Add 'extern "C"' on public headers.

mosquitto_broker.h and mosquitto_plugin.h

Thanks to Wolfgang Petroschka.

Closes #1290.

ChangeLog.txt

@@ -16,6 +16,8 @@ Broker:
   Closes #1273.
 - Improve documentation around the upgrading of persistence files. Closes
   #1276.
+- Add 'extern "C"' on mosquitto_broker.h and mosquitto_plugin.h for C++ plugin
+  writing. Closes #1290.
 
 Client library:
 - Fix typo causing build error on Windows when building without TLS support.

src/mosquitto_broker.h

@@ -17,6 +17,10 @@ Contributors:
 #ifndef MOSQUITTO_BROKER_H
 #define MOSQUITTO_BROKER_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include <stdbool.h>
 
 struct mosquitto;
@@ -161,4 +165,8 @@ const char *mosquitto_client_username(const struct mosquitto *client);
  */
 int mosquitto_set_username(struct mosquitto *client, const char *username);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif

src/mosquitto_plugin.h

@@ -17,6 +17,10 @@ Contributors:
 #ifndef MOSQUITTO_PLUGIN_H
 #define MOSQUITTO_PLUGIN_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define MOSQ_AUTH_PLUGIN_VERSION 4
 
 #define MOSQ_ACL_NONE 0x00
@@ -305,4 +309,10 @@ int mosquitto_auth_psk_key_get(void *user_data, struct mosquitto *client, const
 int mosquitto_auth_start(void *user_data, struct mosquitto *client, const char *method, bool reauth, const void *data_in, uint16_t data_in_len, void **data_out, uint16_t *data_out_len);
 
 int mosquitto_auth_continue(void *user_data, struct mosquitto *client, const char *method, const void *data_in, uint16_t data_in_len, void **data_out, uint16_t *data_out_len);
+
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif