bug#46915: [PATCH] Remove unecessary change_req arg from overlays_at()

[Matt Armstrong]

Tags: patch

I was scratching my head trying to figure out why overlays_at() had such
a complex function signature.  It turns out that it does not need to be
so complex now and, I think, it never did.

>From 0337e4823b32dd15bdae1f61df12b5f68170e360 Mon Sep 17 00:00:00 2001
From: Matt Armstrong <matt@mdeb>
Date: Wed, 3 Mar 2021 16:31:02 -0800
Subject: [PATCH] Remove unecessary change_req arg from overlays_at()

The change_req arg was an unecessary complexity.  It only changed what
might be assigned to the *prev_ptr arg, and all callers that passed a
non-null prev_ptr also passed a true change_req.

This makes it clear that no caller desires the behavior that would
have occurred with a non-null prev_ptr and a false change_req.

For archaeologists, the above invariants appear to have been true from
the beginning, and whatever bug fixed by the commits below need not
have been controlled with a new boolean arg.  See commits
ac869cf715 ((overlays_at): Add CHANGE_REQ parameter, 2000-08-08) and
1d5f4c1de4 ((overlays_at): Only let CHANGE_REQ inhibit an assignment
of startpos to prev when startpos == pos, 2000-10-25).

* src/buffer.c (overlays_at):
* src/buffer.h (GET_OVERLAYS_AT): Remove the change_req arg.
* src/buffer.c (Foverlays_at):
(Fnext_overlay_change):
* src/textprop.c (get_char_property_and_overlay):
(note_mouse_highlight):
* src/xfaces.c (face_at_buffer_position):
* src/xdisp.c (next_overlay_change):
(note_mouse_highlight): Omit the change_req arg.
---
 src/buffer.c   | 13 ++++++-------
 src/buffer.h   | 11 +++++------
 src/textprop.c |  2 +-
 src/xdisp.c    |  4 ++--
 src/xfaces.c   |  2 +-
 5 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/src/buffer.c b/src/buffer.c
index 5bd9b37702..84edf18eb0 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2843,14 +2843,13 @@ DEFUN ("kill-all-local-variables", 
Fkill_all_local_variables,
    and store only as many overlays as will fit.
    But still return the total number of overlays.
 
-   If CHANGE_REQ, any position written into *PREV_PTR or
-   *NEXT_PTR is guaranteed to be not equal to POS, unless it is the
-   default (BEGV or ZV).  */
+   Any position written into *PREV_PTR or *NEXT_PTR is guaranteed to
+   be not equal to POS, unless it is the default (BEGV or ZV).  */
 
 ptrdiff_t
 overlays_at (EMACS_INT pos, bool extend, Lisp_Object **vec_ptr,
             ptrdiff_t *len_ptr,
-            ptrdiff_t *next_ptr, ptrdiff_t *prev_ptr, bool change_req)
+            ptrdiff_t *next_ptr, ptrdiff_t *prev_ptr)
 {
   ptrdiff_t idx = 0;
   ptrdiff_t len = *len_ptr;
@@ -2944,7 +2943,7 @@ overlays_at (EMACS_INT pos, bool extend, Lisp_Object 
**vec_ptr,
       else if (endpos < pos && endpos > prev)
        prev = endpos;
       else if (endpos == pos && startpos > prev
-              && (!change_req || startpos < pos))
+              && startpos < pos)
        prev = startpos;
     }
 
@@ -4232,7 +4231,7 @@ DEFUN ("overlays-at", Foverlays_at, Soverlays_at, 1, 2, 0,
   /* Put all the overlays we want in a vector in overlay_vec.
      Store the length in len.  */
   noverlays = overlays_at (XFIXNUM (pos), 1, &overlay_vec, &len,
-                          NULL, NULL, 0);
+                          NULL, NULL);
 
   if (!NILP (sorted))
     noverlays = sort_overlays (overlay_vec, noverlays,
@@ -4308,7 +4307,7 @@ DEFUN ("next-overlay-change", Fnext_overlay_change, 
Snext_overlay_change,
      Store the length in len.
      endpos gets the position where the next overlay starts.  */
   noverlays = overlays_at (XFIXNUM (pos), 1, &overlay_vec, &len,
-                          &endpos, 0, 1);
+                          &endpos, 0);
 
   /* If any of these overlays ends before endpos,
      use its ending point instead.  */
diff --git a/src/buffer.h b/src/buffer.h
index 24e9c3fcbc..a53b476d72 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -1145,7 +1145,7 @@ #define CHECK_FIXNUM_COERCE_MARKER(x) ((x) = make_fixnum 
(fix_position (x)))
 extern void compact_buffer (struct buffer *);
 extern void evaporate_overlays (ptrdiff_t);
 extern ptrdiff_t overlays_at (EMACS_INT, bool, Lisp_Object **,
-                             ptrdiff_t *, ptrdiff_t *, ptrdiff_t *, bool);
+                             ptrdiff_t *, ptrdiff_t *, ptrdiff_t *);
 extern ptrdiff_t sort_overlays (Lisp_Object *, ptrdiff_t, struct window *);
 extern void recenter_overlay_lists (struct buffer *, ptrdiff_t);
 extern ptrdiff_t overlay_strings (ptrdiff_t, struct window *, unsigned char 
**);
@@ -1195,22 +1195,21 @@ record_unwind_current_buffer (void)
 
 /* Get overlays at POSN into array OVERLAYS with NOVERLAYS elements.
    If NEXTP is non-NULL, return next overlay there.
-   See overlay_at arg CHANGE_REQ for meaning of CHRQ arg.
    This macro might evaluate its args multiple times,
-   and it treat some args as lvalues.  */
+   and it treats some args as lvalues.  */
 
-#define GET_OVERLAYS_AT(posn, overlays, noverlays, nextp, chrq)                
\
+#define GET_OVERLAYS_AT(posn, overlays, noverlays, nextp)              \
   do {                                                                 \
     ptrdiff_t maxlen = 40;                                             \
     SAFE_NALLOCA (overlays, 1, maxlen);                                        
\
     (noverlays) = overlays_at (posn, false, &(overlays), &maxlen,      \
-                              nextp, NULL, chrq);                      \
+                              nextp, NULL);                            \
     if ((noverlays) > maxlen)                                          \
       {                                                                        
\
        maxlen = noverlays;                                             \
        SAFE_NALLOCA (overlays, 1, maxlen);                             \
        (noverlays) = overlays_at (posn, false, &(overlays), &maxlen,   \
-                                  nextp, NULL, chrq);                  \
+                                  nextp, NULL);                        \
       }                                                                        
\
   } while (false)
 
diff --git a/src/textprop.c b/src/textprop.c
index d7d6a66923..854bb1c971 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -636,7 +636,7 @@ get_char_property_and_overlay (Lisp_Object position, 
register Lisp_Object prop,
       set_buffer_temp (XBUFFER (object));
 
       USE_SAFE_ALLOCA;
-      GET_OVERLAYS_AT (pos, overlay_vec, noverlays, NULL, false);
+      GET_OVERLAYS_AT (pos, overlay_vec, noverlays, NULL);
       noverlays = sort_overlays (overlay_vec, noverlays, w);
 
       set_buffer_temp (obuf);
diff --git a/src/xdisp.c b/src/xdisp.c
index cc0a689ba3..f64b42f2d8 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -4070,7 +4070,7 @@ next_overlay_change (ptrdiff_t pos)
   USE_SAFE_ALLOCA;
 
   /* Get all overlays at the given position.  */
-  GET_OVERLAYS_AT (pos, overlays, noverlays, &endpos, true);
+  GET_OVERLAYS_AT (pos, overlays, noverlays, &endpos);
 
   /* If any of these overlays ends before endpos,
      use its ending point instead.  */
@@ -33729,7 +33729,7 @@ note_mouse_highlight (struct frame *f, int x, int y)
       if (BUFFERP (object))
        {
          /* Put all the overlays we want in a vector in overlay_vec.  */
-         GET_OVERLAYS_AT (pos, overlay_vec, noverlays, NULL, false);
+         GET_OVERLAYS_AT (pos, overlay_vec, noverlays, NULL);
          /* Sort overlays into increasing priority order.  */
          noverlays = sort_overlays (overlay_vec, noverlays, w);
        }
diff --git a/src/xfaces.c b/src/xfaces.c
index ab4440f46a..8df318e33e 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -6397,7 +6397,7 @@ face_at_buffer_position (struct window *w, ptrdiff_t pos,
   {
     ptrdiff_t next_overlay;
 
-    GET_OVERLAYS_AT (pos, overlay_vec, noverlays, &next_overlay, false);
+    GET_OVERLAYS_AT (pos, overlay_vec, noverlays, &next_overlay);
     if (next_overlay < endpos)
       endpos = next_overlay;
   }
-- 
2.30.0