Fix some compiler warnings in public headers (#468)

### Motivation

Fix some compiler warnings in public headers when using with -Wextra. These warnings prevent projects using -Wextra -Werror to use pulsar client without modifications.

### Modifications

1. Modified public headers to fix compiler warnings
2. Add compile options "-Wextra -Wno-unused-parameter" to compile examples to help find similar issues

Author: erobot

examples/CMakeLists.txt

@@ -19,6 +19,7 @@
 
 if (NOT MSVC)
   set(CMAKE_C_FLAGS " -std=c99 ${CMAKE_C_FLAGS}")
+  add_compile_options(-Wextra -Wno-unused-parameter)
 endif()
 
 set(SAMPLE_ASYNC_PRODUCER_SOURCES

include/pulsar/BrokerConsumerStats.h

@@ -73,7 +73,7 @@ class PULSAR_PUBLIC BrokerConsumerStats {
     virtual const std::string getConnectedSince() const;
 
     /** Returns Whether this subscription is Exclusive or Shared or Failover */
-    virtual const ConsumerType getType() const;
+    virtual ConsumerType getType() const;
 
     /** Returns the rate of messages expired on this subscription. msg/s */
     virtual double getMsgRateExpired() const;

include/pulsar/Message.h

@@ -176,7 +176,7 @@ class PULSAR_PUBLIC Message {
     /**
      * Get the redelivery count for this message
      */
-    const int getRedeliveryCount() const;
+    int getRedeliveryCount() const;
 
     /**
      * Check if schema version exists

include/pulsar/c/client_configuration.h

@@ -195,13 +195,13 @@ PULSAR_PUBLIC const char *pulsar_client_configuration_get_listener_name(pulsar_c
 PULSAR_PUBLIC void pulsar_client_configuration_set_partitions_update_interval(
     pulsar_client_configuration_t *conf, const unsigned int intervalInSeconds);
 
-PULSAR_PUBLIC const unsigned int pulsar_client_configuration_get_partitions_update_interval(
+PULSAR_PUBLIC unsigned int pulsar_client_configuration_get_partitions_update_interval(
     pulsar_client_configuration_t *conf);
 
 /*
  * Get the stats interval set in the client.
  */
-PULSAR_PUBLIC const unsigned int pulsar_client_configuration_get_stats_interval_in_seconds(
+PULSAR_PUBLIC unsigned int pulsar_client_configuration_get_stats_interval_in_seconds(
     pulsar_client_configuration_t *conf);
 
 PULSAR_PUBLIC void pulsar_client_configuration_set_keep_alive_interval_in_seconds(

lib/BrokerConsumerStats.cc

@@ -63,7 +63,7 @@ const std::string BrokerConsumerStats::getAddress() const { return impl_->getAdd
 
 const std::string BrokerConsumerStats::getConnectedSince() const { return impl_->getConnectedSince(); }
 
-const ConsumerType BrokerConsumerStats::getType() const { return impl_->getType(); }
+ConsumerType BrokerConsumerStats::getType() const { return impl_->getType(); }
 
 double BrokerConsumerStats::getMsgRateExpired() const { return impl_->getMsgRateExpired(); }
 

lib/Message.cc

@@ -184,7 +184,7 @@ const std::string& Message::getTopicName() const {
     return impl_->getTopicName();
 }
 
-const int Message::getRedeliveryCount() const {
+int Message::getRedeliveryCount() const {
     if (!impl_) {
         return 0;
     }

lib/c/c_ClientConfiguration.cc

@@ -173,8 +173,7 @@ void pulsar_client_configuration_set_stats_interval_in_seconds(pulsar_client_con
     conf->conf.setStatsIntervalInSeconds(interval);
 }
 
-const unsigned int pulsar_client_configuration_get_stats_interval_in_seconds(
-    pulsar_client_configuration_t *conf) {
+unsigned int pulsar_client_configuration_get_stats_interval_in_seconds(pulsar_client_configuration_t *conf) {
     return conf->conf.getStatsIntervalInSeconds();
 }
 
@@ -204,8 +203,7 @@ void pulsar_client_configuration_set_partitions_update_interval(pulsar_client_co
     conf->conf.setPartititionsUpdateInterval(intervalInSeconds);
 }
 
-const unsigned int pulsar_client_configuration_get_partitions_update_interval(
-    pulsar_client_configuration_t *conf) {
+unsigned int pulsar_client_configuration_get_partitions_update_interval(pulsar_client_configuration_t *conf) {
     return conf->conf.getPartitionsUpdateInterval();
 }