> why is `close` in libpthread.so? That's because close() is a pthreads "cancellation point" (see https://man7.org/linux/man-pages/man7/pthreads.7.html https:/

> why is `close` in libpthread.so? That's because close() is a pthreads "cancellation point" (see https://man7.org/linux/man-pages/man7/pthreads.7.html https://man7.org/linux/man-pages/man7/pthreads.7.html for details), so it needs special handling when the process is using pthreads. If the process does not link to libpthread.so, the implementation in libc.so (which probably doesn't have cancellation point support) will be used.