Re: Add a common library

["Fabio M. Di Nitto" <fdinitto@xxxxxxxxxx>]

On 2/8/2012 5:31 AM, Fabio M. Di Nitto wrote:
> On 02/08/2012 01:43 AM, Angus Salkeld wrote:
>> Hi
>>
>> Here is a good idea IMO. But as-is will require a re-build of all
>> user applications.
>>
>> We currently have lots of inline functions in header files just to be shared
>> between corosync and the libraries. We also have the same functions
>> been implemented in both places. libqb has helped reduce this but the
>> problem still exists.
>>
>> Another unplesent issue is if we need to apply a fix to any of these
>> inline functions the user applications need to be rebuilt.
>>
>> So choose a rebuild now or multiple times down the line.
>>
>> -Angus
>>
>>
>> cc -o tcpg test/testcpg.c -Iinclude/corosync/ -lcpg
>> /usr/bin/ld: /tmp/ccnqIwOB.o: undefined reference to symbol 'cs_strerror'
>> /usr/bin/ld: note: 'cs_strerror' is defined in DSO /usr/lib64/libcorosync_common.so.4 so try adding it to the linker command line
>> /usr/lib64/libcorosync_common.so.4: could not read symbols: Invalid operation
>> collect2: ld returned 1 exit status
> 
> 
> This is a very good idea, but I think you get that error because libcpg
> is not correctly linked with libcorosync_common in the build system.
> 
> Using your example above, testcpg.c does not use cs_strerror directly.
> libcpg does. In that case libcpg needs to pull corosync_common.
> 
> I can see from the patch that you do link libcpg with common, but
> perhaps it's missing a simple bit somewhere that makes it fail.
> 
> also well done by updating the .pc files.
> 
> Either way +1 to rebuild everything now rather than later.

A rebuild of all application is not necessary. The final installed
result is correct.

Angus test was probably incorrect too.

This is how I tested it to verify that nothing breaks:

current rawhide:

yum install dlm

> [root@fedora-master-node2 coro]# ldd /usr/sbin/dlm_controld |grep corosync_common | wc -l
> 0

upgrade corosync with corosync_common lib,

> [root@fedora-master-node2 coro]# ldd /usr/sbin/dlm_controld |grep corosync_common | wc -l
> 1

note that dlm_controld has NOT been rebuilt at all.

tested at runtime, dlm_controld works just fine.

corosync_common is pulled in correctly from linking libcpg or any other
lib from corosync.

Given the above we can cleanup .pc files differently. libcorosync_common
should ship it´s .pc file and global template can Requires:
corosync_common (it is not strictly necessary). pkg-config can then
resolve the dependencies itself.

Fabio
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