.UNSETFRAME

Generates a WOD_SET_FPREG unwind code entry for the specified register and offset using the current offset in the epilogue.

Syntax

.UNSETFRAME reg, offset

Parameters

reg
The frame pointer register to unset.

offset
The offset into the stack frame where the frame pointer was established.

Remarks

Important

This directive is experimental and is subject to change. Enable Unwind Version 3 with ml64.exe /unwindv3.

.UNSETFRAME is only valid in Unwind Version 3. It's the epilogue counterpart to .SETFRAME.

.UNSETFRAME is only allowed within an epilogue region, between .BEGINEPILOG and .ENDEPILOG. These directives generate unwind metadata (.xdata and .pdata sections) but don't produce executable code.
In Unwind Version 3, .UNSETFRAME must appear before the instruction that restores the stack pointer from the frame pointer register.
It's a good practice to wrap both the unwind directives and the code they're meant to unwind in a macro to ensure agreement.

In Unwind Version 3, epilogue directives are mandatory for epilogue unwind code generation. No epilogue unwind codes are emitted without a .BEGINEPILOG/.ENDEPILOG pair.

Note

In Unwind Version 1, the directive appears after the corresponding instruction. In Unwind Version 3, the directive appears before the instruction.

Example for unwindv3

; ml64 /unwindv3 frmex2.asm /link /entry:frmex2 /SUBSYSTEM:CONSOLE
_text SEGMENT
frmex2 PROC FRAME
   .pushreg rbp
   push rbp
   .allocstack 010h
   sub rsp, 010h
   .setframe rbp, 0
   mov rbp, rsp
.endprolog
   ; modify the stack pointer outside of the prologue (similar to alloca)
   sub rsp, 060h

   ; we can unwind from the following AV because of the frame pointer
   mov rax, 0
   mov rax, [rax] ; AV!

   add rsp, 060h
   .beginepilog
   .unsetframe rbp, 0
   mov rsp, rbp
   .freestack 010h
   add rsp, 010h
   .popreg rbp
   pop rbp
   .endepilog
   ret
frmex2 ENDP
_text ENDS
END

See also

x64 Unwind Version 3 (experimental)
Directives Reference
.SETFRAME
.BEGINEPILOG
MASM BNF Grammar