| c | continue |
| d | step-in |
| b | flag frame for debugging when leaving frame again |
| u | unflag frame for debugging when leaving |
| j | flag frame and disable function-entry breakpoints |
| e | eval expression in minibuffer |
| q | quit |
| r | eval expression and set it as value of frame, continue |
| R | as r, but save to Debugger-record too |
| l | list functions with breakpoints |
Debugger can’t step through primitive functions, i.w. ones written in C.
Compiled functions can’t be stepped through, either. To replace function with an interpreted version visit the source and hit C-M-x.