* src/marker-vector.h (DO_MARKERS_OF_VECTOR, DO_MARKERS): Remove.
(build_for_each_marker_data, next_marker_entry):
(FOR_EACH_MARKER_OF_VECTOR, FOR_EACH_MARKER): New.

* .clang-format (IndentPPDirectives): Add new FOR_EACH_ macros.

* src/alloc.c (unchain_dead_markers):
* src/buffer.c (Fkill_buffer, Fbuffer_swap_text)
(Fset_buffer_multibyte):
* src/coding.c (decode_coding_object, encode_coding_object):
* src/editfns.c (transpose_markers):
* src/marker-vector.c (check_marker_vector, marker_vector_reset)
(marker_vector_adjust_for_insert)
(marker_vector_adjust_for_replace):
* src/undo.c (record_marker_adjustments): Use FOR_EACH_MARKER.

* src/text-index.c (text_index_bytepos_to_charpos): Add a const.
(bytepos_of_head): Removed.
(text_index_charpos_to_bytepos): Don't be clever about choosing
to scan forward or backward.
(bytepos_forward_to_charpos): Use char_start_bytepos.

* src/text-index.c (buf_bytepos_to_charpos): New function.
(buf_charpos_to_bytepos): Use it to avoid scanning backward from next
to prev.

* src/marker-vector.c (marker_vector_remove): Remove a comment.
(marker_vector_reset): Remember old charpos.

* src/lisp.h (struct Lisp_Marker): Extend comment.
* src/marker-vector.c (marker_vector_remove): Store marker
position in marker's entry.
(marker_vector_last_charpos): New function.
* src/marker-vector.h: Add prototype.
* src/marker.c (Fmarker_last_position): Use
marker_vector_last_position.

* src/marker-vector.c (marker_vector_adjust_for_delete): Delete function.
* src/marker-vector.h (marker_vector_adjust_for_delete): Delete declaration.
* src/insdel.c (adjust_markers_for_delete): Use
`marker_vector_adjust_for_replace` instead.
(adjust_markers_for_replace): Move call to`text_index_invalidate` so we
don't do it redundantly.

* src/text-index.c (is_close_enough_charpos): Remove unused arg `ti`.
(narrow_bytepos_bounds_1, narrow_charpos_bounds_1)
(narrow_bytepos_bounds, narrow_charpos_bounds):
Don't short-circuit if a known point is exactly equal to what we're
looking for, thus don't return value.
(text_index_bytepos_to_charpos, text_index_charpos_to_bytepos):
Short-circuit here instead after narrowing.
Make the two functions more alike.  Short-circuit also when the text
remaining to scan is all ASCII.

* src/textconv.c (record_buffer_change, really_set_composing_text)
(locate_and_save_position_in_field): Adjust calls to `build_marker`.