From: Bram Moolenaar <Bram@vim.org>
Date: Sat, 16 Feb 2019 19:05:11 +0100
Subject: patch 8.1.0936: may leak memory when using 'vartabstop'

Problem:    May leak memory when using 'vartabstop'. (Kuang-che Wu)
Solution:   Fix handling allocated memory for 'vartabstop'. (closes #3976)
(cherry picked from commit 55c77cf2ea9c15e1ec75d1faf702ec3c9e325271)
---
 src/buffer.c  |  4 +---
 src/option.c  | 13 +++++++++----
 src/version.c |  2 ++
 3 files changed, 12 insertions(+), 7 deletions(-)

--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2170,9 +2170,7 @@ free_buf_options(
 	vim_free(buf->b_p_vsts_array);
     buf->b_p_vsts_array = NULL;
     clear_string_option(&buf->b_p_vts);
-    if (buf->b_p_vts_array)
-	vim_free(buf->b_p_vts_array);
-    buf->b_p_vts_array = NULL;
+    VIM_CLEAR(buf->b_p_vts_array);
 #endif
 #ifdef FEAT_KEYMAP
     clear_string_option(&buf->b_p_keymap);
--- a/src/option.c
+++ b/src/option.c
@@ -5611,7 +5611,9 @@ didset_options2(void)
     (void)check_clipboard_option();
 #endif
 #ifdef FEAT_VARTABS
+    vim_free(curbuf->b_p_vsts_array);
     tabstop_set(curbuf->b_p_vsts, &curbuf->b_p_vsts_array);
+    vim_free(curbuf->b_p_vts_array);
     tabstop_set(curbuf->b_p_vts,  &curbuf->b_p_vts_array);
 #endif
 }
@@ -7587,14 +7589,14 @@ did_set_string_option(
 	    if (errmsg == NULL)
 	    {
 		int *oldarray = curbuf->b_p_vts_array;
+
 		if (tabstop_set(*varp, &(curbuf->b_p_vts_array)))
 		{
-		    if (oldarray)
-			vim_free(oldarray);
+		    vim_free(oldarray);
 #ifdef FEAT_FOLDING
 		    if (foldmethodIsIndent(curwin))
 			foldUpdateAll(curwin);
-#endif /* FEAT_FOLDING */
+#endif
 		}
 		else
 		    errmsg = e_invarg;
@@ -12800,10 +12802,11 @@ check_ff_value(char_u *p)
     return check_opt_strings(p, p_ff_values, FALSE);
 }
 
-#ifdef FEAT_VARTABS
+#if defined(FEAT_VARTABS) || defined(PROTO)
 
 /*
  * Set the integer values corresponding to the string setting of 'vartabstop'.
+ * "array" will be set, caller must free it if needed.
  */
     int
 tabstop_set(char_u *var, int **array)
@@ -12846,6 +12849,8 @@ tabstop_set(char_u *var, int **array)
     }
 
     *array = (int *)alloc((unsigned) ((valcount + 1) * sizeof(int)));
+    if (*array == NULL)
+	return FALSE;
     (*array)[0] = valcount;
 
     t = 1;
--- a/src/version.c
+++ b/src/version.c
@@ -808,6 +808,8 @@ static int included_patches[] =
 /**/
     948,
 /**/
+    936,
+/**/
     884,
 /**/
     883,