On NVHPC 24.3 for Arm, I got the following:
$ nvc++ caxpy.c -msve-vector-bits=scalable
Internal error: assertion failed at: "cmd_line.cpp", line 12464 in proc_command_line`
Even when I specify forward-match of scalable, like s, sc, sca…, it fails in the same message.
It looks like a tiny bug in the command line parser.