[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: dpkg-shlibdeps couldn't find library ... warning vs error



Thank you Guillem for your response.  I have a few followups that I have put 
inline below.

On Thursday, June 27, 2019 9:09:34 PM EDT Guillem Jover wrote:
> Hi!
> 
> On Wed, 2019-06-26 at 14:58:34 -0400, Crim, Christopher wrote:
> > I am trying to understand the regex rules in the function split_soname
> > from
> > dkpg-shlibdeps.pl.  Working with an old corporate code base that has yet
> > to
> > adopt any versioning, all of the shared objects are named <object>.so. 
> > When attempting to package on a box that does not yet have the dependent
> > packages installed dpkg-shlibdeps will throw warnings, "dpkg-shlibdeps:
> > warning: couldn't find library <lib>.so needed by ..." but packaging will
> > still succeed. We have few shared objects that have ".so." as part of
Just to be clear, an example name would be "libcom.foo.so.system.utility.so".  
The reason we had to add the domain prefix was that we were running into name 
collisions.  "libcom.bar.ss.pos.utility.so" would have conflicted with the 
above without the domains.
> > their name.  When dpkg- shlibdeps encounters these dependencies the
> > warning becomes an error, "dpkg- shlibdeps: error: couldn't find library
> > <lib>.so needed by ..." and packaging fails.  I traced this down to the
> > split_soname function which checks 2 regex comparisons.  The shared
> > objects that only throw warnings fall into the "else" clause of the
> > function.  The ones that fail fall into the first if clause which as
> > regex 1.  What were these regexs meant to match?
> 
> If the installed packages have no shlibs or symbols file information
> then dpkg-shlibdeps cannot know what dependency information to inject,
> which means the generated binaries will end up with missing/incorrect
> dependencies. See below for the distinction.
> 
> > regex 1 (/^(.*)\.so\.(.*)$/):
> > was this meant to capture shared objects with so number and revisons such
> > as libc.6 or libbz2.so.1.0.4?  If so, should the values after "so" be
> > restricted to numbers?
> 
> It cannot be restricted to numbers only because the version might
> include other characters.

I agree now, I did find some examples on my system:
libtidy.so.5deb1.6.0
libKPimSMTP.so.5.9.3.abi1

> 
> This format is the one used commonly for public and stable shared
> libraries, where the format is <name>.so.<version>, and then there's
> at least one symlink of the form <name>.so pointing to the former and
> used by other objects to link to, that gets them the latest <version>.
> 
> The key here is that the SONAME might only include part of the
> SOVERSION, depending on where the <name>.so symlink points to, so you
> could have:
> 
>   libfoo.so.1.2.3
>   libfoo.so.1
>   libfoo.so → libfoo.1
> 
> Because these are public interfaces they are expected to have
> dependency information available.
> 
> > regex 2 (/^(.*)-(\d.*)\.so$/)
> > The terminating so on this regex helps limit its capture but again should
> > the groups be limited to digits only?
> 
> This is the format commonly used for private and/or unstable shared
> libraries, where the whole version is encoded in the SONAME. So you
> could have:
I was not aware of this distinction.  A quick search did not point me to 
anything stating that.  Does this mean that libc on my machine is unstable? 
(libc-2.28.so)

> 
>   libbar-1.2.3.so
>   libbar.so → libbar-1.2.3.so (optionally, otherwise you might be
>                                required to specify the whole SONAME)
> 
> As these are private/unstable interfaces they are to be used at your
> own risk, so that's why they are just warnings.
These do not throw warnings though, they throw errors.  At link time, if the 
library depended on had an soname that name would be put in the NEEDED field.  
If the library depended on did not have an soname or any version info then the 
just the name would be in the NEEDED field.  
libfoo.so.1 will fail
libbar-1.2.3.so will fail
libbaz.so will just be a warning

So it can't be that dpkg-shlibdeps only wants to throw warnings for private/
unstable libraries and errors for everything else.  I guess this gets to the 
heart of my question, why is there a distinction.  If it cannot find a 
dependency should it just always fail?

> 
> >  I have tried searching for inforamtion related to to naming conventions
> >  for
> > 
> > shared library names but the best I can come up with is that they need to
> > be prefixed with "lib" and suffixed with ".so" and possibly the so number
> > and revision.  A name such as "libcom.debian.foo.bar.so" should be valid.
> >  If not I would appreciate being pointed to such requirements.
> 
> I'm not sure now, there's anywhere properly documenting these details.
> I don't think the debian-policy manual contains rationale for these.
> I've for now locallt documented the split_soname() function, willcheck
> whether one of the man pages can also be improved.
> 
> Hope that helps. Even though I'm not sure it resolved your issue at
> hand? :)
> 
> Thanks,
> Guillem

Attachment: signature.asc
Description: This is a digitally signed message part.


Reply to: