No undefined behaviour in parser

closes #2172

CHANGELOG.md

@@ -1,3 +1,4 @@
+* Extra logic error detection in http parser.
 * Move Windows CI to Drone.
 
 --------------------------------------------------------------------------------

include/boost/beast/http/impl/basic_parser.ipp

@@ -82,7 +82,17 @@ basic_parser<isRequest>::
 put(net::const_buffer buffer,
     error_code& ec)
 {
-    BOOST_ASSERT(state_ != state::complete);
+    // If this goes off you have tried to parse more data after the parser
+    // has completed. A common cause of this is re-using a parser, which is
+    // not supported. If you need to re-use a parser, consider storing it
+    // in an optional. Then reset() and emplace() prior to parsing each new
+    // message.
+    BOOST_ASSERT(!is_done());
+    if (is_done())
+    {
+        ec = error::stale_parser;
+        return 0;
+    }
     auto p = static_cast<char const*>(buffer.data());
     auto n = buffer.size();
     auto const p0 = p;