Fix zmq_ctx_get_ext not setting the length of the out string

Author: uyha

src/ctx.cpp

@@ -293,7 +293,7 @@ int zmq::ctx_t::set (int option_, const void *optval_, size_t optvallen_)
     return -1;
 }
 
-int zmq::ctx_t::get (int option_, void *optval_, const size_t *optvallen_)
+int zmq::ctx_t::get (int option_, void *optval_, size_t *optvallen_)
 {
     const bool is_int = (*optvallen_ == sizeof (int));
     int *value = static_cast<int *> (optval_);
@@ -607,7 +607,7 @@ int zmq::thread_ctx_t::set (int option_, const void *optval_, size_t optvallen_)
 
 int zmq::thread_ctx_t::get (int option_,
                             void *optval_,
-                            const size_t *optvallen_)
+                            size_t *optvallen_)
 {
     const bool is_int = (*optvallen_ == sizeof (int));
     int *value = static_cast<int *> (optval_);
@@ -630,6 +630,7 @@ int zmq::thread_ctx_t::get (int option_,
                 scoped_lock_t locker (_opt_sync);
                 memcpy (optval_, _thread_name_prefix.data (),
                         _thread_name_prefix.size ());
+                *optvallen_ = _thread_name_prefix.size ();
                 return 0;
             }
             break;

src/ctx.hpp

@@ -46,7 +46,7 @@ class thread_ctx_t
                        const char *name_ = NULL) const;
 
     int set (int option_, const void *optval_, size_t optvallen_);
-    int get (int option_, void *optval_, const size_t *optvallen_);
+    int get (int option_, void *optval_, size_t *optvallen_);
 
   protected:
     //  Synchronisation of access to context options.
@@ -89,7 +89,7 @@ class ctx_t ZMQ_FINAL : public thread_ctx_t
 
     //  Set and get context properties.
     int set (int option_, const void *optval_, size_t optvallen_);
-    int get (int option_, void *optval_, const size_t *optvallen_);
+    int get (int option_, void *optval_, size_t *optvallen_);
     int get (int option_);
 
     //  Create and destroy a socket.