Re: EPICS database Feature request

[Andrew Johnson <anj@aps.anl.gov>]

Hi Emmanuel,

On 06/06/2014 11:49 AM, Emmanuel Mayssat wrote:
> My goal is also to have this feature supported and be part of the
> epics-base.
> The feature I am asking for is very close to what the alias directive is
> doing.

Something like this could be added (in 3.15 or later, not 3.14 which is
now feature-frozen) quite easily. It would have to re-use the existing
syntax for setting field values though, say allowing a "*" meaning
"whatever" for the record type name when the record must already exist:

record("*", "myAO") {
   field(VAL, "21")
   field(FLNK, "AnotherAO.PROC")
}

That actually only requires a small change to the dbRecordHead() routine
in dbStaticLib to implement, the patch below adds that functionality to
Base-3.15:

=== modified file 'src/ioc/dbStatic/dbLexRoutines.c'
--- src/ioc/dbStatic/dbLexRoutines.c    2014-06-04 19:18:43 +0000
+++ src/ioc/dbStatic/dbLexRoutines.c    2014-06-06 18:01:38 +0000
@@ -931,6 +932,21 @@
     if (ellCount(&tempList))
         yyerrorAbort("dbRecordHead: tempList not empty");
     allocTemp(pdbentry);
+
+    if (recordType[0] == '*' && recordType[1] == 0) {
+        if (dbRecordsOnceOnly)
+            epicsPrintf("Record-type \"*\" not valid with
dbRecordsOnceOnly\n");
+        else {
+            status = dbFindRecord(pdbentry, name);
+            if (status == 0)
+                return; /* done */
+            epicsPrintf("Record \"%s\" not found\n", name);
+        }
+        yyerror(NULL);
+        duplicate = TRUE;
+        return;
+    }
+
     status = dbFindRecordType(pdbentry, recordType);
     if (status) {
         epicsPrintf("Record \"%s\" is of unknown type \"%s\"\n",

I'm not going to provide a patch against 3.14, but it wouldn't be hard
to add the same code there which ought to work...


I don't like the idea that this would silently ignore the new field
values if the named record does not exist though, that strikes me as
rather dangerous; is it essential for your situation? It triggers an
error in the above implementation:

tux% ./bin/linux-x86_64/softIoc -d ~/db/star.db
Record "nonexistent" not found
Error at or before ")" in file "/home/anj/db/star.db" line 11

If there are no complaints I will commit this change to the 3.15 branch.

- Andrew
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