Stabilize cfg rustdoc

1 files changed, 31 insertions, 0 deletions

diff --git a/src/doc/rustdoc/src/the-doc-attribute.md b/src/doc/rustdoc/src/the-doc-attribute.md
index 80ac405eb2f..3aaac9268ff 100644
--- a/src/doc/rustdoc/src/the-doc-attribute.md
+++ b/src/doc/rustdoc/src/the-doc-attribute.md
@@ -214,3 +214,34 @@ the `strip-hidden` pass is removed.
 Since primitive types are defined in the compiler, there's no place to attach documentation
 attributes. This attribute is used by the standard library to provide a way to generate
 documentation for primitive types.
+
+## `#[cfg(rustdoc)]`: Documenting platform-/feature-specific information
+
+For conditional compilation, Rustdoc treats your crate the same way the compiler does: Only things
+from the host target are available (or from the given `--target` if present), and everything else is
+"filtered out" from the crate. This can cause problems if your crate is providing different things
+on different targets and you want your documentation to reflect all the available items you
+provide.
+
+If you want to make sure an item is seen by Rustdoc regardless of what platform it's targeting,
+you can apply `#[cfg(rustdoc)]` to it. Rustdoc sets this whenever it's building documentation, so
+anything that uses that flag will make it into documentation it generates. To apply this to an item
+with other `#[cfg]` filters on it, you can write something like `#[cfg(any(windows, rustdoc))]`.
+This will preserve the item either when built normally on Windows, or when being documented
+anywhere.
+
+Please note that this feature won't be passed when building doctests.
+
+Example:
+
+```rust
+/// Token struct that can only be used on Windows.
+#[cfg(any(windows, rustdoc))]
+pub struct WindowsToken;
+/// Token struct that can only be used on Unix.
+#[cfg(any(unix, rustdoc))]
+pub struct UnixToken;
+```
+
+Here, the respective tokens can only be used by dependent crates on their respective platforms, but
+they will both appear in documentation.