I found the corruption location. Here is the actual stack trace: Degree -3: Generating Optimized Code ISE Eiffel: Session aborted Exception tag: valid_index ecb: system execution failed. Following is the set of recorded exceptions: ------------------------------------------------------------------------------- Class / Object Routine Nature of exception Effect ------------------------------------------------------------------------------- PACKED_BOOLEANS put @1 valid_index: <0000000008FB5188> Precondition violated. Fail ------------------------------------------------------------------------------- EIFFEL_HISTORY mark_used @2 <0000000008FB5148> Routine failure. Fail ------------------------------------------------------------------------------- ATTRIBUTE_BL generate_access_on_type @29 <0000000002D9BC18> Routine failure. Fail ------------------------------------------------------------------------------- ATTRIBUTE_BL generate_end @3 <0000000002D9BC18> (From CALL_ACCESS_B) Routine failure. Fail ------------------------------------------------------------------------------- ATTRIBUTE_BL do_generate @11 <0000000002D9BC18> (From CALL_ACCESS_B) Routine failure. Fail ------------------------------------------------------------------------------- ATTRIBUTE_BL generate_on @1 <0000000002D9BC18> Routine failure. Fail ------------------------------------------------------------------------------- NESTED_BL generate_call @11 <0000000002D9BB88> Routine failure. Fail ------------------------------------------------------------------------------- NESTED_BL generate @6 <0000000002D9BB88> Routine failure. Fail ------------------------------------------------------------------------------- IF_B generate @4 <0000000002D993A8> Routine failure. Fail ------------------------------------------------------------------------------- BYTE_LIST generate @4 <0000000002D996E8> Routine failure. Fail ------------------------------------------------------------------------------- IF_B generate @11 <0000000002D9B1A8> Routine failure. Fail ------------------------------------------------------------------------------- BYTE_LIST generate @4 <0000000002D9B248> Routine failure. Fail ------------------------------------------------------------------------------- STD_BYTE_CODE generate_compound @2 <0000000002D9B268> Routine failure. Fail ------------------------------------------------------------------------------- STD_BYTE_CODE generate @62 <0000000002D9B268> Routine failure. Fail ------------------------------------------------------------------------------- DYN_PROC_I generate @18 <0000000002CC2D28> (From FEATURE_I) Routine failure. Fail ------------------------------------------------------------------------------- CLASS_TYPE generate_feature @3 <000000001651B7F8> Routine failure. Fail ------------------------------------------------------------------------------- CLASS_TYPE pass4 @76 <000000001651B7F8> Routine failure. Fail ------------------------------------------------------------------------------- TYPE_LIST pass4 @4 <0000000008D88278> Routine failure. Fail ------------------------------------------------------------------------------- EIFFEL_CLASS_C pass4 @2 <0000000013C07B18> Routine failure. Fail ------------------------------------------------------------------------------- SYSTEM_I process_degree_minus_3 @16 <000000000381F468> Routine failure. Fail ------------------------------------------------------------------------------- SYSTEM_I finalize_system @48 <000000000381F468> Routine failure. Rescue ------------------------------------------------------------------------------- E_PROJECT finalize @8 <00000000037C07B8> Routine failure. Fail ------------------------------------------------------------------------------- EWB_FINALIZE perform_compilation @3 <00000000037D5318> Routine failure. Fail ------------------------------------------------------------------------------- EWB_FINALIZE compile @4 <00000000037D5318> (From EWB_COMP) Routine failure. Fail ------------------------------------------------------------------------------- EWB_FINALIZE execute @7 <00000000037D5318> Routine failure. Fail ------------------------------------------------------------------------------- EWB_FINALIZE loop_action @11 <00000000037D5318> Routine failure. Fail ------------------------------------------------------------------------------- EWB_LOOP ewb_iterate @12 <00000000037C1858> Routine failure. Fail ------------------------------------------------------------------------------- EWB_LOOP execute @3 <00000000037C1858> Routine failure. Fail ------------------------------------------------------------------------------- ES execute @44 <0000000003755718> Routine failure. Rescue ------------------------------------------------------------------------------- ES make @13 <0000000003755718> Routine failure. Fail ------------------------------------------------------------------------------- ES root's creation <0000000003755718> Routine failure. Exit -------------------------------------------------------------------------------