fix SPIFFS when not enabled in build options (#5249)

Author: d-a-v

cores/esp8266/spiffs_api.cpp

@@ -111,16 +111,6 @@ bool isSpiffsFilenameValid(const char* name)
 // these symbols should be defined in the linker script for each flash layout
 #ifndef CORE_MOCK
 #ifdef ARDUINO
-extern "C" uint32_t _SPIFFS_start;
-extern "C" uint32_t _SPIFFS_end;
-extern "C" uint32_t _SPIFFS_page;
-extern "C" uint32_t _SPIFFS_block;
-
-#define SPIFFS_PHYS_ADDR ((uint32_t) (&_SPIFFS_start) - 0x40200000)
-#define SPIFFS_PHYS_SIZE ((uint32_t) (&_SPIFFS_end) - (uint32_t) (&_SPIFFS_start))
-#define SPIFFS_PHYS_PAGE ((uint32_t) &_SPIFFS_page)
-#define SPIFFS_PHYS_BLOCK ((uint32_t) &_SPIFFS_block)
-
 #ifndef SPIFFS_MAX_OPEN_FILES
 #define SPIFFS_MAX_OPEN_FILES 5
 #endif

cores/esp8266/spiffs_api.h

@@ -35,6 +35,18 @@
 
 using namespace fs;
 
+#ifdef ARDUINO
+extern "C" uint32_t _SPIFFS_start;
+extern "C" uint32_t _SPIFFS_end;
+extern "C" uint32_t _SPIFFS_page;
+extern "C" uint32_t _SPIFFS_block;
+
+#define SPIFFS_PHYS_ADDR ((uint32_t) (&_SPIFFS_start) - 0x40200000)
+#define SPIFFS_PHYS_SIZE ((uint32_t) (&_SPIFFS_end) - (uint32_t) (&_SPIFFS_start))
+#define SPIFFS_PHYS_PAGE ((uint32_t) &_SPIFFS_page)
+#define SPIFFS_PHYS_BLOCK ((uint32_t) &_SPIFFS_block)
+#endif
+
 extern int32_t spiffs_hal_write(uint32_t addr, uint32_t size, uint8_t *src);
 extern int32_t spiffs_hal_erase(uint32_t addr, uint32_t size);
 extern int32_t spiffs_hal_read(uint32_t addr, uint32_t size, uint8_t *dst);
@@ -114,6 +126,10 @@ class SPIFFSImpl : public FSImpl
 
     bool begin() override
     {
+#if defined(ARDUINO) && !defined(CORE_MOCK)
+        if (&_SPIFFS_end <= &_SPIFFS_start)
+            return false;
+#endif
         if (SPIFFS_mounted(&_fs) != 0) {
             return true;
         }