Capturing the Stack or Innermost Stack Frame

A Scheme program can use the make-stack primitive anywhere in its code, with first arg #t, to construct a Scheme value that describes the Scheme stack at that point.

— Scheme Procedure: make-stack obj . args
— C Function: scm_make_stack (obj, args)

Create a new stack. If obj is #t, the current evaluation stack is used for creating the stack frames, otherwise the frames are taken from obj (which must be either a debug object or a continuation).
args should be a list containing any combination of integer, procedure and #t values.
These values specify various ways of cutting away uninteresting stack frames from the top and bottom of the stack that make-stack returns. They come in pairs like this: (inner_cut_1 outer_cut_1 inner_cut_2 outer_cut_2 ...).
Each inner_cut_N can be #t, an integer, or a procedure. #t means to cut away all frames up to but excluding the first user module frame. An integer means to cut away exactly that number of frames. A procedure means to cut away all frames up to but excluding the application frame whose procedure matches the specified one.
Each outer_cut_N can be an integer or a procedure. An integer means to cut away that number of frames. A procedure means to cut away frames down to but excluding the application frame whose procedure matches the specified one.
If the outer_cut_N of the last pair is missing, it is taken as 0.

5.21.1.1 Capturing the Stack or Innermost Stack Frame