.file "test.cpp"
.text
.globl _Z4testv
.type _Z4testv, @function
_Z4testv:
.LFB0:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
movq %rsp, %rbp
.cfi_offset 6, -16
.cfi_def_cfa_register 6
call _Z23functionThatMightUnwindv
addl $1, %eax
leave
.cfi_def_cfa 7, 8
ret
.cfi_endproc
If functionThatMightUnwind does, in fact, unwind, then the unwinder will hit the frame for test(), and see that rsp=rbp and judge it to be an invalid frame.