Define a MSRV, use that toolchain by default.

This PR defines a Minimum Supported Rust Version. It specifies that toolchain in `rust-toolchain`, so `rustup` will use that toolchain by default. The `test-stable` make action is removed, as it is now redundant.

We still need the nightly toolchain for Miri. Instead of specifying the nightly toolchain version via the command line, I created a new `nightly/rust-toolchain.toml` file that specifies the toolchain. The benefit is this makes `rustup` automatically install the nightly toolchain *including Miri*. This should stop the toil we currently have where every time the Rust toolchain is updated, everyone using `make test` has to manually install new toolchains and Miri. The downside is it's kinda ugly.

I set the MSRV to 1.70 so this doesn't conflict with #498.

I will send another PR that adds `rust-version.workspace = true` to all the `Cargo.toml` files in this repository; I didn't want to clutter this PR with those changes.

.gitignore

@@ -1,2 +1,3 @@
 /Cargo.lock
+/nightly/target
 /target

Cargo.toml

@@ -7,8 +7,14 @@ edition = "2021"
 license = "Apache-2.0 OR MIT"
 name = "libtock"
 repository = "https://www.github.com/tock/libtock-rs"
+rust-version.workspace = true
 version = "0.1.0"
 
+[workspace.package]
+# This must be kept in sync with rust-toolchain.toml; please see that file for
+# more information.
+rust-version = "1.70"
+
 [dependencies]
 libtock_adc = { path = "apis/adc"}
 libtock_air_quality = { path = "apis/air_quality" }

Makefile

@@ -45,10 +45,7 @@ endif
 
 .PHONY: setup
 setup: setup-qemu
-	rustup install stable
-	cargo +stable install elf2tab
-	cargo miri setup
-	rustup target add --toolchain stable thumbv7em-none-eabi
+	cargo install elf2tab
 
 # Sets up QEMU in the tock/ directory. We use Tock's QEMU which may contain
 # patches to better support boards that Tock supports.
@@ -108,28 +105,19 @@ EXCLUDE_STD := --exclude libtock_unittest --exclude print_sizes \
                --exclude runner --exclude syscalls_tests \
                --exclude libtock_build_scripts
 
-# Currently, all of our crates should build with a stable toolchain. This
-# verifies our crates don't depend on unstable features by using cargo check. We
-# specify a different target directory so this doesn't flush the cargo cache of
-# the primary toolchain.
-.PHONY: test-stable
-test-stable:
-	cargo +stable check --target-dir=target/stable --workspace \
-		$(EXCLUDE_RUNTIME)
-	LIBTOCK_PLATFORM=nrf52 cargo +stable check $(EXCLUDE_STD) \
-		--target=thumbv7em-none-eabi --target-dir=target/stable --workspace
-
 .PHONY: test
-test: examples test-stable
+test: examples
 	cargo test $(EXCLUDE_RUNTIME) --workspace
 	LIBTOCK_PLATFORM=nrf52 cargo fmt --all -- --check
 	cargo clippy --all-targets $(EXCLUDE_RUNTIME) --workspace
 	LIBTOCK_PLATFORM=nrf52 cargo clippy $(EXCLUDE_STD) \
 		--target=thumbv7em-none-eabi --workspace
 	LIBTOCK_PLATFORM=hifive1 cargo clippy $(EXCLUDE_STD) \
 		--target=riscv32imac-unknown-none-elf --workspace
-	MIRIFLAGS="-Zmiri-strict-provenance -Zmiri-symbolic-alignment-check" \
-		cargo miri test $(EXCLUDE_MIRI) --workspace
+	cd nightly && \
+		MIRIFLAGS="-Zmiri-strict-provenance -Zmiri-symbolic-alignment-check" \
+		cargo miri test $(EXCLUDE_MIRI) --manifest-path=../Cargo.toml \
+		--target-dir=target --workspace
 	echo '[ SUCCESS ] libtock-rs tests pass'
 
 # Helper functions to define make targets to build for specific (flash, ram,

nightly/rust-toolchain.toml

@@ -0,0 +1,4 @@
+# This is the nightly Rust toolchain used by `make test`.
+[toolchain]
+channel = "nightly-2023-08-22"
+components = ["miri"]

rust-toolchain.toml

@@ -0,0 +1,13 @@
+[toolchain]
+# This is libtock-rs' Minimum Supported Rust Version (MSRV).
+#
+# Update policy: Update this if doing so allows you to use a Rust feature that
+# you'd like to use. When you do so, update this to the first Rust version that
+# includes that feature. Whenever this value is updated, the rust-version field
+# in Cargo.toml must be updated as well.
+channel = "1.70"
+components = ["clippy", "rustfmt"]
+targets = ["thumbv6m-none-eabi",
+           "thumbv7em-none-eabi",
+           "riscv32imac-unknown-none-elf",
+           "riscv32imc-unknown-none-elf"]