Bad file descriptor errors from subprocess module in AIX

[ayappanec]

Bug report

Bug description:

# cat python-popen-script.py
import subprocess
p = subprocess.Popen(['ls', '-l'])

# trace -a -x "./python python-popen-script.py"

# trcrpt > capture_trcrpt

# head -25 capture_trcrpt

Mon Nov 17 02:43:50 2025
System: AIX 7.2 Node: fvtvios10
Machine: 00F905D14C00
Internet Address: 0972E2D7 9.114.226.215
At trace startup, the system contained 8 cpus, of which 8 were traced.
Buffering: Kernel Heap
This is from a 64-bit kernel.
Tracing all hooks.

trace -a -x ./python python-popen-script.py     


ID      ELAPSED_SEC     DELTA_MSEC   APPL    SYSCALL KERNEL  INTERRUPT

101     0.000000000       0.000000           close LR = 101CB570
104     0.000000345       0.000345           return from close. error EBADF [0 usec]
101     0.000001187       0.000842           close LR = 101CB580
104     0.000001523       0.000336           return from close. error EBADF [0 usec]
101     0.000002361       0.000838           close LR = 101CB570
104     0.000002705       0.000344           return from close. error EBADF [0 usec]
101     0.000003541       0.000836           close LR = 101CB580
104     0.000003884       0.000343           return from close. error EBADF [0 usec]
101     0.000004734       0.000850           close LR = 101CB570
104     0.000005080       0.000346           return from close. error EBADF [0 usec]
101     0.000005919       0.000839           close LR = 101CB580
104     0.000006253       0.000334           return from close. error EBADF [0 usec]

# grep EBADF capture_trcrpt | wc -l
21409

Looks like _posixsubprocess module uses /proc/self/fd which is not available in AIX. Instead /proc/<PID>/fd should be used in AIX.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Other

Linked PRs

• gh-141659: Fix bad file descriptors from subprocess in AIX #141660
• [3.14] gh-141659: Fix bad file descriptor error in subprocess on AIX (GH-141660) #141738
• gh-141659: Move NEWS entry from Core_and_Builtins to Library #141744
• [3.14] Move the NEWS entry for gh-141659 to the correct section (GH-141744) #141766
• [3.13] gh-141659: Fix bad file descriptor error in subprocess on AIX (GH-141660) #141828