Function ballistics_density_altitude_altitude_m 

#[unsafe(no_mangle)]
pub extern "C" fn ballistics_density_altitude_altitude_m(
    density_altitude_m: c_double,
    explicit_temperature_c: c_double,
) -> c_double

Companion to ballistics_density_altitude_temperature_c: the back-solved station ALTITUDE (meters, geometric) for the same (density_altitude_m, explicit_temperature_c) pair. This is NOT necessarily equal to density_altitude_m — it only is when explicit_temperature_c is FFI_NO_EXPLICIT_TEMPERATURE (see the Rust doc comment’s algebraic identity).