Home Dashboard Directory Help

MASM Encodes LOCK prefix on BT, although that causes #invalid opcode exception on run-time by CA 2 LA



Sign in
to vote
Type: Bug
ID: 785949
Opened: 4/30/2013 10:16:29 AM
Access Restriction: Public
User(s) can reproduce this bug


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
Sign in to post a comment.
Posted by CA 2 LA 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)
Sign in to post a workaround.
File Name Submitted By Submitted On File Size  
BT.txt (restricted) 2/28/2014 -
BT.dll (restricted) 2/28/2014 -