libwebsockets/lib/roles/dbus
Max van Kessel 3fa129172a dbus: prevent double free timeout event
SUL callback triggers a dbus timeout handle, handle removes the linked
list entry and free's the memory attached to the entry. Remove the code
where the the entry was removed by the timer callback, which triggered
a double free of the same linked list entry.
2023-11-23 09:45:12 +00:00
..
CMakeLists.txt sai: xenial 2021-02-28 19:05:25 +00:00
dbus.c dbus: prevent double free timeout event 2023-11-23 09:45:12 +00:00
private-lib-roles-dbus.h role structs to const 2020-01-15 06:31:19 +00:00
README.md role: dbus 2018-10-13 08:16:27 +08:00

DBUS Role Support

Fedora: dbus-devel Debian / Ubuntu: libdbus-1-dev

Enabling for build at cmake

Fedora example:

$ cmake .. -DLWS_ROLE_DBUS=1 -DLWS_DBUS_INCLUDE2="/usr/lib64/dbus-1.0/include"

Ubuntu example:

$ cmake .. -DLWS_ROLE_DBUS=1 -DLWS_DBUS_INCLUDE2="/usr/lib/x86_64-linux-gnu/dbus-1.0/include"

Dbus requires two include paths, which you can force by setting LWS_DBUS_INCLUDE1 and LWS_DBUS_INCLUDE2. Although INCLUDE1 is usually guessable, both can be forced to allow cross-build.

If these are not forced, then lws cmake will try to check some popular places, for LWS_DBUS_INCLUDE1, on both Fedora and Debian / Ubuntu, this is /usr/include/dbus-1.0... if the directory exists, it is used.

For LWS_DBUS_INCLUDE2, it is the arch-specific dbus header which may be packaged separately than the main dbus headers. On Fedora, this is in /usr/lib[64]/dbus-1.0/include... if not given externally, lws cmake will try /usr/lib64/dbus-1.0/include. On Debian / Ubuntu, the package installs it in an arch-specific dir like /usr/lib/x86_64-linux-gnu/dbus-1.0/include, you should force the path.

The library path is usually [lib] "dbus-1", but this can also be forced if you want to build cross or use a special build, via LWS_DBUS_LIB.

Building against local dbus build

If you built your own local dbus and installed it in /usr/local, then this is the incantation to direct lws to use the local version of dbus:

cmake .. -DLWS_ROLE_DBUS=1 -DLWS_DBUS_INCLUDE1="/usr/local/include/dbus-1.0" -DLWS_DBUS_INCLUDE2="/usr/local/lib/dbus-1.0/include" -DLWS_DBUS_LIB="/usr/local/lib/libdbus-1.so"

You'll also need to give the loader a helping hand to do what you want if there's a perfectly good dbus lib already in /usr/lib[64] using LD_PRELOAD like this

LD_PRELOAD=/usr/local/lib/libdbus-1.so.3.24.0 myapp

Lws dbus api exports

Because of the irregular situation with libdbus includes, if lws exports the dbus helpers, which use dbus types, as usual from #include <libwebsockets.h> then if lws was compiled with dbus role support it forces all users to take care about the dbus include path mess whether they use dbus themselves or not.

For that reason, if you need access to the lws dbus apis, you must explicitly include them by

#include <libwebsockets/lws-dbus.h>

This includes <dbus/dbus.h> and so requires the include paths set up. But otherwise non-dbus users that don't include libwebsockets/lws-dbus.h don't have to care about it.

DBUS and valgrind

https://cgit.freedesktop.org/dbus/dbus/tree/README.valgrind

  1. One-time 6KiB "Still reachable" caused by abstract unix domain socket + libc getgrouplist() via nss... bug since 2004(!)

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=273051