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Subject: RE: Problem linking Mclennan stepper motor libraries into x86 IOC app
From: Peter Linardakis <[email protected]>
To: Andrew Johnson <[email protected]>, "[email protected]" <[email protected]>
Date: Sat, 9 Aug 2014 03:05:19 +0000
Thanks Andrew (and also Ron)

Moving the reference to the "Mclennan" lib to before that of "motor" fixes everything.  Seems I've been spending too much time coding in python to remember library linking details in the C family of languages.

Regards
Peter

-----Original Message-----
From: Andrew Johnson [mailto:[email protected]] 
Sent: Saturday, 9 August 2014 1:04 AM
To: Peter Linardakis; [email protected]
Subject: Re: Problem linking Mclennan stepper motor libraries into x86 IOC app

Hi Peter,

On 08/07/2014 10:00 PM, Peter Linardakis wrote:
> 
> # Add all the support libraries needed by this IOC tandem_LIBS += 
> anunuclear djrestore modbus tandem_LIBS += asyn std calc seq pv motor 
> softMotor devIocStats stream streamSynApps tandem_LIBS += tsdaqctl
> tandem_LIBS += Mclennan                            # ADDITION 2

> The result of a compilation via make is an error while trying to build 
> the x86 version, with output:

> /home/peter/epics/trunk/modules/motorR6-5-2/lib/linux-x86/libMclennan.a(drvPM304.o):
> In function `motor_init()':
> drvPM304.cc:(.text+0xa1f): undefined reference to `motor_task(thread_args*)'
> /home/peter/epics/trunk/modules/motorR6-5-2/lib/linux-x86/libMclennan.a(drvPM304.o):(.data.rel+0x24):
> undefined reference to `motor_send(mess_node*, driver_table*)'
> /home/peter/epics/trunk/modules/motorR6-5-2/lib/linux-x86/libMclennan.a(drvPM304.o):(.data.rel+0x28):
> undefined reference to `motor_free(mess_node*, driver_table*)'
...
> /home/peter/epics/trunk/modules/motorR6-5-2/lib/linux-x86/libMclennan.a(devPM304.o):(.data.rel+0x34):
> undefined reference to `motor_update_values(motorRecord*)'
> collect2: ld returned 1 exit status

The problem is that you added the McLennan library in the wrong place in the Makefile; the order of libraries in an xxx_LIBS variable is important, and in this case you just need to move the "tandem_LIBS += Mclennan" line to /above/ the line that mentions motor.

If you had any other motor drivers in the list then it might not have mattered (depending on whereabouts their libraries were listed) because they would have already pulled those motor routines into the binary, but as it is your new module is apparently the only thing that references those parts of the motor record, so the linker didn't link them into the output file when it processed the libmotor.a library. Static linking is normally done in one pass in the order given, so you must list your libraries in the order most-derived through to least-derived, which is why the $(EPICS_BASE_IOC_LIBS) libraries must come last.

HTH,

- Andrew
--
Advertising may be described as the science of arresting the human intelligence long enough to get money from it. -- Stephen Leacock


References:
Problem linking Mclennan stepper motor libraries into x86 IOC app Peter Linardakis
Re: Problem linking Mclennan stepper motor libraries into x86 IOC app Andrew Johnson

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