autocfg=======[![autocfg crate](https://img.shields.io/crates/v/autocfg.svg)](https://crates.io/crates/autocfg)[![autocfg documentation](https://docs.rs/autocfg/badge.svg)](https://docs.rs/autocfg)![minimum rustc 1.0](https://img.shields.io/badge/rustc-1.0+-red.svg)![build status](https://github.com/cuviper/autocfg/workflows/CI/badge.svg)A Rust library for build scripts to automatically configure code based oncompiler support.  Code snippets are dynamically tested to see if the `rustc`will accept them, rather than hard-coding specific version support.## UsageAdd this to your `Cargo.toml`:```toml[build-dependencies]autocfg = "1"```Then use it in your `build.rs` script to detect compiler features.  Forexample, to test for 128-bit integer support, it might look like:```rustextern crate autocfg;fn main() {    let ac = autocfg::new();    ac.emit_has_type("i128");    // (optional) We don't need to rerun for anything external.    autocfg::rerun_path("build.rs");}```If the type test succeeds, this will write a `cargo:rustc-cfg=has_i128` linefor Cargo, which translates to Rust arguments `--cfg has_i128`.  Then in therest of your Rust code, you can add `#[cfg(has_i128)]` conditions on code thatshould only be used when the compiler supports it.## Release Notes- 1.5.1 (2026-05-22)  - Refactor the `test_wrappers` test without any shell script.- 1.5.0 (2025-06-17)  - Add `edition` and `set_edition` to control the Rust edition used in probes.  - Remove probe result files so they don't pollute the output directory.- 1.4.0 (2024-09-26)  - Add `emit_possibility` for Rust 1.80's [checked cfgs], and call that    automatically for methods that conditionally `emit`, by @Techcable.[checked cfgs]: https://blog.rust-lang.org/2024/05/06/check-cfg.html- 1.3.0 (2024-05-03)  - Add `probe_raw` for direct control of the code that will be test-compiled.  - Use wrappers when querying the `rustc` version information too.- 1.2.0 (2024-03-25)  - Add `no_std` and `set_no_std` to control the use of `#![no_std]` in probes.  - Use `RUSTC_WRAPPER` and `RUSTC_WORKSPACE_WRAPPER` when they are set.- 1.1.0 (2022-02-07)  - Use `CARGO_ENCODED_RUSTFLAGS` when it is set.- 1.0.1 (2020-08-20)  - Apply `RUSTFLAGS` for more `--target` scenarios, by @adamreichold.- 1.0.0 (2020-01-08)  - 🎉 Release 1.0! 🎉 (no breaking changes)  - Add `probe_expression` and `emit_expression_cfg` to test arbitrary expressions.  - Add `probe_constant` and `emit_constant_cfg` to test arbitrary constant expressions.- 0.1.7 (2019-10-20)  - Apply `RUSTFLAGS` when probing `$TARGET != $HOST`, mainly for sysroot, by @roblabla.- 0.1.6 (2019-08-19)  - Add `probe`/`emit_sysroot_crate`, by @leo60228.- 0.1.5 (2019-07-16)  - Mask some warnings from newer rustc.- 0.1.4 (2019-05-22)  - Relax `std`/`no_std` probing to a warning instead of an error.  - Improve `rustc` bootstrap compatibility.- 0.1.3 (2019-05-21)  - Auto-detects if `#![no_std]` is needed for the `$TARGET`.- 0.1.2 (2019-01-16)  - Add `rerun_env(ENV)` to print `cargo:rerun-if-env-changed=ENV`.  - Add `rerun_path(PATH)` to print `cargo:rerun-if-changed=PATH`.## Minimum Rust version policyThis crate's minimum supported `rustc` version is `1.0.0`.  Compatibility isits entire reason for existence, so this crate will be extremely conservativeabout raising this requirement.  If this is ever deemed necessary, it will betreated as a major breaking change for semver purposes.## LicenseThis project is licensed under either of * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or   https://www.apache.org/licenses/LICENSE-2.0) * MIT license ([LICENSE-MIT](LICENSE-MIT) or   https://opensource.org/licenses/MIT)at your option.