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 a2a1f7cb6b0d8e13838023e1eb86d8accbbb8753..d09c9fc234270af3eaf652b04970d538eb15e666 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 1.144 2005/06/14 06:43:14 neilc Exp $
+ *       $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.145 2005/06/20 20:44:44 tgl Exp $
  *
  *       This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -182,6 +182,7 @@ static bool compatible_tupdesc(TupleDesc td1, TupleDesc td2);
 static void exec_set_found(PLpgSQL_execstate *estate, bool state);
 static void free_var(PLpgSQL_var *var);
 
+
 /* ----------
  * plpgsql_exec_function       Called by the call handler for
  *                             function execution.
@@ -874,13 +875,15 @@ exec_stmt_block(PLpgSQL_execstate *estate, PLpgSQL_stmt_block *block)
                                        PLpgSQL_var *state_var;
                                        PLpgSQL_var *errm_var;
 
-                                       state_var = (PLpgSQL_var *) (estate->datums[block->exceptions->sqlstate_varno]);
+                                       state_var = (PLpgSQL_var *)
+                                               estate->datums[block->exceptions->sqlstate_varno];
                                        state_var->value = DirectFunctionCall1(textin,
                                                                                                                   CStringGetDatum(unpack_sql_state(edata->sqlerrcode)));
                                        state_var->freeval = true;
                                        state_var->isnull = false;
 
-                                       errm_var = (PLpgSQL_var *) (estate->datums[block->exceptions->sqlerrm_varno]);
+                                       errm_var = (PLpgSQL_var *)
+                                               estate->datums[block->exceptions->sqlerrm_varno];
                                        errm_var->value = DirectFunctionCall1(textin,
                                                                                                                  CStringGetDatum(edata->message));
                                        errm_var->freeval = true;
@@ -2862,8 +2865,6 @@ exec_assign_value(PLpgSQL_execstate *estate,
                                                         errmsg("NULL cannot be assigned to variable \"%s\" declared NOT NULL",
                                                                        var->refname)));
 
-                               free_var(var);
-
                                /*
                                 * If type is by-reference, make sure we have a freshly
                                 * palloc'd copy; the originally passed value may not live
@@ -2874,16 +2875,24 @@ 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.)
+                                */
+                               free_var(var);
+
+                               var->value = newvalue;
                                var->isnull = *isNull;
+                               if (!var->datatype->typbyval && !*isNull)
+                                       var->freeval = true;
                                break;
                        }
 
@@ -3740,6 +3749,14 @@ 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);
@@ -3753,7 +3770,7 @@ exec_move_row(PLpgSQL_execstate *estate,
 
                if (HeapTupleIsValid(tup))
                {
-                       rec->tup = heap_copytuple(tup);
+                       rec->tup = tup;
                        rec->freetup = true;
                }
                else if (tupdesc)
@@ -3774,7 +3791,7 @@ exec_move_row(PLpgSQL_execstate *estate,
 
                if (tupdesc)
                {
-                       rec->tupdesc = CreateTupleDescCopy(tupdesc);
+                       rec->tupdesc = tupdesc;
                        rec->freetupdesc = true;
                }
                else