MASM Encodes LOCK prefix on BT, although that causes #invalid opcode exception on run-time - by internal access 54

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ID 785949 Comments
Status Active Workarounds
Type Bug Repros 0
Opened 4/30/2013 10:16:29 AM
Access Restriction Public

Description

   lock bt DWORD PTR [eax], 2           ; F00FBA2002          

    ; The LOCK prefix is only allowed on BTS, BTR BTC, but
    ; not at BT 

    ; But MASM encodes F0h Opcode = LOCK prefix on this
    ; and reports no error message on assembling

; on execution that causes       #invalid opcode exception

; Microsoft (R) Macro Assembler Version 11.00.50522.1
; Microsoft (R) Incremental Linker Version 11.00.50522.1

; also same behaviour on Microsoft (R) Macro Assembler (x64) Version 11.00.50522.1
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Posted by internal access 54 on 2/28/2014 at 8:14 AM
2 files added
same problem also still on MASM12
Posted by Microsoft on 4/30/2013 at 9:41 PM
Thanks for your feedback.

We are rerouting this issue to the appropriate group within the Visual Studio Product Team for triage and resolution. These specialized experts will follow-up with your issue.
Posted by Microsoft on 4/30/2013 at 11:55 AM
Thank you for your feedback, we are currently reviewing the issue you have submitted. If this issue is urgent, please contact support directly(http://support.microsoft.com)