Re: Get sub field of Union

[Marty Kraimer via Core-talk <core-talk@aps.anl.gov>]

I just tried using pvget with the PVRrestrictedUnion record from exampleCPP/database.

Just like your example it does work with

mrk> pvget -r value PVRrestrictedUnion
PVRrestrictedUnion structure
    union value
        (none)

But with

mrk> pvinfo PVRrestrictedUnion
PVRrestrictedUnion
Server: 10.0.0.19:5075
Type:
    epics:nt/NTUnion:1.0
        union value
            string string
            string[] stringArray
        time_t timeStamp
            long secondsPastEpoch
            int nanoseconds
            int userTag

mrk> pvget -r value.string PVRrestrictedUnion

It does not work and actually causes the IOC to crash.

Is it valid to ask for -r value.string?

Perhaps yes with the expectation that you will  find out if this is the current type of the value field.

If not you  could get valid error message.

Guobao,

Please create a issue in pvDatabaseCPP giving your original message.

Marty

On 3/21/19 11:43 AM, Shen, Guobao via Core-talk wrote:

Hi Core member,

Does anyone have experienced to read sub field of a Union structure?

For example, I have a record:

$ pvinfo Test:Data

…

structure

    uint ArrayId

    double[] Time

    union value

        float[] data1

        double[] data2

 

If I use

$ pvget -r value Test:Data

Test:Data

structure

    union value

        float[]  [-0.034794,-0.0417011, …]

 

But if I do it with:

$ pvget -r value.data1 Test:Data

 

I got an error on my client like

[Test: Data] failed to create channel get: Status [type=FATAL, message=std::bad_alloc]

 

Is that a right way to use it for union?

 

Thanks,

Guobao