Problem: bind_to_device unnecessarily accepts a non-const string parameter

Solution: add const

src/ip.cpp

@@ -237,7 +237,7 @@ int zmq::set_nosigpipe (fd_t s_)
     return 0;
 }
 
-void zmq::bind_to_device (fd_t s_, std::string &bound_device_)
+void zmq::bind_to_device (fd_t s_, const std::string &bound_device_)
 {
 #ifdef ZMQ_HAVE_SO_BINDTODEVICE
     int rc = setsockopt (s_, SOL_SOCKET, SO_BINDTODEVICE,

src/ip.hpp

@@ -56,7 +56,7 @@ void set_ip_type_of_service (fd_t s_, int iptos_);
 int set_nosigpipe (fd_t s_);
 
 // Binds the underlying socket to the given device, eg. VRF or interface
-void bind_to_device (fd_t s_, std::string &bound_device_);
+void bind_to_device (fd_t s_, const std::string &bound_device_);
 
 // Initialize network subsystem. May be called multiple times. Each call must be matched by a call to shutdown_network.
 bool initialize_network ();