Experimental Physics and
Industrial Control System

Andrew Johnson via Core-talk <core-talk at aps.anl.gov> · Mon, 11 Oct 2021 18:13:42 -0000

** Changed in: epics-base
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1938459

Title:
  int64in only checks lower 32 bits for change

Status in EPICS Base:
  Fix Released

Bug description:
  Create an int64in record and write these values
  (example uses bash to convert hex into decimal since caput cannot directly handle hex?):

  caput sixtyfour $(( 16#FF ))
  Old : sixtyfour                      0
  New : sixtyfour                      255

  caput sixtyfour $(( 16#87654321 ))
  Old : sixtyfour                      255
  New : sixtyfour                      2.27156e+09

  caput sixtyfour $(( 16#32187654321 ))
  Old : sixtyfour                      2.27156e+09
  New : sixtyfour                      3.44254e+12

  A camonitor will show 255, then 2.27156e+09, but not 3.44254e+12. A
  caget or a newly started camonitor will see the latest value.

  Reason is this section in int64inRecord.c:

  /* DELTA calculates the absolute difference between its arguments
   * expressed as an unsigned 32-bit integer */
  #define DELTA(last, val) \
      ((epicsUInt32) ((last) > (val) ? (last) - (val) : (val) - (last)))

  It only checks for changes in the lower 32 bits of the value.
  Maybe the motivation was to always perform an _unsigned_ comparison, but "UInt32" was copy/pasted instead of "UInt64"?

  One fix should be to replace epicsUInt32 with epicsUInt64 in DELTA and
  where it's used.

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System