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 247039c639654c49937ee3a2818b48dcd26c7da2..facdbe3e8affc2795c4afd44a7696ad77d7398b0 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
- *   $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.127.4.1 2005/02/01 19:35:29 tgl Exp $
+ *   $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.127.4.2 2005/06/20 20:44:50 tgl Exp $
  *
  *   This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -2835,12 +2835,6 @@ exec_assign_value(PLpgSQL_execstate *estate,
                             errmsg("NULL cannot be assigned to variable \"%s\" declared NOT NULL",
                                    var->refname)));
 
-               if (var->freeval)
-               {
-                   pfree(DatumGetPointer(var->value));
-                   var->freeval = false;
-               }
-
                /*
                 * If type is by-reference, make sure we have a freshly
                 * palloc'd copy; the originally passed value may not live
@@ -2851,16 +2845,28 @@ exec_assign_value(PLpgSQL_execstate *estate,
                if (!var->datatype->typbyval && !*isNull)
                {
                    if (newvalue == value)
-                       var->value = datumCopy(newvalue,
-                                              false,
-                                              var->datatype->typlen);
-                   else
-                       var->value = newvalue;
-                   var->freeval = true;
+                       newvalue = datumCopy(newvalue,
+                                            false,
+                                            var->datatype->typlen);
                }
-               else
-                   var->value = newvalue;
+
+               /*
+                * 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;
+               }
+
+               var->value = newvalue;
                var->isnull = *isNull;
+               if (!var->datatype->typbyval && !*isNull)
+                   var->freeval = true;
                break;
            }
 
@@ -3717,6 +3723,14 @@ 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);
@@ -3730,7 +3744,7 @@ exec_move_row(PLpgSQL_execstate *estate,
 
        if (HeapTupleIsValid(tup))
        {
-           rec->tup = heap_copytuple(tup);
+           rec->tup = tup;
            rec->freetup = true;
        }
        else if (tupdesc)
@@ -3751,7 +3765,7 @@ exec_move_row(PLpgSQL_execstate *estate,
 
        if (tupdesc)
        {
-           rec->tupdesc = CreateTupleDescCopy(tupdesc);
+           rec->tupdesc = tupdesc;
            rec->freetupdesc = true;
        }
        else