When allocating buffers with alignment parameters specified, it
may be necessary to overallocate memory to adjust to the requested
alignment. Previously the padding length was not included in the mmaped
buffer size, leaving unmapped bytes at the end of the buffer.
This caused intermittent SEGV faults and valgrind failures when running
the wayland_threads example.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6104>
By sealing for future writes, we broke Wayland SHM support. It seems like the
wayland library maps the SHM in read/write mode. This is visible through no
display and an error message like this:
wl_shm@7: error 2: failed mmap fd 43: Operation not permitted
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5684>
There is no guarantee that g_get_user_runtime_dir() is in a tmpfs. Using
an explicit shared memory API seems safer for all POSIX platforms.
Note that Android does not have shm_open() and only added memfd_create()
since API level 30 (Android 11).
Sponsored-by: Netflix Inc.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5328>
