patch 8.0.0575: using freed memory when resetting 'indentexpr'

Problem:    Using freed memory when resetting 'indentexpr' while evaluating
            it. (Dominique Pelle)
Solution:   Make a copy of 'indentexpr'.

Author: brammool

src/misc1.c

@@ -9252,6 +9252,7 @@ find_match(int lookfor, linenr_T ourscope)
 get_expr_indent(void)
 {
     int		indent;
+    char_u	*inde_copy;
     pos_T	save_pos;
     colnr_T	save_curswant;
     int		save_set_curswant;
@@ -9268,7 +9269,16 @@ get_expr_indent(void)
     if (use_sandbox)
 	++sandbox;
     ++textlock;
-    indent = (int)eval_to_number(curbuf->b_p_inde);
+
+    /* Need to make a copy, the 'indentexpr' option could be changed while
+     * evaluating it. */
+    inde_copy = vim_strsave(curbuf->b_p_inde);
+    if (inde_copy != NULL)
+    {
+	indent = (int)eval_to_number(inde_copy);
+	vim_free(inde_copy);
+    }
+
     if (use_sandbox)
 	--sandbox;
     --textlock;

src/testdir/test_options.vim

@@ -319,3 +319,16 @@ func Test_set_values()
     throw 'Skipped: opt_test.vim does not exist'
   endif
 endfunc
+
+func ResetIndentexpr()
+  set indentexpr=
+endfunc
+
+func Test_set_indentexpr()
+  " this was causing usage of freed memory
+  set indentexpr=ResetIndentexpr()
+  new
+  call feedkeys("i\<c-f>", 'x')
+  call assert_equal('', &indentexpr)
+  bwipe!
+endfunc

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    575,
 /**/
     574,
 /**/