xmllite/writer: Properly validate DocType name.

dlls/xmllite/tests/writer.c

@@ -2145,6 +2145,14 @@ static void test_WriteDocType(void)
     hr = IXmlWriter_WriteDocType(writer, L"a", pubidW, NULL, NULL);
     ok(hr == WC_E_PUBLICID, "Unexpected hr %#lx.\n", hr);
 
+    /* Invalid multi-character string */
+    hr = IXmlWriter_WriteDocType(writer, L":ax>m", NULL, NULL, NULL);
+    ok(hr == WC_E_NAMECHARACTER, "Unexpected hr %#lx.\n", hr);
+
+    /* Valid multi-character string */
+    hr = IXmlWriter_WriteDocType(writer, L"root", NULL, NULL, NULL);
+    ok(hr == S_OK, "Unexpected hr %#lx.\n", hr);
+
     IStream_Release(stream);
 
     for (i = 0; i < ARRAY_SIZE(doctype_tests); i++)

dlls/xmllite/writer.c

@@ -376,11 +376,12 @@ static HRESULT is_valid_name(const WCHAR *str, unsigned int *out)
     if (!is_namestartchar(*str++))
         return WC_E_NAMECHARACTER;
 
-    while (*str++)
+    while (*str)
     {
         if (!is_namechar(*str))
             return WC_E_NAMECHARACTER;
         len++;
+        str++;
     }
 
     *out = len;