vim-patch:9.2.0385: Integer overflow with "ze" and large 'sidescrolloff' (#39289)

Problem:  Integer overflow with "ze" and large 'sidescrolloff'.
Solution: Check for overflow to avoid negative w_leftcol (zeertzjq).

closes: vim/vim#20026

https://github.com/vim/vim/commit/33f3965087b01dccf4382ed419d34799ffd66cd9
(cherry picked from commit 1569a71c8a)

src/nvim/move.c

@@ -885,9 +885,8 @@ void curs_columns(win_T *wp, int may_scroll)
     // If scrolling is off, wp->w_leftcol is assumed to be 0
 
     // If Cursor is left of the screen, scroll rightwards.
-    // If Cursor is right of the screen, scroll leftwards
-    // If we get closer to the edge than 'sidescrolloff', scroll a little
-    // extra
+    // If Cursor is right of the screen, scroll leftwards.
+    // If we get closer to the edge than 'sidescrolloff', scroll a little extra.
     int64_t siso = get_sidescrolloff_value(wp);
     int64_t off_left = startcol - wp->w_leftcol - siso;
     int64_t off_right = endcol - wp->w_leftcol - (wp->w_view_width - siso) + 1;

src/nvim/normal.c

@@ -2911,9 +2911,10 @@ static void nv_zet(cmdarg_T *cap)
       int n = curwin->w_view_width - win_col_off(curwin);
       if (col + siso < n) {
         col = 0;
-      } else {
-        // TODO(zeertzjq): check for overflow
+      } else if (siso - n < INT_MAX - col) {
         col = (int)(col + siso - n + 1);
+      } else {
+        col = INT_MAX;
       }
       if (curwin->w_leftcol != col) {
         curwin->w_leftcol = col;

test/old/testdir/test_normal.vim

@@ -1202,6 +1202,31 @@ func Test_normal17_z_scroll_hor2()
   bw!
 endfunc
 
+func Test_large_sidescrolloff_no_overflow()
+  10new
+  20vsp
+  setlocal nowrap sidescrolloff=2147483647
+  call setline(1, repeat('a', 40))
+
+  normal! $
+  redraw!
+  call assert_equal(29, winsaveview().leftcol)
+
+  normal! zs
+  redraw!
+  call assert_equal(29, winsaveview().leftcol)
+
+  normal! ze
+  redraw!
+  call assert_equal(29, winsaveview().leftcol)
+
+  normal! 0
+  redraw!
+  call assert_equal(0, winsaveview().leftcol)
+
+  bw!
+endfunc
+
 " Test for commands that scroll the window horizontally. Test with folds.
 "   H, M, L, CTRL-E, CTRL-Y, CTRL-U, CTRL-D, PageUp, PageDown commands
 func Test_vert_scroll_cmds()