Re: [lttng-dev] [PATCH v2] Improve tracef/tracelog to use the stack for small strings - Mathieu Desnoyers via lttng-dev

From: Mathieu Desnoyers via lttng-dev <lttng-dev@lists.lttng.org>
To: Norbert Lange <nolange79@gmail.com>
Cc: lttng-dev <lttng-dev@lists.lttng.org>
Subject: Re: [lttng-dev] [PATCH v2] Improve tracef/tracelog to use the stack for small strings
Date: Mon, 1 Aug 2022 11:24:27 -0400 (EDT)	[thread overview]
Message-ID: <1848659433.93617.1659367467800.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <CADYdroPCRa92zKoAQfB+DW4vte-srd4+w+=vbLZN_eqwdSXZMw@mail.gmail.com>

----- On Aug 1, 2022, at 10:44 AM, Norbert Lange via lttng-dev lttng-dev@lists.lttng.org wrote:
[...]
> 
> Any chance of not having to link liblttng-ust for the tracelog/tracef functions,
> like all other tracepoints (only hard dependency on liblttng-ust-tracepoint)?
> My involvement is limited to "complain-only" for that one, but think of
> how technically great that would be!

Here is how we could do this:

1) move the implementation of src/lib/lttng-ust/tracelog.c to its own .so, e.g.
   liblttng-ust-tracelog.so,
2) modify the tracelog/tracef public headers so they dlopen() this new .so from
   a library constructor, similarly to what tracepoint.h does.

We'd need to make sure the symbols from tracelog.c are still emitted in
liblttng-ust.so, _and_ have another version (with a prefix/suffix) emitted from
liblttng-ust-tracelog.so, so we don't break ABI.

Thoughts ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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