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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