Conditional Keybinding for gdb: gud-step if debugging, otherwise gud-run

Question

I have been trying around getting one keybinding <F7> to perform one gud-step command if a debugging process is running. If it is not running it shall perform gud-run. I am not very familiar with gdb/gud yet, so while trying to get gdb-running to work as a condition for my defun I am exposed to lisp argument errors, that 2 arguments are required (string-or-char-p and nil), where the first argument is a token, as it seems. In the end my goal is to use <F7> to invoke a gud-run and to step-through with the same key afterwards, after reaching a breakpoint.

Following snippet is my first attempt. It becomes obvious that gdb-running is missing 2 arguments as aforementioned.

(require 'gud)
(defun my-gud-run-or-step ()
  (interactive)
  (if (gdb-running)
      (gud-step nil)
    (gud-run nil)))

(global-set-key (kbd "<f7>") 'my-gud-run-or-step)

Answer 1

So the error tells you that gdb-running needs two arguments, but that's kindof a red herring. gdb-running doesn't actually do what you want; it doesn't return true or false to tell you whether gdb is currently running. I think it's called when gdb starts receiving gdb's output, as it appears to set several state variables that are used elsewhere. It looks like you could use the gud-running variable, or gdb-inferior-status. The former will be t, and the latter will be "running", so these might work:

(if gud-running
  ...)

or

(if (equal gdb-inferior-status "running")
  ...)