[wifi/captive_portal/web_server/wifi_info] Use stack allocation for MAC address formatting

esphome/components/captive_portal/captive_portal.cpp

@@ -13,14 +13,16 @@ static const char *const TAG = "captive_portal";
 void CaptivePortal::handle_config(AsyncWebServerRequest *request) {
   AsyncResponseStream *stream = request->beginResponseStream(ESPHOME_F("application/json"));
   stream->addHeader(ESPHOME_F("cache-control"), ESPHOME_F("public, max-age=0, must-revalidate"));
+  char mac_s[18];
+  const char *mac_str = get_mac_address_pretty_into_buffer(mac_s);
 #ifdef USE_ESP8266
   stream->print(ESPHOME_F("{\"mac\":\""));
-  stream->print(get_mac_address_pretty().c_str());
+  stream->print(mac_str);
   stream->print(ESPHOME_F("\",\"name\":\""));
   stream->print(App.get_name().c_str());
   stream->print(ESPHOME_F("\",\"aps\":[{}"));
 #else
-  stream->printf(R"({"mac":"%s","name":"%s","aps":[{})", get_mac_address_pretty().c_str(), App.get_name().c_str());
+  stream->printf(R"({"mac":"%s","name":"%s","aps":[{})", mac_str, App.get_name().c_str());
 #endif
 
   for (auto &scan : wifi::global_wifi_component->get_scan_result()) {

esphome/components/web_server/web_server.cpp

@@ -359,8 +359,8 @@ void WebServer::handle_pna_cors_request(AsyncWebServerRequest *request) {
   AsyncWebServerResponse *response = request->beginResponse(200, "");
   response->addHeader(HEADER_CORS_ALLOW_PNA, "true");
   response->addHeader(HEADER_PNA_NAME, App.get_name().c_str());
-  std::string mac = get_mac_address_pretty();
-  response->addHeader(HEADER_PNA_ID, mac.c_str());
+  char mac_s[18];
+  response->addHeader(HEADER_PNA_ID, get_mac_address_pretty_into_buffer(mac_s));
   request->send(response);
 }
 #endif

esphome/components/wifi/wifi_component.cpp

@@ -334,10 +334,11 @@ void WiFiComponent::setup() {
 }
 
 void WiFiComponent::start() {
+  char mac_s[18];
   ESP_LOGCONFIG(TAG,
                 "Starting\n"
                 "  Local MAC: %s",
-                get_mac_address_pretty().c_str());
+                get_mac_address_pretty_into_buffer(mac_s));
   this->last_connected_ = millis();
 
   uint32_t hash = this->has_sta() ? fnv1_hash(App.get_compilation_time()) : 88491487UL;
@@ -800,7 +801,8 @@ void WiFiComponent::print_connect_params_() {
   char bssid_s[18];
   format_mac_addr_upper(bssid.data(), bssid_s);
 
-  ESP_LOGCONFIG(TAG, "  Local MAC: %s", get_mac_address_pretty().c_str());
+  char mac_s[18];
+  ESP_LOGCONFIG(TAG, "  Local MAC: %s", get_mac_address_pretty_into_buffer(mac_s));
   if (this->is_disabled()) {
     ESP_LOGCONFIG(TAG, "  Disabled");
     return;

esphome/components/wifi_info/wifi_info_text_sensor.h

@@ -126,7 +126,10 @@ class BSSIDWiFiInfo : public PollingComponent, public text_sensor::TextSensor {
 
 class MacAddressWifiInfo : public Component, public text_sensor::TextSensor {
  public:
-  void setup() override { this->publish_state(get_mac_address_pretty()); }
+  void setup() override {
+    char mac_s[18];
+    this->publish_state(get_mac_address_pretty_into_buffer(mac_s));
+  }
   void dump_config() override;
 };
 

esphome/core/helpers.cpp

@@ -638,9 +638,8 @@ std::string get_mac_address() {
 }
 
 std::string get_mac_address_pretty() {
-  uint8_t mac[6];
-  get_mac_address_raw(mac);
-  return format_mac_address_pretty(mac);
+  char buf[18];
+  return std::string(get_mac_address_pretty_into_buffer(buf));
 }
 
 void get_mac_address_into_buffer(std::span<char, 13> buf) {

esphome/core/helpers.h

@@ -1052,6 +1052,16 @@ std::string get_mac_address_pretty();
 /// Assumes buffer length is 13 (12 digits for hexadecimal representation followed by null terminator).
 void get_mac_address_into_buffer(std::span<char, 13> buf);
 
+/// Get the device MAC address into the given buffer, in colon-separated uppercase hex notation.
+/// Buffer must be exactly 18 bytes (17 for "XX:XX:XX:XX:XX:XX" + null terminator).
+/// Returns pointer to the buffer for convenience.
+inline const char *get_mac_address_pretty_into_buffer(std::span<char, 18> buf) {
+  uint8_t mac[6];
+  get_mac_address_raw(mac);
+  format_mac_addr_upper(mac, buf.data());
+  return buf.data();
+}
+
 #ifdef USE_ESP32
 /// Set the MAC address to use from the provided byte array (6 bytes).
 void set_mac_address(uint8_t *mac);