ci: Check various FreeBSD versions

Since we suport multiple versions and this is tier 2, we should make
sure that we can build with a couple versions. This does not run tests.

Additionally, introduce an environment variable for an easy way to
override the version for testing.

This includes an unrelated cleanup adjustment in `verify-build.sh`

build.rs

@@ -48,13 +48,20 @@ fn main() {
     //
     // On CI, we detect the actual FreeBSD version and match its ABI exactly,
     // running tests to ensure that the ABI is correct.
-    let which_freebsd = if libc_ci {
+    println!("cargo:rerun-if-env-changed=RUST_LIBC_UNSTABLE_FREEBSD_VERSION");
+    // Allow overriding the default version for testing
+    let which_freebsd = if let Ok(version) = env::var("RUST_LIBC_UNSTABLE_FREEBSD_VERSION") {
+        let vers = version.parse().unwrap();
+        println!("cargo:warning=setting FreeBSD version to {vers}");
+        vers
+    } else if libc_ci {
         which_freebsd().unwrap_or(12)
     } else if rustc_dep_of_std {
         12
     } else {
         12
     };
+
     match which_freebsd {
         x if x < 10 => panic!("FreeBSD older than 10 is not supported"),
         10 => set_cfg("freebsd10"),

ci/verify-build.sh

@@ -28,6 +28,7 @@ if [ "$TOOLCHAIN" = "nightly" ] ; then
     rustup component add rust-src
 fi
 
+# Run the tests for a specific target
 test_target() {
     target="${1}"
     no_dist="${2:-0}"
@@ -67,8 +68,31 @@ test_target() {
     # Test again without default features, i.e. without "std"
     $cmd --no-default-features
     $cmd --no-default-features --features extra_traits
+
+    # For tier 2 freebsd targets, check with the different versions we support
+    # if on nightly or stable
+    case "$rust-$target" in
+        stable-x86_64-*freebsd*) do_freebsd_checks=1 ;;
+        nightly-i686*freebsd*) do_freebsd_checks=1 ;;
+    esac
+
+    if [ -n "${do_freebsd_checks:-}" ]; then
+        for version in $freebsd_versions; do
+            export RUST_LIBC_UNSTABLE_FREEBSD_VERSION="$version"
+            $cmd
+            $cmd --no-default-features
+        done
+    fi
 }
 
+freebsd_versions="\
+11 \
+12 \
+13 \
+14 \
+15 \
+"
+
 rust_linux_targets="\
 aarch64-linux-android \
 aarch64-unknown-linux-gnu \
@@ -240,21 +264,19 @@ for target in $targets; do
     if echo "$target" | grep -q "$filter"; then
         if [ "$os" = "windows" ]; then
             TARGET="$target" ./ci/install-rust.sh
-            test_target "$target"
-        else
-            # `wasm32-wasip1` was renamed from `wasm32-wasi`
-            if [ "$target" = "wasm32-wasip1" ] && [ "$supports_wasi_pn" = "0" ]; then
-                target="wasm32-wasi"
-            fi
+        fi
 
-            # `wasm32-wasip2` only exists in recent versions of Rust
-            if [ "$target" = "wasm32-wasip2" ] && [ "$supports_wasi_pn" = "0" ]; then
-                continue
-            fi
-
-            test_target "$target"
+        # `wasm32-wasip1` was renamed from `wasm32-wasi`
+        if [ "$target" = "wasm32-wasip1" ] && [ "$supports_wasi_pn" = "0" ]; then
+            target="wasm32-wasi"
         fi
 
+        # `wasm32-wasip2` only exists in recent versions of Rust
+        if [ "$target" = "wasm32-wasip2" ] && [ "$supports_wasi_pn" = "0" ]; then
+            continue
+        fi
+
+        test_target "$target"
         test_run=1
     fi
 done
@@ -263,11 +285,9 @@ for target in ${no_dist_targets:-}; do
     if echo "$target" | grep -q "$filter"; then
         if [ "$os" = "windows" ]; then
             TARGET="$target" ./ci/install-rust.sh
-            test_target "$target" 1
-        else
-            test_target "$target" 1
         fi
 
+        test_target "$target" 1
         test_run=1
     fi
 done

libc-test/build.rs

@@ -4663,9 +4663,16 @@ fn test_linux_like_apis(target: &str) {
 }
 
 fn which_freebsd() -> Option<i32> {
+    if let Ok(version) = env::var("RUST_LIBC_UNSTABLE_FREEBSD_VERSION") {
+        let vers = version.parse().unwrap();
+        println!("cargo:warning=setting FreeBSD version to {vers}");
+        return Some(vers);
+    }
+
     let output = std::process::Command::new("freebsd-version")
         .output()
         .ok()?;
+
     if !output.status.success() {
         return None;
     }