We are std.

Cargo.toml

@@ -16,6 +16,12 @@ categories = ["compression"]
 byteorder = { version = "1.5", default-features = false }
 twox-hash = { version = "1.6", default-features = false, optional = true }
 
+# Internal feature, only used when building as part of libstd, not part of the
+# stable interface of this crate.
+core = { version = '1.0.0', optional = true, package = 'rustc-std-workspace-core' }
+alloc = { version = '1.0.0', optional = true, package = 'rustc-std-workspace-alloc' }
+compiler_builtins = { version = '0.1.2', optional = true }
+
 [dev-dependencies]
 criterion = "0.5"
 rand = { version = "0.8.5", features = ["small_rng"] }
@@ -25,6 +31,10 @@ default = ["hash", "std"]
 hash = ["dep:twox-hash"]
 std = []
 
+# Internal feature, only used when building as part of libstd, not part of the
+# stable interface of this crate.
+rustc-dep-of-std = ["dep:core", "dep:alloc", "dep:compiler_builtins"]
+
 [[bench]]
 name = "reversedbitreader_bench"
 harness = false

src/lib.rs

@@ -4,6 +4,7 @@
 #[cfg(feature = "std")]
 extern crate std;
 
+#[cfg(not(feature = "rustc-dep-of-std"))]
 extern crate alloc;
 
 #[cfg(feature = "std")]