Implement `debug-on-message'.

This allows tracking down what piece of code is outputting stuff in
the echo area.

* eval.c (call_debugger): Make the function non-static so that we
can call it from set_message.

* xdisp.c (set_message): Implement the new variable `debug-on-message'.
(syms_of_xdisp): Defvar it and `inhibit-debug-on-message'.

1 files changed, 4 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 9a38deef05c..e137ebc0665 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1916,6 +1916,10 @@ instead of jumping all the way to the top-level.
 *** Set `debug-on-event' to enter the debugger on events like SIGUSR1.
 This can be useful when `inhibit-quit' is set.
 
+*** Set `debug-on-message' to enter the debugger when a certain
+message is displayed in the echo area.  This can be useful when trying
+to work out which code is doing something.
+
 ** The new function `server-eval-at' allows evaluation of Lisp forms on
 named Emacs server instances.