Py_fopen and Py_fclose not exported from python3.dll on Windows

[sonVishal]

Bug report

Bug description:

The functions Py_fopen and Py_fclose introduced in PR#127821 are not visible on Windows.

Compiler: Microsoft (R) C/C++ Optimizing Compiler Version 19.42.34436 for x64
Windows SDK Version: 10.0.26100.0

Tested on: CPython 3.14.6

Command used for compilation: PCbuild\build.bat -p x64 -r -t Rebuild -e

I am not sure if these two APIs should be part of the stable ABI but we need them for the same reason mentioned in Issue#127350. We are upgrading to Python 3.14 from 3.12 and since _Py_wfopen is no longer exposed we are trying to replace it with Py_fopen and Py_fclose.

We load python3.dll via LoadLibrary Win32 API and then search for Py_fopen and Py_fclose via GetProcAddress Win32 API. These two symbols (Py_fopen and Py_fclose) cannot be found.

dumpbin /exports PCbuild\amd64\python3.dll | findstr Py_fopen returns empty after building.

Potential solution:
Should add the following to stable_abi.toml?

[function.Py_fopen]
    added = '3.14'
[function.Py_fclose]
    added = '3.14'

CPython versions tested on:

3.14

Operating systems tested on:

Windows

[Shrey-N]

Hi @sonVishal,

I believe this behavior is actually by design.

python3.dll represents the Limited API / Stable ABI, which strictly excludes functions using standard FILE* objects. This is because FILE* depends on the specific C Runtime (CRT) version, and exposing it would break cross compiler binary compatibility. Therefore, Py_fopen and Py_fclose cannot be added to stable_abi.toml.

(Note: _Py_wfopen and PyRun_FileExFlags were never part of the Stable ABI or exported by python3.dll either.)

Solution:-
To use Py_fopen and Py_fclose (or PyRun_FileExFlags), you must explicitly load the version specific DLL (e.g., python314.dll), which correctly exports them.

[sonVishal]

That makes sense. Thanks for the response. We will use python314.dll instead. Thanks and Regards, Vishal Sontakke.

…

On Thu, 2 Jul, 2026, 11:08 Shrey Naithani, ***@***.***> wrote: *Shrey-N* left a comment (python/cpython#152805) <#152805 (comment)> Hi @sonVishal <https://github.com/sonVishal>, I believe this behavior is actually by design. python3.dll represents the Limited API / Stable ABI, which strictly excludes functions using standard FILE* objects. This is because FILE* depends on the specific C Runtime (CRT) version, and exposing it would break cross compiler binary compatibility. Therefore, Py_fopen and Py_fclose cannot be added to stable_abi.toml. *(Note: _Py_wfopen and PyRun_FileExFlags were never part of the Stable ABI or exported by python3.dll either.)* Solution:- To use Py_fopen and Py_fclose (or PyRun_FileExFlags), you must explicitly load the version specific DLL (e.g., python314.dll), which correctly exports them. — Reply to this email directly, view it on GitHub <#152805?email_source=notifications&email_token=AEIGK75JHICMJMIWLEHLAW35CXYLZA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIOBWGI2TIMJRGU32M4TFMFZW63VHNVSW45DJN5XKKZLWMVXHJLDGN5XXIZLSL5RWY2LDNM#issuecomment-4862541157>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEIGK7YVZFWUBK5US2PQZAL5CXYLZAVCNFSNUABEKJSXA33TNF2G64TZHM4DCNJZHA4TMMJ3JFZXG5LFHM2DOOBXGM4DQMRZGWQXMAQ> . Triage notifications, keep track of coding agent tasks and review pull requests on the go with GitHub Mobile for iOS <https://github.com/notifications/mobile/ios/AEIGK774YI4XPAZJ2YBGNSD5CXYLZA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIOBWGI2TIMJRGU32M4TFMFZW63VHNVSW45DJN5XKKZLWMVXHJKTGN5XXIZLSL5UW64Y> and Android <https://github.com/notifications/mobile/android/AEIGK77PTLLZWK2CMQYC2VT5CXYLZA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIOBWGI2TIMJRGU32M4TFMFZW63VHNVSW45DJN5XKKZLWMVXHJLTGN5XXIZLSL5QW4ZDSN5UWI>. Download it today! You are receiving this because you were mentioned.Message ID: ***@***.***>