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.SETFRAME

Fills in the frame register field and offset in the unwind information using the specified register (reg) and offset (offset). The offset must be a multiple of 16 and less than or equal to 240. This directive also generates a UWOP_SET_FPREG unwind code entry for the specified register using the current prologue offset.

.SETFRAME reg, offset

.SETFRAME allows ml64.exe users to specify how a frame function unwinds, and is only allowed within the prologue, which extends from the PROC FRAME declaration to the .ENDPROLOG directive. These directives do not generate code; they only generate .xdata and .pdata. .SETFRAME should be preceded by instructions that actually implement the actions to be unwound. It is a good practice to wrap both the unwind directives and the code they are meant to unwind in a macro to ensure agreement.

For more information, see MASM for x64 (ml64.exe).

Description

The following sample shows how to use a frame pointer:

Code

; ml64 frmex2.asm /link /entry:frmex2 /SUBSYSTEM:CONSOLE
_text SEGMENT
frmex2 PROC FRAME
   push rbp
.pushreg rbp
   sub rsp, 010h
.allocstack 010h
   mov rbp, rsp
.setframe rbp, 0
.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
   add rsp, 010h
   pop rbp
   ret
frmex2 ENDP
_text ENDS
END
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