patch 9.0.1144: reading beyond text

Problem:    Reading beyond text.
Solution:   Add strlen_maxlen() and use it.

src/message.c

@@ -3055,7 +3055,8 @@ msg_puts_printf(char_u *str, int maxlen)
     {
 	char_u *tofree = NULL;
 
-	if (maxlen > 0 && STRLEN(p) > (size_t)maxlen)
+	if (maxlen > 0 && vim_strlen_maxlen((char *)p, (size_t)maxlen)
+							     >= (size_t)maxlen)
 	{
 	    tofree = vim_strnsave(p, (size_t)maxlen);
 	    p = tofree;

src/proto/strings.pro

@@ -12,6 +12,7 @@ char_u *strlow_save(char_u *orig);
 void del_trailing_spaces(char_u *ptr);
 void vim_strncpy(char_u *to, char_u *from, size_t len);
 void vim_strcat(char_u *to, char_u *from, size_t tosize);
+size_t vim_strlen_maxlen(char *s, size_t maxlen);
 int vim_stricmp(char *s1, char *s2);
 int vim_strnicmp(char *s1, char *s2, size_t len);
 char_u *vim_strchr(char_u *string, int c);

src/strings.c

@@ -525,6 +525,19 @@ vim_strcat(char_u *to, char_u *from, size_t tosize)
 	mch_memmove(to + tolen, from, fromlen + 1);
 }
 
+/*
+ * A version of strlen() that has a maximum length.
+ */
+    size_t
+vim_strlen_maxlen(char *s, size_t maxlen)
+{
+    size_t i;
+    for (i = 0; i < maxlen; ++i)
+	if (s[i] == NUL)
+	    break;
+    return i;
+}
+
 #if (!defined(HAVE_STRCASECMP) && !defined(HAVE_STRICMP)) || defined(PROTO)
 /*
  * Compare two strings, ignoring case, using current locale.
@@ -582,7 +595,7 @@ vim_strnicmp(char *s1, char *s2, size_t len)
  * 128 to 255 correctly.  It also doesn't return a pointer to the NUL at the
  * end of the string.
  */
-    char_u  *
+    char_u *
 vim_strchr(char_u *string, int c)
 {
     char_u	*p;

src/testdir/test_cmdline.vim

@@ -654,6 +654,17 @@ func Test_getcompletion()
   call assert_fails('call getcompletion("abc", [])', 'E1174:')
 endfunc
 
+func Test_multibyte_expression()
+  " This was using uninitialized memory.
+  let lines =<< trim END
+      set verbose=6
+      norm @=ٷ
+      qall!
+  END
+  call writefile(lines, 'XmultiScript', 'D')
+  call RunVim('', '', '-u NONE -n -e -s -S XmultiScript')
+endfunc
+
 " Test for getcompletion() with "fuzzy" in 'wildoptions'
 func Test_getcompletion_wildoptions()
   let save_wildoptions = &wildoptions

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1144,
 /**/
     1143,
 /**/