Fixes the following warnings:
src/wayland-server.c:1152: warning: documented empty return type of wl_display::wl_display_destroy
src/wayland-server.c:1193: warning: documented empty return type of wl_display::wl_display_set_global_filter
Signed-off-by: Simon Ser <contact@emersion.fr>
Doxygen doesn't support documenting unnamed function arguments.
Fixes the following warnings:
src/wayland-util.h:697: warning: argument 'const' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'void' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'void' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'uint32_t' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'const' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'struct' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'wl_message' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'union' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'wl_argument' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:725: warning: argument 'const' of command @param is not found in the argument list of wl_log_func_t(const char *, va_list)
src/wayland-util.h:725: warning: argument 'char' of command @param is not found in the argument list of wl_log_func_t(const char *, va_list)
src/wayland-util.h:725: warning: argument 'va_list' of command @param is not found in the argument list of wl_log_func_t(const char *, va_list)
src/wayland-util.h:697: warning: argument 'const' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'void' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'void' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'uint32_t' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'const' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'struct' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'wl_message' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'union' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:697: warning: argument 'wl_argument' of command @param is not found in the argument list of wl_dispatcher_func_t(const void *, void *, uint32_t, const struct wl_message *, union wl_argument *)
src/wayland-util.h:725: warning: argument 'const' of command @param is not found in the argument list of wl_log_func_t(const char *, va_list)
src/wayland-util.h:725: warning: argument 'char' of command @param is not found in the argument list of wl_log_func_t(const char *, va_list)
src/wayland-util.h:725: warning: argument 'va_list' of command @param is not found in the argument list of wl_log_func_t(const char *, va_list)
Signed-off-by: Simon Ser <contact@emersion.fr>
Typically this is a number between 0 and 32. Just that the compiler doesn't
know that well. Make the string buffer a bit larger, so that it fits the
longer integers. Fixes build warnings like:
../subprojects/wayland/src/wayland-server.c: In function ‘wl_display_add_socket_auto’:
../subprojects/wayland/src/wayland-server.c:1649:70: error: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size 8 [-Werror=format-truncation=]
1649 | snprintf(display_name, sizeof display_name, "wayland-%d", displayno);
| ^~
../subprojects/wayland/src/wayland-server.c:1649:61: note: directive argument in the range [-2147483647, 32]
1649 | snprintf(display_name, sizeof display_name, "wayland-%d", displayno);
| ^~~~~~~~~~~~
../subprojects/wayland/src/wayland-server.c:1649:17: note: ‘snprintf’ output between 10 and 20 bytes into a destination of size 16
1649 | snprintf(display_name, sizeof display_name, "wayland-%d", displayno);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
Seen in GTK CI.
Signed-off-by: Carlos Garnacho <carlosg@gnome.org>
The usefulness of this is limited, and `libwayland-client` doesn't
provide a way to pass a null `new_id` since the id is generated by the
library and given to the caller as the return value.
Signed-off-by: Ian Douglas Scott <idscott@system76.com>
Nullable arrays, which are not used anywhere, were marshalled the same
way as an empty non-null array. The demarshalling logic did not
recognize anything as a null array. Given this, it seems better to just
explicitly not support it.
Fixes https://gitlab.freedesktop.org/wayland/wayland/-/issues/306.
Signed-off-by: Ian Douglas Scott <idscott@system76.com>
Callers may check errno when wl_map_insert_* functions return an
error (since [1]). Make sure it's always set to a meaningful value
when returning an error, otherwise callers might end up checking an
errno coming from a completely different function.
[1]: https://gitlab.freedesktop.org/wayland/wayland/-/merge_requests/205
Signed-off-by: Simon Ser <contact@emersion.fr>
Fixes: b19488c715 ("util: Limit size of wl_map")
See the previous discussion at [1]: libwayland incorrectly skips
the visibility checks when sending global/global_remove events.
The check is only performed when a client performs a
wl_display.get_registry request.
[1]: https://gitlab.freedesktop.org/wayland/wayland/-/merge_requests/148
Signed-off-by: Simon Ser <contact@emersion.fr>
Assignments to a wl_proxy's queue member are currently not synchronized
with potential reads of that member during event reading/queuing.
Assuming atomic pointer value reads and writes (which is a reasonable
assumption), and using the documented best practices to handle event
queue changes, a queue change should still be safe to perform.
That being said, such implicitly atomic accesses are difficult to assess
for correctness, especially since they do not introduce memory barriers.
To make the code more obviously correct, and handle any potential races
we are not currently aware of, this commit updates wl_proxy_set_queue()
to set the proxy's event queue under the display lock (all other
proxy queue accesses are already done under the display lock).
Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Suggested-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Document the proper way to deal with event queue changes, in order to
guarantee proper handing of all events which were queued before the
queue change takes effect, especially in multi-threaded setups.
Make a special note about queue changes of newly created proxies,
which require the use of a proxy wrapper for thread safety.
Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Suggested-by: Pekka Paalanen <pekka.paalanen@collabora.com>
The [spec][1] reads:
> All paths set in these environment variables must be absolute. If an
> implementation encounters a relative path in any of these variables it should
> consider the path invalid and ignore it.
and
> If $XDG_DATA_HOME is either not set or empty, a default equal to
> $HOME/.local/share should be used.
Testing that the path is absolute also entails that is is non-empty.
[1]: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
Signed-off-by: Antonin Décimo <antonin.decimo@gmail.com>
This allows projects to use Wayland as a Meson subproject and get the
wayland-scanner executable when doing find_program('wayland-scanner').
Signed-off-by: Xavier Claessens <xavier.claessens@collabora.com>
Add a helper to check the advertised version of a global. This can
be handy when checking whether a compositor feature is supported,
instead of having to store the version passed to wl_global_create
separately.
Signed-off-by: Simon Ser <contact@emersion.fr>
Since server IDs are basically indistinguishable from really big client
IDs at many points in the source, it's theoretically possible to overflow
a map and either overflow server IDs into the client ID space, or grow
client IDs into the server ID space. This would currently take a massive
amount of RAM, but the definition of massive changes yearly.
Prevent this by placing a ridiculous but arbitrary upper bound on the
number of items we can put in a map: 0xF00000, somewhere over 15 million.
This should satisfy pathological clients without restriction, but stays
well clear of the 0xFF000000 transition point between server and client
IDs. It will still take an improbable amount of RAM to hit this, and a
client could still exhaust all RAM in this way, but our goal is to prevent
overflow and undefined behaviour.
Fixes#224
Signed-off-by: Derek Foreman <derek.foreman@collabora.com>
Fail when tests/documentation is enabled without libraries. Fail
when neither scanner nor libraries is enabled, because we don't
build anything in that case.
Signed-off-by: Simon Ser <contact@emersion.fr>
FreeBSD doesn't support mremap [1], so we have a fallback
implementation based on munmap+mmap. We memcpy from the old memory
region to the new one, however this is unnecessary because the new
mapping references the same file as the old one.
Use msync to make sure any pending write is flushed to the underlying
file before we map the new region.
[1]: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=59912
Signed-off-by: Simon Ser <contact@emersion.fr>
Commit 5a981ee8 implemented a fallback path for platforms which do not
support mremap() such as FreeBSD.
To do so, the file descriptor for the mmap() is not closed immediately
but instead kept as long as the pool exists.
That induces more file descriptors kept open for longer, which in turn
may cause problems as wl_shm may be using a lot of file descriptors,
especially with Xwayland which can create a lot of pixmaps on behalf of
its X11 clients.
For platforms where mremap() is available, keeping those file
descriptors opened is a bit of a waste and may cause exhaustion of file
descriptors sooner that before commit 5a981ee8.
Only keep the mmap() file descriptor open on platforms which do not
implement mremap() and close it immediately as before on others.
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Closes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1283
Initialiaze the entire msghdr struct to 0 before use.
Example of the report fixed with this change:
AddressSanitizer:DEADLYSIGNAL
=================================================================
==20035==ERROR: AddressSanitizer: SEGV on unknown address 0x2dad4dbffffa0d (pc 0x0055555c7488 bp 0x007fffffc760 sp 0x007fffffc760 T0)
==20035==The signal is caused by a READ memory access.
#0 0x55555c7488 in read_msghdr(void*, __sanitizer::__sanitizer_msghdr*, long) (/home/ftrvx/w/_/uxn/bin/uxnemu+0x77488)
#1 0x55555c810c in sendmsg (/home/ftrvx/w/_/uxn/bin/uxnemu+0x7810c)
#2 0x7ff7f2db20 in wl_connection_flush /home/ftrvx/q/wayland/build/../src/connection.c:315:10
#3 0x7ff7f2d014 in wl_display_flush /home/ftrvx/q/wayland/build/../src/wayland-client.c:2154:9
#4 0x7ff7e80bc0 (/lib/libSDL2-2.0.so.0+0x104bc0)
#5 0x7ff7e523b0 (/lib/libSDL2-2.0.so.0+0xd63b0)
#6 0x7ff7e534e4 (/lib/libSDL2-2.0.so.0+0xd74e4)
#7 0x7ff7e535e8 (/lib/libSDL2-2.0.so.0+0xd75e8)
#8 0x7ff7daad54 (/lib/libSDL2-2.0.so.0+0x2ed54)
#9 0x7ff7dab130 (/lib/libSDL2-2.0.so.0+0x2f130)
#10 0x555565bb40 in main /home/ftrvx/w/_/uxn/src/uxnemu.c:519:2
#11 0x7ff7f62484 in libc_start_main_stage2 /builddir/musl-1.1.24/src/env/__libc_start_main.c:94:2
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (/home/ftrvx/w/_/uxn/bin/uxnemu+0x77488) in read_msghdr(void*, __sanitizer::__sanitizer_msghdr*, long)
==20035==ABORTING
Signed-off-by: Sigrid Solveig Haflínudóttir <ftrvxmtrx@gmail.com>
wl_signal_emit doesn't handle well situations where a listener removes
another listener. This can happen in practice: wlroots and Weston [1]
both have private helpers to workaround this defect.
wl_signal_emit can't be fixed without breaking the API. Instead,
introduce a new function. Callers need to make sure to always remove
listeners when they are free'd.
[1]: https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/457
Signed-off-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Not checking the result of wl_array_add() can cause writes past the end of the
allocated buffer if realloc fails.
Signed-off-by: Aleksandr Mezin <mezin.alexander@gmail.com>
When multiple threads are used, output from different threads was intermixed in one line. That what breaking parsing of the log messages. Now, intermixing is prevented by using a memstream.
Signed-off-by: Alexander Irion <alexander_irion@mentor.com>
When allocating memory for structs, use zalloc instead of malloc.
This ensures the memory is zero-initialized, and reduces the risk
of forgetting to initialize all struct fields.
Signed-off-by: Simon Ser <contact@emersion.fr>
Make it easier to use Wayland as a Meson subproject by overriding
dependencies we define. This allows to easily build Wayland as a
subproject like so:
subproject('wayland', required: false, default_options: ['documentation=false'])
After this statement, the wayland-* dependencies will use the subproject
instead of the system if available.
Signed-off-by: Simon Ser <contact@emersion.fr>
In 11623e8f, SIGBUS handlers aren't set if F_SEAL_SHRINK is configured on
the memory. This helps avoid setting up handlers with cooperative clients;
however, if an application gives an incorrect size, the compositor would
access it anyways, figuring SIGBUS is impossible, and crash.
This can be fixed by simply removing the seal-checking logic and always
setting the signal handler. However, it seems that fstat can give the size
of the memfd, so we can check that the size we were told is within the
region. Since it's sealed to shrinking, it must never be shrunk in future,
so we can really (hopefully) ignore SIGBUS.
I was worried that fstat wasn't supported for this, but shm_overview(7) does
mention that it is a possible use.
The best solution would likely be avoiding SIGBUS entirely with
MAP_NOSIGBUS, but that hasn't been merged yet and wouldn't help systems
without it (e.g. with older kernels).
A proof-of-concept of this crash is attached with the merge request. Running
it with this patch gives an invalid-shm error, which is correct.
Signed-off-by: Duncan McIntosh <duncan82013@live.ca>
The client side closure traces have incorrect object ids for new server
generated objects. This is because create_proxies() overwrites the id in
'n' type arguments by storing a pointer to the actual object in the 'o'
field of the union.
Getting back to an id from this pointer requires accessing a structure
that isn't visible outside of wayland-client.c.
Add a function pointer to fish the correct value out of the argument and
pass it to wl_closure_print.
Signed-off-by: Derek Foreman <derek.foreman@collabora.com>
The ABI of a shared library on Linux is given by a major version, which
is part of the SONAME and is incremented (rarely) on incompatible
changes, and a minor version, which is part of the basename of the
regular file to which the SONAME provides a symlink.
Until now, the ABI minor version was hard-coded, which means we can't
tell which of a pair of Wayland libraries is newer (and therefore
likely to have more symbols and/or fewer bugs).
libwayland-egl already had ABI major version 1, so we can use the
"marketing" version number as the ABI major.minor version number
directly, so Wayland 1.19.90 would produce
libwayland-egl.so.1 -> libwayland-egl.so.1.19.90.
libwayland-cursor and libwayland-server have ABI major version 0,
and OS distributions don't like it when there's a SONAME bump for no
good reason, so use their existing ABI major version together with
the "marketing" minor version:
libwayland-cursor.so.0 -> libwayland-cursor.so.0.19.90.
If the Wayland major version number is incremented to 2, we'll have to
rethink this, so add some error() to break the build if/when that
happens. Assuming that Wayland 2.0 would involve breaking changes,
the best way would probably to bump all the SONAMEs to
libwayland-foo.so.2.
Resolves: https://gitlab.freedesktop.org/wayland/wayland/-/issues/175
Signed-off-by: Simon McVittie <smcv@collabora.com>
This makes wl_display_connect fail immediately instead of
succeeding when the integer provided by WAYLAND_SOCKET does
not refer to a valid file descriptor.
Signed-off-by: Manuel Stoeckl <code@mstoeckl.com>
Calling wl_display_terminate() will exit the wl_display event loop
at the start of the next loop iteration. This works fine when
wl_display_terminate() is called after the event loop wakes up
from polling on the added event sources. If, however, it is
called before polling starts, the event loop will not exit until
one or more event sources trigger. Depending on the types of event
sources, they may never trigger (or may not trigger for a long time),
so the event loop may never exit.
Add an extra event source to the wl_display event loop that will trigger
whenever wl_display_terminate() is called, so that the event loop will
always exit.
Fixes#201
Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp>
shm_pool_create_buffer() can raise a false WL_SHM_ERROR_INVALID_STRIDE
error under some circumstances because of integer division.
Fix this by using a strict comparison operator instead of lower or
equal.
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>
Closes: https://gitlab.freedesktop.org/wayland/wayland/-/issues/235
If we are compiling against a version of FreeBSD where MSG_CMSG_CLOEXEC
does not work, use the fallback directly. This was only fixed recently
(in https://cgit.freebsd.org/src/commit/?id=6ceacebdf52211).
Signed-off-by: Alex Richardson <Alexander.Richardson@cl.cam.ac.uk>
Some operating systems (e.g. FreeBSD) do not implement mremap.
In that case we can grow the mapping by trying to map adjacent memory.
If that fails we can fall back to creating a new larger mapping and
moving the old memory contents there.
Co-authored-by: Koop Mast <kwm@rainbow-runner.nl>
Signed-off-by: Alex Richardson <Alexander.Richardson@cl.cam.ac.uk>
On FreeBSD we have to use getsockopt(fd, SOL_LOCAL, LOCAL_PEERCRED)
instead. This change is based on a downstream patch in FreeBSD ports.
Co-authored-by: Greg V <greg@unrelenting.technology>
Co-authored-by: Koop Mast <kwm@rainbow-runner.nl>
Signed-off-by: Alex Richardson <Alexander.Richardson@cl.cam.ac.uk>
FreeBSD does not provide epoll(7) and instead requires an external library,
epoll-shim, that implements epoll() using kqueue(2)
Co-authored-by: Jan Beich <jbeich@FreeBSD.org>
Signed-off-by: Alex Richardson <Alexander.Richardson@cl.cam.ac.uk>
struct wl_buffer has other meaning in wayland, thus making this a pretty
confusing structure name. Function names like wl_buffer_put() just
compound the confusion.
Rename the struct and the associated functions (none of which are called
from outside this file anyway). The struct retains a wl_ prefix, as is
the custom for wayland internal data structures. The function names
have not retained this prefix, as we have many static function that
aren't prefixed.
Signed-off-by: Derek Foreman <derek.foreman@collabora.com>
Use the new flagged marshal+destroy function in generated code.
It's intended as a replacement for all existing wl_proxy_marshal_*
functions, so I've used it to replace them all. This results in a large
update to the scanner test files as well.
We now pass the new WL_MARSHAL_FLAG_DESTROY flag when appropriate, so
the race condition in #86 caused by releasing the display mutex between
marshalling the proxy and destroying the proxy is now gone.
Fixes#86
Signed-off-by: Derek Foreman <derek.foreman@collabora.com>
There's a race when destroying wayland objects in a multi-threaded client.
This occurs because we call:
wl_proxy_marshal(foo);
wl_proxy_destroy(foo);
And each of these functions takes, and releases, the display mutex.
Between the two calls, the display is not locked.
In order to allow atomically marshalling the proxy and destroying the
proxy without releasing the lock, add yet more wl_proxy_marshal_*
functions. This time add flags and jam in all existing warts with the
hope that we can make it future proof this time.
Signed-off-by: Derek Foreman <derek.foreman@collabora.com>
Split wl_proxy_destroy into two pieces, wl_proxy_destroy_unlocked which
performs the critical section code with no locking, and wl_proxy_destroy
which locks before calling that.
We'll use the new unlocked variant later in code that already holds the
lock.
There is a slight functional change - an aborting check is now called
with the lock held. This should be harmless as wl_abort() performs
no locking.
Signed-off-by: Derek Foreman <derek.foreman@collabora.com>
Specifically, in the log formed when WAYLAND_DEBUG is set, this commit
ensures that floating point numbers are formatted using '.' instead of
the locale-specific decimal separator. As the debug logs are not
otherwise localized for end-users, and may be parsed by scripts, it is
better to have consistent output here.
The 24.8 fixed point numbers are now represented with 8 digits after
the decimal, since this is both exact and simpler to compute.
Signed-off-by: Manuel Stoeckl <code@mstoeckl.com>
This function constructs a socket path in sun_path using snprintf, which
returns the amount of space that would have been used if the buffer was
large enough. It then checks if this is larger then the actual buffer size
and, if so, returns ENAMETOOLONG. This is correct.
However, after calling snprintf and before checking that the length isn't too
long, it tries to compute a pointer to the part of the path that matches the
input name. It does this by adding the computed path length to the pointer to
the start of the path buffer, which will take it to one-past the null
terminator, and then walking backwards. If the path fits in the buffer, this
will take it at most one-past-the-end of the allocation, which is allowed, but
if the path is longer then the buffer then the pointer addition is undefined behavior.
Fix this by moving the display name computation past the check that the path
length is not too long.
This is detected by the test socket_path_overflow_server_create under ubsan.
Signed-off-by: Fergus Dall <sidereal@google.com>
for_each_helper tries to calculate a one-past-the-end pointer for its
wl_array input. This is fine when the array has one or more entries, but we
initialize arrays by setting wl_array.data to NULL. Pointer arithmetic is
only defined when both the pointer operand and the result point to the same
allocation, or one-past-the-end of that allocation. As NULL points to no
allocation, no pointer arithmetic can be performed on it, not even adding 0,
even if the result is never dereferenced.
This is caught by clang's ubsan from version 10.
Many tests already hit this case, but I added an explicit test for iterating
over an empty wl_map.
Signed-off-by: Fergus Dall <sidereal@google.com>
Before this patch, setting WAYLAND_DEBUG=1 or WAYLAND_DEBUG=client made
a program log all requests sent and events that it processes. However,
some events received are not processed. This can happen when a Wayland
server sends an event to an object that does not exist, or was recently
destroyed by the client program (either before the event was decoded,
or after being decoded but before being dispatched.)
This commit prints all discarded messages in the debug log, producing
lines like:
[1234567.890] discarded [unknown]@42.[event 0](0 fd, 12 byte)
[1234567.890] discarded wl_callback@3.done(34567)
[1234567.890] discarded [zombie]@13.[event 1](3 fd, 8 byte)
The first indicates an event to an object that does not exist; the
second, an event to an object that was deleted after decoding, but
before dispatch; the third, an event to an object that left a
'zombie' marker behind to indicate which events have associated
file descriptors.
Signed-off-by: Manuel Stoeckl <code@mstoeckl.com>
