Qsys suddenly fails to generate HDL for my working code.

Could you check if the Window update might have accidentally mess up the WSL (Windows Subsystem for Linux) feature?

For older Quartus version 14.1, you will need to turn OFF the WSL as stated in the KDB below.

Link: https://www.intel.com/content/www/us/en/support/programmable/articles/000080619.html

p.s. For Quartus version > Std19.1/Pro19.2, Nios II currently does not support WSL2, as mentioned here.

To check which version of WSL you are running currently:

1. Open a command prompt as administrator and type wsl --list –verbose. You should get something like the following:

PS C:\Users\xxx> wsl --list --verbose

NAME STATE VERSION

* Ubuntu Stopped 1

Regards,

Richard Tan