Add no-std tests

Author: nyonson

.github/actions/prepare/action.yml

@@ -12,23 +12,26 @@ inputs:
 runs:
   using: "composite"
   steps:
+    - name: "Install ARM cross-compiler for no-std"
+      shell: bash
+      run: |
+        sudo apt-get update && sudo apt-get install -y gcc-arm-none-eabi
+        echo "CC_thumbv7m_none_eabi=arm-none-eabi-gcc" >> $GITHUB_ENV
+
     - name: "Determine toolchain"
       id: toolchain
       shell: bash
       run: |
-        if [ "${{ inputs.toolchain }}" = "nightly" ]; then
-          TOOLCHAIN="$(cat nightly-version)"
-        else
-          TOOLCHAIN="${{ inputs.toolchain }}"
-        fi
+        [[ "${{ inputs.toolchain }}" == "nightly" ]] && TOOLCHAIN=$(cat nightly-version) || TOOLCHAIN="${{ inputs.toolchain }}"
         echo "version=$TOOLCHAIN" >> $GITHUB_OUTPUT
 
     - name: "Setup requested toolchain"
       uses: actions-rust-lang/setup-rust-toolchain@v1
       with:
-        toolchain: ${{ steps.toolchain.outputs.version }}
+        toolchain: stable,${{ steps.toolchain.outputs.version }}
         components: ${{ inputs.components }}
+        target: thumbv7m-none-eabi
 
     - name: "Install RBMT"
       shell: bash
-      run: cargo install --git https://github.com/rust-bitcoin/rust-bitcoin-maintainer-tools.git --rev "$(cat rbmt-version)" cargo-rbmt --locked
+      run: cargo +stable install --git https://github.com/rust-bitcoin/rust-bitcoin-maintainer-tools.git --rev "$(cat rbmt-version)" cargo-rbmt --locked

rbmt-version

@@ -1 +1 @@
-bcff6290c9e3f5b4d7e832acb5a8c6bf890fd1ce
+554c939298cac198aab6d9704890a832a2ed839b

src/lib.rs

@@ -8,12 +8,15 @@
 //! [BIP-174]: <https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki>
 //! [BIP-370]: <https://github.com/bitcoin/bips/blob/master/bip-0370.mediawiki>
 
-#![cfg_attr(all(not(feature = "std"), not(test)), no_std)]
+#![no_std]
 // Experimental features we need.
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 // Coding conventions
 #![warn(missing_docs)]
 
+#[cfg(any(feature = "std", test))]
+extern crate std;
+
 #[macro_use]
 extern crate alloc;
 
@@ -76,5 +79,8 @@ mod prelude {
     #[cfg(any(feature = "std", test))]
     pub use std::collections::{BTreeMap, BTreeSet, btree_map, BinaryHeap};
 
+    #[cfg(any(feature = "std", test))]
+    pub use std::{println, print, format, write, writeln};
+
     pub use bitcoin::hex::DisplayHex;
 }

src/v0/miniscript/util.rs

@@ -1,7 +1,8 @@
 // SPDX-License-Identifier: CC0-1.0
 
 //! Private utils copied from `rust-miniscript`'s `util` module.
-    
+
+use crate::prelude::*;
 use bitcoin::consensus::encode::VarInt;
 use miniscript::miniscript::satisfy::Placeholder;
 use miniscript::MiniscriptKey;