This is a relatively minimal testcase illustrating a problem I'm having with LTTNG where I can define two providers, both in shared libraries, and only the first provider's events can be enabled - though it seems LTTNG knows about both of them. In particular, the message of the form:
Provider "XXX" accepted, version 1.0 is compatible with...
appears only for the one of the providers when LTTNG_UST_DEBUG=1 is set.
After some further analysis it seems that one of the providers' shared library is built with -fvisibility=hidden. Without a suitable __attribute__((visibility="xxx")) on the tracepoint-related symbols that provider's events won't be visible. This testcase reflects that situation.