Resource ... alt_flash.h does not exist

When debugging my project in Nios II IDE 9.1 I get the error

resource ... alt_flash.h does not exist

when calling ...

alt_flash_open_dev(EXT_FLASH_NAME);

Prior to this the project is compiled and built in Nios II 9.1 command shell without errors. And both the app and bsp projects are imported into Nios II 9.1 IDE with "File, Import, Import Nios II Software Build Tools Project". After pointing to the project location dirs I answer no in the dialog "Do you want the NIOS II Software Build tools for eclipse to manage your makefile for you ? .... "

The programs starts as expected but stops when it calls alt_flash_open_dev(EXT_FLASH_NAME); !!!??? But the alt_flash.h file is really there. Its in my ..\HAL\inc\sys directory along with several other files and the system.h file contains flash info as it should.

I also get some strange error messages ...

No symbol ”auto” in current context

No symbol ”new” in current context

Which I have not seen before when running Nios II IDE 9.0

Any help here ???