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Title: [C API] script must not include PyType_HasFeature() static inline function in the stable ABI
Type: Stage: resolved
Components: C API Versions: Python 3.10
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: Nosy List: pablogsal, petr.viktorin, vstinner
Priority: normal Keywords: patch

Created on 2021-04-01 09:37 by vstinner, last changed 2022-04-11 14:59 by admin. This issue is now closed.

Pull Requests
URL Status Linked Edit
PR 25136 merged vstinner, 2021-04-01 10:38
Messages (4)
msg389964 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2021-04-01 09:37
I just ran "make regen-limited-abi" and it added PyType_HasFeature():

commit baf10da75072d1f8ec714d3c2c8550d34db343a9
Author: Victor Stinner <>
Date:   Thu Apr 1 11:29:46 2021 +0200

    bpo-43688: Run make regen-limited-abi (GH-25134)

diff --git a/Doc/data/stable_abi.dat b/Doc/data/stable_abi.dat
index 3adee103bc..ed20521b7f 100644
--- a/Doc/data/stable_abi.dat
+++ b/Doc/data/stable_abi.dat
@@ -192,6 +192,7 @@ PyExc_ConnectionRefusedError
@@ -615,6 +616,7 @@ PyType_GetFlags

The problem is that PyType_HasFeature() is currently implemented as a static inline function in the limited C API for best performance.

Issue about PyType_HasFeature() performance in CPython itself:

Currently, PyType_HasFeature() is declared in Include/object.h as:

static inline int
PyType_HasFeature(PyTypeObject *type, unsigned long feature)
    unsigned long flags;
    // PyTypeObject is opaque in the limited C API
    flags = PyType_GetFlags(type);
    flags = type->tp_flags;
    return ((flags & feature) != 0);

IMO static inline functions must not be listed in the stable *ABI*. At the ABI level, libpython doesn't export "PyType_HasFeature" symbol:

$ objdump -T /lib64/|grep '\<PyObject_CallFunction\>'
00000000000fedf0 g    DF .text	00000000000000d0  Base        PyObject_CallFunction
$ objdump -T /lib64/|grep '\<PyType_HasFeature\>'
# nothing

"PyObject_CallFunction" symbol is exported, but not "PyType_HasFeature".


Maybe for the stable ABI, it would be a good idea to export PyType_HasFeature() as an opaque function. But that's out of the scope of this issue which is about the script ;-)
msg389976 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2021-04-01 12:14
New changeset 61092a99c4840f36dbde8457cb566fc3c012930f by Victor Stinner in branch 'master':
bpo-43690: no longer parses macros (GH-25136)
msg389977 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2021-04-01 12:16
Pablo: My previous commit added PyType_HasFeature to Doc/data/stable_abi.dat. But it prevented me to fix another bug, PR 25135. So I merged this change (PR 25136) to unblock the CI. Feel free to revert/adjust my change as soon as it doesn't add PyType_HasFeature back into Doc/data/stable_abi.dat :-)
msg389978 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2021-04-01 12:20
Oh, I forgot the mention "Tests / Check if generated files are up to date" job error message:

LD_LIBRARY_PATH=/home/runner/work/cpython/cpython:/opt/hostedtoolcache/Python/3.9.2/x64/lib ./python ./Tools/scripts/ check ./Doc/data/stable_abi.dat
Some symbols from the limited API are missing: PyType_HasFeature

This error means that there are some missing symbols among the ones exported
in the Python library ("libpythonx.x.a" or ""). This normally
means that some symbol, function implementation or a prototype, belonging to
a symbol in the limited API has been deleted or is missing.

Check if this was a mistake and if not, update the file containing the limited
API symbols. This file is located at:


You can read more about the limited API and its contracts at:

And in PEP 384:
Date User Action Args
2022-04-11 14:59:43adminsetgithub: 87856
2021-04-01 12:20:27vstinnersetmessages: + msg389978
2021-04-01 12:16:45vstinnersetstatus: open -> closed
resolution: fixed
messages: + msg389977

stage: patch review -> resolved
2021-04-01 12:14:08vstinnersetmessages: + msg389976
2021-04-01 10:38:38vstinnersetkeywords: + patch
stage: patch review
pull_requests: + pull_request23883
2021-04-01 09:37:33vstinnercreate