ONE SOURCE. SIX EXECUTION POINTS.

00 execution matrix

10 the program

portable_runtime_parity.dby computes a small fixed-width integer transform twice, combines the values and returns 42 only when the exact result is reached. A non-42 status triggers a deliberate divide-by-zero at the top level so “wrong value but process returned” cannot look green.

fn mix(value: u32) -> u32:
    let x: u32 = value * (3 as u32)
    x = x + (7 as u32)
    if x > (100 as u32):
        x = x - (11 as u32)
    return x

pub fn main() -> i32:
    let left: u32 = mix(40 as u32)
    let right: u32 = mix(10 as u32)
    let total: u32 = left + right
    if total == (153 as u32):
        return 42 as i32
    return 1 as i32

let status: i32 = main()
if status != (42 as i32):
    let crash: i32 = (1 as i32) / (0 as i32)

20 what this proves

It checks that one admitted fixed-width source keeps its observable result across the named execution paths. It does not prove every DBYTE program is portable. The portability analyzer first rejects target-dependent source; parity then executes a known portable fixture.

30 how to read a failure

If hosted and VM agree but one native target differs, start below HIR: Native MIR legalization, selector, ABI or object path. If O0 passes and O1 fails, optimization becomes the first suspect. If every backend rejects the project during check-portable, that is a source-contract failure, not runtime parity.