userland@localhost:~$ gnat krunch discrete_random_example.adb
diranexa.adb
userland@localhost:~$ gnatmake diranexa.adb
aarch64-linux-gnu-gcc-10 -c diranexa.adb
diranexa.adb:4:11: warning: file name does not match unit name, should be “discrete_random_example.adb”
aarch64-linux-gnu-gnatbind-10 -x diranexa.ali
aarch64-linux-gnu-gnatlink-10 diranexa.ali
userland@localhost:~$
So gnatmake isn’t behaving as it should (gnat krunch should enable portability to old systems with 8.3 name convention, such as IBM 3090 with Ada 83 compiler, or MSDOS with its Ada 83/95 compilers such as DJGPP or Janus Ada) or I have antiquated toolchain.