Extended Description

(lldb) set set interpreter.expand-regex-aliases 1
(lldb) jump +1
thread jump --by +1
error: invalid line offset: '+1'.

And indeed:

(lldb) thread jump --by +1
error: invalid line offset: '+1'.

The option parser calls:

option_arg.getAsInteger(0, m_line_offset);

where m_line_offset it the storage for the integer read in. Either StringRef::getAsInteger should support this, or we should strip off the leading +.