Error compiling for board Arduino Uno.

Development Tools IDE 1.x
1 


Arduino: 1.8.12 (Windows 10), Board: "Arduino Uno"

D:\Arduino\arduino-builder -dump-prefs -logger=machine -hardware D:\Arduino\hardware -tools D:\Arduino\tools-builder -tools D:\Arduino\hardware\tools\avr -built-in-libraries D:\Arduino\libraries -libraries C:\Users\acros\Documents\Arduino\libraries -fqbn=arduino:avr:uno -vid-pid=1A86_7523 -ide-version=10812 -build-path C:\Users\acros\AppData\Local\Temp\arduino_build_684070 -warnings=none -build-cache C:\Users\acros\AppData\Local\Temp\arduino_cache_454448 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.avr-gcc.path=D:\Arduino\hardware\tools\avr -prefs=runtime.tools.avr-gcc-7.3.0-atmel3.6.1-arduino5.path=D:\Arduino\hardware\tools\avr -prefs=runtime.tools.avrdude.path=D:\Arduino\hardware\tools\avr -prefs=runtime.tools.avrdude-6.3.0-arduino17.path=D:\Arduino\hardware\tools\avr -prefs=runtime.tools.arduinoOTA.path=D:\Arduino\hardware\tools\avr -prefs=runtime.tools.arduinoOTA-1.3.0.path=D:\Arduino\hardware\tools\avr -verbose C:\Users\acros\AppData\Local\Temp\untitled1558919894.tmp\sketch_jun04a\sketch_jun04a.ino
D:\Arduino\arduino-builder -compile -logger=machine -hardware D:\Arduino\hardware -tools D:\Arduino\tools-builder -tools D:\Arduino\hardware\tools\avr -built-in-libraries D:\Arduino\libraries -libraries C:\Users\acros\Documents\Arduino\libraries -fqbn=arduino:avr:uno -vid-pid=1A86_7523 -ide-version=10812 -build-path C:\Users\acros\AppData\Local\Temp\arduino_build_684070 -warnings=none -build-cache C:\Users\acros\AppData\Local\Temp\arduino_cache_454448 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.avr-gcc.path=D:\Arduino\hardware\tools\avr -prefs=runtime.tools.avr-gcc-7.3.0-atmel3.6.1-arduino5.path=D:\Arduino\hardware\tools\avr -prefs=runtime.tools.avrdude.path=D:\Arduino\hardware\tools\avr -prefs=runtime.tools.avrdude-6.3.0-arduino17.path=D:\Arduino\hardware\tools\avr -prefs=runtime.tools.arduinoOTA.path=D:\Arduino\hardware\tools\avr -prefs=runtime.tools.arduinoOTA-1.3.0.path=D:\Arduino\hardware\tools\avr -verbose C:\Users\acros\AppData\Local\Temp\untitled1558919894.tmp\sketch_jun04a\sketch_jun04a.ino
Using board 'uno' from platform in folder: D:\Arduino\hardware\arduino\avr
Using core 'arduino' from platform in folder: D:\Arduino\hardware\arduino\avr
Detecting libraries used...
Error compiling for board Arduino Uno.
2

This is a problem with the core board definitions. You just uninstall Arduino IDE, uninstall all drivers and then reinstall Arduino IDE and the drivers. This will fix the problem.