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From c8c19570aa9e46b67d44228241e7401af96cbccd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20G=C3=B3rny?= <mgorny@gentoo.org>
Date: Mon, 29 Jan 2024 17:48:40 +0100
Subject: [PATCH] Fix finding pthread_*name_np on vanilla musl libc
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Fix the `pthread_getname_np` and `pthread_setname_np` search logic
to support vanilla versions of musl and CPython, e.g. as used on Gentoo
musl systems. On such systems, there is no "libpthread.so" (there is
only a static library) and the relevant functions are found
in "libc.so". Additionally, `ctypes.util.find_library("c")` does not
work because of an old unsolved bug in CPython (linked in the code).
To resolve the problem, add a fallback to trying `libc.so` if no pthread
library can be found. This roughly covers three possibilities:
- a "typical" system with `libpthread.so` will find that library
and use it
- a musl system will fall back to `libc.so`, load that library and find
pthread functions there
- any other system will try to load `libc.so`, and fail
The code in `get_os_thread_name_func()` remains fully relaxed, allowing
either CDLL construction (i.e. finding the library) to fail,
or the library not to contain `pthread_setname_np`.
The code in `test_threads.py` was made more relaxed — rather than
skipping if `libpthread.so` does not exist, it tries to load `libc.so`
as a fallback, and skips if that fails.
Originally reported as https://bugs.gentoo.org/923257.
---
newsfragments/2939.bugfix.rst | 1 +
src/trio/_core/_thread_cache.py | 9 +++++++--
src/trio/_tests/test_threads.py | 12 ++++++++++--
3 files changed, 18 insertions(+), 4 deletions(-)
create mode 100644 newsfragments/2939.bugfix.rst
diff --git a/src/trio/_tests/test_threads.py b/src/trio/_tests/test_threads.py
index aefb4ba27..326cffd6b 100644
--- a/src/trio/_tests/test_threads.py
+++ b/src/trio/_tests/test_threads.py
@@ -237,9 +237,17 @@ def _get_thread_name(ident: int | None = None) -> str | None:
libpthread_path = ctypes.util.find_library("pthread")
if not libpthread_path:
- print(f"no pthread on {sys.platform})")
+ # musl includes pthread functions directly in libc.so
+ # (but note that find_library("c") does not work on musl,
+ # see: https://github.com/python/cpython/issues/65821)
+ # so try that library instead
+ # if it doesn't exist, CDLL() will fail below
+ libpthread_path = "libc.so"
+ try:
+ libpthread = ctypes.CDLL(libpthread_path)
+ except Exception:
+ print(f"no pthread on {sys.platform}")
return None
- libpthread = ctypes.CDLL(libpthread_path)
pthread_getname_np = getattr(libpthread, "pthread_getname_np", None)
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