96 lines
2.9 KiB
Markdown
96 lines
2.9 KiB
Markdown
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autocfg
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=======
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[](https://crates.io/crates/autocfg)
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[](https://docs.rs/autocfg)
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A Rust library for build scripts to automatically configure code based on
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compiler support. Code snippets are dynamically tested to see if the `rustc`
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will accept them, rather than hard-coding specific version support.
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## Usage
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Add this to your `Cargo.toml`:
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```toml
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[build-dependencies]
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autocfg = "1"
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```
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Then use it in your `build.rs` script to detect compiler features. For
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example, to test for 128-bit integer support, it might look like:
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```rust
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extern crate autocfg;
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fn main() {
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let ac = autocfg::new();
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ac.emit_has_type("i128");
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// (optional) We don't need to rerun for anything external.
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autocfg::rerun_path("build.rs");
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}
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```
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If the type test succeeds, this will write a `cargo:rustc-cfg=has_i128` line
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for Cargo, which translates to Rust arguments `--cfg has_i128`. Then in the
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rest of your Rust code, you can add `#[cfg(has_i128)]` conditions on code that
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should only be used when the compiler supports it.
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## Release Notes
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- 1.1.0 (2022-02-07)
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- Use `CARGO_ENCODED_RUSTFLAGS` when it is set.
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- 1.0.1 (2020-08-20)
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- Apply `RUSTFLAGS` for more `--target` scenarios, by @adamreichold.
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- 1.0.0 (2020-01-08)
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- 🎉 Release 1.0! 🎉 (no breaking changes)
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- Add `probe_expression` and `emit_expression_cfg` to test arbitrary expressions.
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- Add `probe_constant` and `emit_constant_cfg` to test arbitrary constant expressions.
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- 0.1.7 (2019-10-20)
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- Apply `RUSTFLAGS` when probing `$TARGET != $HOST`, mainly for sysroot, by @roblabla.
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- 0.1.6 (2019-08-19)
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- Add `probe`/`emit_sysroot_crate`, by @leo60228.
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- 0.1.5 (2019-07-16)
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- Mask some warnings from newer rustc.
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- 0.1.4 (2019-05-22)
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- Relax `std`/`no_std` probing to a warning instead of an error.
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- Improve `rustc` bootstrap compatibility.
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- 0.1.3 (2019-05-21)
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- Auto-detects if `#![no_std]` is needed for the `$TARGET`.
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- 0.1.2 (2019-01-16)
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- Add `rerun_env(ENV)` to print `cargo:rerun-if-env-changed=ENV`.
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- Add `rerun_path(PATH)` to print `cargo:rerun-if-changed=PATH`.
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## Minimum Rust version policy
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This crate's minimum supported `rustc` version is `1.0.0`. Compatibility is
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its entire reason for existence, so this crate will be extremely conservative
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about raising this requirement. If this is ever deemed necessary, it will be
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treated as a major breaking change for semver purposes.
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## License
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This project is licensed under either of
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* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
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http://www.apache.org/licenses/LICENSE-2.0)
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* MIT license ([LICENSE-MIT](LICENSE-MIT) or
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http://opensource.org/licenses/MIT)
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at your option.
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