plpgsql's exec_assign_value() freed the old value of a variable before

copying/converting the new value, which meant that it failed badly on
"var := var" if var is of pass-by-reference type.  Fix this and a similar
hazard in exec_move_row(); not sure that the latter can manifest before
8.0, but patch it all the way back anyway.  Per report from Dave Chapeskie.

diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index b6d6df21c23896b58d442565d896a548d5fc191d..0aff35752aa18546ebe6bdcd837d2c341b5765e8 100644 (file)
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -3,7 +3,7 @@
  *                       procedural language
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.52.2.1 2002/03/25 07:41:21 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.52.2.2 2005/06/20 20:45:12 tgl Exp $
  *
  *       This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -2665,12 +2665,6 @@ exec_assign_value(PLpgSQL_execstate * estate,
                         */
                        var = (PLpgSQL_var *) target;
 
-                       if (var->freeval)
-                       {
-                               pfree((void *) (var->value));
-                               var->freeval = false;
-                       }
-
                        newvalue = exec_cast_value(value, valtype, var->datatype->typoid,
                                                                           &(var->datatype->typinput),
                                                                           var->datatype->typelem,
@@ -2690,23 +2684,28 @@ exec_assign_value(PLpgSQL_execstate * estate,
                        if (!var->datatype->typbyval && !*isNull)
                        {
                                if (newvalue == value)
-                               {
-                                       int                     len;
+                                       newvalue = datumCopy(newvalue,
+                                                                                false,
+                                                                                var->datatype->typlen);
+                       }
 
-                                       if (var->datatype->typlen < 0)
-                                               len = VARSIZE(newvalue);
-                                       else
-                                               len = var->datatype->typlen;
-                                       var->value = (Datum) palloc(len);
-                                       memcpy((void *) (var->value), (void *) newvalue, len);
-                               }
-                               else
-                                       var->value = newvalue;
-                               var->freeval = true;
+                       /*
+                        * Now free the old value.  (We can't do this any earlier
+                        * because of the possibility that we are assigning the
+                        * var's old value to it, eg "foo := foo".  We could optimize
+                        * out the assignment altogether in such cases, but it's too
+                        * infrequent to be worth testing for.)
+                        */
+                       if (var->freeval)
+                       {
+                               pfree(DatumGetPointer(var->value));
+                               var->freeval = false;
                        }
-                       else
-                               var->value = newvalue;
+
+                       var->value = newvalue;
                        var->isnull = *isNull;
+                       if (!var->datatype->typbyval && !*isNull)
+                               var->freeval = true;
                        break;
 
                case PLPGSQL_DTYPE_RECFIELD:
@@ -3145,6 +3144,14 @@ exec_move_row(PLpgSQL_execstate * estate,
         */
        if (rec != NULL)
        {
+               /*
+                * copy input first, just in case it is pointing at variable's value
+                */
+               if (HeapTupleIsValid(tup))
+                       tup = heap_copytuple(tup);
+               if (tupdesc)
+                       tupdesc = CreateTupleDescCopy(tupdesc);
+
                if (rec->freetup)
                {
                        heap_freetuple(rec->tup);
@@ -3158,8 +3165,8 @@ exec_move_row(PLpgSQL_execstate * estate,
 
                if (HeapTupleIsValid(tup))
                {
-                       rec->tup = heap_copytuple(tup);
-                       rec->tupdesc = CreateTupleDescCopy(tupdesc);
+                       rec->tup = tup;
+                       rec->tupdesc = tupdesc;
                        rec->freetup = true;
                        rec->freetupdesc = true;
                }