oracle - Is this a PL/SQL bug? -

here's excerpt pl/sql code believe demonstrates pl/sql bug:

if guid_ null    dbms_output.put_line('guid_ null: ' || guid_); end if; 

when these lines executed, prints

guid_ null: 07d242fcc55000fce0530a30d4928a21 

i on oracle 11r2

select * v$version;  oracle database 11g enterprise edition release 11.2.0.4.0 - 64bit production pl/sql release 11.2.0.4.0 - production core    11.2.0.4.0      production tns ibm/aix risc system/6000: version 11.2.0.4.0 - production nlsrtl version 11.2.0.4.0 - production 

i can reproduce following types , anonymous block. sorry length, believe cannot shorten more:

create type tq84_t table of varchar2(32); /  create type tq84_o object (   dummy number(1),    not final member procedure clear  ) not final; /  show errors  create type tq84_d under tq84_o (    g varchar2(32),   constructor function tq84_d return self result,    overriding member procedure clear   ); / show errors   create package tq84_h      t tq84_t;  end tq84_h; / show errors    create package body tq84_h begin    t := tq84_t(); end; / show errors  create type body tq84_o     member procedure clear begin       null;    end clear;  end; /  create type body tq84_d    constructor function tq84_d return self result   begin        g := sys_guid;       return;    end tq84_d;    overriding member procedure clear begin        tq84_h.t.extend;       tq84_h.t(tq84_h.t.count) := g;        g := null;    end clear;  end; / show errors   declare    b  tq84_o;  -- change tq84_d ...    guid_ varchar2(32);  begin    b := new tq84_d;    guid_ := treat(b tq84_d).g;    b.clear;    if guid_ null      dbms_output.put_line('guid_ null: ' || guid_);   end if;   end; /  drop type tq84_t; drop type tq84_d; drop type tq84_o; drop package tq84_h; 

note also, when change b tq84_o b tq84_d, error not occur anymore.

can verify if happening on other systems well?

to me bug. in if variable guid_ not treated same in the string concatenation put_line. find strange before b.clear statement is null works:

declare   b  tq84_o;  -- change tq84_d ...   guid_ varchar2(32); begin   b := new tq84_d;   guid_ := treat(b tq84_d).g;    if guid_ null      dbms_output.put_line('before clear: guid_  null: ' || guid_);   end if;    b.clear;    if guid_ null      dbms_output.put_line('after clear: guid_ null: ' || guid_);   end if; end; / 

output:

after clear: guid_ null: 07d43acb728a2173e054a0481c66cf28 

i workaround problem when returning guid function:

declare   b  tq84_o;  -- change tq84_d ...   guid_ varchar2(32);   function get_guid    return varchar2    begin      return treat(b tq84_d).g;   end;   begin   b := new tq84_d;   guid_ := get_guid; -- treat(b tq84_d).g;    if guid_ null      dbms_output.put_line('before clear: guid_  null: ' || guid_);   end if;    b.clear;    if guid_ null      dbms_output.put_line('after clear: guid_ null: ' || guid_);   end if; end; / 

the above code not go neither of if guid_ null. me proves it:

this bug.