5 The LTTng User Space Tracing (LTTng-UST) library allows any C/C++
6 application to be instrumented for and traced by
7 [LTTng](http://lttng.org/). LTTng-UST also includes a logging
8 back-end for Java applications and various dynamically loadable
9 user space tracing helpers for any application.
15 LTTng-UST depends on **[liburcu](http://liburcu.org/) >= 0.12** at build
16 time. It also optionally depends on libnuma.
24 This source tree is based on the Autotools suite from GNU to simplify
25 portability. Here are some things you should have on your system in order to
26 compile the Git repository tree:
28 - [GNU Autotools](http://www.gnu.org/software/autoconf/)
29 (**Automake >= 1.12**, **Autoconf >= 2.69**,
30 **Autoheader >= 2.69**;
31 make sure your system-wide `automake` points to a recent version!)
32 - **[GNU Libtool](https://www.gnu.org/software/libtool/) >= 2.2**
33 - **[pkg-config](https://www.freedesktop.org/wiki/Software/pkg-config/)**
36 ### Optional dependencies
38 Optional packages to build LTTng-ust man pages:
40 - **[AsciiDoc](http://www.methods.co.nz/asciidoc/) >= 8.4.5**
41 (previous versions may work, but were not tested)
42 - **[xmlto](https://fedorahosted.org/xmlto/) >= 0.0.21** (previous
43 versions may work, but were not tested)
45 Note that the man pages are already built in a distribution tarball.
46 In this case, you only need AsciiDoc and xmlto if you indend to modify
47 the AsciiDoc man page sources.
49 Needed for `make check` and tests:
51 - **[Perl](https://www.perl.org/)**
56 If you get the tree from the Git repository, you will need to run
60 in its root. It calls all the GNU tools needed to prepare the tree
63 To build LTTng-UST, do:
70 **Note:** the `configure` script sets `/usr/local` as the default prefix for
71 files it installs. However, this path is not part of most distributions'
72 default library path, which will cause builds depending on `liblttng-ust`
73 to fail unless `-L/usr/local/lib` is added to `LDFLAGS`. You may provide a
74 custom prefix to `configure` by using the `--prefix` switch
75 (e.g., `--prefix=/usr`). LTTng-UST needs to be a shared library, _even if_
76 the tracepoint probe provider is statically linked into the application.
82 First of all, create an instrumentation header following the
83 [tracepoint examples](doc/examples).
85 There are two ways to compile the tracepoint provider and link it with
86 your application: statically or dynamically. Please follow carefully one
92 This method links the tracepoint provider with the application,
93 either directly or through a static library (`.a`):
95 1. Into exactly one unit (C/C++ source file) of your _application_,
96 define `LTTNG_UST_TRACEPOINT_DEFINE` and include the tracepoint provider
98 2. Include the tracepoint provider header into all C/C++ files using
99 the provider and insert tracepoints using the `tracepoint()` macro.
100 3. Use `-I.` when compiling the unit defining `LTTNG_UST_TRACEPOINT_DEFINE`
102 4. Link the application with `-ldl` on Linux, or with `-lc` on BSD,
103 and with `-llttng-ust`.
109 gcc -c other-source.c
110 gcc -o my-app tp.o some-source.o other-source.o -ldl -llttng-ust
112 Run the application directly:
116 Other relevant examples:
118 - [`doc/examples/easy-ust`](doc/examples/easy-ust)
119 - [`doc/examples/hello-static-lib`](doc/examples/hello-static-lib)
124 This method decouples the tracepoint provider from the application,
125 making it dynamically loadable.
127 1. Into exactly one unit of your _application_, define
128 `LTTNG_UST_TRACEPOINT_DEFINE` _and_ `LTTNG_UST_TRACEPOINT_PROBE_DYNAMIC_LINKAGE`,
129 then include the tracepoint provider header.
130 2. Include the tracepoint provider header into all C/C++ files using
131 the provider and insert tracepoints using the `tracepoint()` macro.
132 3. Use `-I.` and `-fpic` when compiling the tracepoint provider
134 4. Link the tracepoint provider with `-llttng-ust` and make it a
135 shared object with `-shared`.
136 5. Link the application with `-ldl` on Linux, or with `-lc` on BSD.
140 gcc -c -I. -fpic tp.c
141 gcc -o tp.so -shared tp.o -llttng-ust
142 gcc -o my-app some-source.c other-source.c -ldl
144 To run _without_ LTTng-UST support:
148 To run with LTTng-UST support (register your tracepoint provider,
151 LD_PRELOAD=./tp.so ./my-app
153 You could also use `libdl` directly in your application and `dlopen()`
154 your tracepoint provider shared object (`tp.so`) to make LTTng-UST
157 Other relevant examples:
159 - [`doc/examples/demo`](doc/examples/demo)
162 ### Controlling tracing and viewing traces
164 Use [LTTng-tools](https://lttng.org/download) to control the tracer.
165 Use [Babeltrace](https://lttng.org/babeltrace) to print traces as a
166 human-readable text log.
169 ### Environment variables and compile flags
171 - `liblttng-ust` debug can be activated by setting the environment
172 variable `LTTNG_UST_DEBUG` when launching the user application. It
173 can also be enabled at build time by compiling LTTng-UST with
175 - `liblttng-ust` abort on critical can be activated by setting the
176 environment variable `LTTNG_UST_ABORT_ON_CRITICAL` when launching the user
177 application. It can also be enabled at build time by compiling LTTng-UST with
178 `-DLTTNG_UST_ABORT_ON_CRITICAL`.
179 - The environment variable `LTTNG_UST_REGISTER_TIMEOUT` can be used to
180 specify how long the applications should wait for the session
181 daemon _registration done_ command before proceeding to execute the
182 main program. The default is 3000 ms (3 seconds). The timeout value
183 is specified in milliseconds. The value 0 means _don't wait_. The
184 value -1 means _wait forever_. Setting this environment variable to 0
185 is recommended for applications with time constraints on the process
187 - The compilation flag `-DLTTNG_UST_DEBUG_VALGRIND` should be enabled
188 at build time to allow `liblttng-ust` to be used with Valgrind
189 (side-effect: disables per-CPU buffering).
196 Since LTTng-UST 2.3, both tracepoints and tracepoint providers can be
197 compiled in C++. To compile tracepoint probes in C++, you need
198 G++ >= 4.7 or Clang >= 4.0. The C++ compilers need to support C++11.
204 Maintainer: [Mathieu Desnoyers](mailto:mathieu.desnoyers@efficios.com)
206 Mailing list: [`lttng-dev@lists.lttng.org`](https://lttng.org/cgi-bin/mailman/listinfo/lttng-dev)
212 This package contains the following elements:
214 - `doc`: LTTng-UST documentation and examples.
215 - `include`: the public header files that will be installed on the
217 - `liblttng-ust`: the actual userspace tracing library that must be
218 linked to the instrumented programs.
219 - `liblttng-ust-comm`: a static library shared between `liblttng-ust`
220 and LTTng-tools, that provides functions that allow these components
221 to communicate together.
222 - `liblttng-ust-ctl`: a library to control tracing in other processes;
224 - `liblttng-ust-cyg-profile`: a library that can be preloaded (using
225 `LD_PRELOAD`) to instrument function entries and exits when the target
226 application is built with the GCC flag `-finstrument-functions`.
227 - `liblttng-ust-dl`: a library that can be preloaded to instrument
228 calls to `dlopen()` and `dlclose()`.
229 - `liblttng-ust-fork`: a library that is preloaded and that hijacks
230 calls to several system calls in order to trace across these calls.
231 It _has_ to be preloaded in order to hijack calls. In contrast,
232 `liblttng-ust` may be linked at build time.
233 - `liblttng-ust-java`: a simple library that uses JNI to allow tracing
234 in Java programs. (Configure with `--enable-jni-interface`).
235 - `liblttng-ust-java-agent`: a package that includes a JNI library and a
236 JAR library to provide an LTTng-UST logging back-end for Java
237 applications using Java Util Logging or Log4j. (Configure with
238 `--enable-java-agent-jul` or `--enable-java-agent-log4j` or
239 `--enable-java-agent-log4j2` or `--enable-java-agent-all`).
240 - `liblttng-ust-libc-wrapper`: an example library that can be
241 preloaded to instrument some calls to libc (currently `malloc()` and
242 `free()`) and to POSIX threads (mutexes currently instrumented) in
243 any program without need to recompile it.
244 - `liblttng-ust-python-agent`: a library used by python-lttngust to allow
245 tracing in Python applications. (Configure with `--enable-python-agent`)
246 - `libringbuffer`: the ring buffer implementation used within LTTng-UST.
247 - `python-lttngust`: a package to provide an LTTng-UST logging back-end
248 for Python applications using the standard logging framework.
249 - `snprintf`: an asynchronous signal-safe version of `snprintf()`.
250 - `tests`: various test programs.
251 - `tools`: home of `lttng-gen-tp`.