Re: Emacs hangs enabling debug-on-error

[Richard Stallman]

    in xdisp.c :

              /* Build desired tool-bar items from keymaps.  */
              BLOCK_INPUT;
              f->tool_bar_items
                = tool_bar_items (f->tool_bar_items, &f->n_tool_bar_items);
              UNBLOCK_INPUT;

The code to update the menu bar does not block input.  It produces the
data in a Lisp format, then converts that to internal format.  The
first stage can run Lisp code, and the second stage needs to block
input.

I think the tool bar needs to be handled the same way.