Merge emacs-25 into master (using imerge)emacs-25-merge

1 files changed, 22 insertions, 1 deletions

diff --git a/src/insdel.c b/src/insdel.c
index 24807b1e8f4..bb3171b14ce 100644
--- a/src/insdel.c
+++ b/src/insdel.c
@@ -1765,6 +1765,18 @@ modify_text (ptrdiff_t start, ptrdiff_t end)
   bset_point_before_scroll (current_buffer, Qnil);
 }
 
+/* Signal that we are about to make a change that may result in new
+   undo information.
+ */
+static void
+run_undoable_change (void)
+{
+  if (EQ (BVAR (current_buffer, undo_list), Qt))
+    return;
+
+  call0 (Qundo_auto__undoable_change);
+}
+
 /* Check that it is okay to modify the buffer between START and END,
    which are char positions.
 
@@ -1773,7 +1785,12 @@ modify_text (ptrdiff_t start, ptrdiff_t end)
    any modification properties the text may have.
 
    If PRESERVE_PTR is nonzero, we relocate *PRESERVE_PTR
-   by holding its value temporarily in a marker.  */
+   by holding its value temporarily in a marker.
+
+   This function runs Lisp, which means it can GC, which means it can
+   compact buffers, including the current buffer being worked on here.
+   So don't you dare calling this function while manipulating the gap,
+   or during some other similar "critical section".  */
 
 void
 prepare_to_modify_buffer_1 (ptrdiff_t start, ptrdiff_t end,
@@ -1786,6 +1803,8 @@ prepare_to_modify_buffer_1 (ptrdiff_t start, ptrdiff_t end,
   if (!NILP (BVAR (current_buffer, read_only)))
     Fbarf_if_buffer_read_only (temp);
 
+  run_undoable_change();
+
   bset_redisplay (current_buffer);
 
   if (buffer_intervals (current_buffer))
@@ -2187,6 +2206,8 @@ syms_of_insdel (void)
   combine_after_change_list = Qnil;
   combine_after_change_buffer = Qnil;
 
+  DEFSYM (Qundo_auto__undoable_change, "undo-auto--undoable-change");
+
   DEFVAR_LISP ("combine-after-change-calls", Vcombine_after_change_calls,
 	       doc: /* Used internally by the function `combine-after-change-calls' macro.  */);
   Vcombine_after_change_calls = Qnil;