bug#57684: locked narrowing breaks existing code without an apparent way to repair

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > Even if Elisp code is buggy, Emacs itself should never allow it to fall 
into an infinite loop and stop
  > > responding to C-g, leaving full restart as the only way out.

It used to be impossible to have an infinite loop in Emacs Lisp that
you could not quit out of.  The Lisp interpreter and tye bytecode
interpreter both had calls to QUIT in all the loops of Lisp execution.
Likewise, all the loops in C code that corresponded to Lisp loops, and
might fail to terminate if given circular lists, such as Fmemq,
had calls to QUIT.

If that is now no longertrue, what made it cease to be true?

-- 
Dr Richard Stallman (https://stallman.org)
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)