How to break out of function indirection loop

Question

I have a problem that I suspect is a general Emacs problem. If I run a certain package, simple-rtm, and then try and use M-x to run any command, I get the error in the bottom line of the screen:

Symbol's chain of function indirections contains a loop: def-rtm-authenticated-scalar-method

I understand at a superficial level what this means - simple-rtm calls rtm, and in rtm.el there is a function def-rtm-authenticated-scalar-method and it has an infinite loop. Given enough time I will learn enough Lisp to work out why and fix it. But that might take me a while. Meanwhile I would like to just continue using Emacs for other things, but I find the only way I can use M-x after running simple-rtm is to exit Emacs and run it again.

My question therefore is: is there a simple Emacs command I can use to break out of the function indirection loop so I can use M-x again?

Emacs version is 24.5.1 running on Windows 10.

Answer 1

Function indirection refers to the ability for a symbol's function cell to contain another symbol as its value, rather than a function object. In that case, the function cell of the latter symbol is used (which might be yet another symbol, etc...) until a function object is found.

Thus if symbol A points to symbol B in this way, and symbol B points back to symbol A, there is a function indirection loop, and any attempt to call either A or B as a function cannot succeed.

It's very difficult to suggest exactly what you should do without seeing the code in question. You could prevent the loop by explicitly redefining one of the functions involved (as an actual function), but I can't guess at the correct solution without seeing the code.

edit:

Well, I looked at the rtm package via Melpa, and it contains

(defalias 'def-rtm-authenticated-scalar-method 'def-rtm-authenticated-scalar-method)

which is setting a symbol's function cell to its own symbol! I don't know what that was intended to be, but that's the cause of the problem. Log a bug report with the author, if you're able.

Try the following...

1. Re-evaluate the initial definition (type C-x C-e with point after the closing parenthesis)

   (def-rtm-macro def-rtm-authenticated-scalar-method
                  rtm-call-authenticated rtm-get-scalar-from-response)
   

2. Comment out the bad code from rtm.el and save the file.

   ;; (defalias 'def-rtm-authenticated-scalar-method 'def-rtm-authenticated-scalar-method)
   

   and

   ;; (put 'def-rtm-authenticated-scalar-method 'lisp-indent-function 1)
   

3. Byte-compile the file with M-x byte-compile-file (assuming that's now working again since step 1), or use B in dired.

edit 2

FYI if I manufacture the same basic error in Emacs 24.5, Emacs does not get stuck in an infinite loop. It detects the problem, reports it, and returns control to me. I certainly don't lose the ability to use M-x. So there's likely some compounding factor at work here which is making a normally-recoverable error less so.