head: errors on very large argument to -c but shouldn't

[jfinkels]

Environment: Ubuntu 20.04, uutils main branch (git commit d39dcad), GNU coreutils v9.6.3-3189c-dirty.

Steps to reproduce:

head --bytes=-18446744073709551616000 < /dev/null

What happens now: uutils head complains that the number is too large:

head: invalid number of bytes: '18446744073709551616000': Value too large for defined data type

What I expected to happen: GNU head terminates successfully with no output.

Notes: this is causing a failure in the GNU test file tests/head/head-c.sh.

[RenjiSann]

Can we know what the behavior is in case the number of bytes overflows unsigned long long without actually testing it (it would be kind of costly I guess) ? Like is it said somewhere esle than the actual int type in the GNU code ?

If not, maybe we can cap the value to u64::MAX, and assume this will be enough until someone proves us otherwise.