Add support for building on Windows mingw platforms

Changelog.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Fix false positive missing pyinit warning on arm64 macOS in [#673](https://github.com/PyO3/maturin/pull/673)
 * Build without rustls on arm64 Windows by nsait-linaro in [#674](https://github.com/PyO3/maturin/pull/674)
 * Publish Windows arm64 wheels to PyPI by nsait-linaro in [#675](https://github.com/PyO3/maturin/pull/675)
+* Add support for building on Windows mingw platforms in [#677](https://github.com/PyO3/maturin/pull/677)
 * Allow building for non-abi3 pypy wheels when the abi3 feature is enabled in [#678](https://github.com/PyO3/maturin/pull/678)
 * Add support for cross compiling to different operating systems in [#680](https://github.com/PyO3/maturin/pull/680)
 

src/build_options.rs

@@ -572,6 +572,7 @@ pub fn find_interpreter(
                         interpreter_kind,
                         abi_tag,
                         libs_dir: PathBuf::from(cross_lib_dir),
+                        platform: None,
                     }];
                 }
             }
@@ -618,6 +619,7 @@ pub fn find_interpreter(
                         interpreter_kind: InterpreterKind::CPython,
                         abi_tag: None,
                         libs_dir: PathBuf::from(manual_base_prefix),
+                        platform: None,
                     }])
                 } else {
                     let interp = interpreter

src/get_interpreter_metadata.py

@@ -25,8 +25,9 @@
     "interpreter": platform.python_implementation().lower(),
     "ext_suffix": ext_suffix,
     "abi_tag": (sysconfig.get_config_var("SOABI") or "-").split("-")[1] or None,
+    "platform": sysconfig.get_platform(),
     # This one isn't technically necessary, but still very useful for sanity checks
-    "platform": platform.system().lower(),
+    "system": platform.system().lower(),
     # We need this one for windows abi3 builds
     "base_prefix": sys.base_prefix,
 }

src/python_interpreter.rs

@@ -252,7 +252,10 @@ struct IntepreterMetadataMessage {
     abiflags: Option<String>,
     interpreter: String,
     ext_suffix: Option<String>,
+    // comes from `sysconfig.get_platform()`
     platform: String,
+    // comes from `platform.system()`
+    system: String,
     abi_tag: Option<String>,
     base_prefix: String,
 }
@@ -287,6 +290,10 @@ pub struct PythonInterpreter {
     pub abi_tag: Option<String>,
     /// We need this value for windows abi3 linking
     pub libs_dir: PathBuf,
+    /// Comes from `sysconfig.get_platform()`
+    ///
+    /// Note that this can be `None` when cross compiling
+    pub platform: Option<String>,
 }
 
 /// Returns the abiflags that are assembled through the message, with some
@@ -301,12 +308,12 @@ fn fun_with_abiflags(
     bridge: &BridgeModel,
 ) -> Result<String> {
     if bridge != &BridgeModel::Cffi
-        && target.get_python_os() != message.platform
+        && target.get_python_os() != message.system
         && !is_cross_compiling(target)?
     {
         bail!(
-            "sys.platform in python, {}, and the rust target, {:?}, don't match ಠ_ಠ",
-            message.platform,
+            "platform.system() in python, {}, and the rust target, {:?}, don't match ಠ_ಠ",
+            message.system,
             target,
         )
     }
@@ -322,11 +329,11 @@ fn fun_with_abiflags(
     if message.interpreter == "pypy" {
         // pypy does not specify abi flags
         Ok("".to_string())
-    } else if message.platform == "windows" {
-        if message.abiflags.is_some() {
-            bail!("A python 3 interpreter on windows does not define abiflags in its sysconfig ಠ_ಠ")
-        } else {
+    } else if message.system == "windows" {
+        if matches!(message.abiflags.as_deref(), Some("") | None) {
             Ok("".to_string())
+        } else {
+            bail!("A python 3 interpreter on windows does not define abiflags in its sysconfig ಠ_ಠ")
         }
     } else if let Some(ref abiflags) = message.abiflags {
         if message.minor >= 8 {
@@ -350,9 +357,17 @@ impl PythonInterpreter {
     ///
     /// If abi3 is true, cpython wheels use the generic abi3 with the given version as minimum
     pub fn get_tag(&self, platform_tag: PlatformTag, universal2: bool) -> String {
+        let platform = if self.target.is_windows() {
+            // Restrict `sysconfig.get_platform()` usage to Windows only for now
+            // so we don't need to deal with macOS deployment target
+            self.platform
+                .clone()
+                .unwrap_or_else(|| self.target.get_platform_tag(platform_tag, universal2))
+        } else {
+            self.target.get_platform_tag(platform_tag, universal2)
+        };
         match self.interpreter_kind {
             InterpreterKind::CPython => {
-                let platform = self.target.get_platform_tag(platform_tag, universal2);
                 if self.target.is_unix() {
                     format!(
                         "cp{major}{minor}-cp{major}{minor}{abiflags}-{platform}",
@@ -372,7 +387,6 @@ impl PythonInterpreter {
                 }
             }
             InterpreterKind::PyPy => {
-                let platform = self.target.get_platform_tag(platform_tag, universal2);
                 // pypy uses its version as part of the ABI, e.g.
                 // pypy 3.7 7.3 => numpy-1.20.1-pp37-pypy37_pp73-manylinux2010_x86_64.whl
                 format!(
@@ -471,8 +485,8 @@ impl PythonInterpreter {
         match message.interpreter.as_str() {
             "cpython" => interpreter = InterpreterKind::CPython,
             "pypy" => interpreter = InterpreterKind::PyPy,
-            _ => {
-                bail!("Invalid interpreter");
+            other => {
+                bail!("Unsupported interpreter {}", other);
             }
         };
 
@@ -481,6 +495,23 @@ impl PythonInterpreter {
             executable.as_ref().display()
         ))?;
 
+        let platform = if message.platform.starts_with("macosx") {
+            // macOS contains system version in platform name so need special handle
+            let mut parts = message.platform.splitn(3, '-');
+            let err_ctx = "Invalid platform string from `sysconfig.get_platform()`";
+            let prefix = parts.next().context(err_ctx)?;
+            let base_version = parts.next().context(err_ctx)?;
+            let suffix = parts.next().context(err_ctx)?;
+            let (major_ver, minor_ver) = base_version.split_once('.').context(err_ctx)?;
+            let major_ver: u64 = major_ver.parse()?;
+            let minor_ver = if major_ver > 10 { "0" } else { minor_ver };
+            // FIXME: We should also take MACOSX_DEPLOYMENT_TARGET env var into account
+            format!("{}_{}_{}_{}", prefix, major_ver, minor_ver, suffix)
+        } else {
+            message.platform
+        };
+        let platform = platform.to_lowercase().replace('-', "_").replace('.', "_");
+
         Ok(Some(PythonInterpreter {
             major: message.major,
             minor: message.minor,
@@ -493,6 +524,7 @@ impl PythonInterpreter {
             interpreter_kind: interpreter,
             abi_tag: message.abi_tag,
             libs_dir: PathBuf::from(message.base_prefix).join("libs"),
+            platform: Some(platform),
         }))
     }