I installed iniFile via PlatformIO (V1.3) for my ESP8266 project. Building resulted in the following error at line 389:
error invalid conversion from char to uint8 t aka unsigned char
line 389 = size_t bytesRead = file.read(buffer, len);
but adding an OR that included the ESP8266 define at line 386 seems to have fixed it.
line 386 = #if (defined(ARDUINO_ARCH_ESP32) || defined(ESP8266)) && !defined(PREFER_SDFAT_LIBRARY)