cmake: use the same default system bus address as for autotools

The system bus is unsupported (and rather meaningless) on Windows anyway,
so we can use anything. Also, make it clear that it has to be a
"specific" address that can be listened on *and* connected to,
like unix:path=/xxx - a listen-only address like unix:tmpdir=/xxx or
nonce-tcp: would not be suitable.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=38201
Reviewed-by: David Zeuthen <davidz@redhat.com>

3 files changed, 23 insertions, 7 deletions

diff --git a/README.cmake b/README.cmake
index 5feaf551..0e923356 100644
--- a/README.cmake
+++ b/README.cmake
@@ -80,7 +80,7 @@ Configuration flags
 
 When using the cmake build system the dbus-specific configuration flags that can be given 
 to the cmake program are these (use -D<key>=<value> on command line). The listed values 
-are the defaults.
+are the defaults (in a typical build - some are platform-specific).
 
 // Choose the type of build, options are: None(CMAKE_CXX_FLAGS or
 // CMAKE_C_FLAGS used) Debug Release RelWithDebInfo MinSizeRel.
@@ -132,8 +132,8 @@ DBUS_INSTALL_SYSTEM_LIBS:BOOL=OFF
 // session bus default address
 DBUS_SESSION_BUS_DEFAULT_ADDRESS:STRING=nonce-tcp:
 
-// system bus default address
-DBUS_SYSTEM_BUS_DEFAULT_ADDRESS:STRING=nonce-tcp:
+// system bus default address (only useful on Unix)
+DBUS_SYSTEM_BUS_DEFAULT_ADDRESS:STRING=unix:path=/var/run/dbus/system_bus_socket
 
 // Use atomic integer implementation for 486
 DBUS_USE_ATOMIC_INT_486:BOOL=OFF
diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
index 000acda2..5174469d 100644
--- a/cmake/CMakeLists.txt
+++ b/cmake/CMakeLists.txt
@@ -431,9 +431,17 @@ endif (WIN32)
 
 set (DBUS_USER )
 
+# This won't work on Windows. It's not meant to - the system bus is
+# meaningless on Windows anyway.
+#
+# This has to be suitable for hard-coding in client libraries as well as
+# in the dbus-daemon's configuration, so it has to be valid to listen on
+# and also to connect to. If this ever changes, it'll need to be split into
+# two variables, one for the listening address and one for the connecting
+# address.
+set (DBUS_SYSTEM_BUS_DEFAULT_ADDRESS "unix:path=${EXPANDED_LOCALSTATEDIR}/run/dbus/system_bus_socket" CACHE STRING "system bus default address")
 
 if (WIN32)
-  set (DBUS_SYSTEM_BUS_DEFAULT_ADDRESS "nonce-tcp:" CACHE STRING "system bus default address")
   set (DBUS_SESSION_BUS_DEFAULT_ADDRESS "nonce-tcp:" CACHE STRING "session bus default address")
 
   set (DBUS_SYSTEM_CONFIG_FILE "etc/dbus-1/system.conf")
@@ -441,7 +449,6 @@ if (WIN32)
   # bus-test expects a non empty string
   set (DBUS_USER "Administrator")
 else (WIN32)
-  set (DBUS_SYSTEM_BUS_DEFAULT_ADDRESS "unix:tmpdir=" CACHE STRING "system bus default address")
   set (DBUS_SESSION_BUS_DEFAULT_ADDRESS "unix:path=${DBUS_SESSION_SOCKET_DIR}" CACHE STRING "session bus default address")
   set (sysconfdir "")
   set (configdir ${sysconfdir}/dbus-1 )
diff --git a/configure.ac b/configure.ac
index e8fc1aef..12847c4a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1521,8 +1521,17 @@ fi
 AC_SUBST(DBUS_SYSTEM_SOCKET)
 AC_DEFINE_UNQUOTED(DBUS_SYSTEM_SOCKET,"$DBUS_SYSTEM_SOCKET",[The name of the socket the system bus listens on by default])
 
-## system bus only listens on local domain sockets, and never
-## on an abstract socket (so only root can create the socket)
+## System bus only listens on local domain sockets, and never
+## on an abstract socket (so only root can create the socket).
+##
+## This won't work on Windows. It's not meant to - the system bus is
+## meaningless on Windows anyway.
+##
+## This has to be suitable for hard-coding in client libraries as well as
+## in the dbus-daemon's configuration, so it has to be valid to listen on
+## and also to connect to. If this ever changes, it'll need to be split into
+## two variables, one for the listening address and one for the connecting
+## address.
 DBUS_SYSTEM_BUS_DEFAULT_ADDRESS="unix:path=$DBUS_SYSTEM_SOCKET"
 AC_SUBST(DBUS_SYSTEM_BUS_DEFAULT_ADDRESS)
 AC_DEFINE_UNQUOTED(DBUS_SYSTEM_BUS_DEFAULT_ADDRESS, "$DBUS_SYSTEM_BUS_DEFAULT_ADDRESS",[The default D-Bus address of the system bus])