--- a/src/ops.c
+++ b/src/ops.c
@@ -1949,7 +1949,7 @@ op_delete(oap)
 							    );
 	    curwin->w_cursor = curpos;		/* restore curwin->w_cursor */
 
-	    (void)do_join(FALSE);
+	    (void)do_join(2, FALSE, FALSE);
 	}
     }
 
@@ -4140,138 +4140,137 @@ dis_msg(p, skip_esc)
 }
 
 /*
- * join 'count' lines (minimal 2), including u_save()
- */
-    void
-do_do_join(count, insert_space)
-    long    count;
-    int	    insert_space;
-{
-    colnr_T	col = MAXCOL;
-
-    if (u_save((linenr_T)(curwin->w_cursor.lnum - 1),
-		    (linenr_T)(curwin->w_cursor.lnum + count)) == FAIL)
-	return;
-
-    while (--count > 0)
-    {
-	line_breakcheck();
-	if (got_int || do_join(insert_space) == FAIL)
-	{
-	    beep_flush();
-	    break;
-	}
-	if (col == MAXCOL && vim_strchr(p_cpo, CPO_JOINCOL) != NULL)
-	    col = curwin->w_cursor.col;
-    }
-
-    /* Vi compatible: use the column of the first join */
-    if (col != MAXCOL && vim_strchr(p_cpo, CPO_JOINCOL) != NULL)
-	curwin->w_cursor.col = col;
-
-#if 0
-    /*
-     * Need to update the screen if the line where the cursor is became too
-     * long to fit on the screen.
-     */
-    update_topline_redraw();
-#endif
-}
-
-/*
- * Join two lines at the cursor position.
- * "redraw" is TRUE when the screen should be updated.
- * Caller must have setup for undo.
+ * Join 'count' lines (minimal 2) at cursor position.
+ * When "save_undo" is TRUE save lines for undo first.
  *
  * return FAIL for failure, OK otherwise
  */
     int
-do_join(insert_space)
-    int		insert_space;
+do_join(count, insert_space, save_undo)
+    long    count;
+    int	    insert_space;
+    int	    save_undo;
 {
-    char_u	*curr;
-    char_u	*next, *next_start;
+    char_u	*curr = NULL;
+    char_u	*cend;
     char_u	*newp;
+    char_u	*spaces;	/* number of spaces inserte before a line */
     int		endcurr1, endcurr2;
-    int		currsize;	/* size of the current line */
-    int		nextsize;	/* size of the next line */
-    int		spaces;		/* number of spaces to insert */
+    int		currsize = 0;	/* size of the current line */
+    int		sumsize = 0;	/* size of the long new line */
     linenr_T	t;
-
-    if (curwin->w_cursor.lnum == curbuf->b_ml.ml_line_count)
-	return FAIL;		/* can't join on last line */
-
-    curr = ml_get_curline();
-    currsize = (int)STRLEN(curr);
-    endcurr1 = endcurr2 = NUL;
-    if (insert_space && currsize > 0)
-    {
-#ifdef FEAT_MBYTE
-	if (has_mbyte)
-	{
-	    next = curr + currsize;
-	    mb_ptr_back(curr, next);
-	    endcurr1 = (*mb_ptr2char)(next);
-	    if (next > curr)
-	    {
-		mb_ptr_back(curr, next);
-		endcurr2 = (*mb_ptr2char)(next);
-	    }
-	}
-	else
-#endif
-	{
-	    endcurr1 = *(curr + currsize - 1);
-	    if (currsize > 1)
-		endcurr2 = *(curr + currsize - 2);
-	}
-    }
-
-    next = next_start = ml_get((linenr_T)(curwin->w_cursor.lnum + 1));
-    spaces = 0;
-    if (insert_space)
-    {
-	next = skipwhite(next);
-	if (*next != ')' && currsize != 0 && endcurr1 != TAB
-#ifdef FEAT_MBYTE
-		&& (!has_format_option(FO_MBYTE_JOIN)
-			|| (mb_ptr2char(next) < 0x100 && endcurr1 < 0x100))
-		&& (!has_format_option(FO_MBYTE_JOIN2)
-			|| mb_ptr2char(next) < 0x100 || endcurr1 < 0x100)
-#endif
-		)
-	{
-	    /* don't add a space if the line is ending in a space */
-	    if (endcurr1 == ' ')
-		endcurr1 = endcurr2;
-	    else
-		++spaces;
-	    /* extra space when 'joinspaces' set and line ends in '.' */
-	    if (       p_js
-		    && (endcurr1 == '.'
-			|| (vim_strchr(p_cpo, CPO_JOINSP) == NULL
-			    && (endcurr1 == '?' || endcurr1 == '!'))))
-		++spaces;
-	}
-    }
-    nextsize = (int)STRLEN(next);
-
-    newp = alloc_check((unsigned)(currsize + nextsize + spaces + 1));
-    if (newp == NULL)
+    colnr_T	col = 0;
+    int		ret = OK;
+
+    if (save_undo && u_save((linenr_T)(curwin->w_cursor.lnum - 1),
+			    (linenr_T)(curwin->w_cursor.lnum + count)) == FAIL)
+	return FAIL;
+
+    /* Allocate an array to store the number of spaces inserted before each
+     * line.  We will use it to pre-compute the length of the new line and the
+     * proper placement of each original line in the new one. */
+    spaces = lalloc_clear((long_u)count, TRUE);
+    if (spaces == NULL)
 	return FAIL;
 
     /*
-     * Insert the next line first, because we already have that pointer.
-     * Curr has to be obtained again, because getting next will have
-     * invalidated it.
+     * Don't move anything, just compute the final line length
+     * and setup the array of space strings lengths
      */
-    mch_memmove(newp + currsize + spaces, next, (size_t)(nextsize + 1));
-
-    curr = ml_get_curline();
-    mch_memmove(newp, curr, (size_t)currsize);
-
-    copy_spaces(newp + currsize, (size_t)spaces);
-
+    for (t = 0; t < count; ++t)
+    {
+	curr = ml_get((linenr_T)(curwin->w_cursor.lnum + t));
+	if (insert_space && t > 0)
+	{
+	    curr = skipwhite(curr);
+	    if (*curr != ')' && currsize != 0 && endcurr1 != TAB
+#ifdef FEAT_MBYTE
+		    && (!has_format_option(FO_MBYTE_JOIN)
+			|| (mb_ptr2char(curr) < 0x100 && endcurr1 < 0x100))
+		    && (!has_format_option(FO_MBYTE_JOIN2)
+			|| mb_ptr2char(curr) < 0x100 || endcurr1 < 0x100)
+#endif
+	       )
+	    {
+		/* don't add a space if the line is ending in a space */
+		if (endcurr1 == ' ')
+		    endcurr1 = endcurr2;
+		else
+		    ++spaces[t];
+		/* extra space when 'joinspaces' set and line ends in '.' */
+		if (       p_js
+			&& (endcurr1 == '.'
+			    || (vim_strchr(p_cpo, CPO_JOINSP) == NULL
+				&& (endcurr1 == '?' || endcurr1 == '!'))))
+		    ++spaces[t];
+	    }
+	}
+	currsize = (int)STRLEN(curr);
+	sumsize += currsize + spaces[t];
+	endcurr1 = endcurr2 = NUL;
+	if (insert_space && currsize > 0)
+	{
+#ifdef FEAT_MBYTE
+	    if (has_mbyte)
+	    {
+		cend = curr + currsize;
+		mb_ptr_back(curr, cend);
+		endcurr1 = (*mb_ptr2char)(cend);
+		if (cend > curr)
+		{
+		    mb_ptr_back(curr, cend);
+		    endcurr2 = (*mb_ptr2char)(cend);
+		}
+	    }
+	    else
+#endif
+	    {
+		endcurr1 = *(curr + currsize - 1);
+		if (currsize > 1)
+		    endcurr2 = *(curr + currsize - 2);
+	    }
+	}
+	line_breakcheck();
+	if (got_int)
+	{
+	    ret = FAIL;
+	    goto theend;
+	}
+    }
+
+    /* store the column position before last line */
+    col = sumsize - currsize - spaces[count - 1];
+
+    /* allocate the space for the new line */
+    newp = alloc_check((unsigned)(sumsize + 1));
+    cend = newp + sumsize;
+    *cend = 0;
+
+    /*
+     * Move affected lines to the new long one.
+     *
+     * Move marks from each deleted line to the joined line, adjusting the
+     * column.  This is not Vi compatible, but Vi deletes the marks, thus that
+     * should not really be a problem.
+     */
+    for (t = count - 1; ; --t)
+    {
+	cend -= currsize;
+	mch_memmove(cend, curr, (size_t)currsize);
+	if (spaces[t] > 0)
+	{
+	    cend -= spaces[t];
+	    copy_spaces(cend, (size_t)(spaces[t]));
+	}
+	mark_col_adjust(curwin->w_cursor.lnum + t, (colnr_T)0, (linenr_T)-t,
+				 (long)(cend - newp + spaces[t]));
+	if (t == 0)
+	    break;
+	curr = ml_get((linenr_T)(curwin->w_cursor.lnum + t - 1));
+	if (insert_space && t > 1)
+	    curr = skipwhite(curr);
+	currsize = (int)STRLEN(curr);
+    }
     ml_replace(curwin->w_cursor.lnum, newp, FALSE);
 
     /* Only report the change in the first line here, del_lines() will report
@@ -4280,32 +4279,32 @@ do_join(insert_space)
 					       curwin->w_cursor.lnum + 1, 0L);
 
     /*
-     * Delete the following line. To do this we move the cursor there
+     * Delete following lines. To do this we move the cursor there
      * briefly, and then move it back. After del_lines() the cursor may
      * have moved up (last line deleted), so the current lnum is kept in t.
-     *
-     * Move marks from the deleted line to the joined line, adjusting the
-     * column.  This is not Vi compatible, but Vi deletes the marks, thus that
-     * should not really be a problem.
      */
     t = curwin->w_cursor.lnum;
-    mark_col_adjust(t + 1, (colnr_T)0, (linenr_T)-1,
-			     (long)(currsize + spaces - (next - next_start)));
     ++curwin->w_cursor.lnum;
-    del_lines(1L, FALSE);
+    del_lines(count - 1, FALSE);
     curwin->w_cursor.lnum = t;
 
     /*
-     * go to first character of the joined line
+     * Set the cursor column:
+     * Vi compatible: use the column of the first join
+     * vim:           use the column of the last join
      */
-    curwin->w_cursor.col = currsize;
+    curwin->w_cursor.col =
+		    (vim_strchr(p_cpo, CPO_JOINCOL) != NULL ? currsize : col);
     check_cursor_col();
+
 #ifdef FEAT_VIRTUALEDIT
     curwin->w_cursor.coladd = 0;
 #endif
     curwin->w_set_curswant = TRUE;
 
-    return OK;
+theend:
+    vim_free(spaces);
+    return ret;
 }
 
 #ifdef FEAT_COMMENTS
@@ -4718,7 +4717,7 @@ format_lines(line_count, avoid_fex)
 		curwin->w_cursor.lnum++;
 		curwin->w_cursor.col = 0;
 		if (line_count < 0 && u_save_cursor() == FAIL)
-			break;
+		    break;
 #ifdef FEAT_COMMENTS
 		(void)del_bytes((long)next_leader_len, FALSE, FALSE);
 		if (next_leader_len > 0)
@@ -4726,7 +4725,7 @@ format_lines(line_count, avoid_fex)
 						      (long)-next_leader_len);
 #endif
 		curwin->w_cursor.lnum--;
-		if (do_join(TRUE) == FAIL)
+		if (do_join(2, TRUE, FALSE) == FAIL)
 		{
 		    beep_flush();
 		    break;