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Re: libtool versioning

From: Ralf Wildenhues
Subject: Re: libtool versioning
Date: Mon, 3 May 2010 20:00:31 +0200
User-agent: Mutt/1.5.20 (2009-10-28)

Hello Jef,

* Jef Driesen wrote on Mon, May 03, 2010 at 09:08:14AM CEST:
> On 02/05/10 03:33, Bob Friesenhahn wrote:
> >On Sun, 2 May 2010, Jef Driesen wrote:
> >
> >>I'm trying to understand the libtool current:revision:age versioning scheme.
> >>I think I understand how it works, but I noticed that filename of the shared
> >>library seems to get different numbers (current-age.age.revision). Is that
> >>expected?
> >
> >The filename generation is dependent on the OS.  It is usually best
> >not to pay any attention to the filenames at all unless you are
> >switching from some other existing numbering scheme and need to avoid
> >a collision.  I keep these notes in my configure script (taken from
> >various libtool related documentation) so that I remember how things
> >work:
> The reason why I found the filename confusing, is because in the
> article I was looking at, they make it look like the libtool version
> c:r:a ends up in the filename as "".

I'm adding John in Cc:, he should be able to say more about this.

> I have seen this a couple of other places as well.

Like, the GNU Libtool manual?  Have you looked there?

> As a newbe to the
> libtool versionning scheme, it took me a while to figure out what
> was really going on. Very confusing.
> ># Here are a set of rules to help you update your library version
> ># information:
> >#
> >#  1. Start with version information of `0:0:0' for each libtool library.
> >#  2. Update the version information only immediately before a public
> >#     release of your software. More frequent updates are unnecessary, and
> >#     only guarantee that the current interface number gets larger faster.
> >#  3. If the library source code has changed at all since the last update,
> >#     then increment revision (`c:r:a' becomes `c:r+1:a').
> >#  4. If any interfaces have been added, removed, or changed since the last
> >#     update, increment current, and set revision to 0.
> >#  5. If any interfaces have been added since the last public release, then
> >#     increment age.
> >#  6. If any interfaces have been removed since the last public release,
> >#     then set age to 0.
> Shouldn't step #6 included "changed" as well as "removed"? If you
> change the interface (for example modifying function parameters),
> backwards compatibility is broken too. But only "removed" is listed
> here.

Well, it is listed in step 4 already.

> Personally, I think the last three steps are easier to understand
> when written as if cases, rather than steps:
> 1. Interface unchanged: C:R+1:A
> 2. Interface changed in a backwards compatible way: C+1:0:A+1
> 3. Interface changed and backwards compatibility is broken: C+1:0:0

The git master version of Libtool is hopefully a bit easier to
understand, it has an alternate description added, which is similar to


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