Re: softiIoc and softIocPVA incomplete on VxWorks (and others?)

["Johnson, Andrew N. via Core-talk" <core-talk at aps.anl.gov>]

Hi Dirk,

On Jun 9, 2021, at 3:35 AM, Zimoch Dirk (PSI) via Core-talk <core-talk at aps.anl.gov> wrote:

On VxWorks, softIoc.munch and softioc.PVA.munch are statically linked. As normal with static linkage, only those symbols actually used in the program are copied into the program. While this is usually totally sufficient, it becomes a problem when the statically linked program dynamically loads plugins as possible with 'dlload' (or 'ld' on VxWorks).
Those dynamically loaded plugins may use EPICS functions that are defined but not used in EPICS Base itself, resulting in load errors like this:
Warning: module 0x76a130 holds reference to undefined symbol epicsMessageQueueReceiveWithTimeout.

I have seen this on VxWorks only, as this is the only platform where I use static linkage with dynamic loading of modules. But I guess that other platforms may be affected as well. As I have never seen any complaints about this behavior, I may be the only one who uses softIoc this way.

Anyway, the problem is easy to fix, and I would appreciate to have the fix included future EPICS releases:
Add the linker flag -whole-archive when building softIoc/softIocPVA.
I have added PROD_LDFLAGS_vxWorks = --whole-archive to modules/database/src/std/softIoc/Makefile and modules/pva2pva/pdbApp/Makefile.
Maybe this or something similar (I don't know the corresponding Windows linker flag) should be done not only for VxWorks but for all statically built versions.

Is there a recent change that has caused this, or has it always been a problem?

Could you instead try adding the --whole-archive flag to either MUNCH_LDFLAGS or OP_SYS_LDFLAGS in your Base configure/os/CONFIG_SITE.Common.vxWorksCommon file. It’s only your site which needs that flag, and I don’t know what effect it will have on the memory needed by our VxWorks IOCs (APS does not use dynamic loading of plugins on any IOC architecture).

- Andrew

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