Do not use xwin to compile on Windows when MSVC compiler can build …

…for the target (#2353)

Cargo.toml

@@ -98,7 +98,7 @@ clap_complete_command = { version = "0.6.1", optional = true }
 
 # cross compile
 cargo-zigbuild = { version = "0.19.5", default-features = false, optional = true }
-cargo-xwin = { version = "0.17.4", default-features = false, optional = true }
+cargo-xwin = { version = "0.17.5", default-features = false, optional = true }
 
 # log
 tracing = "0.1.36"

guide/src/environment-variables.md

@@ -34,5 +34,6 @@ See [environment variables Cargo reads](https://doc.rust-lang.org/cargo/referenc
 * `SOURCE_DATE_EPOCH`: The time to use for the timestamp in the wheel metadata
 * `MATURIN_EMSCRIPTEN_VERSION`: The version of emscripten to use for emscripten builds
 * `MATURIN_NO_MISSING_BUILD_BACKEND_WARNING`: Suppress missing build backend warning
+* `MATURIN_USE_XWIN`: Set to `1` to force to use `xwin` for cross compiling even on Windows that supports native compilation
 * `TARGET_SYSROOT`: The sysroot to use for auditwheel wheel when cross compiling
 * `ARCHFLAGS`: Flags to control the architecture of the build on macOS, for example you can use `ARCHFLAGS="-arch x86_64 -arch arm64"` to build universal2 wheels

src/compile.rs

@@ -287,9 +287,12 @@ fn cargo_build_command(
             .extend(["-C".to_string(), "strip=symbols".to_string()]);
     }
 
-    let mut build_command = if target.is_msvc() && target.cross_compiling() {
+    let mut build_command = if target.is_msvc()
+        && (target.cross_compiling() || env::var("MATURIN_USE_XWIN").ok().as_deref() == Some("1"))
+    {
         #[cfg(feature = "xwin")]
         {
+            println!("🛠️ Using xwin for cross-compiling to {target_triple}");
             let xwin_options = {
                 use clap::Parser;
 
@@ -320,6 +323,7 @@ fn cargo_build_command(
                     build.target = vec![target_triple.to_string()];
                 }
             } else {
+                println!("🛠️ Using zig for cross-compiling to {target_triple}");
                 build.enable_zig_ar = true;
                 let zig_triple = if target.is_linux() && !target.is_musl_libc() {
                     match context.platform_tag.iter().find(|tag| tag.is_manylinux()) {

src/cross_compile.rs

@@ -27,6 +27,21 @@ pub fn is_cross_compiling(target: &Target) -> Result<bool> {
         // Not cross-compiling to compile for 32-bit Python from windows 64-bit
         return Ok(false);
     }
+    if (target_triple == "aarch64-pc-windows-msvc" && host == "x86_64-pc-windows-msvc")
+        || (target_triple == "x86_64-pc-windows-msvc" && host == "aarch64-pc-windows-msvc")
+    {
+        // Not cross-compiling if the Windows MSVC compiler can compile to the target
+        let native_compile = cc::Build::new()
+            .opt_level(0)
+            .host(host)
+            .target(target_triple)
+            .cargo_metadata(false)
+            .cargo_warnings(false)
+            .cargo_output(false)
+            .try_get_compiler()
+            .is_ok();
+        return Ok(!native_compile);
+    }
     if target_triple.ends_with("windows-gnu") && host.ends_with("windows-msvc") {
         // Not cross-compiling to compile for Windows GNU from Windows MSVC host
         return Ok(false);