Making the crate no_std and alloc compatible

.github/workflows/rust.yml

@@ -61,3 +61,13 @@ jobs:
       run: cargo install cargo-fuzz
     - name: "Fuzz for 3 minutes"
       run: cargo fuzz run int_in_range -- -max_total_time=$((3 * 60))
+  no_std_build:
+    name: no_std Build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - run: rustup update
+      - run: cargo build --verbose --no-default-features
+      - run: cargo test --verbose --no-default-features
+      - run: cargo build --verbose --no-default-features --features=alloc
+      - run: cargo test --verbose --no-default-features --features=alloc

Cargo.toml

@@ -2,12 +2,12 @@
 name = "arbitrary"
 version = "1.4.2" # Make sure this matches the derive crate version (not including the patch version)
 authors = [
-    "The Rust-Fuzz Project Developers",
-    "Nick Fitzgerald <[email protected]>",
-    "Manish Goregaokar <[email protected]>",
-    "Simonas Kazlauskas <[email protected]>",
-    "Brian L. Troutwine <[email protected]>",
-    "Corey Farwell <[email protected]>",
+  "The Rust-Fuzz Project Developers",
+  "Nick Fitzgerald <[email protected]>",
+  "Manish Goregaokar <[email protected]>",
+  "Simonas Kazlauskas <[email protected]>",
+  "Brian L. Troutwine <[email protected]>",
+  "Corey Farwell <[email protected]>",
 ]
 categories = ["development-tools::testing"]
 edition = "2021"
@@ -23,8 +23,12 @@ rust-version = "1.63.0" # Keep in sync with version documented in the README.md
 derive_arbitrary = { version = "~1.4.0", path = "./derive", optional = true }
 
 [features]
+default = ["std"]
+
+alloc = []
 # Turn this feature on to enable support for `#[derive(Arbitrary)]`.
 derive = ["derive_arbitrary"]
+std = ["alloc"]
 
 [[example]]
 name = "derive_enum"

fuzz/fuzz_targets/int_in_range.rs

@@ -1,8 +1,8 @@
 #![no_main]
 
 use arbitrary::{unstructured::Int, Arbitrary, Result, Unstructured};
+use core::{fmt::Display, ops::RangeInclusive};
 use libfuzzer_sys::fuzz_target;
-use std::{fmt::Display, ops::RangeInclusive};
 
 fuzz_target!(|data: &[u8]| {
     fuzz(data).expect("`int_in_range` should never return an error");

src/error.rs

@@ -1,4 +1,4 @@
-use std::{error, fmt};
+use core::{error, fmt};
 
 /// An enumeration of buffer creation errors
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -41,14 +41,14 @@ impl error::Error for Error {}
 /// A `Result` with the error type fixed as `arbitrary::Error`.
 ///
 /// Either an `Ok(T)` or `Err(arbitrary::Error)`.
-pub type Result<T, E = Error> = std::result::Result<T, E>;
+pub type Result<T, E = Error> = core::result::Result<T, E>;
 
 #[cfg(test)]
 mod tests {
     // Often people will import our custom `Result` type because 99.9% of
     // results in a file will be `arbitrary::Result` but then have that one last
     // 0.1% that want to have a custom error type. Don't make them prefix that
-    // 0.1% as `std::result::Result`; instead, let `arbitrary::Result` have an
+    // 0.1% as `core::result::Result`; instead, let `arbitrary::Result` have an
     // overridable error type.
     #[test]
     fn can_use_custom_error_types_with_result() -> super::Result<(), String> {

src/foreign/alloc/borrow.rs

@@ -1,6 +1,6 @@
 use {
     crate::{size_hint, Arbitrary, Result, Unstructured},
-    std::borrow::{Cow, ToOwned},
+    alloc::borrow::{Cow, ToOwned},
 };
 
 impl<'a, A> Arbitrary<'a> for Cow<'a, A>

src/foreign/alloc/boxed.rs

@@ -1,6 +1,6 @@
 use {
     crate::{size_hint, Arbitrary, Result, Unstructured},
-    std::boxed::Box,
+    alloc::{boxed::Box, string::String},
 };
 
 impl<'a, A> Arbitrary<'a> for Box<A>

src/foreign/alloc/collections/binary_heap.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::collections::binary_heap::BinaryHeap,
+    alloc::collections::binary_heap::BinaryHeap,
 };
 
 impl<'a, A> Arbitrary<'a> for BinaryHeap<A>

src/foreign/alloc/collections/btree_map.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::collections::btree_map::BTreeMap,
+    alloc::collections::btree_map::BTreeMap,
 };
 
 impl<'a, K, V> Arbitrary<'a> for BTreeMap<K, V>

src/foreign/alloc/collections/btree_set.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::collections::btree_set::BTreeSet,
+    alloc::collections::btree_set::BTreeSet,
 };
 
 impl<'a, A> Arbitrary<'a> for BTreeSet<A>

src/foreign/alloc/collections/linked_list.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::collections::linked_list::LinkedList,
+    alloc::collections::linked_list::LinkedList,
 };
 
 impl<'a, A> Arbitrary<'a> for LinkedList<A>

src/foreign/alloc/collections/vec_deque.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::collections::vec_deque::VecDeque,
+    alloc::collections::vec_deque::VecDeque,
 };
 
 impl<'a, A> Arbitrary<'a> for VecDeque<A>

src/foreign/alloc/ffi/c_str.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::ffi::CString,
+    alloc::{ffi::CString, vec::Vec},
 };
 
 impl<'a> Arbitrary<'a> for CString {

src/foreign/alloc/rc.rs

@@ -1,6 +1,6 @@
 use {
     crate::{size_hint, Arbitrary, Result, Unstructured},
-    std::rc::Rc,
+    alloc::rc::Rc,
 };
 
 impl<'a, A> Arbitrary<'a> for Rc<A>

src/foreign/alloc/string.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::string::String,
+    alloc::string::String,
 };
 
 impl<'a> Arbitrary<'a> for String {

src/foreign/alloc/sync.rs

@@ -1,6 +1,6 @@
 use {
     crate::{size_hint, Arbitrary, Result, Unstructured},
-    std::sync::Arc,
+    alloc::sync::Arc,
 };
 
 impl<'a, A> Arbitrary<'a> for Arc<A>

src/foreign/alloc/vec.rs

@@ -1,6 +1,6 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::vec::Vec,
+    alloc::vec::Vec,
 };
 
 impl<'a, A> Arbitrary<'a> for Vec<A>

src/foreign/mod.rs

@@ -2,6 +2,8 @@
 //!
 //! [`Arbitrary`]: crate::Arbitrary
 
+#[cfg(feature = "alloc")]
 mod alloc;
 mod core;
+#[cfg(feature = "std")]
 mod std;

src/foreign/std/collections/hash_map.rs

@@ -1,9 +1,7 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::{
-        collections::hash_map::HashMap,
-        hash::{BuildHasher, Hash},
-    },
+    core::hash::{BuildHasher, Hash},
+    std::collections::hash_map::HashMap,
 };
 
 impl<'a, K, V, S> Arbitrary<'a> for HashMap<K, V, S>

src/foreign/std/collections/hash_set.rs

@@ -1,9 +1,7 @@
 use {
     crate::{Arbitrary, Result, Unstructured},
-    std::{
-        collections::hash_set::HashSet,
-        hash::{BuildHasher, Hash},
-    },
+    core::hash::{BuildHasher, Hash},
+    std::collections::hash_set::HashSet,
 };
 
 impl<'a, A, S> Arbitrary<'a> for HashSet<A, S>

src/lib.rs

@@ -14,6 +14,7 @@
 //! [`Arbitrary`] trait's documentation for details on
 //! automatically deriving, implementing, and/or using the trait.
 
+#![cfg_attr(not(any(feature = "std", test)), no_std)]
 #![deny(bad_style)]
 #![deny(missing_docs)]
 #![deny(future_incompatible)]
@@ -22,6 +23,9 @@
 #![deny(rust_2018_idioms)]
 #![deny(unused)]
 
+#[cfg(feature = "alloc")]
+extern crate alloc;
+
 mod error;
 mod foreign;
 pub mod size_hint;
@@ -49,7 +53,7 @@ impl core::fmt::Display for MaxRecursionReached {
     }
 }
 
-impl std::error::Error for MaxRecursionReached {}
+impl core::error::Error for MaxRecursionReached {}
 
 /// Generate arbitrary structured values from raw, unstructured data.
 ///
@@ -122,9 +126,9 @@ impl std::error::Error for MaxRecursionReached {}
 ///
 /// ```
 /// # #[cfg(feature = "derive")] mod foo {
-/// # pub struct MyCollection<T> { _t: std::marker::PhantomData<T> }
+/// # pub struct MyCollection<T> { _t: core::marker::PhantomData<T> }
 /// # impl<T> MyCollection<T> {
-/// #     pub fn new() -> Self { MyCollection { _t: std::marker::PhantomData } }
+/// #     pub fn new() -> Self { MyCollection { _t: core::marker::PhantomData } }
 /// #     pub fn insert(&mut self, element: T) {}
 /// # }
 /// use arbitrary::{Arbitrary, Result, Unstructured};
@@ -554,7 +558,7 @@ pub struct CompileFailTests;
 
 // Support for `#[derive(Arbitrary)]`.
 #[doc(hidden)]
-#[cfg(feature = "derive")]
+#[cfg(all(feature = "derive", feature = "std"))]
 pub mod details {
     use super::*;
 

src/size_hint.rs

@@ -67,10 +67,10 @@ pub fn and_all(hints: &[(usize, Option<usize>)]) -> (usize, Option<usize>) {
 /// `lhs` and `rhs` size hints.
 #[inline]
 pub fn or(lhs: (usize, Option<usize>), rhs: (usize, Option<usize>)) -> (usize, Option<usize>) {
-    let lower = std::cmp::min(lhs.0, rhs.0);
+    let lower = core::cmp::min(lhs.0, rhs.0);
     let upper = lhs
         .1
-        .and_then(|lhs| rhs.1.map(|rhs| std::cmp::max(lhs, rhs)));
+        .and_then(|lhs| rhs.1.map(|rhs| core::cmp::max(lhs, rhs)));
     (lower, upper)
 }
 

src/tests.rs

@@ -1,6 +1,9 @@
+#[cfg(feature = "alloc")]
+use alloc::{rc::Rc, string::String, sync::Arc, vec::Vec};
 use {
     super::{Arbitrary, Result, Unstructured},
-    std::{collections::HashSet, fmt::Debug, hash::Hash, rc::Rc, sync::Arc},
+    core::{fmt::Debug, hash::Hash},
+    std::collections::HashSet,
 };
 
 /// Assert that the given expected values are all generated.
@@ -154,6 +157,7 @@ fn arbitrary_take_rest_for_bytes() {
 }
 
 #[test]
+#[cfg(feature = "alloc")]
 fn arbitrary_for_vec_u8() {
     assert_generates::<Vec<u8>>([
         vec![],
@@ -175,6 +179,7 @@ fn arbitrary_for_vec_u8() {
 }
 
 #[test]
+#[cfg(feature = "alloc")]
 fn arbitrary_for_vec_vec_u8() {
     assert_generates::<Vec<Vec<u8>>>([
         vec![],
@@ -193,6 +198,7 @@ fn arbitrary_for_vec_vec_u8() {
 }
 
 #[test]
+#[cfg(feature = "alloc")]
 fn arbitrary_for_vec_vec_vec_u8() {
     assert_generates::<Vec<Vec<Vec<u8>>>>([
         vec![],
@@ -217,11 +223,13 @@ fn arbitrary_for_vec_vec_vec_u8() {
 }
 
 #[test]
+#[cfg(feature = "alloc")]
 fn arbitrary_for_string() {
     assert_generates::<String>(["".into(), "a".into(), "aa".into(), "aaa".into()]);
 }
 
 #[test]
+#[cfg(feature = "alloc")]
 fn arbitrary_collection() {
     let x = [
         1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 8, 12,
@@ -257,6 +265,7 @@ fn arbitrary_collection() {
 }
 
 #[test]
+#[cfg(feature = "alloc")]
 fn arbitrary_take_rest() {
     // Basic examples
     let x = [1, 2, 3, 4];
@@ -307,6 +316,7 @@ fn arbitrary_take_rest() {
 }
 
 #[test]
+#[cfg(feature = "alloc")]
 fn size_hint_for_tuples() {
     assert_eq!(
         (7, Some(7)),