Documentation: document undefined behavior for NULL pointers

[lttng-ust.git] / README

diff --git a/README b/README
index ad9acd77b5664753b5947d5fe9c4c2a3ffa1f73c..dadcd1f5ac5f91975d904cf6d6644c460fe1c0e0 100644 (file)
--- a/README
+++ b/README
@@ -1,12 +1,11 @@
 LTTNG USERSPACE TRACER (LTTng-UST)
 ----------------------------
 
-UST web site: http://lttng.org/lttng2.0
+UST web site: http://lttng.org
 
 Updated versions of this package may be found at:
 
-  * Website:  http://lttng.org/lttng2.0
-  * Releases: http://lttng.org/files/lttng-ust
+  * Releases: http://lttng.org/download
   * GitWeb:   http://git.lttng.org (project: lttng-ust)
   * Git:      git://git.lttng.org/lttng-ust.git
 
@@ -16,7 +15,7 @@ PREREQUISITES:
   - liburcu
     Userspace RCU library, by Mathieu Desnoyers and Paul E. McKenney
 
-    -> This release depends on liburcu v0.6.6
+    -> This release depends on liburcu v0.7.2
 
       * Debian/Ubuntu package: liburcu-dev
       * Website:  http://lttng.org/urcu
@@ -34,6 +33,8 @@ compile the git repository tree :
   (make sure your system wide "automake" points to a recent version!)
 - GNU Libtool >=2.2
   (for more information, go to http://www.gnu.org/software/autoconf/)
+- Perl (optional)
+  Needed for make check and tests.
 
 If you get the tree from the repository, you will need to use the "bootstrap"
 script in the root of the tree. It calls all the GNU tools needed to prepare the
@@ -67,15 +68,15 @@ USAGE:
       "TRACEPOINT_DEFINE" and include the tracepoint provider.
     - Use "-I." for the compilation unit containing the tracepoint
       provider include (e.g. tp.c).
-    - Link application with "-ldl".
+    - Link application with "-ldl" on Linux, with "-lc" on BSD.
     - If building the provider directly into the application,
       link the application with "-llttng-ust".
     - If building a static library for the provider, link the static
-      library with "-lllttng-ust".
+      library with "-llttng-ust".
     - Include the tracepoint provider header into all C files using
       the provider.
     - Example:
-        tests/hello/  hello.c tp.c ust_tests_hello.h Makefile.example
+      - tests/hello/  hello.c tp.c ust_tests_hello.h Makefile.example.*
 
   2) Compile the Tracepoint Provider separately from the application,
      using dynamic linking:
@@ -87,7 +88,7 @@ USAGE:
       files that use the provider.
     - Compile the tracepoint provider with "-I.".
     - Link the tracepoint provider with "-llttng-ust".
-    - Link application with "-ldl".
+    - Link application with "-ldl" on Linux, "-lc" on BSD.
     - Set a LD_PRELOAD environment to preload the tracepoint provider
       shared object before starting the application when tracing is
       needed. Another way is to dlopen the tracepoint probe when needed
@@ -97,6 +98,10 @@ USAGE:
 
   - Enable instrumentation and control tracing with the "lttng" command
     from lttng-tools. See lttng-tools doc/quickstart.txt.
+  - Note about dlclose() usage: it is not safe to use dlclose on a
+    provider shared object that is being actively used for tracing due
+    to a lack of reference counting from lttng-ust to the used shared
+    object.
 
 ENVIRONMENT VARIABLES:
 
@@ -113,10 +118,14 @@ ENVIRONMENT VARIABLES:
     recommended for applications with time constraints on the process
     startup time.
 
+  - The compilation flag "-DLTTNG_UST_DEBUG_VALGRIND" should be enabled
+    at build time to allow liblttng-ust to be used with valgrind
+    (side-effect: disables per-cpu buffering).
+
 
 TRACE VIEWER:
 
-  Use babeltrace for viewing traces generated by LTTng UST 2.0.
+  Use babeltrace for viewing traces generated by LTTng UST 2.x.
   See http://lttng.org for download.