imenu-default-create-index-function
imenu-default-create-index-function is a compiled Lisp function in `imenu.el
'.
(imenu-default-create-index-function)
Default function to create an index alist of the current buffer.
The most general method is to move point to end of buffer, then repeatedly call
`imenu-prev-index-position-function' and `imenu-extract-index-name-function'.
All the results returned by the latter are gathered into an index alist.
This method is used if those two variables are non-nil.
The alternate method, which is the one most often used, is to call
`imenu--generic-function' with `imenu-generic-expression' as argument.