Struct Location

1.10.0 · Source

pub struct Location<'a> { /* private fields */ }

Expand description

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.

Implementations§

Source §

impl<'a> Location<'a>

1.46.0 (const: 1.79.0) · Source

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;

/// ```
///      |1        |11       |21       |31       |41
///    +-|---------|---------|---------|---------|--------
/// 15 | #[track_caller]
/// 16 | fn new_location() -> &'static Location<'static> {
/// 17 |     Location::caller()
///    |     ------------------| the value of this expression depends on the caller,
///    |                       | since the function is marked #[track_caller]
/// 18 | }
/// ```
#[track_caller]
fn new_location() -> &'static Location<'static> {
    Location::caller()
}

/// ```
///      |1  |5    |11       |21       |31       |41       |51
///    +-|---|-----|---------|---------|---------|---------|---
/// 29 | fn constant_location() -> &'static Location<'static> {
/// 30 |     new_location()
///    |     ^ any invocation of constant_location() points here,
///    |       no matter the location it is called from
/// 31 | }
/// ```
fn constant_location() -> &'static Location<'static> {
    new_location()
}

fn main() {
    //      |1  |5    |11       |21       |31       |41       |51
    //    +-|---|-----|---------|---------|---------|---------|---
    // 29 | fn constant_location() -> &'static Location<'static> {
    // 30 |     new_location()
    //    |     ^ `let constant` points here
    // 31 | }
    let constant = constant_location();
    assert_eq!(constant.file(), file!());
    assert_eq!((constant.line(), constant.column()), (30, 5));

    let constant_2 = constant_location();
    assert_eq!(
        (constant.file(), constant.line(), constant.column()),
        (constant_2.file(), constant_2.line(), constant_2.column())
    );

    //      |1        |11  |16  |21       |31
    //    +-|---------|----|----|---------|------
    // 55 |     let here = new_location();
    //    |                ^ `let here` points here, as `new_location()` is the callsite
    // 56 |     assert_eq!(here.file(), file!());
    let here = new_location();
    assert_eq!(here.file(), file!());
    assert_eq!((here.line(), here.column()), (55, 16));

    //      |1        |11       |21       ||32      |41       |51
    //    +-|---------|---------|---------||--------|---------|------
    // 64 |     let yet_another_location = new_location();
    //    |                                ^ `let yet_another_location` points here
    // 65 |     assert_eq!(here.file(), yet_another_location.file());
    let yet_another_location = new_location();
    assert_eq!(here.file(), yet_another_location.file());
    assert_ne!(
        (here.line(), here.column()),
        (yet_another_location.line(), yet_another_location.column())
    );
}

1.10.0 (const: 1.79.0) · Source

pub const fn file(&self) -> &'a 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");

1.92.0 (const: 1.92.0) · Source

pub const fn file_as_c_str(&self) -> &'a CStr

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*.

1.10.0 (const: 1.79.0) · Source

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");

1.25.0 (const: 1.79.0) · Source

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");