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Error

The syscalls of ckb are influenced by the Unix syscall convention, where a return value of 0 usually indicates success and any non-zero value indicates failure. () However, in Rust, it's more convenient to handle errors using Result<T, E>. Therefore, most functions in ckb-std return a Result, with errors represented by the SysError enum.

note

Note that the variants of SysError do not correspond one-to-one with the raw syscall return codes. For example, the spawn syscall may return 3, but in ckb-std, this error is represented as Encoding.

Syntax​

#[derive(Eq, PartialEq, Debug, Clone, Copy)]
pub enum SysError {
    IndexOutOfBound,
    ItemMissing,
    LengthNotEnough(usize),
    Encoding,
    WaitFailure,
    InvalidFd,
    OtherEndClosed,
    MaxVmsSpawned,
    MaxFdsCreated,
    #[cfg(feature = "type-id")]
    TypeIDError,
    Unknown(u64),
}

Constants​

IndexOutOfBound : Index out of bound. Often used as a signal for the end of iteration. In ckb_std::high_level, iterators are recommended, so this is rarely encountered.

ItemMissing : Field is missing for the target. Typically occurs when trying to read a non-existent field related to a Type Script in ckb_std::syscalls. In ckb_std::high_level, it usually returns Option::None.

LengthNotEnough(usize) : Buffer length is not enough, error contains actual data length. This is usually handled automatically in ckb_std::high_level by allocating enough memory and retrying the read.

Encoding : Data encoding error. Normally not encountered during typical development.

WaitFailure : Failed to wait. Its value is 5.

InvalidFd : Invalid file descriptor.

OtherEndClosed : Reading from or writing to file descriptor failed due to other end closed.

MaxVmsSpawned : Max vms has been spawned.

MaxFdsCreated : Max fds has been spawned.

TypeIDError : Type ID Error.

Unknown(u64) : Unknown syscall error number. ckb-vm may return some unknown value and will generally be saved here.

Remarks​

The errors WaitFailure, InvalidFd, OtherEndClosed, MaxVmsSpawned, and MaxFdsCreated typically only occur when executing functions related to spawn.

Example​

See the example at ckb-rust-script/error. This is a Lock Script that uses args[0] to select which error type to trigger. You can verify the behavior with the tests in tests/src/test_error.rs.