Fix SEGFAULT in MQTT server

PUBLISHED_FROM=6455082726781aab819a7f8645e81adaa7fc7669

docs/c-api/mqtt_server.h/LIST_ENTRY.md

@@ -0,0 +1,10 @@
+---
+title: "LIST_ENTRY()"
+decl_name: "LIST_ENTRY"
+symbol_kind: "func"
+signature: |
+    LIST_ENTRY(mg_mqtt_session);
+---
+
+Broker 
+

docs/c-api/mqtt_server.h/intro.md

@@ -3,9 +3,7 @@ title: "MQTT Server API reference"
 symbol_kind: "intro"
 decl_name: "mqtt_server.h"
 items:
-  - { name: mg_mqtt_broker.md }
-  - { name: mg_mqtt_broker_init.md }
-  - { name: mg_mqtt_next.md }
+  - { name: LIST_ENTRY.md }
   - { name: struct_mg_mqtt_broker.md }
   - { name: struct_mg_mqtt_session.md }
 ---

docs/c-api/mqtt_server.h/mg_mqtt_broker.md

@@ -1,32 +0,0 @@
----
-title: "mg_mqtt_broker()"
-decl_name: "mg_mqtt_broker"
-symbol_kind: "func"
-signature: |
-  void mg_mqtt_broker(struct mg_connection *brk, int ev, void *data);
----
-
-Processes a MQTT broker message.
-
-The listening connection expects a pointer to an initialised
-`mg_mqtt_broker` structure in the `user_data` field.
-
-Basic usage:
-
-```c
-mg_mqtt_broker_init(&brk, NULL);
-
-if ((nc = mg_bind(&mgr, address, mg_mqtt_broker)) == NULL) {
-  // fail;
-}
-nc->user_data = &brk;
-```
-
-New incoming connections will receive a `mg_mqtt_session` structure
-in the connection `user_data`. The original `user_data` will be stored
-in the `user_data` field of the session structure. This allows the user
-handler to store user data before `mg_mqtt_broker` creates the session.
-
-Since only the MG_EV_ACCEPT message is processed by the listening socket,
-for most events the `user_data` will thus point to a `mg_mqtt_session`. 
-

docs/c-api/mqtt_server.h/mg_mqtt_broker_init.md

@@ -1,10 +0,0 @@
----
-title: "mg_mqtt_broker_init()"
-decl_name: "mg_mqtt_broker_init"
-symbol_kind: "func"
-signature: |
-  void mg_mqtt_broker_init(struct mg_mqtt_broker *brk, void *user_data);
----
-
-Initialises a MQTT broker. 
-

docs/c-api/mqtt_server.h/mg_mqtt_next.md

@@ -1,18 +0,0 @@
----
-title: "mg_mqtt_next()"
-decl_name: "mg_mqtt_next"
-symbol_kind: "func"
-signature: |
-  struct mg_mqtt_session *mg_mqtt_next(struct mg_mqtt_broker *brk,
-                                       struct mg_mqtt_session *s);
----
-
-Iterates over all MQTT session connections. Example:
-
-```c
-struct mg_mqtt_session *s;
-for (s = mg_mqtt_next(brk, NULL); s != NULL; s = mg_mqtt_next(brk, s)) {
-  // Do something
-}
-``` 
-

docs/c-api/mqtt_server.h/struct_mg_mqtt_broker.md

@@ -4,8 +4,8 @@ decl_name: "struct mg_mqtt_broker"
 symbol_kind: "struct"
 signature: |
   struct mg_mqtt_broker {
-    struct mg_mqtt_session *sessions; /* Session list */
-    void *user_data;                  /* User data */
+    LIST_HEAD(, mg_mqtt_session) sessions; /* Session list */
+    void *user_data;                       /* User data */
   };
 ---
 

docs/c-api/mqtt_server.h/struct_mg_mqtt_session.md

@@ -4,12 +4,12 @@ decl_name: "struct mg_mqtt_session"
 symbol_kind: "struct"
 signature: |
   struct mg_mqtt_session {
-    struct mg_mqtt_broker *brk;          /* Broker */
-    struct mg_mqtt_session *next, *prev; /* mg_mqtt_broker::sessions linkage */
-    struct mg_connection *nc;            /* Connection with the client */
-    size_t num_subscriptions;            /* Size of `subscriptions` array */
+    struct mg_mqtt_broker *brk;       /* Broker */
+    LIST_ENTRY(mg_mqtt_session) link; /* mg_mqtt_broker::sessions linkage */
+    struct mg_connection *nc;         /* Connection with the client */
+    size_t num_subscriptions;         /* Size of `subscriptions` array */
+    void *user_data;                  /* User data */
     struct mg_mqtt_topic_expression *subscriptions;
-    void *user_data; /* User data */
   };
 ---