Struct Location

pub struct Location<'a> {
    filename: NonNull<str>,
    line: u32,
    col: u32,
    _filename: PhantomData<&'a str>,
}

A struct containing information about the location of a panic.

This structure is created by PanicHookInfo::location() and PanicInfo::location().

Examples

use std::panic;

panic::set_hook(Box::new(|panic_info| {
    if let Some(location) = panic_info.location() {
        println!("panic occurred in file '{}' at line {}", location.file(), location.line());
    } else {
        println!("panic occurred but can't get location information...");
    }
}));

panic!("Normal panic");

Comparisons

Comparisons for equality and ordering are made in file, line, then column priority. Files are compared as strings, not Path, which could be unexpected. See Location::file’s documentation for more discussion.

Fields

filename: NonNull<str>

line: u32

col: u32

_filename: PhantomData<&'a str>

Implementations

impl<'a> Location<'a>

pub const fn caller() -> &'static Location<'static>

Returns the source location of the caller of this function. If that function’s caller is annotated then its call location will be returned, and so on up the stack to the first call within a non-tracked function body.

Examples

use std::panic::Location;

/// Returns the [`Location`] at which it is called.
#[track_caller]
fn get_caller_location() -> &'static Location<'static> {
    Location::caller()
}

/// Returns a [`Location`] from within this function's definition.
fn get_just_one_location() -> &'static Location<'static> {
    get_caller_location()
}

let fixed_location = get_just_one_location();
assert_eq!(fixed_location.file(), file!());
assert_eq!(fixed_location.line(), 14);
assert_eq!(fixed_location.column(), 5);

// running the same untracked function in a different location gives us the same result
let second_fixed_location = get_just_one_location();
assert_eq!(fixed_location.file(), second_fixed_location.file());
assert_eq!(fixed_location.line(), second_fixed_location.line());
assert_eq!(fixed_location.column(), second_fixed_location.column());

let this_location = get_caller_location();
assert_eq!(this_location.file(), file!());
assert_eq!(this_location.line(), 28);
assert_eq!(this_location.column(), 21);

// running the tracked function in a different location produces a different value
let another_location = get_caller_location();
assert_eq!(this_location.file(), another_location.file());
assert_ne!(this_location.line(), another_location.line());
assert_ne!(this_location.column(), another_location.column());

pub const fn file(&self) -> &str

Returns the name of the source file from which the panic originated.

&str, not &Path

The returned name refers to a source path on the compiling system, but it isn’t valid to represent this directly as a &Path. The compiled code may run on a different system with a different Path implementation than the system providing the contents and this library does not currently have a different “host path” type.

The most surprising behavior occurs when “the same” file is reachable via multiple paths in the module system (usually using the #[path = "..."] attribute or similar), which can cause what appears to be identical code to return differing values from this function.

Cross-compilation

This value is not suitable for passing to Path::new or similar constructors when the host platform and target platform differ.

Examples

use std::panic;

panic::set_hook(Box::new(|panic_info| {
    if let Some(location) = panic_info.location() {
        println!("panic occurred in file '{}'", location.file());
    } else {
        println!("panic occurred but can't get location information...");
    }
}));

panic!("Normal panic");

pub const fn file_with_nul(&self) -> &CStr

🔬This is a nightly-only experimental API. (file_with_nul)

Returns the name of the source file as a nul-terminated CStr.

This is useful for interop with APIs that expect C/C++ __FILE__ or std::source_location::file_name, both of which return a nul-terminated const char*.

pub const fn line(&self) -> u32

Returns the line number from which the panic originated.

Examples

use std::panic;

panic::set_hook(Box::new(|panic_info| {
    if let Some(location) = panic_info.location() {
        println!("panic occurred at line {}", location.line());
    } else {
        println!("panic occurred but can't get location information...");
    }
}));

panic!("Normal panic");

pub const fn column(&self) -> u32

Returns the column from which the panic originated.

Examples

use std::panic;

panic::set_hook(Box::new(|panic_info| {
    if let Some(location) = panic_info.location() {
        println!("panic occurred at column {}", location.column());
    } else {
        println!("panic occurred but can't get location information...");
    }
}));

panic!("Normal panic");

Trait Implementations

impl<'a> Clone for Location<'a>

fn clone(&self) -> Location<'a>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Location<'_>

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Display for Location<'_>

fn fmt(&self, formatter: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Hash for Location<'_>

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Location<'_>

fn cmp(&self, other: &Location<'_>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Location<'_>

fn eq(&self, other: &Location<'_>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Location<'_>

fn partial_cmp(&self, other: &Location<'_>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a> Copy for Location<'a>

impl Eq for Location<'_>

impl Send for Location<'_>

impl Sync for Location<'_>