Function: backtrace-eval

backtrace-eval is a function defined in eval.c.

Signature

(backtrace-eval EXP NFRAMES &optional BASE)

Documentation

Evaluate EXP in the context of some activation frame.

NFRAMES and BASE specify the activation frame to use, as in backtrace-frame.

Source Code

// Defined in /usr/src/emacs/src/eval.c
{
  union specbinding *pdl = get_backtrace_frame (nframes, base);
  specpdl_ref count = SPECPDL_INDEX ();
  ptrdiff_t distance = specpdl_ptr - pdl;
  eassert (distance >= 0);

  if (!backtrace_p (pdl))
    error ("Activation frame not found!");

  backtrace_eval_unrewind (distance);
  record_unwind_protect_int (backtrace_eval_unrewind, -distance);

  /* Use eval_sub rather than Feval since the main motivation behind
     backtrace-eval is to be able to get/set the value of lexical variables
     from the debugger.  */
  return unbind_to (count, eval_sub (exp));
}