When an error occurs inside a process sentinel or during font-locking, then Emacs doesn't show a backtrace even though
debug-on-error was previously enabled.
I understand why these errors are caught, the same error might be triggered again while trying to present the backtrace. However when I want to actually debug that error it is not very helpful. I would rather risk Emacs becoming unresponsive than having to work from this:
error in process sentinel: Wrong type argument: stringp, nil
After all I can just start a second instance, if the first starts going crazy. A little more context would help when there are many places where such an error could theoretically occur in a sentinel.
So how can I force Emacs to show a backtrace even in cases where
debug-on-error has no effect?