LowLevelManual

Debugger

Debugging works within a dynamic environment with the following dynamic variables defined:

• sys:*backtrace* - A list of backtrace frames.
• sys:*ihs-top* - The index of the stack frame with the highest index.
• sys:*ihs-base* - The index of the stack frame with the lowest index. This is the most recent frame.
• sys:*ihs-mode* - The backtrace can display only lisp frames (set to 'sys:ihs-common-lisp) or all frames (set to sys:ihs-all).
• sys:*ihs-current* - The index of the current frame.

Backtrace frames are simple structs of type vector, they are essentially defined using the following. Read accessors are defined for all of the slots and write accessors for just a few of them.

(defstruct (sys:backtrace-frame (:named) (:type vector))
  type return-address raw-name function-name print-name
  frame-size frame-offset function-start-address function-end-address
  base-pointer arguments closure function-description)

Convenience functions are defined for working with the backtrace:

• sys:ihs-bounded (index) - Returns index if index is a valid index into the backtrace otherwise if index is negative it returns 0 or too large it returns (1- (length sys:*backtrace*))
• sys:ihs-backtrace-frame (index) - Returns the frame at index.
• sys:ihs-source-information (&optional (index sys:*ihs-current*)) - Return the source information for the frame at index as values: filename function-name source line column function-start-line discriminator
• sys:ihs-return-address (&optional (index sys:*ihs-current*)) - Return a pointer containing the return address of this frame.