New alloc feature

Allows use of `Secp256k1::new` and related API if an allocator is available

Cargo.toml

@@ -20,6 +20,8 @@ features = [ "rand", "rand-std", "serde", "recovery" ]
 unstable = ["recovery", "rand-std"]
 default = ["std"]
 std = ["secp256k1-sys/std"]
+# allow use of Secp256k1::new and related API that requires an allocator
+alloc = []
 rand-std = ["rand/std"]
 recovery = ["secp256k1-sys/recovery"]
 lowmemory = ["secp256k1-sys/lowmemory"]

contrib/test.sh

@@ -76,6 +76,7 @@ if [ "$DO_ASAN" = true ]; then
     RUSTFLAGS='-Zsanitizer=memory -Zsanitizer-memory-track-origins -Cforce-frame-pointers=yes'   \
     cargo test --lib --all --features="$FEATURES" -Zbuild-std --target x86_64-unknown-linux-gnu &&
     cargo run --release --manifest-path=./no_std_test/Cargo.toml | grep -q "Verified Successfully"
+    cargo run --release --features=alloc --manifest-path=./no_std_test/Cargo.toml | grep -q "Verified alloc Successfully"
 fi
 
 # Test if panic in C code aborts the process (either with a real panic or with SIGILL)

no_std_test/Cargo.toml

@@ -3,7 +3,11 @@ name = "no_std_test"
 version = "0.1.0"
 authors = ["Elichai Turkel <elichai.turkel@gmail.com>"]
 
+[features]
+alloc = ["secp256k1/alloc", "wee_alloc"]
+
 [dependencies]
+wee_alloc = { version = "0.4.5", optional = true }
 secp256k1 = { path = "../", default-features = false, features = ["serde", "rand", "recovery"] }
 libc = { version = "0.2", default-features = false }
 serde_cbor = { version = "0.10", default-features = false } # A random serializer that supports no-std.

no_std_test/src/main.rs

@@ -43,11 +43,24 @@
 #![feature(start)]
 #![feature(core_intrinsics)]
 #![feature(panic_info_message)]
+#![feature(alloc_error_handler)]
 #![no_std]
 extern crate libc;
 extern crate secp256k1;
 extern crate serde_cbor;
 
+#[cfg(feature = "alloc")]
+extern crate alloc;
+
+use core::alloc::Layout;
+
+#[cfg(feature = "alloc")]
+extern crate wee_alloc;
+
+#[cfg(feature = "alloc")]
+#[global_allocator]
+static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
+
 use core::fmt::{self, write, Write};
 use core::intrinsics;
 use core::panic::PanicInfo;
@@ -120,6 +133,17 @@ fn start(_argc: isize, _argv: *const *const u8) -> isize {
     assert_ne!(x_arr, [0u8; 32]);
     assert_ne!(&y_arr[..], &[0u8; 32][..]);
 
+    #[cfg(feature = "alloc")]
+    {
+        let secp_alloc = Secp256k1::new();
+        let public_key = PublicKey::from_secret_key(&secp_alloc, &secret_key);
+        let message = Message::from_slice(&[0xab; 32]).expect("32 bytes");
+
+        let sig = secp_alloc.sign(&message, &secret_key);
+        assert!(secp_alloc.verify(&message, &sig, &public_key).is_ok());
+        unsafe { libc::printf("Verified alloc Successfully!\n\0".as_ptr() as _) };
+    }
+
     unsafe { libc::printf("Verified Successfully!\n\0".as_ptr() as _) };
     0
 }
@@ -171,3 +195,9 @@ fn panic(info: &PanicInfo) -> ! {
     buf.print();
     intrinsics::abort()
 }
+
+#[alloc_error_handler]
+fn alloc_error(_layout: Layout) -> ! {
+    unsafe { libc::printf("alloc shi1\n\0".as_ptr() as _) };
+    intrinsics::abort()
+}

src/context.rs

@@ -5,8 +5,8 @@ use ffi::types::{c_uint, c_void};
 use Error;
 use Secp256k1;
 
-#[cfg(feature = "std")]
-pub use self::std_only::*;
+#[cfg(any(feature = "std", feature = "alloc"))]
+pub use self::alloc_only::*;
 
 #[cfg(feature = "global-context-less-secure")]
 /// Module implementing a singleton pattern for a global `Secp256k1` context
@@ -93,14 +93,18 @@ mod private {
     impl<'buf> Sealed for SignOnlyPreallocated<'buf> {}
 }
 
-#[cfg(feature = "std")]
-mod std_only {
+#[cfg(any(feature = "std", feature = "alloc"))]
+mod alloc_only {
+    #[cfg(feature = "std")]
+    use std::alloc;
+    #[cfg(not(feature = "std"))]
+    use alloc::alloc;
+
     impl private::Sealed for SignOnly {}
     impl private::Sealed for All {}
     impl private::Sealed for VerifyOnly {}
 
     use super::*;
-    use std::alloc;
     const ALIGN_TO: usize = mem::align_of::<AlignedType>();
 
     /// Represents the set of capabilities needed for signing.

src/lib.rs

@@ -135,6 +135,7 @@ pub use secp256k1_sys as ffi;
 #[cfg(any(test, feature = "rand"))] use rand::Rng;
 #[cfg(any(test, feature = "std"))] extern crate core;
 #[cfg(all(test, target_arch = "wasm32"))] extern crate wasm_bindgen_test;
+#[cfg(feature = "alloc")] extern crate alloc;
 
 use core::{fmt, ptr, str};