Hi hackers,
I found a small bug in commit e2f289e5b9b ("Make many cast functions error safe").
In timestamptz_date(), the SOFT_ERROR_OCCURRED() check mistakenly
uses fcinfo->args instead of fcinfo->context:
result = timestamptz2date_safe(timestamp, fcinfo->context);
if (SOFT_ERROR_OCCURRED(fcinfo->args)) /* should be fcinfo->context */
PG_RETURN_NULL();
fcinfo->args is a NullableDatum[] array, not a Node *. The
SOFT_ERROR_OCCURRED macro casts its argument to Node * and reads
the NodeTag field. When given fcinfo->args, it interprets the first
argument's Datum value (a TimestampTz) as a NodeTag, which will
almost never match T_ErrorSaveContext. This causes the soft error
check to always evaluate to false.
As a result, when the timestamptz-to-date conversion encounters an
overflow in error-safe mode, the function returns a wrong date value
instead of the expected NULL.
All three sibling functions modified in the same commit (date_timestamp,
timestamp_date, date_timestamptz) correctly use fcinfo->context.
This appears to be a copy-paste oversight.
The fix is a one-line change: fcinfo->args → fcinfo->context.
