uccessful exit, otherwise nonzero).

'^Z^Zsignalled'
     The program exited with a signal.  After the '^Z^Zsignalled', the
     annotation continues:

          INTRO-TEXT
          ^Z^Zsignal-name
          NAME
          ^Z^Zsignal-name-end
          MIDDLE-TEXT
          ^Z^Zsignal-string
          STRING
          ^Z^Zsignal-string-end
          END-TEXT

     where NAME is the name of the signal, such as 'SIGILL' or
     'SIGSEGV', and STRING is the explanation of the signal, such as
     'Illegal Instruction' or 'Segmentation fault'.  INTRO-TEXT,
     MIDDLE-TEXT, and END-TEXT are for the user's benefit and have no
     particular format.

'^Z^Zsignal'
     The syntax of this annotation is just like 'signalled', but GDB is
     just saying that the program received the signal, not that it was
     terminated with it.

'^Z^Zbreakpoint NUMBER'
     The program hit breakpoint number NUMBER.

'^Z^Zwatchpoint NUMBER'
     The program hit watchpoint number NUMBER.