Re: totally confused by versioning system of libtool...

[Daniel Reed]

On Fri, 13 May 2005, Ed Hartnett wrote:
> Bob Friesenhahn <address@hidden> writes:
> > > That implies that when I install a new version, the old version says
> > > around. Is that correct?
> > Yes.  Unless it is explicitly deleted.
> Suppose that we discover a bug which doesn't require any API change to
> fix, but which will cause he users' computers to go into self-destruct
> mode, and catch on fire.
 ...
> But now, we have the additional option of deleting the version of the
> library file that contains the bug, during the install of the next
> version. Then, their applications would crash horribly. But at least
> their computer would not explode.

Do not simply delete the broken file, replace it.

If libexample-0.0.0, which installs as libexample.so.0, contains a bug, 
release a bug fix libexample-0.0.1, which will also install as 
libexample.so.0, replacing the broken version.

Programs that were running at the time of the upgrade will continue to use 
the buggy version (even if the file is removed from the directory 
hierarchy, it will be kept available for processes that had it open before 
it was removed).

Programs that start after the upgrade will automatically use the new 
version, with no relinking or explosions, horrible or otherwise.


Many projects will continue to make bug fix releases even if a newer API 
is currently under development--including Libtool itself. For this example 
scenario, if libexample-1.0.2 is the current release, but a critical bug 
is found in both it and libexample-0.0.5, then you can feel free to 
release libexample-0.0.6 and libexample-1.0.3 at the same time.

People using software that depends on libexample's 0 series will get the 
bug fix without having to rebuild or, worse, rewrite their software.

People using software that depends on libexample's 1 series should not be 
confused by the new release for the older 0 series, because 0.0.6 is still 
less than 1.0.anything. The only down side is that installing libexample 
0.0.6 might cause libexample.so to be re-pointed to libexample.so.0 and 
libexample 0's headers to overwrite libexample 1's headers, so software 
that is compiled after an upgrade might be forced to use the libexample 0 
API and ABI instead of libexample 1's (which would not necessarily cause 
explosions, just different-than-expected but still functional behavior). 
The next time the libexample 1 series was upgraded everything would go 
back to normal.

--
Daniel Reed <address@hidden>      http://naim-users.org/nmlorg/   
http://naim.n.ml.org/
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore all progress
depends on the unreasonable man. -- George Bernard Shaw