Use the alloc crate for no_std (Rust 1.36+)

.travis.yml

@@ -5,6 +5,7 @@ rust:
   - 1.22.0 # rand
   - 1.26.0 # has_i128
   - 1.31.0 # 2018!
+  - 1.36.0 # alloc
   - stable
   - beta
   - nightly
@@ -19,6 +20,14 @@ matrix:
         apt:
           packages:
             - gcc-multilib
+    # try a target that doesn't have std at all, but does have alloc
+    - name: "no_std"
+      rust: stable
+      env: TARGET=thumbv6m-none-eabi
+      before_script:
+        - rustup target add $TARGET
+      script:
+        - cargo build --verbose --target $TARGET --no-default-features --features "i128 serde"
     - name: "rustfmt"
       rust: 1.31.0
       before_script:

Cargo.toml

@@ -52,7 +52,6 @@ features = ["std"]
 optional = true
 version = "1.0"
 default-features = false
-features = ["std"]
 
 [dependencies.quickcheck]
 optional = true
@@ -64,9 +63,6 @@ optional = true
 version = "0.8"
 default-features = false
 
-[dev-dependencies.serde_test]
-version = "1.0"
-
 [features]
 default = ["std"]
 i128 = ["num-integer/i128", "num-traits/i128"]

README.md

@@ -24,10 +24,10 @@ extern crate num_bigint;
 
 ## Features
 
-The `std` crate feature is mandatory and enabled by default.  If you depend on
-`num-bigint` with `default-features = false`, you must manually enable the
-`std` feature yourself.  In the future, we hope to support `#![no_std]` with
-the `alloc` crate when `std` is not enabled.
+The `std` crate feature is enabled by default, and is mandatory before Rust
+1.36 and the stabilized `alloc` crate.  If you depend on `num-bigint` with
+`default-features = false`, you must manually enable the `std` feature yourself
+if your compiler is not new enough.
 
 Implementations for `i128` and `u128` are only available with Rust 1.26 and
 later.  The build script automatically detects this, but you can make it

ci/big_serde/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "big_serde"
+version = "0.1.0"
+authors = ["Josh Stone <cuviper@gmail.com>"]
+
+[dependencies]
+num-traits = "0.2.11"
+serde_test = "1.0"
+
+[dependencies.num-bigint]
+features = ["serde"]
+path = "../.."

tests/serde.rs → ci/big_serde/src/lib.rs

@@ -3,8 +3,12 @@
 //! The serialized formats should not change, even if we change our
 //! internal representation, because we want to preserve forward and
 //! backward compatibility of serialized data!
+//!
+//! This test is in a completely separate crate so its `serde_test`
+//! dependency does not "infect" the rest of the build with `serde`'s
+//! default features, especially not `serde/std`.
 
-#![cfg(feature = "serde")]
+#![cfg(test)]
 
 extern crate num_bigint;
 extern crate num_traits;

ci/rustup.sh

@@ -5,7 +5,7 @@
 set -ex
 
 export TRAVIS_RUST_VERSION
-for TRAVIS_RUST_VERSION in 1.15.0 1.22.0 1.26.0 stable beta nightly; do
+for TRAVIS_RUST_VERSION in 1.15.0 1.22.0 1.26.0 1.31.0 1.36.0 stable beta nightly; do
     run="rustup run $TRAVIS_RUST_VERSION"
     $run cargo build --verbose
     $run $PWD/ci/test_full.sh

ci/test_full.sh

@@ -4,16 +4,17 @@ set -ex
 
 echo Testing num-bigint on rustc ${TRAVIS_RUST_VERSION}
 
-FEATURES="serde"
-if [[ "$TRAVIS_RUST_VERSION" =~ ^(nightly|beta|stable.*|1.31.0|1.26.0|1.22.0)$ ]]; then
-  FEATURES="$FEATURES rand"
-fi
-if [[ "$TRAVIS_RUST_VERSION" =~ ^(nightly|beta|stable.*|1.31.0|1.26.0)$ ]]; then
-  FEATURES="$FEATURES i128"
-fi
-if [[ "$TRAVIS_RUST_VERSION" =~ ^(nightly|beta|stable.*|1.31.0)$ ]]; then
-  FEATURES="$FEATURES quickcheck quickcheck_macros"
-fi
+case "$TRAVIS_RUST_VERSION" in
+  1.1[5-9].* | 1.2[0-1].*) STD_FEATURES="serde" ;;
+  1.2[2-5].*) STD_FEATURES="serde rand" ;;
+  1.2[6-9].* | 1.30.*) STD_FEATURES="serde rand i128" ;;
+  *) STD_FEATURES="serde rand i128 quickcheck quickcheck_macros" ;;
+esac
+
+case "$TRAVIS_RUST_VERSION" in
+  1.1[5-9].* | 1.2[0-9].* | 1.3[0-5].*) ;;
+  *) NO_STD_FEATURES="i128 serde" ;;
+esac
 
 # num-bigint should build and test everywhere.
 cargo build --verbose
@@ -24,16 +25,36 @@ cargo build --no-default-features --features="std"
 cargo test --no-default-features --features="std"
 
 # Each isolated feature should also work everywhere.
-for feature in $FEATURES; do
+for feature in $STD_FEATURES; do
   cargo build --verbose --no-default-features --features="std $feature"
   cargo test --verbose --no-default-features --features="std $feature"
 done
 
 # test all supported features together
-cargo build --features="std $FEATURES"
-cargo test --features="std $FEATURES"
+cargo build --features="std $STD_FEATURES"
+cargo test --features="std $STD_FEATURES"
+
+if test -n "${NO_STD_FEATURES:+true}"; then
+  # It should build with minimal features too.
+  cargo build --no-default-features
+  cargo test --no-default-features
+
+  # Each isolated feature should also work everywhere.
+  for feature in $NO_STD_FEATURES; do
+    cargo build --verbose --no-default-features --features="$feature"
+    cargo test --verbose --no-default-features --features="$feature"
+  done
+
+  # test all supported features together
+  cargo build --no-default-features --features="$NO_STD_FEATURES"
+  cargo test --no-default-features --features="$NO_STD_FEATURES"
+fi
 
 # make sure benchmarks can be built
 if [[ "$TRAVIS_RUST_VERSION" == "nightly" ]]; then
   cargo bench --all-features --no-run
 fi
+
+case "$STD_FEATURES" in
+  *serde*) cargo test --manifest-path ci/big_serde/Cargo.toml
+esac

src/algorithms.rs

@@ -1,8 +1,8 @@
-use std::borrow::Cow;
-use std::cmp;
-use std::cmp::Ordering::{self, Equal, Greater, Less};
-use std::iter::repeat;
-use std::mem;
+use core::cmp;
+use core::cmp::Ordering::{self, Equal, Greater, Less};
+use core::iter::repeat;
+use core::mem;
+use std_alloc::{Cow, Vec};
 use traits;
 use traits::{One, Zero};
 

src/bigint.rs

@@ -1,18 +1,22 @@
-#[allow(deprecated, unused_imports)]
-use std::ascii::AsciiExt;
-use std::cmp::Ordering::{self, Equal, Greater, Less};
-use std::default::Default;
-use std::fmt;
-use std::iter::{Product, Sum};
-use std::mem;
-use std::ops::{
+use core::cmp::Ordering::{self, Equal, Greater, Less};
+use core::default::Default;
+use core::fmt;
+use core::iter::{Product, Sum};
+use core::mem;
+use core::ops::{
     Add, AddAssign, BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign, Div, DivAssign,
     Mul, MulAssign, Neg, Not, Rem, RemAssign, Shl, ShlAssign, Shr, ShrAssign, Sub, SubAssign,
 };
-use std::str::{self, FromStr};
+use core::str::{self, FromStr};
 #[cfg(has_i128)]
-use std::{i128, u128};
-use std::{i64, u64};
+use core::{i128, u128};
+use core::{i64, u64};
+#[cfg(feature = "std")]
+#[allow(deprecated, unused_imports)]
+use std::ascii::AsciiExt;
+#[cfg(feature = "quickcheck")]
+use std_alloc::Box;
+use std_alloc::{String, Vec};
 
 #[cfg(feature = "serde")]
 use serde;

src/bigrand.rs

@@ -58,7 +58,7 @@ impl<R: Rng + ?Sized> RandBigInt for R {
 
     #[cfg(u64_digit)]
     fn gen_biguint(&mut self, bit_size: usize) -> BigUint {
-        use std::slice;
+        use core::slice;
 
         let (digits, rem) = bit_size.div_rem(&32);
         let native_digits = bit_size.div_ceil(&64);