dynamic linker in RTEMS 5 ?

[Till Straumann]

I think it would not be very difficult to add support for dlopen to cexpsh.

On 12/19/2017 03:47 PM, Chris Johns wrote:
> On 19/12/2017 23:44, Goetz Pfeiffer wrote:
>> at the Helmholtz-Zentrum Berlin we control an electron storage ring facility
>> with the EPICS controlsystem framework.
>>
>> We have about 20 mvme2100 VME CPU boards which run RTEMS 4.9 with
>> cexp and GeSys.
> This sounds like a nice system.
>
>> We would like to use RTEMS 5 but cexp is not compatible with this version.
>>
>> We are looking for the following features in RTEMS 5:
>>
>>    * dynamic loading of object files
>>    * dynamic linking of objects
>>    * calling functions on the command line (optional)
>>
>> With cexp and RTEMS 4.9, dynamic loading works like this in the startup script:
>>
>>    cexpModuleLoad("Com.obj")
>>    cexpModuleLoad("ca.obj")
>>    cexpModuleLoad("dbStaticIoc.obj")
>>    cexpModuleLoad("registryIoc.obj")
>>    cexpModuleLoad("dbIoc.obj")
>>     ...
> The cexp C parser and caller is not present. I also suspect other alternatives
> such as another language like lua would not help because your existing scripts
> would need to change as well as the related documentation.
>
>> Is it possible to implement a dynamic linker in RTEMS 5 ? It seems that
>> dynamic loading with dl_open(), dl_sym() and dl_close() is already
>> implemented.
> Dynamic loading is present. I am not across all the features cexp provides so I
> cannot be 100% certain there is a complete match. For example the dlopen API
> currently does not search archives to automatically pull in dependences. I
> avoided this when I first implemented libdl and I now think this feature should
> be added.
>
>> In another mail it was suggested to adapt cexp for RTEMS 5 but it seems
>> that this product is too hard to maintain and too hardware dependent.
> This is understandable.
>
>> We think that it would make RTEMS even more attractive, if it would
>> incorporate a dynamic loader.
> Do you mean bringing cexp into RTEMS and making it use the libdl loader?
>
> Any work to help ease EPICS integration and maintenance is a good thing.
>
>> It would be a great alternative to vxWorks.
> I suspect there are other users with this issue. It would be good to have an
> easy upgrade path to RTEMS 5.
>
> Chris
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