vim-patch:8.1.1642: may use uninitialized variable

Problem:    May use uninitialized variable. (Patrick Palka)
Solution:   Initialize variables earlier. (closes vim/vim#4623)
https://github.com/vim/vim/commit/ec572ad6a6cb0d4e71901951a70a4f038d48cb17

3 files changed, 29 insertions, 18 deletions

diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 323c6cf9c3..9069c5adcb 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -412,9 +412,9 @@ EXTERN vimmenu_T        *root_menu INIT(= NULL);
  */
 EXTERN int sys_menu INIT(= FALSE);
 
-/* While redrawing the screen this flag is set.  It means the screen size
- * ('lines' and 'rows') must not be changed. */
-EXTERN int updating_screen INIT(= FALSE);
+// While redrawing the screen this flag is set.  It means the screen size
+// ('lines' and 'rows') must not be changed.
+EXTERN int updating_screen INIT(= 0);
 
 /*
  * All windows are linked in a list. firstwin points to the first entry,
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index b6da02d9c3..4cdfec9670 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -334,10 +334,10 @@ int update_screen(int type)
     }
     return FAIL;
   }
+  updating_screen = 1;
 
-  updating_screen = TRUE;
-  ++display_tick;           /* let syntax code know we're in a next round of
-                             * display updating */
+  display_tick++;           // let syntax code know we're in a next round of
+                            // display updating
 
   // Tricky: vim code can reset msg_scrolled behind our back, so need
   // separate bookkeeping for now.
@@ -565,7 +565,7 @@ int update_screen(int type)
     wp->w_buffer->b_mod_set = false;
   }
 
-  updating_screen = FALSE;
+  updating_screen = 0;
 
   /* Clear or redraw the command line.  Done last, because scrolling may
    * mess up the command line. */
@@ -2215,9 +2215,10 @@ win_line (
 
   int n_skip = 0;                       /* nr of chars to skip for 'nowrap' */
 
-  int fromcol = 0, tocol = 0;           // start/end of inverting
+  int fromcol = -10;                    // start of inverting
+  int tocol = MAXCOL;                   // end of inverting
   int fromcol_prev = -2;                // start of inverting after cursor
-  int noinvcur = false;                 // don't invert the cursor
+  bool noinvcur = false;                // don't invert the cursor
   pos_T *top, *bot;
   int lnum_in_visual_area = false;
   pos_T pos;
@@ -2416,27 +2417,26 @@ win_line (
       capcol_lnum = 0;
     }
 
-    //
-    // handle visual active in this window
-    //
-    fromcol = -10;
-    tocol = MAXCOL;
+    // handle Visual active in this window
     if (VIsual_active && wp->w_buffer == curwin->w_buffer) {
-      // Visual is after curwin->w_cursor
       if (ltoreq(curwin->w_cursor, VIsual)) {
+        // Visual is after curwin->w_cursor
         top = &curwin->w_cursor;
         bot = &VIsual;
-      } else {                          // Visual is before curwin->w_cursor
+      } else {
+        // Visual is before curwin->w_cursor
         top = &VIsual;
         bot = &curwin->w_cursor;
       }
       lnum_in_visual_area = (lnum >= top->lnum && lnum <= bot->lnum);
-      if (VIsual_mode == Ctrl_V) {        // block mode
+      if (VIsual_mode == Ctrl_V) {
+        // block mode
         if (lnum_in_visual_area) {
           fromcol = wp->w_old_cursor_fcol;
           tocol = wp->w_old_cursor_lcol;
         }
-      } else {                          // non-block mode
+      } else {
+        // non-block mode
         if (lnum > top->lnum && lnum <= bot->lnum) {
           fromcol = 0;
         } else if (lnum == top->lnum) {
diff --git a/src/nvim/testdir/test_number.vim b/src/nvim/testdir/test_number.vim
index 59debcea0d..3c9afc41d5 100644
--- a/src/nvim/testdir/test_number.vim
+++ b/src/nvim/testdir/test_number.vim
@@ -252,3 +252,14 @@ func Test_numberwidth_adjusted()
   call s:compare_lines(expect, lines)
   call s:close_windows()
 endfunc
+
+" This was causing a memcheck error
+func Test_relativenumber_uninitialised()
+  new
+  set rnu
+  call setline(1, ["a", "b"])
+  redraw
+  call feedkeys("j", 'xt')
+  redraw
+  bwipe!
+endfunc