Bug #311

Compatibility issue between liblttng-ust stable-2.0 and master

Added by Mathieu Desnoyers about 8 years ago. Updated about 8 years ago.

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11:42 < Compudj> that's a weird scenario
11:43 < Compudj> you had you app linked with liblttng-ust 2.0.4, generating
packet headers with the uin32_t field
11:43 < Compudj> but the lttng-consumerd you have is probably linked with
liblttng-ust master
11:44 < Compudj> which has generated unsigned long (64-bit) fields when
flushing the last packets of each buffer
11:47 < Compudj> so it falls into compatibility issues between liblttng-ust
stable-2.0 and master, in the case the consumer is linked to a
newer version

11:52 < Compudj> we don't want to break compatibility between UST and
lttng-tools in the 2.x series, not without a deprecation phase
11:52 < Compudj> so I have to find a fix
11:53 < Compudj> I'm wondering, in terms of library versioning, if I should
bump the master branch UST lib version
11:54 < Compudj> then I could pass, for each stream, which UST version they
belong to (to the consumer)
11:54 < Compudj> and let the consumer use compatibility mode for older streams


Updated by Mathieu Desnoyers about 8 years ago

  • Status changed from Confirmed to Resolved

Fixed by bumping an "internal version" number for UST to 3.0.0. Therefore, lttng-sessiond 2.1 will reject UST 2.0 (internal version number 2.x), and lttng-sessiond 2.0 will reject UST 2.1 (internal version number 3.x).

lttng-ust commit:

commit 0f4eaec3e738fa0f33296a46fe08266a60787c23
Author: Mathieu Desnoyers <>
Date: Fri Aug 17 15:26:59 2012 -0400

ABI change: bump internal version to 3.0.0
We keep compatiblity with applications (so we're still in the 2.x
versions), but we are breaking compatibility with lttng-consumerd.
Therefore, push the internal version number to 3.0.0.
Signed-off-by: Mathieu Desnoyers &lt;&gt;

lttng-tools commit:

commit aee0cea039d432fc5f5186dfaf102074562591e1
Author: David Goulet <>
Date: Fri Aug 17 15:23:09 2012 -0400

Fix: UST app major version check


commit 68264071f9d1b789de1350cbec479b52a9b54acf
Author: David Goulet <>
Date: Fri Aug 17 15:50:00 2012 -0400

Update version to v2.1.0-rc1
Bump internal UST major version.
Fix comments and debug output to follow this change.
Signed-off-by: David Goulet &lt;&gt;

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