weak hook early_setup() esp8266#2111 esp8266#2133 esp8266#2136

Author: d-a-v

cores/esp8266/Arduino.h

@@ -219,6 +219,7 @@ uint8_t shiftIn(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder);
 void attachInterrupt(uint8_t pin, void (*)(void), int mode);
 void detachInterrupt(uint8_t pin);
 
+void early_setup(void);
 void setup(void);
 void loop(void);
 

cores/esp8266/core_esp8266_main.cpp

@@ -63,7 +63,7 @@ static uint32_t s_micros_at_task_start;
 
 extern "C" {
 extern const uint32_t __attribute__((section(".ver_number"))) core_version = ARDUINO_ESP8266_GIT_VER;
-const char* core_release = 
+const char* core_release =
 #ifdef ARDUINO_ESP8266_RELEASE
     ARDUINO_ESP8266_RELEASE;
 #else
@@ -145,6 +145,7 @@ void init_done() {
     system_set_os_print(1);
     gdb_init();
     do_global_ctors();
+    early_setup(); // <-- here after global constructors, or in user_init() ?
     esp_schedule();
 }
 
@@ -212,13 +213,19 @@ extern "C" void ICACHE_RAM_ATTR app_entry (void)
     return app_entry_custom();
 }
 
+extern "C" void early_setup (void) __attribute__((weak));
+extern "C" void early_setup (void)
+{
+    /* do nothing by default */
+}
+
 extern "C" void user_init(void) {
     struct rst_info *rtc_info_ptr = system_get_rst_info();
     memcpy((void *) &resetInfo, (void *) rtc_info_ptr, sizeof(resetInfo));
 
     uart_div_modify(0, UART_CLK_FREQ / (115200));
 
-    init();
+    init(); // in core_esp8266_wiring.c
 
     initVariant();