mysterious ERROR during sketches compiling.

Hi, I'm quite new to Arduino and I recently reported a problem which doesn't allow me to upload sketches on my board.

I own an Arduino Uno, a fully udated IDE (1.8.3) running on a late 2011 macBook PRO.

This problem comes with every sketch I try, and the copied message is the following:

Arduino: 1.8.3 (Mac OS X), Board: "Arduino/Genuino Uno"

fork/exec /Users/utente/Library/Arduino15/packages/arduino/tools/avr-gcc/4.9.2-atmel3.5.4-arduino2/bin/avr-g++: no such file or directory
Error compiling for board Arduino/Genuino Uno.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

do anyone has a clue for what's happening?

thank you very much!!