Experimental Physics and
Industrial Control System

Andrew Johnson via Core-talk <core-talk at aps.anl.gov> · Tue, 26 Jul 2022 17:20:32 -0000

@mdavidsave correct, pnRequest must never be NULL since (unless you pass
in a bad dbrType) it will always be dereferenced to populate
parser->elems and will be written to if the parse succeeds.

Could the two "if (status == S_db_badField)" tests in dbConstLink.c
become just "if (status)" please, since we'd almost certainly want the
same context message to be printed for any other error status values get
returned from the same routine. Add a space after the ellipsis in each
message perhaps?

With those suggestions this looks good to me, thanks!

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https://bugs.launchpad.net/bugs/1982847

Title:
  cryptic error message "parse error: premature EOF"

Status in EPICS Base:
  New

Bug description:
  In EPICS 7, if an array input link (e.g. waveform.INP) is an explicit
  empty string, the parser prints a cryptic message without any helpful
  context.

  Example:
  record(waveform, "x")
  {
      field(INP, "")
  }

  dbConvertJSON: parse error: premature EOF

                       (right here) ------^

  Not very enlightening.

  It does not happen if INP is not set at all and it does not happen at least up to R3.16.1 but at least since 7.0.4.1 (I have not tested anything in between) and up to commit d82ab81.
  It also does not happen with scalar input links (e.g. ai.INP).

  First of all, any parser error should print a context (I prefer record.field) similar to this:
  dbConvertJSON: parse error: premature EOF in x.INP

  Unfortunately, dbPutConvertJSON (the function printing the
  dbConvertJSON message) does not have the context. All it has is the
  string. So maybe it should not print the message at all but leave it
  to the caller. The only callers are in dbConstLink.c. The interface
  should be modified to pass either the context (plink instead of
  plink->value.constantStr) or the error message (which is complicated)
  or an additional message should be printed by the outer context
  (difficult to find out when dbPutConvertJSON actually printed an error
  message).

  Second, passing "" should not result in an error at all.

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System