vim-patch:8.1.0126: various problems with 'vartabstop'

Problem:    Various problems with 'vartabstop'.
Solution:   Fix memory leak.  Fix crash. Add a few more tests. (Christian
            Brabandt, closes vim/vim#3076)
307ac5c68e

src/nvim/ex_cmds.c

@@ -853,7 +853,6 @@ void ex_retab(exarg_T *eap)
     if (tabstop_count(old_vts_ary) > 0 || tabstop_count(new_vts_array) > 1) {
       set_string_option_direct("vts", -1, new_ts_str,
                                OPT_FREE | OPT_LOCAL, 0);
-      xfree(new_ts_str);
       curbuf->b_p_vts_array = new_vts_array;
       xfree(old_vts_ary);
     } else {
@@ -862,6 +861,7 @@ void ex_retab(exarg_T *eap)
       curbuf->b_p_ts = tabstop_first(new_vts_array);
       xfree(new_vts_array);
     }
+    xfree(new_ts_str);
   }
   coladvance(curwin->w_curswant);
 

src/nvim/option.c

@@ -7215,7 +7215,7 @@ colnr_T tabstop_start(colnr_T col, long ts, long *vts)
 // to another.
 void tabstop_fromto(colnr_T start_col,
                     colnr_T end_col,
-                    long ts,
+                    long ts_arg,
                     long *vts,
                     int *ntabs,
                     int *nspcs)
@@ -7225,10 +7225,13 @@ void tabstop_fromto(colnr_T start_col,
   int padding = 0;
   int tabcount;
   int t;
+  long ts = ts_arg == 0 ? curbuf->b_p_ts : ts_arg;
 
   if (vts == NULL || vts[0] == 0) {
     int tabs = 0;
-    int initspc = (int)ts - (start_col % (int)ts);
+    int initspc = 0;
+
+    initspc = (int)ts - (start_col % (int)ts);
     if (spaces >= initspc) {
       spaces -= initspc;
       tabs++;

src/nvim/screen.c

@@ -3543,6 +3543,10 @@ static int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow,
             xfree(p_extra_free);
             p_extra_free = p;
             for (i = 0; i < tab_len; i++) {
+              if (*p == NUL) {
+                tab_len = i;
+                break;
+              }
               int lcs = wp->w_p_lcs_chars.tab2;
 
               // if tab3 is given, need to change the char

src/nvim/testdir/test_vartabs.vim

@@ -262,21 +262,37 @@ func! Test_vartabs_breakindent()
 endfunc
 
 func! Test_vartabs_linebreak()
-  if winwidth(0) < 80
+  if winwidth(0) < 40
     return
   endif
   new
-  70vnew
+  40vnew
   %d
-  setl linebreak vartabstop=10,15,20,40
+  setl linebreak vartabstop=10,20,30,40
   call setline(1, "\tx\tx\tx\tx")
 
-  let lines = ScreenLines([1, 2], winwidth(0))
+  let expect = ['          x                             ',
-  let expect = ['          x              x                   x                        ',
+        \       'x                   x                   ',
         \       'x                                       ']
+  let lines = ScreenLines([1, 3], winwidth(0))
+  call s:compare_lines(expect, lines)
+  setl list listchars=tab:>-
+  let expect = ['>---------x>------------------          ',
+        \       'x>------------------x>------------------',
+        \       'x                                       ']
+  let lines = ScreenLines([1, 3], winwidth(0))
+  call s:compare_lines(expect, lines)
+  setl linebreak vartabstop=40
+  let expect = ['>---------------------------------------',
+        \       'x>--------------------------------------',
+        \       'x>--------------------------------------',
+        \       'x>--------------------------------------',
+        \       'x                                       ']
+  let lines = ScreenLines([1, 5], winwidth(0))
   call s:compare_lines(expect, lines)
 
   " cleanup
   bw!
   bw!
+  set nolist listchars&vim
 endfunc