Can't compile code for Atmega328

It's not necessary to modify avrdude.conf. MiniCore supports ATmega328. You only need to select Tools > Variant > ATmega328 / 328A.

stevehunt100:
Thanks, can you tell me how I can set the compiler flag for minicore?

Well... It's better to just fix the errors instead of telling the compiler to downgrade them. -fpermissive was intentionally left off by MiniCore's author:

If you do want to add it:

  • Tools > Board > select a MiniCore board
  • File > Examples > SPI (MiniCore) > BarometricPressureSensor
  • Sketch > Show Sketch Folder
  • Navigate up 4 folder levels to C:\Users\steve\AppData\Local\Arduino15\packages\MiniCore\hardware\avr\2.0.1
  • Use a text editor to create a file named platform.local.txt at this location that contains the line:
compiler.cpp.flags=-c -g -Os {compiler.warning_flags} -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -MMD
  • Save the file.
  • Close all Arduino IDE windows.
  • Restart the Arduino IDE and try compiling again.

Note that you will need to repeat that process everytime you update to a new version of MiniCore.