fix(wifi) Ensure esp_netif_t* is freed in destructor (#431)

* fix(wifi): Ensure esp_netif_t* is freed in destructor
* Save returned pointer from esp_netif_create_default_wifi_sta/ap
* Ensure saved pointer is freed in destructor

Closes #430

Build and run `wifi/example` on QtPy ESP32s3 and ensure both STA and AP still run

* fix wifi error message

Author: finger563

components/wifi/example/main/wifi_example.cpp

@@ -28,6 +28,7 @@ extern "C" void app_main(void) {
 #endif
 
   {
+    fmt::print("Starting WiFi STA example...\n");
     //! [wifi sta example]
     espp::WifiSta wifi_sta({.ssid = CONFIG_ESP_WIFI_SSID,
                             .password = CONFIG_ESP_WIFI_PASSWORD,
@@ -44,14 +45,17 @@ extern "C" void app_main(void) {
     //! [wifi sta example]
 
     std::this_thread::sleep_for(num_seconds_to_run * 1s);
+    fmt::print("WiFi STA example complete!\n");
   }
 
   {
+    fmt::print("Starting WiFi AP example...\n");
     //! [wifi ap example]
     espp::WifiAp wifi_ap({.ssid = CONFIG_ESP_WIFI_SSID, .password = CONFIG_ESP_WIFI_PASSWORD});
     //! [wifi ap example]
 
     std::this_thread::sleep_for(num_seconds_to_run * 1s);
+    fmt::print("WiFi AP example complete!\n");
   }
 
   fmt::print("WiFi example complete!\n");

components/wifi/include/wifi_ap.hpp

@@ -54,8 +54,12 @@ class WifiAp : public BaseComponent {
     if (err != ESP_OK) {
       logger_.error("Could not create default event loop: {}", err);
     }
+
     logger_.debug("Creating default WiFi AP");
-    esp_netif_create_default_wifi_ap();
+    netif_ = esp_netif_create_default_wifi_ap();
+    if (netif_ == nullptr) {
+      logger_.error("Could not create default WiFi AP");
+    }
 
     // NOTE: Configure phase
     wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
@@ -129,6 +133,9 @@ class WifiAp : public BaseComponent {
       logger_.error("Could not deinit WiFiAp: {}", err);
     }
     logger_.info("WiFi stopped");
+    // destroy (free the memory)
+    logger_.debug("Destroying default WiFi AP");
+    esp_netif_destroy_default_wifi(netif_);
   }
 
 protected:
@@ -150,6 +157,7 @@ class WifiAp : public BaseComponent {
     }
   }
 
+  esp_netif_t *netif_{nullptr}; ///< Pointer to the default WiFi AP netif.
   esp_event_handler_instance_t *event_handler_instance_{nullptr};
 };
 } // namespace espp

components/wifi/include/wifi_sta.hpp

@@ -83,7 +83,12 @@ class WifiSta : public BaseComponent {
     if (err != ESP_OK) {
       logger_.error("Could not create default event loop: {}", err);
     }
-    esp_netif_create_default_wifi_sta();
+
+    // Create default WiFi STA
+    netif_ = esp_netif_create_default_wifi_sta();
+    if (netif_ == nullptr) {
+      logger_.error("Could not create default WiFi STA");
+    }
 
     wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
     err = esp_wifi_init(&cfg);
@@ -164,6 +169,9 @@ class WifiSta : public BaseComponent {
       logger_.error("Could not deinit WiFiSta: {}", err);
     }
     logger_.info("WiFi stopped");
+    // destroy (free the memory)
+    logger_.debug("Destroying default WiFi STA");
+    esp_netif_destroy_default_wifi(netif_);
   }
 
   /**
@@ -213,6 +221,7 @@ class WifiSta : public BaseComponent {
 
   size_t attempts_{0};
   size_t num_retries_{0};
+  esp_netif_t *netif_{nullptr};
   connect_callback connect_callback_{nullptr};
   disconnect_callback disconnect_callback_{nullptr};
   ip_callback ip_callback_{nullptr};