Misleading error message when no cpu flags found

[corneliusroemer]

I tried out x86-64-level on aarch64 ubuntu through docker on macOS arm64 (I know this is not supported, but I was curious what the result would be).

The error message I get is a bit misleading:

$ x86-64-level 
ERROR: Cannot reliably infer the CPU x86-64 level, because the format of the CPU flags comprise of other symbols than only lower-case letters, digits, and underscores: ''

IIUC, the CPU flags are '' which does match lower-case letters, digits, and underscores. The error message should rather state "CPU flags empty".

Here's cat /proc/cpuinfo:

processor       : 0
BogoMIPS        : 48.00
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp flagm2 frint
CPU implementer : 0x61
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0x000
CPU revision    : 0

processor       : 1
BogoMIPS        : 48.00
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp flagm2 frint
CPU implementer : 0x61
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0x000
CPU revision    : 0

processor       : 2
BogoMIPS        : 48.00
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp flagm2 frint
CPU implementer : 0x61
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0x000
CPU revision    : 0

processor       : 3
BogoMIPS        : 48.00
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp flagm2 frint
CPU implementer : 0x61
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0x000
CPU revision    : 0

processor       : 4
BogoMIPS        : 48.00
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp flagm2 frint
CPU implementer : 0x61
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0x000
CPU revision    : 0

processor       : 5
BogoMIPS        : 48.00
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp flagm2 frint
CPU implementer : 0x61
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0x000
CPU revision    : 0

processor       : 6
BogoMIPS        : 48.00
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp flagm2 frint
CPU implementer : 0x61
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0x000
CPU revision    : 0

processor       : 7
BogoMIPS        : 48.00
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp flagm2 frint
CPU implementer : 0x61
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0x000
CPU revision    : 0

processor       : 8
BogoMIPS        : 48.00
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp flagm2 frint
CPU implementer : 0x61
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0x000
CPU revision    : 0

processor       : 9
BogoMIPS        : 48.00
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp flagm2 frint
CPU implementer : 0x61
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0x000
CPU revision    : 0

[corneliusroemer]

Same behaviour when getting the linux/amd64 docker image for ubuntu and running on macOS arm64:

❯  DOCKER_DEFAULT_PLATFORM=linux/amd64 docker run -it -v $(pwd):/mnt ubuntu bash            
root@4ca3a1af7641:/# ./mnt/x86-64-level 
ERROR: Cannot reliably infer the CPU x86-64 level, because the format of the CPU flags comprise of other symbols than only lower-case letters, digits, and underscores: ''
root@4ca3a1af7641:/# uname -a
Linux 4ca3a1af7641 6.6.32-linuxkit #1 SMP Thu Jun 13 14:13:01 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
root@4ca3a1af7641:/#