1 Sections in this file describe:
2 - introduction and overview
3 - low-level vs. high-level API
5 - options to the configure script
11 D-Bus is a simple system for interprocess communication and coordination.
13 The "and coordination" part is important; D-Bus provides a bus daemon that does things like:
14 - notify applications when other apps exit
15 - start services on demand
16 - support single-instance applications
18 See http://www.freedesktop.org/software/dbus/ for lots of documentation,
21 See also the file HACKING for notes of interest to developers working on D-Bus.
23 If you're considering D-Bus for use in a project, you should be aware
24 that D-Bus was designed for a couple of specific use cases, a "system
25 bus" and a "desktop session bus." These are documented in more detail
26 in the D-Bus specification and FAQ available on the web site.
28 If your use-case isn't one of these, D-Bus may still be useful, but
29 only by accident; so you should evaluate carefully whether D-Bus makes
30 sense for your project.
32 Note: low-level API vs. high-level binding APIs
35 A core concept of the D-Bus implementation is that "libdbus" is
36 intended to be a low-level API. Most programmers are intended to use
37 the bindings to GLib, Qt, Python, Mono, Java, or whatever. These
38 bindings have varying levels of completeness and are maintained as
39 separate projects from the main D-Bus package. The main D-Bus package
40 contains the low-level libdbus, the bus daemon, and a few command-line
41 tools such as dbus-launch.
43 If you use the low-level API directly, you're signing up for some
44 pain. Think of the low-level API as analogous to Xlib or GDI, and the
45 high-level API as analogous to Qt/GTK+/HTML.
50 D-Bus uses the common "Linux kernel" versioning system, where
51 even-numbered minor versions are stable and odd-numbered minor
52 versions are development snapshots.
54 So for example, development snapshots: 1.1.1, 1.1.2, 1.1.3, 1.3.4
55 Stable versions: 1.0, 1.0.1, 1.0.2, 1.2.1, 1.2.3
57 All pre-1.0 versions were development snapshots.
59 Development snapshots make no ABI stability guarantees for new ABI
60 introduced since the last stable release. Development snapshots are
61 likely to have more bugs than stable releases, obviously.
66 These are the dbus-specific configuration flags that can be given to
67 the ./configure program.
69 --enable-tests enable unit test code
70 --enable-ansi enable -ansi -pedantic gcc flags
71 --enable-verbose-mode support verbose debug mode
72 --enable-asserts include assertion checks
73 --enable-checks include sanity checks on public API
74 --enable-xml-docs build XML documentation (requires xmlto)
75 --enable-doxygen-docs build DOXYGEN documentation (requires Doxygen)
76 --enable-gcov compile with coverage profiling instrumentation (gcc only)
77 --enable-abstract-sockets
78 use abstract socket namespace (linux only)
79 --enable-selinux build with SELinux support
80 --enable-dnotify build with dnotify support (linux only)
81 --enable-kqueue build with kqueue support (*BSD only)
82 --with-xml=libxml/expat XML library to use
83 --with-init-scripts=redhat Style of init scripts to install
84 --with-session-socket-dir=dirname Where to put sockets for the per-login-session message bus
85 --with-test-socket-dir=dirname Where to put sockets for make check
86 --with-system-pid-file=pidfile PID file for systemwide daemon
87 --with-system-socket=filename UNIX domain socket for systemwide daemon
88 --with-console-auth-dir=dirname directory to check for console ownerhip
89 --with-dbus-user=<user> User for running the DBUS daemon (messagebus)
90 --with-gnu-ld assume the C compiler uses GNU ld [default=no]
91 --with-tags[=TAGS] include additional configurations [automatic]
92 --with-x use the X Window System
98 Now that D-Bus has reached version 1.0, the objective is that all
99 applications dynamically linked to libdbus will continue working
100 indefinitely with the most recent system and session bus daemons.
102 - The protocol will never be broken again; any message bus should
103 work with any client forever. However, extensions are possible
104 where the protocol is extensible.
106 - If the library API is modified incompatibly, we will rename it
107 as in http://ometer.com/parallel.html - in other words,
108 it will always be possible to compile against and use the older
109 API, and apps will always get the API they expect.
111 Interfaces can and probably will be _added_. This means both new
112 functions and types in libdbus, and new methods exported to
113 applications by the bus daemon.
115 The above policy is intended to make D-Bus as API-stable as other
116 widely-used libraries (such as GTK+, Qt, Xlib, or your favorite
117 example). If you have questions or concerns they are very welcome on
118 the D-Bus mailing list.
120 NOTE ABOUT DEVELOPMENT SNAPSHOTS AND VERSIONING
122 Odd-numbered minor releases (1.1.x, 1.3.x, 2.1.x, etc. -
123 major.minor.micro) are devel snapshots for testing, and any new ABI
124 they introduce relative to the last stable version is subject to
125 change during the development cycle.
127 Any ABI found in a stable release, however, is frozen.
129 ABI will not be added in a stable series if we can help it. i.e. the
130 ABI of 1.2.0 and 1.2.5 you can expect to be the same, while the ABI of
131 1.4.x may add more stuff not found in 1.2.x.
133 NOTE ABOUT STATIC LINKING
135 We are not yet firmly freezing all runtime dependencies of the libdbus
136 library. For example, the library may read certain files as part of
137 its implementation, and these files may move around between versions.
139 As a result, we don't yet recommend statically linking to
140 libdbus. Also, reimplementations of the protocol from scratch might
141 have to work to stay in sync with how libdbus behaves.
143 To lock things down and declare static linking and reimplementation to
144 be safe, we'd like to see all the internal dependencies of libdbus
145 (for example, files read) well-documented in the specification, and
146 we'd like to have a high degree of confidence that these dependencies
147 are supportable over the long term and extensible where required.
149 NOTE ABOUT HIGH-LEVEL BINDINGS
151 Note that the high-level bindings are _separate projects_ from the
152 main D-Bus package, and have their own release cycles, levels of
153 maturity, and ABI stability policies. Please consult the documentation