Struct autocfg::AutoCfg

pub struct AutoCfg { /* private fields */ }

Helper to detect compiler features for cfg output in build scripts.

Implementations

impl AutoCfg

pub fn new() -> Result<Self, Error>

Creates a new AutoCfg instance.

Common errors

• rustc can’t be executed, from RUSTC or in the PATH.
• The version output from rustc can’t be parsed.
• OUT_DIR is not set in the environment, or is not a writable directory.

pub fn with_dir<T: Into<PathBuf>>(dir: T) -> Result<Self, Error>

Creates a new AutoCfg instance with the specified output directory.

Common errors

• rustc can’t be executed, from RUSTC or in the PATH.
• The version output from rustc can’t be parsed.
• dir is not a writable directory.

Examples found in repository

examples/versions.rs (line 5)

fn main() {
    // Normally, cargo will set `OUT_DIR` for build scripts.
    let ac = autocfg::AutoCfg::with_dir("target").unwrap();
    for i in 0..100 {
        ac.emit_rustc_version(1, i);
    }
}

examples/integers.rs (line 5)

fn main() {
    // Normally, cargo will set `OUT_DIR` for build scripts.
    let ac = autocfg::AutoCfg::with_dir("target").unwrap();
    for i in 3..8 {
        ac.emit_has_type(&format!("i{}", 1 << i));
    }
}

examples/paths.rs (line 5)

fn main() {
    // Normally, cargo will set `OUT_DIR` for build scripts.
    let ac = autocfg::AutoCfg::with_dir("target").unwrap();

    // since ancient times...
    ac.emit_has_path("std::vec::Vec");
    ac.emit_path_cfg("std::vec::Vec", "has_vec");

    // rustc 1.10.0
    ac.emit_has_path("std::panic::PanicInfo");
    ac.emit_path_cfg("std::panic::PanicInfo", "has_panic_info");

    // rustc 1.20.0
    ac.emit_has_path("std::mem::ManuallyDrop");
    ac.emit_path_cfg("std::mem::ManuallyDrop", "has_manually_drop");

    // rustc 1.25.0
    ac.emit_has_path("std::ptr::NonNull");
    ac.emit_path_cfg("std::ptr::NonNull", "has_non_null");
}

examples/traits.rs (line 5)

fn main() {
    // Normally, cargo will set `OUT_DIR` for build scripts.
    let ac = autocfg::AutoCfg::with_dir("target").unwrap();

    // since ancient times...
    ac.emit_has_trait("std::ops::Add");
    ac.emit_trait_cfg("std::ops::Add", "has_ops");

    // trait parameters have to be provided
    ac.emit_has_trait("std::borrow::Borrow<str>");
    ac.emit_trait_cfg("std::borrow::Borrow<str>", "has_borrow");

    // rustc 1.8.0
    ac.emit_has_trait("std::ops::AddAssign");
    ac.emit_trait_cfg("std::ops::AddAssign", "has_assign_ops");

    // rustc 1.12.0
    ac.emit_has_trait("std::iter::Sum");
    ac.emit_trait_cfg("std::iter::Sum", "has_sum");

    // rustc 1.28.0
    ac.emit_has_trait("std::alloc::GlobalAlloc");
    ac.emit_trait_cfg("std::alloc::GlobalAlloc", "has_global_alloc");
}

pub fn no_std(&self) -> bool

Returns whether AutoCfg is using #![no_std] in its probes.

This is automatically detected during construction – if an empty probe fails while one with #![no_std] succeeds, then the attribute will be used for all further probes. This is usually only necessary when the TARGET lacks std altogether. If neither succeeds, no_std is not set, but that AutoCfg will probably only work for version checks.

This attribute changes the implicit prelude from std to core, which may affect the paths you need to use in other probes. It also restricts some types that otherwise get additional methods in std, like floating-point trigonometry and slice sorting.

See also set_no_std.

pub fn set_no_std(&mut self, no_std: bool)

Sets whether AutoCfg should use #![no_std] in its probes.

See also no_std.

pub fn probe_rustc_version(&self, major: usize, minor: usize) -> bool

Tests whether the current rustc reports a version greater than or equal to “major.minor”.

pub fn emit_rustc_version(&self, major: usize, minor: usize)

Sets a cfg value of the form rustc_major_minor, like rustc_1_29, if the current rustc is at least that version.

Examples found in repository

examples/versions.rs (line 7)

fn main() {
    // Normally, cargo will set `OUT_DIR` for build scripts.
    let ac = autocfg::AutoCfg::with_dir("target").unwrap();
    for i in 0..100 {
        ac.emit_rustc_version(1, i);
    }
}

pub fn probe_sysroot_crate(&self, name: &str) -> bool

Tests whether the given sysroot crate can be used.

The test code is subject to change, but currently looks like:

extern crate CRATE as probe;

pub fn emit_sysroot_crate(&self, name: &str)

Emits a config value has_CRATE if probe_sysroot_crate returns true.

pub fn probe_path(&self, path: &str) -> bool

Tests whether the given path can be used.

The test code is subject to change, but currently looks like:

pub use PATH;

pub fn emit_has_path(&self, path: &str)

Emits a config value has_PATH if probe_path returns true.

Any non-identifier characters in the path will be replaced with _ in the generated config value.

Examples found in repository

examples/paths.rs (line 8)

fn main() {
    // Normally, cargo will set `OUT_DIR` for build scripts.
    let ac = autocfg::AutoCfg::with_dir("target").unwrap();

    // since ancient times...
    ac.emit_has_path("std::vec::Vec");
    ac.emit_path_cfg("std::vec::Vec", "has_vec");

    // rustc 1.10.0
    ac.emit_has_path("std::panic::PanicInfo");
    ac.emit_path_cfg("std::panic::PanicInfo", "has_panic_info");

    // rustc 1.20.0
    ac.emit_has_path("std::mem::ManuallyDrop");
    ac.emit_path_cfg("std::mem::ManuallyDrop", "has_manually_drop");

    // rustc 1.25.0
    ac.emit_has_path("std::ptr::NonNull");
    ac.emit_path_cfg("std::ptr::NonNull", "has_non_null");
}

pub fn emit_path_cfg(&self, path: &str, cfg: &str)

Emits the given cfg value if probe_path returns true.

Examples found in repository

examples/paths.rs (line 9)

fn main() {
    // Normally, cargo will set `OUT_DIR` for build scripts.
    let ac = autocfg::AutoCfg::with_dir("target").unwrap();

    // since ancient times...
    ac.emit_has_path("std::vec::Vec");
    ac.emit_path_cfg("std::vec::Vec", "has_vec");

    // rustc 1.10.0
    ac.emit_has_path("std::panic::PanicInfo");
    ac.emit_path_cfg("std::panic::PanicInfo", "has_panic_info");

    // rustc 1.20.0
    ac.emit_has_path("std::mem::ManuallyDrop");
    ac.emit_path_cfg("std::mem::ManuallyDrop", "has_manually_drop");

    // rustc 1.25.0
    ac.emit_has_path("std::ptr::NonNull");
    ac.emit_path_cfg("std::ptr::NonNull", "has_non_null");
}

pub fn probe_trait(&self, name: &str) -> bool

Tests whether the given trait can be used.

The test code is subject to change, but currently looks like:

pub trait Probe: TRAIT + Sized {}

pub fn emit_has_trait(&self, name: &str)

Emits a config value has_TRAIT if probe_trait returns true.

Any non-identifier characters in the trait name will be replaced with _ in the generated config value.

Examples found in repository

examples/traits.rs (line 8)

fn main() {
    // Normally, cargo will set `OUT_DIR` for build scripts.
    let ac = autocfg::AutoCfg::with_dir("target").unwrap();

    // since ancient times...
    ac.emit_has_trait("std::ops::Add");
    ac.emit_trait_cfg("std::ops::Add", "has_ops");

    // trait parameters have to be provided
    ac.emit_has_trait("std::borrow::Borrow<str>");
    ac.emit_trait_cfg("std::borrow::Borrow<str>", "has_borrow");

    // rustc 1.8.0
    ac.emit_has_trait("std::ops::AddAssign");
    ac.emit_trait_cfg("std::ops::AddAssign", "has_assign_ops");

    // rustc 1.12.0
    ac.emit_has_trait("std::iter::Sum");
    ac.emit_trait_cfg("std::iter::Sum", "has_sum");

    // rustc 1.28.0
    ac.emit_has_trait("std::alloc::GlobalAlloc");
    ac.emit_trait_cfg("std::alloc::GlobalAlloc", "has_global_alloc");
}

pub fn emit_trait_cfg(&self, name: &str, cfg: &str)

Emits the given cfg value if probe_trait returns true.

Examples found in repository

examples/traits.rs (line 9)

fn main() {
    // Normally, cargo will set `OUT_DIR` for build scripts.
    let ac = autocfg::AutoCfg::with_dir("target").unwrap();

    // since ancient times...
    ac.emit_has_trait("std::ops::Add");
    ac.emit_trait_cfg("std::ops::Add", "has_ops");

    // trait parameters have to be provided
    ac.emit_has_trait("std::borrow::Borrow<str>");
    ac.emit_trait_cfg("std::borrow::Borrow<str>", "has_borrow");

    // rustc 1.8.0
    ac.emit_has_trait("std::ops::AddAssign");
    ac.emit_trait_cfg("std::ops::AddAssign", "has_assign_ops");

    // rustc 1.12.0
    ac.emit_has_trait("std::iter::Sum");
    ac.emit_trait_cfg("std::iter::Sum", "has_sum");

    // rustc 1.28.0
    ac.emit_has_trait("std::alloc::GlobalAlloc");
    ac.emit_trait_cfg("std::alloc::GlobalAlloc", "has_global_alloc");
}

pub fn probe_type(&self, name: &str) -> bool

Tests whether the given type can be used.

The test code is subject to change, but currently looks like:

pub type Probe = TYPE;

pub fn emit_has_type(&self, name: &str)

Emits a config value has_TYPE if probe_type returns true.

Any non-identifier characters in the type name will be replaced with _ in the generated config value.

Examples found in repository

examples/integers.rs (line 7)

fn main() {
    // Normally, cargo will set `OUT_DIR` for build scripts.
    let ac = autocfg::AutoCfg::with_dir("target").unwrap();
    for i in 3..8 {
        ac.emit_has_type(&format!("i{}", 1 << i));
    }
}

pub fn emit_type_cfg(&self, name: &str, cfg: &str)

Emits the given cfg value if probe_type returns true.

pub fn probe_expression(&self, expr: &str) -> bool

Tests whether the given expression can be used.

The test code is subject to change, but currently looks like:

pub fn probe() { let _ = EXPR; }

pub fn emit_expression_cfg(&self, expr: &str, cfg: &str)

Emits the given cfg value if probe_expression returns true.

pub fn probe_constant(&self, expr: &str) -> bool

Tests whether the given constant expression can be used.

The test code is subject to change, but currently looks like:

pub const PROBE: () = ((), EXPR).0;

pub fn emit_constant_cfg(&self, expr: &str, cfg: &str)

Emits the given cfg value if probe_constant returns true.

Trait Implementations

impl Clone for AutoCfg

fn clone(&self) -> AutoCfg

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for AutoCfg

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

Formats the value using the given formatter.