i solve it.
the postion of avr-g++ is
~/.arduino15/packages/arduino/tools/avr-gcc/7.3.0-atmel3.6.1-arduino5/bin/avr-g++
[\code]
i solve it.
the postion of avr-g++ is
~/.arduino15/packages/arduino/tools/avr-gcc/7.3.0-atmel3.6.1-arduino5/bin/avr-g++
[\code]