patch 8.2.4739: accessing freed memory after WinScrolled autocmd event

Problem:    Accessing freed memory after WinScrolled autocmd event.
Solution:   Check the window pointer is still valid. (closes #10156)
            Remove the argument from may_trigger_winscrolled().

src/edit.c

@@ -1528,7 +1528,7 @@ ins_redraw(int ready)	    // not busy with something
     }
 
     if (ready)
-	may_trigger_winscrolled(curwin);
+	may_trigger_winscrolled();
 
     // Trigger SafeState if nothing is pending.
     may_trigger_safestate(ready

src/gui.c

@@ -5238,7 +5238,7 @@ gui_update_screen(void)
     }
 
     if (!finish_op)
-	may_trigger_winscrolled(curwin);
+	may_trigger_winscrolled();
 
 # ifdef FEAT_CONCEAL
     if (conceal_update_lines

src/main.c

@@ -1342,7 +1342,7 @@ main_loop(
 	    validate_cursor();
 
 	    if (!finish_op)
-		may_trigger_winscrolled(curwin);
+		may_trigger_winscrolled();
 
 	    // If nothing is pending and we are going to wait for the user to
 	    // type a character, trigger SafeState.

src/proto/window.pro

@@ -17,7 +17,7 @@ void curwin_init(void);
 void close_windows(buf_T *buf, int keep_curwin);
 int one_window(void);
 int win_close(win_T *win, int free_buf);
-void may_trigger_winscrolled(win_T *wp);
+void may_trigger_winscrolled(void);
 void win_close_othertab(win_T *win, int free_buf, tabpage_T *tp);
 void win_free_all(void);
 win_T *winframe_remove(win_T *win, int *dirp, tabpage_T *tp);

src/testdir/test_autocmd.vim

@@ -364,6 +364,30 @@ func Test_WinScrolled()
   call delete('Xtest_winscrolled')
 endfunc
 
+func Test_WinScrolled_close_curwin()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+    set nowrap scrolloff=0
+    call setline(1, ['aaa', 'bbb'])
+    vsplit
+    au WinScrolled * close
+    au VimLeave * call writefile(['123456'], 'Xtestout')
+  END
+  call writefile(lines, 'Xtest_winscrolled_close_curwin')
+  let buf = RunVimInTerminal('-S Xtest_winscrolled_close_curwin', {'rows': 6})
+
+  " This was using freed memory
+  call term_sendkeys(buf, "\<C-E>")
+  call TermWait(buf)
+  call StopVimInTerminal(buf)
+
+  call assert_equal(['123456'], readfile('Xtestout'))
+
+  call delete('Xtest_winscrolled_close_curwin')
+  call delete('Xtestout')
+endfunc
+
 func Test_WinClosed()
   " Test that the pattern is matched against the closed window's ID, and both
   " <amatch> and <afile> are set to it.

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4739,
 /**/
     4738,
 /**/

src/window.c

@@ -2784,9 +2784,13 @@ trigger_winclosed(win_T *win)
     recursive = FALSE;
 }
 
+/*
+ * Trigger WinScrolled for "curwin" if needed.
+ */
     void
-may_trigger_winscrolled(win_T *wp)
+may_trigger_winscrolled(void)
 {
+    win_T	    *wp = curwin;
     static int	    recursive = FALSE;
     char_u	    winid[NUMBUFLEN];
 
@@ -2804,12 +2808,16 @@ may_trigger_winscrolled(win_T *wp)
 	apply_autocmds(EVENT_WINSCROLLED, winid, winid, FALSE, wp->w_buffer);
 	recursive = FALSE;
 
+	// an autocmd may close the window, "wp" may be invalid now
+	if (win_valid_any_tab(wp))
+	{
 	    wp->w_last_topline = wp->w_topline;
 	    wp->w_last_leftcol = wp->w_leftcol;
 	    wp->w_last_width = wp->w_width;
 	    wp->w_last_height = wp->w_height;
 	}
     }
+}
 
 /*
  * Close window "win" in tab page "tp", which is not the current tab page.