Add example for cross compilation env

README.md

@@ -182,6 +182,7 @@ Some examples (assume `nixpkgs` had the overlay applied):
     };
   }
   ```
+- See more examples in directory `examples`.
 
 For more details, see also the source code of `./rust-overlay.nix`.
 

examples/cross-aarch64/.cargo/config

@@ -0,0 +1,3 @@
+[target.aarch64-unknown-linux-gnu]
+linker = "aarch64-unknown-linux-gnu-gcc"
+runner = "qemu-aarch64"

examples/cross-aarch64/Cargo.lock

@@ -0,0 +1,98 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "autocfg"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
+
+[[package]]
+name = "bitflags"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
+
+[[package]]
+name = "cc"
+version = "1.0.66"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c0496836a84f8d0495758516b8621a622beb77c0fed418570e50764093ced48"
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "cross-aarch64"
+version = "0.1.0"
+dependencies = [
+ "openssl",
+]
+
+[[package]]
+name = "foreign-types"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f6f339eb8adc052cd2ca78910fda869aefa38d22d5cb648e6485e4d3fc06f3b1"
+dependencies = [
+ "foreign-types-shared",
+]
+
+[[package]]
+name = "foreign-types-shared"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "00b0228411908ca8685dba7fc2cdd70ec9990a6e753e89b6ac91a84c40fbaf4b"
+
+[[package]]
+name = "lazy_static"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+
+[[package]]
+name = "libc"
+version = "0.2.85"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7ccac4b00700875e6a07c6cde370d44d32fa01c5a65cdd2fca6858c479d28bb3"
+
+[[package]]
+name = "openssl"
+version = "0.10.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "038d43985d1ddca7a9900630d8cd031b56e4794eecc2e9ea39dd17aa04399a70"
+dependencies = [
+ "bitflags",
+ "cfg-if",
+ "foreign-types",
+ "lazy_static",
+ "libc",
+ "openssl-sys",
+]
+
+[[package]]
+name = "openssl-sys"
+version = "0.9.60"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "921fc71883267538946025deffb622905ecad223c28efbfdef9bb59a0175f3e6"
+dependencies = [
+ "autocfg",
+ "cc",
+ "libc",
+ "pkg-config",
+ "vcpkg",
+]
+
+[[package]]
+name = "pkg-config"
+version = "0.3.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3831453b3449ceb48b6d9c7ad7c96d5ea673e9b470a1dc578c2ce6521230884c"
+
+[[package]]
+name = "vcpkg"
+version = "0.2.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b00bca6106a5e23f3eee943593759b7fcddb00554332e856d990c893966879fb"

examples/cross-aarch64/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "cross-aarch64"
+version = "0.1.0"
+edition = "2018"
+
+[dependencies]
+openssl = "0.10.32"

examples/cross-aarch64/Makefile

@@ -0,0 +1,9 @@
+.PHONY: all test
+
+test: all
+	nix-shell ./shell.nix --command \
+		"cargo test --target aarch64-unknown-linux-gnu"
+
+all: Cargo.toml Cargo.lock src/main.rs
+	nix-shell ./shell.nix --command \
+		"cargo test --target aarch64-unknown-linux-gnu --no-run"

examples/cross-aarch64/shell.nix

@@ -0,0 +1,18 @@
+with import <nixpkgs> {
+  crossSystem = "aarch64-linux";
+  overlays = [ (import ../..) ];
+};
+mkShell {
+  nativeBuildInputs = [
+    # Manual `buildPackages` is required here. See: https://github.com/NixOS/nixpkgs/issues/49526
+    # build = host = x86_64, target = aarch64
+    buildPackages.rust-bin.stable.latest.rust
+    buildPackages.pkg-config
+    # build = host = target = x86_64, just to avoid re-build.
+    pkgsBuildBuild.qemu
+  ];
+  buildInputs = [
+    # build = x86_64, host = target = aarch64
+    openssl
+  ];
+}

examples/cross-aarch64/src/main.rs

@@ -0,0 +1,7 @@
+#[test]
+fn test_openssl_version() {
+    openssl::init();
+    assert!(openssl::version::version().starts_with("OpenSSL "));
+}
+
+fn main() {}