Re: Add a common library

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

On 2/8/2012 2:52 PM, Steven Dake wrote:
> On 02/07/2012 05:43 PM, 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
>>
>>
> 
> Angus,
> 
> I know we had talked about a static library and linking that into each
> so.  I had some concerns about symbol collisions.  I tested that out,
> and it seems to work.  I'd prefer that approach to requiring the need of
> a separate -lcorosync_common.  I'll send my patch to the list so you can
> see what I did.  I'll also send my test program linked against cpg and cmap.

How do you get symbol collisions?

Assuming you are upgrading from version X to X+1, the symbols will
simply move from static inline to the share object. Specially in this
case where the application is not affected directly.

application -> libfoo (with static inline)
application -> libfoo -> libcommon

Even in a downgrade case, libcorosync_common would not be referenced by
any of the libraries.

I don´t have a strong opinion here, but I would prefer to have it a
shared lib. We had some nasty issues with static before (ask Jan how
long it took for him to debug that handle_ corruption when linking static).

Fabio
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