# Trait std::fmt::Debug [−] [src]

    pub trait Debug {
        fn fmt(&self, &mut Formatter) -> Result<(), Error>;
    }

Format trait for the `?` character.

`Debug` should format the output in a programmer-facing, debugging context.

Generally speaking, you should just `derive` a `Debug` implementation.

When used with the alternate format specifier `#?`, the output is pretty-printed.

For more information on formatters, see the module-level documentation.

This trait can be used with `#[derive]`.

# Examples

Deriving an implementation:

fn main() { #[derive(Debug)] struct Point { x: i32, y: i32, } let origin = Point { x: 0, y: 0 }; println!("The origin is: {:?}", origin); }

    #[derive(Debug)]
    struct Point {
        x: i32,
        y: i32,
    }

    let origin = Point { x: 0, y: 0 };

    println!("The origin is: {:?}", origin);

Manually implementing:

fn main() { use std::fmt; struct Point { x: i32, y: i32, } impl fmt::Debug for Point { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "Point {{ x: {}, y: {} }}", self.x, self.y) } } let origin = Point { x: 0, y: 0 }; println!("The origin is: {:?}", origin); }

    use std::fmt;

    struct Point {
        x: i32,
        y: i32,
    }

    impl fmt::Debug for Point {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "Point {{ x: {}, y: {} }}", self.x, self.y)
        }
    }

    let origin = Point { x: 0, y: 0 };

    println!("The origin is: {:?}", origin);

This outputs:

    The origin is: Point { x: 0, y: 0 }

There are a number of `debug_*` methods on `Formatter` to help you with manual implementations, such as `debug_struct`.

`Debug` implementations using either `derive` or the debug builder API on `Formatter` support pretty printing using the alternate flag: `{:#?}`.

Pretty printing with `#?`:

fn main() { #[derive(Debug)] struct Point { x: i32, y: i32, } let origin = Point { x: 0, y: 0 }; println!("The origin is: {:#?}", origin); }

    #[derive(Debug)]
    struct Point {
        x: i32,
        y: i32,
    }

    let origin = Point { x: 0, y: 0 };

    println!("The origin is: {:#?}", origin);

This outputs:

    The origin is: Point {
        x: 0,
        y: 0
    }

## Required Methods

### `fn fmt(&self, &mut Formatter) -> Result<(), Error>`

Formats the value using the given formatter.

## Implementors

- `impl<T> Debug for Wrapping<T> where T: Debug`
- `impl Debug for Decoded`
- `impl Debug for FullDecoded`
- `impl<'a> Debug for Part<'a>`
- `impl Debug for Sign`
- `impl Debug for Unpacked`
- `impl Debug for Sign`
- `impl<'a> Debug for Decimal<'a>`
- `impl<'a> Debug for ParseResult<'a>`
- `impl Debug for ParseFloatError`
- `impl Debug for FloatErrorKind`
- `impl Debug for Big32x40`
- `impl Debug for Big8x3`
- `impl Debug for Fp`
- `impl Debug for FpCategory`
- `impl Debug for ParseIntError`
- `impl Debug for IntErrorKind`
- `impl<T> Debug for NonZero<T> where T: Zeroable + Debug`
- `impl<Ret> Debug for fn() -> Ret`
- `impl<Ret> Debug for extern "C" fn() -> Ret`
- `impl<Ret> Debug for unsafe fn() -> Ret`
- `impl<Ret> Debug for unsafe extern "C" fn() -> Ret`
- `impl<Ret, A> Debug for fn(A) -> Ret`
- `impl<Ret, A> Debug for extern "C" fn(A) -> Ret`
- `impl<Ret, A> Debug for unsafe fn(A) -> Ret`
- `impl<Ret, A> Debug for unsafe extern "C" fn(A) -> Ret`
- `impl<Ret, A, B> Debug for fn(A, B) -> Ret`
- `impl<Ret, A, B> Debug for extern "C" fn(A, B) -> Ret`
- `impl<Ret, A, B> Debug for unsafe fn(A, B) -> Ret`
- `impl<Ret, A, B> Debug for unsafe extern "C" fn(A, B) -> Ret`
- `impl<Ret, A, B, C> Debug for fn(A, B, C) -> Ret`
- `impl<Ret, A, B, C> Debug for extern "C" fn(A, B, C) -> Ret`
- `impl<Ret, A, B, C> Debug for unsafe fn(A, B, C) -> Ret`
- `impl<Ret, A, B, C> Debug for unsafe extern "C" fn(A, B, C) -> Ret`
- `impl<Ret, A, B, C, D> Debug for fn(A, B, C, D) -> Ret`
- `impl<Ret, A, B, C, D> Debug for extern "C" fn(A, B, C, D) -> Ret`
- `impl<Ret, A, B, C, D> Debug for unsafe fn(A, B, C, D) -> Ret`
- `impl<Ret, A, B, C, D> Debug for unsafe extern "C" fn(A, B, C, D) -> Ret`
- `impl<Ret, A, B, C, D, E> Debug for fn(A, B, C, D, E) -> Ret`
- `impl<Ret, A, B, C, D, E> Debug for extern "C" fn(A, B, C, D, E) -> Ret`
- `impl<Ret, A, B, C, D, E> Debug for unsafe fn(A, B, C, D, E) -> Ret`
- `impl<Ret, A, B, C, D, E> Debug for unsafe extern "C" fn(A, B, C, D, E) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Debug for fn(A, B, C, D, E, F) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Debug for extern "C" fn(A, B, C, D, E, F) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Debug for unsafe fn(A, B, C, D, E, F) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Debug for unsafe extern "C" fn(A, B, C, D, E, F) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Debug for fn(A, B, C, D, E, F, G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Debug for extern "C" fn(A, B, C, D, E, F, G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Debug for unsafe fn(A, B, C, D, E, F, G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Debug for fn(A, B, C, D, E, F, G, H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Debug for extern "C" fn(A, B, C, D, E, F, G, H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Debug for unsafe fn(A, B, C, D, E, F, G, H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G, H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Debug for fn(A, B, C, D, E, F, G, H, I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Debug for extern "C" fn(A, B, C, D, E, F, G, H, I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Debug for unsafe fn(A, B, C, D, E, F, G, H, I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Debug for fn(A, B, C, D, E, F, G, H, I, J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Debug for extern "C" fn(A, B, C, D, E, F, G, H, I, J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Debug for unsafe fn(A, B, C, D, E, F, G, H, I, J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Debug for fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Debug for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Debug for unsafe fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Debug for fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Debug for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Debug for unsafe fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret`
- `impl Debug for RangeFull`
- `impl<Idx> Debug for Range<Idx> where Idx: Debug`
- `impl<Idx> Debug for RangeFrom<Idx> where Idx: Debug`
- `impl<Idx> Debug for RangeTo<Idx> where Idx: Debug`
- `impl Debug for Ordering`
- `impl Debug for Any + 'static`
- `impl Debug for Any + 'static + Send`
- `impl Debug for TypeId`
- `impl<T> Debug for [T; 0] where T: Debug`
- `impl<T> Debug for [T; 1] where T: Debug`
- `impl<T> Debug for [T; 2] where T: Debug`
- `impl<T> Debug for [T; 3] where T: Debug`
- `impl<T> Debug for [T; 4] where T: Debug`
- `impl<T> Debug for [T; 5] where T: Debug`
- `impl<T> Debug for [T; 6] where T: Debug`
- `impl<T> Debug for [T; 7] where T: Debug`
- `impl<T> Debug for [T; 8] where T: Debug`
- `impl<T> Debug for [T; 9] where T: Debug`
- `impl<T> Debug for [T; 10] where T: Debug`
- `impl<T> Debug for [T; 11] where T: Debug`
- `impl<T> Debug for [T; 12] where T: Debug`
- `impl<T> Debug for [T; 13] where T: Debug`
- `impl<T> Debug for [T; 14] where T: Debug`
- `impl<T> Debug for [T; 15] where T: Debug`
- `impl<T> Debug for [T; 16] where T: Debug`
- `impl<T> Debug for [T; 17] where T: Debug`
- `impl<T> Debug for [T; 18] where T: Debug`
- `impl<T> Debug for [T; 19] where T: Debug`
- `impl<T> Debug for [T; 20] where T: Debug`
- `impl<T> Debug for [T; 21] where T: Debug`
- `impl<T> Debug for [T; 22] where T: Debug`
- `impl<T> Debug for [T; 23] where T: Debug`
- `impl<T> Debug for [T; 24] where T: Debug`
- `impl<T> Debug for [T; 25] where T: Debug`
- `impl<T> Debug for [T; 26] where T: Debug`
- `impl<T> Debug for [T; 27] where T: Debug`
- `impl<T> Debug for [T; 28] where T: Debug`
- `impl<T> Debug for [T; 29] where T: Debug`
- `impl<T> Debug for [T; 30] where T: Debug`
- `impl<T> Debug for [T; 31] where T: Debug`
- `impl<T> Debug for [T; 32] where T: Debug`
- `impl Debug for AtomicUsize`
- `impl Debug for AtomicIsize`
- `impl Debug for AtomicBool`
- `impl<T> Debug for AtomicPtr<T>`
- `impl Debug for BorrowState`
- `impl<T> Debug for Option<T> where T: Debug`
- `impl<T, E> Debug for Result<T, E> where T: Debug, E: Debug`
- `impl Debug for SearchStep`
- `impl<'a, 'b> Debug for StrSearcher<'a, 'b>`
- `impl Debug for StrSearcherImpl`
- `impl Debug for EmptyNeedle`
- `impl Debug for TwoWaySearcher`
- `impl Debug for ParseBoolError`
- `impl Debug for Utf8Error`
- `impl Debug for RadixFmt<isize, Radix>`
- `impl Debug for isize`
- `impl Debug for RadixFmt<usize, Radix>`
- `impl Debug for usize`
- `impl Debug for RadixFmt<i8, Radix>`
- `impl Debug for i8`
- `impl Debug for RadixFmt<u8, Radix>`
- `impl Debug for u8`
- `impl Debug for RadixFmt<i16, Radix>`
- `impl Debug for i16`
- `impl Debug for RadixFmt<u16, Radix>`
- `impl Debug for u16`
- `impl Debug for RadixFmt<i32, Radix>`
- `impl Debug for i32`
- `impl Debug for RadixFmt<u32, Radix>`
- `impl Debug for u32`
- `impl Debug for RadixFmt<i64, Radix>`
- `impl Debug for i64`
- `impl Debug for RadixFmt<u64, Radix>`
- `impl Debug for u64`
- `impl Debug for Error`
- `impl<'a> Debug for Arguments<'a>`
- `impl<'a, T> Debug for &'a T where T: Debug + ?Sized`
- `impl<'a, T> Debug for &'a mut T where T: Debug + ?Sized`
- `impl Debug for bool`
- `impl Debug for str`
- `impl Debug for char`
- `impl Debug for f32`
- `impl Debug for f64`
- `impl<T> Debug for *const T`
- `impl<T> Debug for *mut T`
- `impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11> Debug for (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11) where T1: Debug, T11: Debug, T5: Debug, T0: Debug, T6: Debug, T9: Debug, T3: Debug, T10: Debug, T8: Debug, T7: Debug, T2: Debug, T4: Debug`
- `impl<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11> Debug for (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11) where T9: Debug, T4: Debug, T3: Debug, T11: Debug, T2: Debug, T7: Debug, T1: Debug, T5: Debug, T10: Debug, T8: Debug, T6: Debug`
- `impl<T2, T3, T4, T5, T6, T7, T8, T9, T10, T11> Debug for (T2, T3, T4, T5, T6, T7, T8, T9, T10, T11) where T9: Debug, T5: Debug, T7: Debug, T6: Debug, T4: Debug, T11: Debug, T2: Debug, T3: Debug, T10: Debug, T8: Debug`
- `impl<T3, T4, T5, T6, T7, T8, T9, T10, T11> Debug for (T3, T4, T5, T6, T7, T8, T9, T10, T11) where T9: Debug, T8: Debug, T10: Debug, T11: Debug, T3: Debug, T4: Debug, T5: Debug, T7: Debug, T6: Debug`
- `impl<T4, T5, T6, T7, T8, T9, T10, T11> Debug for (T4, T5, T6, T7, T8, T9, T10, T11) where T8: Debug, T9: Debug, T6: Debug, T5: Debug, T11: Debug, T4: Debug, T10: Debug, T7: Debug`
- `impl<T5, T6, T7, T8, T9, T10, T11> Debug for (T5, T6, T7, T8, T9, T10, T11) where T5: Debug, T6: Debug, T7: Debug, T10: Debug, T8: Debug, T11: Debug, T9: Debug`
- `impl<T6, T7, T8, T9, T10, T11> Debug for (T6, T7, T8, T9, T10, T11) where T11: Debug, T10: Debug, T9: Debug, T7: Debug, T6: Debug, T8: Debug`
- `impl<T7, T8, T9, T10, T11> Debug for (T7, T8, T9, T10, T11) where T8: Debug, T9: Debug, T11: Debug, T10: Debug, T7: Debug`
- `impl<T8, T9, T10, T11> Debug for (T8, T9, T10, T11) where T8: Debug, T9: Debug, T10: Debug, T11: Debug`
- `impl<T9, T10, T11> Debug for (T9, T10, T11) where T10: Debug, T9: Debug, T11: Debug`
- `impl<T10, T11> Debug for (T10, T11) where T10: Debug, T11: Debug`
- `impl<T11> Debug for (T11,) where T11: Debug`
- `impl<T> Debug for [T] where T: Debug`
- `impl Debug for ()`
- `impl<T> Debug for PhantomData<T> where T: ?Sized`
- `impl<T> Debug for Cell<T> where T: Copy + Debug`
- `impl<T> Debug for RefCell<T> where T: Debug + ?Sized`
- `impl<'b, T> Debug for Ref<'b, T> where T: Debug + ?Sized`
- `impl<'b, T> Debug for RefMut<'b, T> where T: Debug + ?Sized`
- `impl<T> Debug for Box<T> where T: Debug + ?Sized`
- `impl<T> Debug for Weak<T> where T: Debug + ?Sized`
- `impl<T> Debug for Arc<T> where T: Debug + ?Sized`
- `impl<T> Debug for Rc<T> where T: Debug + ?Sized`
- `impl<T> Debug for Weak<T> where T: Debug + ?Sized`
- `impl<T> Debug for BinaryHeap<T> where T: Ord + Debug`
- `impl<K, V> Debug for BTreeMap<K, V> where V: Debug, K: Debug`
- `impl<T> Debug for BTreeSet<T> where T: Debug`
- `impl<'a, B> Debug for Cow<'a, B> where B: Debug + ToOwned + ?Sized, B::Owned: Debug`
- `impl<E> Debug for EnumSet<E> where E: CLike + Debug`
- `impl<A> Debug for LinkedList<A> where A: Debug`
- `impl Debug for FromUtf8Error`
- `impl Debug for FromUtf16Error`
- `impl Debug for String`
- `impl Debug for ParseError`
- `impl<T> Debug for Vec<T> where T: Debug`
- `impl<T> Debug for VecDeque<T> where T: Debug`
- `impl<T> Debug for Bound<T> where T: Debug`
- `impl Debug for Thread`
- `impl<K, V, S> Debug for HashMap<K, V, S> where K: Eq + Hash + Debug, V: Debug, S: BuildHasher`
- `impl<T, S> Debug for HashSet<T, S> where T: Eq + Hash + Debug, S: BuildHasher`
- `impl Debug for VarError`
- `impl Debug for JoinPathsError`
- `impl Debug for NulError`
- `impl Debug for IntoStringError`
- `impl Debug for CString`
- `impl Debug for CStr`
- `impl Debug for OsString`
- `impl Debug for OsStr`
- `impl Debug for Permissions`
- `impl Debug for File`
- `impl<R> Debug for BufReader<R> where R: Debug`
- `impl<W: Debug> Debug for IntoInnerError<W>`
- `impl<W: Write> Debug for BufWriter<W> where W: Debug`
- `impl<W: Write> Debug for LineWriter<W> where W: Debug`
- `impl<T: Debug> Debug for Cursor<T>`
- `impl Debug for Error`
- `impl Debug for ErrorKind`
- `impl Debug for SeekFrom`
- `impl Debug for CharsError`
- `impl Debug for IpAddr`
- `impl Debug for Ipv6MulticastScope`
- `impl Debug for Ipv4Addr`
- `impl Debug for Ipv6Addr`
- `impl Debug for SocketAddr`
- `impl Debug for SocketAddrV4`
- `impl Debug for SocketAddrV6`
- `impl Debug for TcpStream`
- `impl Debug for TcpListener`
- `impl Debug for UdpSocket`
- `impl Debug for AddrParseError`
- `impl Debug for Shutdown`
- `impl<'a> Debug for Prefix<'a>`
- `impl<'a> Debug for PrefixComponent<'a>`
- `impl<'a> Debug for Component<'a>`
- `impl Debug for PathBuf`
- `impl Debug for StripPrefixError`
- `impl Debug for Path`
- `impl<'a> Debug for Display<'a>`
- `impl Debug for Command`
- `impl Debug for Output`
- `impl Debug for ExitStatus`
- `impl Debug for RecvError`
- `impl Debug for TryRecvError`
- `impl<T> Debug for SendError<T>`
- `impl<T> Debug for TrySendError<T>`
- `impl Debug for WaitTimeoutResult`
- `impl<T: ?Sized + Debug + 'static> Debug for Mutex<T>`
- `impl<T: ?Sized + Debug> Debug for RwLock<T>`
- `impl Debug for Duration`
- `impl Debug for SystemTimeError`
- `impl Debug for Instant`
- `impl Debug for SystemTime`
- `impl<T> Debug for PoisonError<T>`
- `impl<T> Debug for TryLockError<T>`

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