Cython: Segfault in compiled code with return max(*args)

[Khaelenmore]

I have an issue with running following code compiled by cython.

import decimal


async def fo():
    a = decimal.Decimal(1)
    b = decimal.Decimal(0)
    return min(a - b, 0)

This file was compiled with cython cython smth.py -3

Then compiled it with gcc -shared -pthread -fPIC -I/usr/include/python3.8/ smth.c

gcc version is 9.2.0

When you import the module and run coroutine fo, like this:

import asyncio
from smth import fo

async def foo():
    a = await fo()
    print(a)

asyncio.get_event_loop().run_until_complete(foo())

Python segfaults.

This issue is caused by return min(a - b, 0) and is also valid for return max(a - b, 0)
If I split the code like

x = min(a - b, 0)
return x

Then the problem is not present

[bigbn]

Having the same issue on ubuntu 16.04

[scoder]

I see a duplicated DECREF() being generated for the temporary variable that holds the return value. That explains the crash.

  __pyx_r = NULL; __Pyx_ReturnWithStopIteration(__pyx_t_2);
  __Pyx_DECREF(__pyx_t_2); __pyx_t_2 = 0;
  __Pyx_DECREF(__pyx_t_2); __pyx_t_2 = 0;

[scoder]

Thanks for the detailed report.