diff --git a/src/algorithms/signal_source/gnuradio_blocks/gr_complex_ip_packet_source.cc b/src/algorithms/signal_source/gnuradio_blocks/gr_complex_ip_packet_source.cc
index 78f27282c..fdc36dc2c 100644
--- a/src/algorithms/signal_source/gnuradio_blocks/gr_complex_ip_packet_source.cc
+++ b/src/algorithms/signal_source/gnuradio_blocks/gr_complex_ip_packet_source.cc
@@ -319,7 +319,7 @@ void Gr_Complex_Ip_Packet_Source::my_pcap_loop_thread(pcap_t *pcap_handle)
 }
 
 
-void Gr_Complex_Ip_Packet_Source::demux_samples(gr_vector_void_star output_items, int num_samples_readed)
+void Gr_Complex_Ip_Packet_Source::demux_samples(const gr_vector_void_star& output_items, int num_samples_readed)
 {
     int8_t real;
     int8_t imag;
diff --git a/src/algorithms/signal_source/gnuradio_blocks/gr_complex_ip_packet_source.h b/src/algorithms/signal_source/gnuradio_blocks/gr_complex_ip_packet_source.h
index 0e07af4e4..579bdd1dd 100644
--- a/src/algorithms/signal_source/gnuradio_blocks/gr_complex_ip_packet_source.h
+++ b/src/algorithms/signal_source/gnuradio_blocks/gr_complex_ip_packet_source.h
@@ -98,7 +98,7 @@ private:
     size_t d_item_size;
     bool d_IQ_swap;
     boost::thread *d_pcap_thread;
-    void demux_samples(gr_vector_void_star output_items, int num_samples_readed);
+    void demux_samples(const gr_vector_void_star& output_items, int num_samples_readed);
     void my_pcap_loop_thread(pcap_t *pcap_handle);
     void pcap_callback(u_char *args, const struct pcap_pkthdr *pkthdr, const u_char *packet);
     static void static_pcap_callback(u_char *args, const struct pcap_pkthdr *pkthdr, const u_char *packet);
diff --git a/src/core/libs/supl/asn-rrlp/constraints.c b/src/core/libs/supl/asn-rrlp/constraints.c
index 1bdda73e5..742735f8a 100644
--- a/src/core/libs/supl/asn-rrlp/constraints.c
+++ b/src/core/libs/supl/asn-rrlp/constraints.c
@@ -68,8 +68,6 @@ _asn_i_ctfailcb(void *key, asn_TYPE_descriptor_t *td, const void *sptr, const ch
 		memcpy(arg->errbuf, "<broken vsnprintf>", arg->errlen);
 		arg->errbuf[arg->errlen] = 0;
 	}
-
-	return;
 }
 
 int
diff --git a/src/core/libs/supl/asn-supl/constraints.c b/src/core/libs/supl/asn-supl/constraints.c
index 1bdda73e5..742735f8a 100644
--- a/src/core/libs/supl/asn-supl/constraints.c
+++ b/src/core/libs/supl/asn-supl/constraints.c
@@ -68,8 +68,6 @@ _asn_i_ctfailcb(void *key, asn_TYPE_descriptor_t *td, const void *sptr, const ch
 		memcpy(arg->errbuf, "<broken vsnprintf>", arg->errlen);
 		arg->errbuf[arg->errlen] = 0;
 	}
-
-	return;
 }
 
 int
diff --git a/src/core/receiver/gnss_flowgraph.cc b/src/core/receiver/gnss_flowgraph.cc
index 060adfb5d..20e959dc0 100644
--- a/src/core/receiver/gnss_flowgraph.cc
+++ b/src/core/receiver/gnss_flowgraph.cc
@@ -1166,7 +1166,7 @@ void GNSSFlowgraph::remove_signal(const Gnss_Signal& gs)
 
 
 // project Doppler from primary frequency to secondary frequency
-double GNSSFlowgraph::project_doppler(std::string searched_signal, double primary_freq_doppler_hz)
+double GNSSFlowgraph::project_doppler(const std::string& searched_signal, double primary_freq_doppler_hz)
 {
     switch (mapStringValues_[searched_signal])
         {
diff --git a/src/core/receiver/gnss_flowgraph.h b/src/core/receiver/gnss_flowgraph.h
index 121271b62..d193cd3c1 100644
--- a/src/core/receiver/gnss_flowgraph.h
+++ b/src/core/receiver/gnss_flowgraph.h
@@ -181,7 +181,7 @@ private:
     void push_back_signal(const Gnss_Signal& gs);
     void remove_signal(const Gnss_Signal& gs);
 
-    double project_doppler(std::string searched_signal, double primary_freq_doppler_hz);
+    double project_doppler(const std::string& searched_signal, double primary_freq_doppler_hz);
     bool connected_;
     bool running_;
     int sources_count_;