Protobuf Python 5.28.0 crashes in __str__ on Windows x64

[mtnpke]

What version of protobuf and what language are you using?
Version: v5.28.0

Language: Python

What operating system (Linux, Windows, ...) and version?
Windows 11 23H2 Build 22631.4037

What runtime / compiler are you using (e.g., python version or gcc version)
Python 3.12.5 (tags/v3.12.5:ff3bc82, Aug 6 2024, 20:45:27) [MSC v.1940 64 bit (AMD64)] on win32

What did you do?

• Create Python venv
• Run pip install protobuf (as of today: installs protobuf 5.28.0)
• Create test.proto with this content:

syntax = "proto3";

message MyMessage {
    string test = 1;
}

• Run protoc --python_out=. -I. test.proto
• Create test.py with this content:

import test_pb2
for i in range(100):
    print(i)
    m = test_pb2.MyMessage()
    print(m)
print("ok")

• Run python test.py

What did you expect to see
Counting from 0 to 99 and then "ok"

What did you see instead?
Crash at i = 1

Note: There is no crash with protobuf Python package 5.27.4. Crashing starts with 5.28.0rc1.

Note: If you include an integer field instead of a string, it will not crash, but display random values for the field.

[aaltat]

I am seeing something similar within my project. Update to protobuf broke my test in Windows https://github.com/MarketSquare/robotframework-browser/actions/runs/10608698864/job/29403939266?pr=3765

[liqunfu]

We have same failure with windows build: https://github.com/onnx/onnx/actions/runs/10687189577/job/29624209865?pr=6327

[mkruskal-google]

I was able to reproduce this using x64 python 3.12.5. I also tried x86 3.12.5 and x64 3.10.4 first and had no luck. So this looks like something very tied to python version we likely missed in our test coverage

[mkruskal-google]

It looks like this is only reproducible under all of the conditions:

1. windows
2. 64-bit protobuf wheel
3. optimized build
4. python 3.12

4 is a little less clear, as our GHA show segfaults under all python versions when I switch to opt

[aaltat]

Hmmm, at least on my GitHub actions error is not tied to specific python version, example this uses 3.9 https://github.com/MarketSquare/robotframework-browser/actions/runs/10660730916/job/29545167895?pr=3765

But in the other I have pytest in the picture too

[mtnpke]

I have confirmed this on both 3.11 and 3.12 (both x64); I did not test other versions.