ccan dependencies seems to break external projects

[Jelmer Vernooij]

On 02/12/2012 06:57 PM, Matthieu Patou wrote:
> On 02/12/2012 04:52 AM, Jelmer Vernooij wrote:
>> On Sat, Feb 11, 2012 at 02:49:20PM -0800, Matthieu Patou wrote:
>>> I'm trying to compile openchange as described here : 
>>> http://tracker.openchange.org/projects/openchange/wiki/HowTo_Install_OpenChange_From_Source
>>>
>>> I'm using the latest git tree instead of alpha17, after a couple of
>>> tweak in the script that setup the prerequisits I have a samba4 with
>>> using system talloc/tdb/tevent and ldb.
>>>
>>> Then I try to build openchange and got:
>>>
>>>
>>> /usr/local/src/openchange$ make
>>> Linking sample application bin/libmapixx-test
>>> g++ -I.  -O3 -Wall -g3 -fstrict-aliasing -Wp,-D_FORTIFY_SOURCE=2
>>> -DHAVE_IMMEDIATE_STRUCTURES=1 -D_GNU_SOURCE=1
>>> -Wl,-rpath,/usr/local/samba/lib -I/usr/local/samba/include
>>>     -I/usr/local/samba/include   -I/usr/local/samba/include
>>> -I/usr/local/samba/include     -o bin/libmapixx-test
>>> libmapi++/tests/test.cpp libmapipp.so.0.11 libmapi.so.0
>>> .11 -Wl,-rpath,/usr/local/samba/lib -L/usr/local/samba/lib -ldcerpc
>>> -ldcerpc-binding -lndr -lsamba-hostconfig -lsamba-util -ltevent
>>> -ltalloc   -Wl,-rpath,/usr/local/samb
>>> a/lib -L/usr/local/samba/lib -lldb -ltalloc
>>> -Wl,-rpath,/usr/local/samba/lib -L/usr/local/samba/lib -ltalloc
>>> -lpthread
>>> /usr/local/samba/lib/libsmbconf.so.0: undefined reference to
>>> `hash_any at SAMBA_4.0.0ALPHA18_GIT_0B3A262'
>>>
>>>
>>> The hash_any symbol comes from the ccan library and is included in
>>> libsmbconf.so via source3/util/
>>>
>>> I suspect there is a symbols collision when you build samba 4 with
>>> system libs as ldb has its own version of ccan but obviously with a
>>> different version although it seems that ldb didn't directly need
>>> ccan (no ccan in the output of ldd libldb.so), the following command
>>> ls /usr/local/systemsamba/lib/ldb/libccan.so.0* output this:
>>>
>>> /usr/local/systemsamba/lib/ldb/libccan.so.0
>>> /usr/local/systemsamba/lib/ldb/libccan.so.0.1-init-1161-g661d41f
>>>
>>> There is no way to have a system ccan and it seems that there is no
>>> easy way to use the one built for ldb as the "system" ccan.
>>>
>>> I don't know what can be done, the cheapest is to have a
>>> source3/util not to depend on ccan if --disable-tdb2 was specified
>>> on the command line.
>> Does ccan really have to be a separate library? Its goal seems to be
>> the same as the 'samba-util' library.
>>
>> If I understand correctly ccan isn't really meant as a shared library
>> with utility functions but rather as a collection of C files that you
>> can pick a few useful ones from.
>>
>> Would it perhaps be possible to just include the relevant files from
>> ccan in libsamba-util?
> I'm not sure how this will fix the problem.
> Let say that we have ccan in samba-util, instead of depending on ccan, 
> ldb will depend on samba-util.
> It means if I understand well that we will have a libsambautil.so with 
> a version 1.4.1 (the version of ldb) but as it seems that we have no 
> way to use a system samba-util library when building samba4 will have 
> also a version of this library SAMBA_4.0.0ALPHA...
tdb can include whatever it needs from ccan in the same way as 
samba-util does (AFAIK it only uses a single macro from ccan at the moment).

ccan doesn't have a well-defined ABI. The problem with the way you're 
building ldb and Samba is that you end up with two versions of the ccan 
library - one which does have hash_any and one which doesn't. The linker 
only tries to load one and not the other, because it remembers it has 
already loaded ccan.

Another fix would be to define a specific set of functions to include in 
ccan and create an ABI.

Cheers,

Jelmer