[SR-Users] why function result -1 cannot be assigned to variable?

[Juha Heinanen]

i have a local function x that returns a positive integer or -1.  when
it returns -1, assignment

$var(tmp) = function_x("$rd");

produces to syslog an error:

Feb 19 07:32:44 sip /usr/sbin/sip-proxy[27284]: ERROR: <core> [lvalue.c:411]: assignment failed at pos: (1415,40-1415,40)

i have had that function for years, but have not noticed these errors in
earlier versions than 3.1.

any ideas why the error is produced and how to get rid of it?

-- juha