[template] Use a user provided default constructor for TemplateTime

esphome/components/datetime/date_entity.h

@@ -32,9 +32,9 @@ struct DateEntityRestoreState {
 
 class DateEntity : public DateTimeBase {
  protected:
-  uint16_t year_;
+  uint16_t year_{0};
-  uint8_t month_;
+  uint8_t month_{0};
-  uint8_t day_;
+  uint8_t day_{0};
 
  public:
   void publish_state();

esphome/components/datetime/datetime_base.h

@@ -27,7 +27,7 @@ class DateTimeBase : public EntityBase {
   LazyCallbackManager<void()> state_callback_;
 
 #ifdef USE_TIME
-  time::RealTimeClock *rtc_;
+  time::RealTimeClock *rtc_{nullptr};
 #endif
 };
 

esphome/components/datetime/datetime_entity.h

@@ -35,12 +35,12 @@ struct DateTimeEntityRestoreState {
 
 class DateTimeEntity : public DateTimeBase {
  protected:
-  uint16_t year_;
+  uint16_t year_{0};
-  uint8_t month_;
+  uint8_t month_{0};
-  uint8_t day_;
+  uint8_t day_{0};
-  uint8_t hour_;
+  uint8_t hour_{0};
-  uint8_t minute_;
+  uint8_t minute_{0};
-  uint8_t second_;
+  uint8_t second_{0};
 
  public:
   void publish_state();

esphome/components/datetime/time_entity.h

@@ -33,9 +33,9 @@ struct TimeEntityRestoreState {
 
 class TimeEntity : public DateTimeBase {
  protected:
-  uint8_t hour_;
+  uint8_t hour_{0};
-  uint8_t minute_;
+  uint8_t minute_{0};
-  uint8_t second_;
+  uint8_t second_{0};
 
  public:
   void publish_state();

esphome/components/template/datetime/template_time.h

@@ -15,6 +15,8 @@ namespace esphome::template_ {
 
 class TemplateTime final : public datetime::TimeEntity, public PollingComponent {
  public:
+  // User provided, not "= default": `new(p) TemplateTime()` would zero-fill .bss that is already zero.
+  TemplateTime() {}
   template<typename F> void set_template(F &&f) { this->f_.set(std::forward<F>(f)); }
 
   void setup() override;