dd: exit when bs/ibs/obs/cbs isn't positive

[iburaky2]

Match GNU coreutils behavior:

$ dd bs=0
dd: invalid number: '0'
$ dd ibs=0
dd: invalid number: '0'
$ dd obs=0
dd: invalid number: '0'
$ dd cbs=0
dd: invalid number: '0'

$ dd bs=-5
dd: invalid number: '-5'
$ dd ibs=-5
dd: invalid number: '-5'
$ dd obs=-5
dd: invalid number: '-5'
$ dd cbs=-5
dd: invalid number: '-5'

Currently:

• bs/ibs/obs=0 panics, see dd bs=0 panics (attempt to divide by zero) #11580.
• cbs=0 seems to allow normal dd operation???
• bs/ibs/obs/cbs=-1 errors correctly after reaching parse_bytes_with_opt_multiplier

Another option would be to check in parse_bytes / parse_bytes_with_opt_multiplier but I think it's better to exit earlier.

[github-actions]

GNU testsuite comparison:

Note: The gnu test tests/csplit/csplit-heap is now being skipped but was previously passing.
Note: The gnu test tests/dd/no-allocate is now being skipped but was previously passing.
Note: The gnu test tests/tail/tail-n0f is now being skipped but was previously passing.

[oech3]

Our dd already rejects negative value. So this PR might have duplicated logic with it.

[oech3]

Also clippy is failing.

[iburaky2]

mb I got the order wrong parse_bytes comes before validate(). Since parse_bytes is only used with those 4 parameters and all should reject 0 we can handle the check there.

Negative numbers are handled here:

fn parse_bytes_no_x(full: &str, s: &str) -> Result<u64, ParseError> {
    let parser = SizeParser {
        capital_b_bytes: true,
        no_empty_numeric: true,
        ..Default::default()
    };
    let (num, multiplier) = match (s.find('c'), s.rfind('w'), s.rfind('b')) {
        (None, None, None) => match parser.parse_u64(s) { // -5 can't be parsed as y64
            Ok(n) => (n, 1),
            Err(ParseSizeError::SizeTooBig(_)) => (u64::MAX, 1),
            Err(_) => return Err(ParseError::InvalidNumber(full.to_string())), // error here
        },
        (Some(i), None, None) => (parse_bytes_only(s, i)?, 1),
        (None, Some(i), None) => (parse_bytes_only(s, i)?, 2),
        (None, None, Some(i)) => (parse_bytes_only(s, i)?, 512),
        _ => return Err(ParseError::MultiplierStringParseFailure(full.to_string())),
    };
    num.checked_mul(multiplier)
        .ok_or_else(|| ParseError::MultiplierStringOverflow(full.to_string()))
}

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/pr/bounded-memory (was skipped on 'main', now failing)