From a4f12b7c1aa1e76021130cb574475fc60cae3592 Mon Sep 17 00:00:00 2001
From: John Litborn <11260241+jakkdl@users.noreply.github.com>
Date: Sun, 17 Sep 2023 10:07:42 +0200
Subject: [PATCH] Add comment and assertion to `pidfd_open` workaround (#2799)

* add assertion check to os.pidfd_open on linux, clarifying it's for <3.9 and pypy
---
 trio/_subprocess.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/trio/_subprocess.py b/trio/_subprocess.py
index 978f7e6188..5ade2d4dc7 100644
--- a/trio/_subprocess.py
+++ b/trio/_subprocess.py
@@ -49,6 +49,8 @@ def pidfd_open(fd: int, flags: int) -> int:
         from os import pidfd_open
     except ImportError:
         if sys.platform == "linux":
+            # This workaround is only needed on 3.8 and pypy
+            assert sys.version_info < (3, 9) or sys.implementation.name != "cpython"
             import ctypes
 
             _cdll_for_pidfd_open = ctypes.CDLL(None, use_errno=True)
@@ -69,7 +71,7 @@ def pidfd_open(fd: int, flags: int) -> int:
 
             def pidfd_open(fd: int, flags: int) -> int:
                 result = _cdll_for_pidfd_open.syscall(__NR_pidfd_open, fd, flags)
-                if result < 0:
+                if result < 0:  # pragma: no cover
                     err = ctypes.get_errno()
                     raise OSError(err, os.strerror(err))
                 return result