Why the -1 ? No ARM or Thumb instruction is 1 byte long. Instructions are 4 bytes long if in ARM state and could be 2 or 4 bytes if Thumb state.The -1 just points to the middle of previous instruction, so that supposedly it can be looked up in debug info etc.
Right, that works quite well with gdb, addr2line, etc. I once tried adding proper handling of ARM/Thumb but this complicated code with no real benefit.
-Y
