    py3_unicode_utf8_chars[0] = '\0';
+    PyObject* bytes = PyUnicode_AsUTF8String(str);
+    if (bytes)
+    {
+	char *chars;
+	Py_ssize_t len;
+	if (PyBytes_AsStringAndSize(bytes, &chars, &len) != -1)
+	{
+	    if (len < (Py_ssize_t)sizeof(py3_unicode_utf8_chars))
+		// PyBytes_AsStringAndSize guarantees null-termination
+		memcpy(py3_unicode_utf8_chars, chars, len + 1);
+	}
+	Py_DECREF(bytes);
+    }
+    return py3_unicode_utf8_chars;
+}
+# endif
+#endif
+
 // NOTE: Must always be used at the start of a block, since it declares "name".
 #define GET_ATTR_STRING(name, nameobj) \
    char	*name = ""; \
    if (PyUnicode_Check(nameobj)) \
-	name = (char *)_PyUnicode_AsString(nameobj)
+	name = (char *)PY_UNICODE_GET_UTF8_CHARS(nameobj)

 #define PY3OBJ_DELETED(obj) (obj->ob_base.ob_refcnt<=0)

@@ -1008,6 +1115,10 @@ python3_end(void)
 #endif
    if (Py_IsInitialized())
    {
+#ifdef USE_LIMITED_API
+	shutdown_types();
+#endif
+
 	// acquire lock before finalizing
 	PyGILState_Ensure();

@@ -1956,4 +2067,14 @@ do_py3eval(char_u *str, typval_T *rettv)
 set_ref_in_python3(int copyID)
 {
    return set_ref_in_py(copyID);
+}
+
+    int
+python3_version()
+{
+#ifdef USE_LIMITED_API
+    return Py_LIMITED_API;
+#else
+    return PY_VERSION_HEX;
+#endif
 }