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Add more documentation to cargo::rustc-check-cfg #13869

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merged 3 commits into from
May 6, 2024
Merged

Add more documentation to cargo::rustc-check-cfg #13869

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84b9169
Add note about single column rustc-check-cfg
Urgau May 6, 2024
5a43a45
Add check-cfg blog post in the documentation
Urgau May 6, 2024
1ddc6b6
Link the build-script-examples page in cargo::rustc-check-cfg
Urgau May 6, 2024
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10 changes: 10 additions & 0 deletions src/doc/src/reference/build-scripts.md
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Expand Up @@ -258,12 +258,16 @@ identifier, the value should be a string.

### `cargo::rustc-check-cfg=CHECK_CFG` {#rustc-check-cfg}

*See the announcement [blog post][check-cfg-blog-post] for more a global view of the feature.*

Add to the list of expected config names and values that is used when checking
the _reachable_ cfg expressions.

For details on the syntax of `CHECK_CFG`, see `rustc` [`--check-cfg` flag][option-check-cfg].
See also the [`unexpected_cfgs`][unexpected-cfgs] lint.

> Note: `cargo:rustc-check-cfg` (single-colon) can be used if your MSRV is below Rust 1.77

The instruction can be used like this:

```rust,no_run
Expand All @@ -288,7 +292,13 @@ if foo_bar_condition {
}
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Unrelated to this PR. Instead of putting an example here, do you think it's better to just have a link to the conditional compilation build script example?

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I think having a example right in the documentation is very valuable, however linking to a more complete example is quite valuable to, so I added a link to it.

```

For a more complete example see in the [build script examples][build-script-examples] page
the [conditional compilation][conditional-compilation-example] example.

[check-cfg-blog-post]: https://blog.rust-lang.org/2024/05/06/check-cfg.html
[option-check-cfg]: ../../rustc/command-line-arguments.md#option-check-cfg
[build-script-examples]: build-script-examples.md
[conditional-compilation-example]: build-script-examples.md#conditional-compilation

### `cargo::rustc-env=VAR=VALUE` {#rustc-env}

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