Build error: #else if in header should be #elif

[Aaron Fontaine]

Note sure if this works differently on different systems. I am building in PlatformIO for ESP32 DevKitC with following settings:

[env:esp32dev]
platform = espressif32
build_type = debug
debug_tool = esp-prog
board = esp32dev
framework = arduino
lib_deps = lennarthennigs/ESP Telnet@^1.1.0

I changed
#else if defined(ARDUINO_ARCH_ESP8266)
to
#elif defined(ARDUINO_ARCH_ESP8266)

[Lennart Hennigs]

Ah, I'll thx. I'll change this. (It works on the Arduino IDE.)

[Aaron Fontaine]

Hi Lennart, I was able to verify what's happening in the Arduino IDE. I realized that PlatformIO is showing a warning but building anyway. This is what the Arduino IDE is doing, except that it normally suppresses warnings. To see the warning in Arduino, go to File -> Preferences and make sure the "compilation" option is checked for "Show verbose output during:". Also, make sure compiler warnings is set to "More" or higher. After you do this and rebuild, you should get the following warning.

D:\Users\AFont\Documents\Arduino\libraries\ESP_Telnet\src/ESPTelnet.h:19:7: warning: extra tokens at end of #else directive [-Wendif-labels]
 #else if defined(ARDUINO_ARCH_ESP8266)
       ^

There is no such thing as #else if, only #elif. Everything following #else is not evaluated, which is why gcc calls them extra tokens. See documentation here. In this case, it doesn't end up affecting the build.