EEPROM.h uses data types which are declared through Arduino.h but that file does not contain an #include directive for Arduino.h. This does not cause any problems when the EEPROM library is #included from a .ino file because the Arduino IDE automatically adds an #include directive for Arduino.h but this is not the case for .cpp files. If a .cpp file has an #include directive for EEPROM.h that does not follow an #include directive for Arduino.h then compilation fails:
E:\arduino\hardware\espressif\esp32\libraries\EEPROM/EEPROM.h:91:5: error: 'float_t' does not name a type
float_t readFloat(int address);
^
E:\arduino\hardware\espressif\esp32\libraries\EEPROM/EEPROM.h:92:5: error: 'double_t' does not name a type
double_t readDouble(int address);
^
E:\arduino\hardware\espressif\esp32\libraries\EEPROM/EEPROM.h:95:5: error: 'String' does not name a type
String readString(int address);
^
E:\arduino\hardware\espressif\esp32\libraries\EEPROM/EEPROM.h:110:36: error: 'float_t' has not been declared
size_t writeFloat(int address, float_t value);
^
E:\arduino\hardware\espressif\esp32\libraries\EEPROM/EEPROM.h:111:37: error: 'double_t' has not been declared
size_t writeDouble(int address, double_t value);
^
E:\arduino\hardware\espressif\esp32\libraries\EEPROM/EEPROM.h:114:37: error: 'String' has not been declared
size_t writeString(int address, String value);
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