Check tcp port range

src/scheme_repl_server.cpp

@@ -3,6 +3,7 @@
 #include "scheme.hpp"
 #include <godot_cpp/classes/os.hpp>
 #include <godot_cpp/variant/utility_functions.hpp>
+#include <limits>
 
 using namespace godot;
 using gd = UtilityFunctions;
@@ -49,14 +50,21 @@ void SchemeReplServer::server_loop(int tcp_port, const String &tcp_bind_address)
   tcp_server->stop();
 }
 
-std::optional<std::pair<uint16_t, String>> parse_repl_args() {
+using tcp_port_t = uint16_t;
+
+std::optional<std::pair<tcp_port_t, String>> parse_repl_args() {
   // TODO: accept --s7-tcp-address=<address>
   String tcp_bind_address = "127.0.0.1";
+  String tcp_port_option = "--s7-tcp-port";
   for (const auto &arg : OS::get_singleton()->get_cmdline_args()) {
-    if (arg.begins_with("--s7-tcp-port")) {
+    if (arg.begins_with(tcp_port_option)) {
       auto parts = arg.split("=");
       auto tcp_port = parts.size() > 1 ? parts[1].to_int() : 0;
-      return std::make_pair(tcp_port, tcp_bind_address);
+      auto max_tcp_port = std::numeric_limits<tcp_port_t>::max();
+      if (tcp_port < 0 || tcp_port >= max_tcp_port) {
+        gd::printerr(tcp_port_option, " argument must be a value between 0 and ", max_tcp_port, ".");
+      }
+      return std::make_pair(static_cast<tcp_port_t>(tcp_port), std::move(tcp_bind_address));
     }
   }
   return std::nullopt;