Variable: debug-on-error
debug-on-error is a customizable variable defined in eval.c.
Value
nil
Documentation
Non-nil means enter debugger if an error is signaled.
Does not apply to errors handled by condition-case or those
matched by debug-ignored-errors.
If the value is a list, an error only means to enter the debugger
if one of its condition symbols appears in the list.
When you evaluate an expression interactively, this variable
is temporarily non-nil if eval-expression-debug-on-error is non-nil.
The command toggle-debug-on-error toggles this.
See also the variable debug-on-quit and inhibit-debugger.
Probably introduced at or before Emacs version 1.2.
Source Code
// Defined in /usr/src/emacs/src/eval.c
DEFVAR_LISP ("debug-on-error", Vdebug_on_error,
doc: /* Non-nil means enter debugger if an error is signaled.
Does not apply to errors handled by `condition-case' or those
matched by `debug-ignored-errors'.
If the value is a list, an error only means to enter the debugger
if one of its condition symbols appears in the list.
When you evaluate an expression interactively, this variable
is temporarily non-nil if `eval-expression-debug-on-error' is non-nil.
The command `toggle-debug-on-error' toggles this.
See also the variable `debug-on-quit' and `inhibit-debugger'. */);