Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Jan Kiszka wrote:
>>> Gilles Chanteperdrix wrote:
>>>> Jan Kiszka wrote:
>>>>> Gilles Chanteperdrix wrote:
>>>>>> Jan Kiszka wrote:
>>>>>>> Gilles Chanteperdrix wrote:
>>>>>>>> Jan Kiszka wrote:
>>>>>>>>> Gilles Chanteperdrix wrote:
>>>>>>>>>> Jan Kiszka wrote:
>>>>>>>>>>> Gilles Chanteperdrix wrote:
>>>>>>>>>>>> GIT version control wrote:
>>>>>>>>>>>>> Module: xenomai-jki
>>>>>>>>>>>>> Branch: for-upstream
>>>>>>>>>>>>> Commit: 6b40653e9c3c4a2433bb4e91344fc378eb860f75
>>>>>>>>>>>>> URL:    
>>>>>>>>>>>>> http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=6b40653e9c3c4a2433bb4e91344fc378eb860f75
>>>>>>>>>>>>>
>>>>>>>>>>>>> Author: Jan Kiszka <jan.kis...@siemens.com>
>>>>>>>>>>>>> Date:   Wed Feb 10 13:24:29 2010 +0100
>>>>>>>>>>>>>
>>>>>>>>>>>>> Make xnarch_init_timeconv an uninlined weak function
>>>>>>>>>>>>>
>>>>>>>>>>>>> Otherwise the wrong set of time conversion variables might get
>>>>>>>>>>>>> initialized when using > 1 skin libraries.
>>>>>>>>>>>> If that would be possible, then it is the conversion variables 
>>>>>>>>>>>> which
>>>>>>>>>>>> should made be weak, not the function.
>>>>>>>>>>>>
>>>>>>>>>>>> The way I see it, the posix and native skins currently get a 
>>>>>>>>>>>> different
>>>>>>>>>>>> set of variables and functions, which works, but with your change, 
>>>>>>>>>>>> since
>>>>>>>>>>>> there is only one function, only one set of variable gets 
>>>>>>>>>>>> initialized by
>>>>>>>>>>>> the two function calls. And one skin just broke.
>>>>>>>>>>>>
>>>>>>>>>>>> Or am I missing something? Does the patch fix a problem you really 
>>>>>>>>>>>> had?
>>>>>>>>>>> Frankly, I wasn't able to test in the field yet as replacing the 
>>>>>>>>>>> libs
>>>>>>>>>>> there is non-trivial. But I was able to observe that only one set of
>>>>>>>>>>> functions is used - which is logical considering the weak marks. And
>>>>>>>>>>> this breaks due to the static inline initialization.
>>>>>>>>>>>
>>>>>>>>>>> However, let's mark both functions and variables weak to fix the 
>>>>>>>>>>> issue
>>>>>>>>>>> and avoid leaving unused variables around. Will update my patch in 
>>>>>>>>>>> a minute.
>>>>>>>>>> Ok. I am reverting this patch until you provide me with another
>>>>>>>>>> solution. It causes latency to segfault purely and simply at startup 
>>>>>>>>>> on
>>>>>>>>>> my dual PIII.
>>>>>>>>>>
>>>>>>>>> Cannot reproduce yet. Do you have a backtrace?
>>>>>>>> No. But the problem is probably the same as the one signaled by Henri,
>>>>>>>> a misplaced weak directive ending up in a symbol with no address at 
>>>>>>>> all.
>>>>>>>> Since the current situation works, I am going to wait for the "clean"
>>>>>>>> fix which puts some code/data in the src/skins/common directory.
>>>>>>>>
>>>>>>> Find it in my tree. But it's not yet well tested.
>>>>>> I do not like it either. Functions which are in src/skins/common should
>>>>>> still be weak, since this lib is included in all the skins libraries.
>>>>> Those functions are now in libxeno_common only, so I see no point in
>>>>> allowing them to be overloaded.
>>>> Yes, but libxeno_common is included in libpthread_rt.so and
>>>> libnative.so. So, if you link with both libraries, you get
>>>> libxeno_common twice.
>>>>
>>> Do we link libxeno_common statically? Otherwise, this conflict is not
>>> logical to me. Also, there are other symbols in bind.c that are non-weak.
>> libxeno_common is a "convenience library", which means that when
>> libpthread_rt.so is assembled, the object files from libxeno_common are
>> included.
> 
> BTW, what speaks against making it a dynamic library?

Complications. Currently the way of linking a native application is to do:

`xeno-config --ldflags` -lnative

Since when linking, the order matter, we can not hide this new library
in xeno-config --ldflags, so we would have to turn this into:

`xeno-config --ldflags` -lnative -lxeno-common

i.e. breaking user way of building applications. I do not think the gain
is worth the trouble: linking against only one xenomai library looks to
me like the most common case.


> 
>> I guess the loader eliminates the duplicates.
>>
> 
> It has to. For the same reason, we should be able to clean up
> skins/common/current.c now.

I am not that confident about that change. By using the weak directive,
we make sure that the same __thread variable is used for instance. If we
do not do that, what prevents the code from using the local symbols in
each library ? IOW, removing the duplicate could work for libxeno_common
symbols when invoked externally (which probably almost never happens),
but not inside the skin libraries. I do not know about that, which is
why I kept the weak declarations.

-- 
                                            Gilles.

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