Support using std without getrandom or rand_chacha

Cargo.toml

@@ -28,13 +28,13 @@ features = ["small_rng", "serde1"]
 
 [features]
 # Meta-features:
-default = ["std", "std_rng"]
+default = ["std", "std_rng", "getrandom"]
 nightly = [] # some additions requiring nightly Rust
 serde1 = ["serde", "rand_core/serde1"]
 
 # Option (enabled by default): without "std" rand uses libcore; this option
 # enables functionality expected to be available on a standard platform.
-std = ["rand_core/std", "rand_chacha/std", "alloc", "getrandom", "libc"]
+std = ["rand_core/std", "rand_chacha?/std", "alloc", "libc"]
 
 # Option: "alloc" enables support for Vec and Box when not using "std"
 alloc = ["rand_core/alloc"]
@@ -65,7 +65,7 @@ members = [
 ]
 
 [dependencies]
-rand_core = { path = "rand_core", version = "0.7.0" }
+rand_core = { path = "rand_core", version = "0.7.0", default-features = false }
 log = { version = "0.4.4", optional = true }
 serde = { version = "1.0.103", features = ["derive"], optional = true }
 rand_chacha = { path = "rand_chacha", version = "0.4.0", default-features = false, optional = true }

rand_core/Cargo.toml

@@ -25,7 +25,7 @@ rustdoc-args = ["--cfg", "doc_cfg", "--generate-link-to-definition"]
 all-features = true
 
 [features]
-std = ["alloc", "getrandom", "getrandom/std"]    # use std library; should be default but for above bug
+std = ["alloc", "getrandom?/std"]
 alloc = []  # enables Vec and Box support without std
 serde1 = ["serde"] # enables serde for BlockRng wrapper
 

rand_core/src/error.rs

@@ -50,9 +50,7 @@ impl Error {
     #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
     #[inline]
     pub fn new<E>(err: E) -> Self
-    where
-        E: Into<Box<dyn std::error::Error + Send + Sync + 'static>>,
-    {
+    where E: Into<Box<dyn std::error::Error + Send + Sync + 'static>> {
         Error { inner: err.into() }
     }
 
@@ -125,7 +123,7 @@ impl fmt::Debug for Error {
         {
             getrandom::Error::from(self.code).fmt(f)
         }
-        #[cfg(not(feature = "getrandom"))]
+        #[cfg(not(any(feature = "getrandom", feature = "std")))]
         {
             write!(f, "Error {{ code: {} }}", self.code)
         }
@@ -142,7 +140,7 @@ impl fmt::Display for Error {
         {
             getrandom::Error::from(self.code).fmt(f)
         }
-        #[cfg(not(feature = "getrandom"))]
+        #[cfg(not(any(feature = "getrandom", feature = "std")))]
         {
             write!(f, "error code {}", self.code)
         }

rand_distr/Cargo.toml

@@ -35,7 +35,7 @@ serde_with = { version = "1.14.0", optional = true }
 [dev-dependencies]
 rand_pcg = { version = "0.4.0", path = "../rand_pcg" }
 # For inline examples
-rand = { path = "..", version = "0.9.0", default-features = false, features = ["std_rng", "std", "small_rng"] }
+rand = { path = "..", version = "0.9.0", features = ["small_rng"] }
 # Histogram implementation for testing uniformity
 average = { version = "0.13", features = [ "std" ] }
 # Special functions for testing distributions

src/lib.rs

@@ -101,11 +101,11 @@ pub mod rngs;
 pub mod seq;
 
 // Public exports
-#[cfg(all(feature = "std", feature = "std_rng"))]
+#[cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))]
 pub use crate::rngs::thread::thread_rng;
 pub use rng::{Fill, Rng};
 
-#[cfg(all(feature = "std", feature = "std_rng"))]
+#[cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))]
 use crate::distributions::{Distribution, Standard};
 
 /// Generates a random value using the thread-local random number generator.
@@ -152,8 +152,8 @@ use crate::distributions::{Distribution, Standard};
 ///
 /// [`Standard`]: distributions::Standard
 /// [`ThreadRng`]: rngs::ThreadRng
-#[cfg(all(feature = "std", feature = "std_rng"))]
-#[cfg_attr(doc_cfg, doc(cfg(all(feature = "std", feature = "std_rng"))))]
+#[cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))]
+#[cfg_attr(doc_cfg, doc(cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))))]
 #[inline]
 pub fn random<T>() -> T
 where Standard: Distribution<T> {
@@ -173,7 +173,7 @@ mod test {
     }
 
     #[test]
-    #[cfg(all(feature = "std", feature = "std_rng"))]
+    #[cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))]
     fn test_random() {
         let _n: usize = random();
         let _f: f32 = random();

src/prelude.rs

@@ -25,10 +25,10 @@ pub use crate::rngs::SmallRng;
 #[cfg(feature = "std_rng")]
 #[doc(no_inline)] pub use crate::rngs::StdRng;
 #[doc(no_inline)]
-#[cfg(all(feature = "std", feature = "std_rng"))]
+#[cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))]
 pub use crate::rngs::ThreadRng;
 #[doc(no_inline)] pub use crate::seq::{IteratorRandom, SliceRandom};
 #[doc(no_inline)]
-#[cfg(all(feature = "std", feature = "std_rng"))]
+#[cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))]
 pub use crate::{random, thread_rng};
 #[doc(no_inline)] pub use crate::{CryptoRng, Rng, RngCore, SeedableRng};

src/rngs/mod.rs

@@ -109,11 +109,11 @@ mod xoshiro128plusplus;
 #[cfg(feature = "small_rng")] mod small;
 
 #[cfg(feature = "std_rng")] mod std;
-#[cfg(all(feature = "std", feature = "std_rng"))] pub(crate) mod thread;
+#[cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))] pub(crate) mod thread;
 
 #[cfg(feature = "small_rng")] pub use self::small::SmallRng;
 #[cfg(feature = "std_rng")] pub use self::std::StdRng;
-#[cfg(all(feature = "std", feature = "std_rng"))] pub use self::thread::ThreadRng;
+#[cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))] pub use self::thread::ThreadRng;
 
 #[cfg_attr(doc_cfg, doc(cfg(feature = "getrandom")))]
 #[cfg(feature = "getrandom")] pub use rand_core::OsRng;

src/rngs/std.rs

@@ -10,6 +10,7 @@
 
 use crate::{CryptoRng, Error, RngCore, SeedableRng};
 
+#[cfg(feature = "getrandom")]
 pub(crate) use rand_chacha::ChaCha12Core as Core;
 
 use rand_chacha::ChaCha12Rng as Rng;

src/rngs/thread.rs

@@ -63,7 +63,7 @@ const THREAD_RNG_RESEED_THRESHOLD: u64 = 1024 * 64;
 ///
 /// [`ReseedingRng`]: crate::rngs::adapter::ReseedingRng
 /// [`StdRng`]: crate::rngs::StdRng
-#[cfg_attr(doc_cfg, doc(cfg(all(feature = "std", feature = "std_rng"))))]
+#[cfg_attr(doc_cfg, doc(cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))))]
 #[derive(Clone)]
 pub struct ThreadRng {
     // Rc is explicitly !Send and !Sync
@@ -107,7 +107,7 @@ thread_local!(
 /// println!("A simulated die roll: {}", rng.gen_range(1..=6));
 /// # }
 /// ```
-#[cfg_attr(doc_cfg, doc(cfg(all(feature = "std", feature = "std_rng"))))]
+#[cfg_attr(doc_cfg, doc(cfg(all(feature = "std", feature = "std_rng", feature = "getrandom"))))]
 pub fn thread_rng() -> ThreadRng {
     let rng = THREAD_RNG_KEY.with(|t| t.clone());
     ThreadRng { rng }