[core] Convert components, devices, and areas vectors to static allocation (#10020)

esphome/core/application.h

@@ -214,14 +214,6 @@ class Application {
 #endif
 
   /// Reserve space for components to avoid memory fragmentation
-  void reserve_components(size_t count) { this->components_.reserve(count); }
-
-#ifdef USE_AREAS
-  void reserve_area(size_t count) { this->areas_.reserve(count); }
-#endif
-#ifdef USE_DEVICES
-  void reserve_device(size_t count) { this->devices_.reserve(count); }
-#endif
 
   /// Register the component in this Application instance.
   template<class C> C *register_component(C *c) {
@@ -316,7 +308,7 @@ class Application {
     } \
     return nullptr; \
   }
-  const std::vector<Device *> &get_devices() { return this->devices_; }
+  const auto &get_devices() { return this->devices_; }
 #else
 #define GET_ENTITY_METHOD(entity_type, entity_name, entities_member) \
   entity_type *get_##entity_name##_by_key(uint32_t key, bool include_internal = false) { \
@@ -328,7 +320,7 @@ class Application {
   }
 #endif  // USE_DEVICES
 #ifdef USE_AREAS
-  const std::vector<Area *> &get_areas() { return this->areas_; }
+  const auto &get_areas() { return this->areas_; }
 #endif
 #ifdef USE_BINARY_SENSOR
   auto &get_binary_sensors() const { return this->binary_sensors_; }
@@ -462,12 +454,7 @@ class Application {
   const char *comment_{nullptr};
   const char *compilation_time_{nullptr};
 
-  // size_t members
+  // std::vector (3 pointers each: begin, end, capacity)
-  size_t dump_config_at_{SIZE_MAX};
-
-  // Vectors (largest members)
-  std::vector<Component *> components_{};
-
   // Partitioned vector design for looping components
   // =================================================
   // Components are partitioned into [active | inactive] sections:
@@ -485,12 +472,54 @@ class Application {
   //   and active_end_ is incremented
   // - This eliminates branch mispredictions from flag checking in the hot loop
   std::vector<Component *> looping_components_{};
+#ifdef USE_SOCKET_SELECT_SUPPORT
+  std::vector<int> socket_fds_;  // Vector of all monitored socket file descriptors
+#endif
+
+  // std::string members (typically 24-32 bytes each)
+  std::string name_;
+  std::string friendly_name_;
+
+  // size_t members
+  size_t dump_config_at_{SIZE_MAX};
+
+  // 4-byte members
+  uint32_t last_loop_{0};
+  uint32_t loop_component_start_time_{0};
+
+#ifdef USE_SOCKET_SELECT_SUPPORT
+  int max_fd_{-1};  // Highest file descriptor number for select()
+#endif
+
+  // 2-byte members (grouped together for alignment)
+  uint16_t loop_interval_{16};                 // Loop interval in ms (max 65535ms = 65.5 seconds)
+  uint16_t looping_components_active_end_{0};  // Index marking end of active components in looping_components_
+  uint16_t current_loop_index_{0};             // For safe reentrant modifications during iteration
+
+  // 1-byte members (grouped together to minimize padding)
+  uint8_t app_state_{0};
+  bool name_add_mac_suffix_;
+  bool in_loop_{false};
+  volatile bool has_pending_enable_loop_requests_{false};
+
+#ifdef USE_SOCKET_SELECT_SUPPORT
+  bool socket_fds_changed_{false};  // Flag to rebuild base_read_fds_ when socket_fds_ changes
+#endif
+
+#ifdef USE_SOCKET_SELECT_SUPPORT
+  // Variable-sized members
+  fd_set base_read_fds_{};  // Cached fd_set rebuilt only when socket_fds_ changes
+  fd_set read_fds_{};       // Working fd_set for select(), copied from base_read_fds_
+#endif
+
+  // StaticVectors (largest members - contain actual array data inline)
+  StaticVector<Component *, ESPHOME_COMPONENT_COUNT> components_{};
 
 #ifdef USE_DEVICES
-  std::vector<Device *> devices_{};
+  StaticVector<Device *, ESPHOME_DEVICE_COUNT> devices_{};
 #endif
 #ifdef USE_AREAS
-  std::vector<Area *> areas_{};
+  StaticVector<Area *, ESPHOME_AREA_COUNT> areas_{};
 #endif
 #ifdef USE_BINARY_SENSOR
   StaticVector<binary_sensor::BinarySensor *, ESPHOME_ENTITY_BINARY_SENSOR_COUNT> binary_sensors_{};
@@ -556,41 +585,6 @@ class Application {
 #ifdef USE_UPDATE
   StaticVector<update::UpdateEntity *, ESPHOME_ENTITY_UPDATE_COUNT> updates_{};
 #endif
-
-#ifdef USE_SOCKET_SELECT_SUPPORT
-  std::vector<int> socket_fds_;  // Vector of all monitored socket file descriptors
-#endif
-
-  // String members
-  std::string name_;
-  std::string friendly_name_;
-
-  // 4-byte members
-  uint32_t last_loop_{0};
-  uint32_t loop_component_start_time_{0};
-
-#ifdef USE_SOCKET_SELECT_SUPPORT
-  int max_fd_{-1};  // Highest file descriptor number for select()
-#endif
-
-  // 2-byte members (grouped together for alignment)
-  uint16_t loop_interval_{16};  // Loop interval in ms (max 65535ms = 65.5 seconds)
-  uint16_t looping_components_active_end_{0};
-  uint16_t current_loop_index_{0};  // For safe reentrant modifications during iteration
-
-  // 1-byte members (grouped together to minimize padding)
-  uint8_t app_state_{0};
-  bool name_add_mac_suffix_;
-  bool in_loop_{false};
-  volatile bool has_pending_enable_loop_requests_{false};
-
-#ifdef USE_SOCKET_SELECT_SUPPORT
-  bool socket_fds_changed_{false};  // Flag to rebuild base_read_fds_ when socket_fds_ changes
-
-  // Variable-sized members at end
-  fd_set base_read_fds_{};  // Cached fd_set rebuilt only when socket_fds_ changes
-  fd_set read_fds_{};       // Working fd_set for select(), copied from base_read_fds_
-#endif
 };
 
 /// Global storage of Application pointer - only one Application can exist.

esphome/core/config.py

@@ -459,10 +459,8 @@ async def to_code(config: ConfigType) -> None:
             config[CONF_NAME_ADD_MAC_SUFFIX],
         )
     )
-    # Reserve space for components to avoid reallocation during registration
+    # Define component count for static allocation
-    cg.add(
+    cg.add_define("ESPHOME_COMPONENT_COUNT", len(CORE.component_ids))
-        cg.RawStatement(f"App.reserve_components({len(CORE.component_ids)});"),
-    )
 
     CORE.add_job(_add_platform_defines)
 
@@ -531,8 +529,8 @@ async def to_code(config: ConfigType) -> None:
     all_areas.extend(config[CONF_AREAS])
 
     if all_areas:
-        cg.add(cg.RawStatement(f"App.reserve_area({len(all_areas)});"))
         cg.add_define("USE_AREAS")
+        cg.add_define("ESPHOME_AREA_COUNT", len(all_areas))
 
         for area_conf in all_areas:
             area_id: core.ID = area_conf[CONF_ID]
@@ -549,9 +547,9 @@ async def to_code(config: ConfigType) -> None:
     if not devices:
         return
 
-    # Reserve space for devices
+    # Define device count for static allocation
-    cg.add(cg.RawStatement(f"App.reserve_device({len(devices)});"))
     cg.add_define("USE_DEVICES")
+    cg.add_define("ESPHOME_DEVICE_COUNT", len(devices))
 
     # Process each device
     for dev_conf in devices:

esphome/core/defines.h

@@ -240,7 +240,10 @@
 
 #define USE_DASHBOARD_IMPORT
 
-// Default entity counts for static analysis
+// Default counts for static analysis
+#define ESPHOME_COMPONENT_COUNT 50
+#define ESPHOME_DEVICE_COUNT 10
+#define ESPHOME_AREA_COUNT 10
 #define ESPHOME_ENTITY_ALARM_CONTROL_PANEL_COUNT 1
 #define ESPHOME_ENTITY_BINARY_SENSOR_COUNT 1
 #define ESPHOME_ENTITY_BUTTON_COUNT 1

esphome/core/helpers.h

@@ -5,6 +5,7 @@
 #include <cstdint>
 #include <cstring>
 #include <functional>
+#include <iterator>
 #include <limits>
 #include <memory>
 #include <string>
@@ -100,6 +101,8 @@ template<typename T, size_t N> class StaticVector {
   using value_type = T;
   using iterator = typename std::array<T, N>::iterator;
   using const_iterator = typename std::array<T, N>::const_iterator;
+  using reverse_iterator = std::reverse_iterator<iterator>;
+  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
  private:
   std::array<T, N> data_{};
@@ -114,6 +117,7 @@ template<typename T, size_t N> class StaticVector {
   }
 
   size_t size() const { return count_; }
+  bool empty() const { return count_ == 0; }
 
   T &operator[](size_t i) { return data_[i]; }
   const T &operator[](size_t i) const { return data_[i]; }
@@ -123,6 +127,12 @@ template<typename T, size_t N> class StaticVector {
   iterator end() { return data_.begin() + count_; }
   const_iterator begin() const { return data_.begin(); }
   const_iterator end() const { return data_.begin() + count_; }
+
+  // Reverse iterators
+  reverse_iterator rbegin() { return reverse_iterator(end()); }
+  reverse_iterator rend() { return reverse_iterator(begin()); }
+  const_reverse_iterator rbegin() const { return const_reverse_iterator(end()); }
+  const_reverse_iterator rend() const { return const_reverse_iterator(begin()); }
 };
 
 ///@}