Support finding windows tools on non-Windows host

src/lib.rs

@@ -87,7 +87,7 @@ mod vs_instances;
 #[cfg(windows)]
 mod windows_sys;
 
-pub mod windows_registry;
+pub mod windows_helper;
 
 /// A builder for compilation of a native library.
 ///
@@ -2187,7 +2187,7 @@ impl Build {
         } else {
             "ml.exe"
         };
-        let mut cmd = windows_registry::find(&target, tool).unwrap_or_else(|| self.cmd(tool));
+        let mut cmd = windows_helper::find(&target, tool).unwrap_or_else(|| self.cmd(tool));
         cmd.arg("-nologo"); // undocumented, yet working with armasm[64]
         for directory in self.include_directories.iter() {
             cmd.arg("-I").arg(&**directory);
@@ -2540,7 +2540,7 @@ impl Build {
             traditional
         };
 
-        let cl_exe = windows_registry::find_tool(&target, "cl.exe");
+        let cl_exe = windows_helper::find_tool(&target, "cl.exe");
 
         let tool_opt: Option<Tool> = self
             .env_tool(env)
@@ -3008,7 +3008,7 @@ impl Build {
 
                     if lib.is_empty() {
                         name = String::from("lib.exe");
-                        match windows_registry::find(&target, "lib.exe") {
+                        match windows_helper::find(&target, "lib.exe") {
                             Some(t) => t,
                             None => self.cmd("lib.exe"),
                         }
@@ -3543,7 +3543,6 @@ impl Tool {
         Self::with_features(path, clang_driver, false)
     }
 
-    #[cfg(windows)]
     /// Explicitly set the `ToolFamily`, skipping name-based detection.
     fn with_family(path: PathBuf, family: ToolFamily) -> Self {
         Self {

src/windows_registry.rs → src/windows_helper.rs

@@ -8,20 +8,21 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//! A helper module to probe the Windows Registry when looking for
-//! windows-specific tools.
+//! A helper module to looking for windows-specific tools:
+//! 1. On Windows host, probe the Windows Registry if needed;
+//! 2. On non-Windows host, check specified environment variables.
 
 use std::process::Command;
 
 use crate::Tool;
-#[cfg(windows)]
 use crate::ToolFamily;
 
-#[cfg(windows)]
 const MSVC_FAMILY: ToolFamily = ToolFamily::Msvc { clang_cl: false };
 
-/// Attempts to find a tool within an MSVC installation using the Windows
-/// registry as a point to search from.
+/// Attempts to find a tool within an MSVC installation:
+/// 1. On Windows host, using the Windows registry as a point to search from;
+/// 2. On non-Windows host, using related environment variables to search from.
+///
 ///
 /// The `target` argument is the target that the tool should work for (e.g.
 /// compile or link for) and the `tool` argument is the tool to find (e.g.
@@ -39,13 +40,6 @@ pub fn find(target: &str, tool: &str) -> Option<Command> {
 /// Similar to the `find` function above, this function will attempt the same
 /// operation (finding a MSVC tool in a local install) but instead returns a
 /// `Tool` which may be introspected.
-#[cfg(not(windows))]
-pub fn find_tool(_target: &str, _tool: &str) -> Option<Tool> {
-    None
-}
-
-/// Documented above.
-#[cfg(windows)]
 pub fn find_tool(target: &str, tool: &str) -> Option<Tool> {
     // This logic is all tailored for MSVC, if we're not that then bail out
     // early.
@@ -54,12 +48,13 @@ pub fn find_tool(target: &str, tool: &str) -> Option<Tool> {
     }
 
     // Looks like msbuild isn't located in the same location as other tools like
-    // cl.exe and lib.exe. To handle this we probe for it manually with
-    // dedicated registry keys.
+    // cl.exe and lib.exe.
     if tool.contains("msbuild") {
         return impl_::find_msbuild(target);
     }
 
+    // Looks like devenv isn't located in the same location as other tools like
+    // cl.exe and lib.exe.
     if tool.contains("devenv") {
         return impl_::find_devenv(target);
     }
@@ -152,6 +147,7 @@ pub fn find_vs_version() -> Result<VsVers, String> {
     }
 }
 
+/// Windows Implementation.
 #[cfg(windows)]
 mod impl_ {
     use crate::com;
@@ -882,6 +878,7 @@ mod impl_ {
         }
     }
 
+    // To find devenv we probe for it manually with dedicated registry keys.
     pub fn find_devenv(target: &str) -> Option<Tool> {
         find_devenv_vs15(&target)
     }
@@ -890,6 +887,7 @@ mod impl_ {
         find_tool_in_vs15_path(r"Common7\IDE\devenv.exe", target)
     }
 
+    // To find msbuild we probe for it manually with dedicated registry keys.
     // see http://stackoverflow.com/questions/328017/path-to-msbuild
     pub fn find_msbuild(target: &str) -> Option<Tool> {
         // VS 15 (2017) changed how to locate msbuild
@@ -927,3 +925,64 @@ mod impl_ {
             })
     }
 }
+
+/// Non-Windows Implementation.
+#[cfg(not(windows))]
+mod impl_ {
+    use std::{env, ffi::OsString};
+
+    use super::MSVC_FAMILY;
+    use crate::Tool;
+
+    /// Finding msbuild.exe tool under unix system is not currently supported.
+    /// Maybe can check it using an environment variable looks like `MSBUILD_BIN`.
+    pub fn find_msbuild(_target: &str) -> Option<Tool> {
+        None
+    }
+
+    // Finding devenv.exe tool under unix system is not currently supported.
+    // Maybe can check it using an environment variable looks like `DEVENV_BIN`.
+    pub fn find_devenv(_target: &str) -> Option<Tool> {
+        None
+    }
+
+    /// Attempt to find the tool using environment variables set by vcvars.
+    pub fn find_msvc_environment(tool: &str, _target: &str) -> Option<Tool> {
+        // Early return if the environment doesn't contain a VC install.
+        let _vc_install_dir = env::var_os("VCINSTALLDIR")?;
+        let vs_install_dir = env::var_os("VSINSTALLDIR")?;
+
+        let search = |path: OsString| {
+            env::split_paths(&path)
+                .map(|p| p.join(tool))
+                .find(|p| p.exists())
+        };
+
+        search(vs_install_dir)
+            .or_else(|| {
+                // Fallback to simply using the current environment.
+                env::var_os("PATH").and_then(search)
+            })
+            .map(|path| Tool::with_family(path.into(), MSVC_FAMILY))
+    }
+
+    pub fn find_msvc_15plus(_tool: &str, _target: &str) -> Option<Tool> {
+        None
+    }
+
+    // For MSVC 14 we need to find the Universal CRT as well as either
+    // the Windows 10 SDK or Windows 8.1 SDK.
+    pub fn find_msvc_14(_tool: &str, _target: &str) -> Option<Tool> {
+        None
+    }
+
+    // For MSVC 12 we need to find the Windows 8.1 SDK.
+    pub fn find_msvc_12(_tool: &str, _target: &str) -> Option<Tool> {
+        None
+    }
+
+    // For MSVC 11 we need to find the Windows 8 SDK.
+    pub fn find_msvc_11(_tool: &str, _target: &str) -> Option<Tool> {
+        None
+    }
+}