fixed warnings on linux

contrib/epee/include/net/net_utils_base.h

@@ -79,6 +79,8 @@ namespace net_utils
                                m_started(time(NULL))
     {}
 
+    connection_context_base(const connection_context_base& a) = default;
+
     connection_context_base& operator=(const connection_context_base& a)
     {
       set_details(a.m_connection_id, a.m_remote_ip, a.m_remote_port, a.m_is_income);

src/crypto/crypto-sugar.h

@@ -844,8 +844,11 @@ namespace crypto
     // zeroes all elements
     void zero()
     {
+      PUSH_GCC_WARNINGS()
+      DISABLE_GCC_AND_CLANG_WARNING(class-memaccess)
       size_t size_bytes = sizeof(scalar_t) * size();
       memset(data(), 0, size_bytes);
+      POP_GCC_WARNINGS()
     }
 
     // invert all elements in-place efficiently: 4*N muptiplications + 1 inversion

src/currency_core/currency_format_utils_abstract.h

@@ -193,7 +193,7 @@ namespace currency
   }
   //---------------------------------------------------------------
   inline
-  const bool get_key_image_from_txin_v(const txin_v& in_v, crypto::key_image& result) noexcept
+  bool get_key_image_from_txin_v(const txin_v& in_v, crypto::key_image& result) noexcept
   {
     try
     {
@@ -218,6 +218,7 @@ namespace currency
     catch(...)
     {
       // should never go here, just precaution
+      return false;
     }
 
     return false;