In (lldb), there is a bug that positions the source code location on the
last character of the previous line if lldb doesn't report a column number.

Example, save the following as "t.s" and compile (on x86-64) with "gcc -g
t.s -o t":

        .global _main
_main:
        xor %eax,%eax
        ret

and debug using (lldb "lldb ./t"):

(lldb) *b main*
  :
(lldb) *run*
  :
(lldb)
*disas*t`main:
    0x555555555129 <+0>: xorl   %eax, %eax
->  0x55555555512b <+2>: retq

but the source code location ends up at the last character of the "xor
%eax..." line.

Attaching proposed pach against 66ef930ebea4618c1dac71a09495766476ced1d6.