32.6.5 GDB Graphical Interface
By default, the command gdb starts GDB using a graphical
interface where you view and control the program's data using Emacs
windows. You can still interact with GDB through the GUD buffer, but
the point of this mode is that you can do it through menus and clicks,
without needing to know GDB commands. For example, you can click
Mouse-1 in the fringe or display margin of a source buffer to
set a breakpoint there and, on a graphical display, a red bullet will
appear. If a breakpoint already exists on that line, this action will
remove it. You can also enable or disable a breakpoint by clicking
Mouse-3 on the bullet. If you drag the debugger arrow in the
fringe with Mouse-1, execution will continue to the line where
you release the button, provided it is still in the same frame
(gdb-mouse-until). Alternatively, you can click Mouse-2
at some point in the fringe of this buffer and execution will advance
to there.
This mode requires that GDB think that the screen size is unlimited,
and sets the height and width accordingly. For correct operation it
is important that you don't change these values during the session.
You can also run GDB in text command mode, which creates a buffer
for input and output to GDB. To do this, set
gud-gdb-command-name to "gdb --fullname" or edit the
startup command in the minibuffer to say that. You need to do use
text command mode to run multiple debugging sessions within one Emacs
session. If you have customized gud-gdb-command-name in that
way, then you can use M-x gdba to invoke GDB in graphical mode.
