epicsExportRegistrar() must be inside extern "C" block

pvAccessApp/v3ioc/PVAClientRegister.cpp

@@ -67,6 +67,7 @@ static void stopPVAClientRegister(void)
     }
 }
 
-
-epicsExportRegistrar(startPVAClientRegister);
-epicsExportRegistrar(stopPVAClientRegister);
+extern "C" {
+    epicsExportRegistrar(startPVAClientRegister);
+    epicsExportRegistrar(stopPVAClientRegister);
+}

pvAccessApp/v3ioc/PVAServerRegister.cpp

@@ -125,5 +125,7 @@ static void stopPVAServerRegister(void)
     }
 }
 
-epicsExportRegistrar(startPVAServerRegister);
-epicsExportRegistrar(stopPVAServerRegister);
+extern "C" {
+    epicsExportRegistrar(startPVAServerRegister);
+    epicsExportRegistrar(stopPVAServerRegister);
+}