2 files changed, 23 insertions, 11 deletions
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 70d4f02f5a..67740e8d9f 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -7083,14 +7083,15 @@ bool tabstop_set(char_u *var, long **array)
   int t;
   char_u *cp;
 
-  if ((!var[0] || (var[0] == '0' && !var[1]))) {
+  if (var[0] == NUL || (var[0] == '0' && var[1] == NUL)) {
     *array = NULL;
     return true;
   }
 
-  for (cp = var; *cp; cp++) {
-    if (cp == var || *(cp - 1) == ',') {
+  for (cp = var; *cp != NUL; cp++) {
+    if (cp == var || cp[-1] == ',') {
       char_u *end;
+
       if (strtol((char *)cp, (char **)&end, 10) <= 0) {
         if (cp != end) {
           EMSG(_(e_positive));
@@ -7104,7 +7105,7 @@ bool tabstop_set(char_u *var, long **array)
     if (ascii_isdigit(*cp)) {
       continue;
     }
-    if (*cp == ',' && cp > var && *(cp - 1) != ',') {
+    if (cp[0] == ',' && cp > var && cp[-1] != ',' && cp[1] != NUL) {
       valcount++;
       continue;
     }
@@ -7116,12 +7117,12 @@ bool tabstop_set(char_u *var, long **array)
   (*array)[0] = valcount;
 
   t = 1;
-  for (cp = var; *cp;) {
+  for (cp = var; *cp != NUL;) {
     (*array)[t++] = atoi((char *)cp);
-    while (*cp && *cp != ',') {
+    while (*cp  != NUL && *cp != ',') {
       cp++;
     }
-    if (*cp) {
+    if (*cp != NUL) {
       cp++;
     }
   }
diff --git a/src/nvim/testdir/test_vartabs.vim b/src/nvim/testdir/test_vartabs.vim
index c43e178309..c8470952d1 100644
--- a/src/nvim/testdir/test_vartabs.vim
+++ b/src/nvim/testdir/test_vartabs.vim
@@ -5,11 +5,11 @@ if !has("vartabs")
 endif
 
 source view_util.vim
-function! s:compare_lines(expect, actual)
+func s:compare_lines(expect, actual)
   call assert_equal(join(a:expect, "\n"), join(a:actual, "\n"))
-endfunction
+endfunc
 
-func! Test_vartabs()
+func Test_vartabs()
   new
   %d
 
@@ -261,7 +261,7 @@ func! Test_vartabs_breakindent()
   bwipeout!
 endfunc
 
-func! Test_vartabs_linebreak()
+func Test_vartabs_linebreak()
   if winwidth(0) < 40
     return
   endif
@@ -296,3 +296,14 @@ func! Test_vartabs_linebreak()
   bw!
   set nolist listchars&vim
 endfunc
+
+func Test_vartabs_failures()
+  call assert_fails('set vts=8,')
+  call assert_fails('set vsts=8,')
+  call assert_fails('set vts=8,,8')
+  call assert_fails('set vsts=8,,8')
+  call assert_fails('set vts=8,,8,')
+  call assert_fails('set vsts=8,,8,')
+  call assert_fails('set vts=,8')
+  call assert_fails('set vsts=,8')
+endfunc