out_of_range in substr()

[arvidn]

my instance terminated with this message:

terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::substr: __pos (which is 2) > this->size() (which is 0)

unfortunately I did not build it with -rdynamic, so there was no backtrace.

Looking through the code, I couldn't find any direct uses of substr(), so I suspect there are some indirect ones. It needs some more digging.