detect-targets: Add fallback to windows

crates/detect-targets/Cargo.toml

@@ -14,5 +14,9 @@ tokio = { version = "1.28.2", features = ["rt", "process", "sync"], default-feat
 cfg-if = "1.0.0"
 guess_host_triple = "0.1.3"
 
+[target.'cfg(target_os = "windows")'.dependencies]
+windows-sys = { version = "0.42.0", features = ["Win32_System_Threading", "Win32_System_SystemInformation", "Win32_Foundation"] }
+windows-dll = { version = "0.4.1", features = ["windows"], default-features = false }
+
 [dev-dependencies]
 tokio = { version = "1.28.2", features = ["macros"], default-features = false }

crates/detect-targets/src/detect/windows.rs

@@ -1,6 +1,111 @@
-pub(super) fn detect_alternative_targets(target: &str) -> Option<String> {
-    let (prefix, abi) = target.rsplit_once('-')?;
+use std::mem;
+use windows_dll::dll;
+use windows_sys::{
+    core::HRESULT,
+    Win32::System::{
+        SystemInformation::{
+            IMAGE_FILE_MACHINE, IMAGE_FILE_MACHINE_AMD64, IMAGE_FILE_MACHINE_ARM,
+            IMAGE_FILE_MACHINE_ARM64, IMAGE_FILE_MACHINE_I386,
+        },
+        Threading::{UserEnabled, Wow64Container, MACHINE_ATTRIBUTES},
+    },
+};
 
-    // detect abi in ["gnu", "gnullvm", ...]
-    (abi != "msvc").then(|| format!("{prefix}-msvc"))
+#[dll("Kernel32")]
+extern "system" {
+    #[allow(non_snake_case)]
+    #[fallible]
+    fn GetMachineTypeAttributes(
+        machine: IMAGE_FILE_MACHINE,
+        machine_attributes: *mut MACHINE_ATTRIBUTES,
+    ) -> HRESULT;
+}
+
+fn is_arch_supported(arch: IMAGE_FILE_MACHINE) -> bool {
+    let mut machine_attributes = mem::MaybeUninit::uninit();
+
+    // SAFETY: GetMachineTypeAttributes takes type IMAGE_FILE_MACHINE
+    // plus it takes a pointer to machine_attributes which is only
+    // written to.
+    match unsafe { GetMachineTypeAttributes(arch, machine_attributes.as_mut_ptr()) } {
+        Ok(0) => {
+            // SAFETY: Symbol GetMachineTypeAttributes exists and calls to it
+            // succceeds.
+            //
+            // Thus, machine_attributes is initialized.
+            let machine_attributes = unsafe { machine_attributes.assume_init() };
+
+            (machine_attributes & (Wow64Container | UserEnabled)) != 0
+        }
+        _ => false,
+    }
+}
+
+pub(super) fn detect_alternative_targets(target: &str) -> impl Iterator<Item = String> {
+    let (prefix, abi) = target
+        .rsplit_once('-')
+        .expect("unwrap: target always has a -");
+
+    let arch = prefix
+        .split_once('-')
+        .expect("unwrap: target always has at least two -")
+        .0;
+
+    let msvc_fallback_target = (abi != "msvc").then(|| format!("{prefix}-msvc"));
+
+    let gnu_fallback_targets = (abi == "msvc")
+        .then(|| [format!("{prefix}-gnu"), format!("{prefix}-gnullvm")])
+        .into_iter()
+        .flatten();
+
+    let x64_fallback_targets = (arch != "x86_64" && is_arch_supported(IMAGE_FILE_MACHINE_AMD64))
+        .then_some([
+            "x86_64-pc-windows-msvc",
+            "x86_64-pc-windows-gnu",
+            "x86_64-pc-windows-gnullvm",
+        ])
+        .into_iter()
+        .flatten()
+        .map(ToString::to_string);
+
+    let x86_fallback_targets = (arch != "x86" && is_arch_supported(IMAGE_FILE_MACHINE_I386))
+        .then_some([
+            "i586-pc-windows-msvc",
+            "i586-pc-windows-gnu",
+            "i586-pc-windows-gnullvm",
+            "i686-pc-windows-msvc",
+            "i686-pc-windows-gnu",
+            "i686-pc-windows-gnullvm",
+        ])
+        .into_iter()
+        .flatten()
+        .map(ToString::to_string);
+
+    let arm32_fallback_targets = (arch != "thumbv7a" && is_arch_supported(IMAGE_FILE_MACHINE_ARM))
+        .then_some([
+            "thumbv7a-pc-windows-msvc",
+            "thumbv7a-pc-windows-gnu",
+            "thumbv7a-pc-windows-gnullvm",
+        ])
+        .into_iter()
+        .flatten()
+        .map(ToString::to_string);
+
+    let arm64_fallback_targets = (arch != "aarch64" && is_arch_supported(IMAGE_FILE_MACHINE_ARM64))
+        .then_some([
+            "aarch64-pc-windows-msvc",
+            "aarch64-pc-windows-gnu",
+            "aarch64-pc-windows-gnullvm",
+        ])
+        .into_iter()
+        .flatten()
+        .map(ToString::to_string);
+
+    msvc_fallback_target
+        .into_iter()
+        .chain(gnu_fallback_targets)
+        .chain(x64_fallback_targets)
+        .chain(x86_fallback_targets)
+        .chain(arm32_fallback_targets)
+        .chain(arm64_fallback_targets)
 }