[ltt-dev] UST communication library

Alexandre Montplaisir alexandre.montplaisir at polymtl.ca
Wed Jun 15 15:11:31 EDT 2011

On 11-06-15 01:16 PM, Mathieu Desnoyers wrote:
> * Yannick Brosseau (yannick.brosseau at gmail.com) wrote:
>> Changing an dependency from UST to ustcomm is not
>> removing any dependency, its just adding one more and it makes it harder
>> to maintain.
> It removes the dependency from:
> lttng-tools ->  libust
> by splitting the dependency chain like this:
> lttng-tools ->  ustcomm
> libust ->  ustcomm
> So this part of your argumentation does not hold: we are in fact
> removing a dependency from lttng-tools to libust by creating a separate
> "ustcomm" package/lib/header.

I've been wondering, why is the lttng-tools -> libust dependency so "bad" ?

And what changes by moving to lttng-tools -> libustcomm ? That is still 
asking people to compile/install another library before installing 

> [...]
> So basically, my point is that we should design this so we can do
> changes in the API between libust and the applications without requiring
> *all* applications to upgrade to the new libust to stay compatible with
> lttng-tools.

libtool takes care of this. And even if they are part of the same source 
tarball / git tree, libust and libustcomm can each have their own 
libtool version number.

Obviously you decide ;)  but I agree with Yannick : if libustcomm does 
not provide any functionality of its own, it shouldn't be isolated. A 
case where it would make sense to have a separate library is if you want 
to export the "UST protocol" to other applications so they can use that 
protocol outside of libust and lttng-tools. This do not seem to be the 
case, at least for now.

> Thanks,
> Mathieu

Alexandre Montplaisir
École Polytechnique de Montréal

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