Try to detect the Universal CRT on MSVC installs

Visual Studio 2015, recently releases, includes the Universal CRT, a different
flavor than was provided before. The binaries and header files for this library
are included in new locations not previously known about by gcc-rs, and this
commit adds support for the necessary probing to find these (for now).

appveyor.yml

@@ -2,14 +2,22 @@ environment:
   matrix:
   - TARGET: x86_64-pc-windows-msvc
     ARCH: amd64
+    VS: C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat
+  - TARGET: x86_64-pc-windows-msvc
+    ARCH: amd64
+    VS: C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat
+  - TARGET: i686-pc-windows-msvc
+    ARCH: x86
+    VS: C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat
   - TARGET: i686-pc-windows-msvc
     ARCH: x86
+    VS: C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat
   - TARGET: i686-pc-windows-gnu
     ARCH: x86
 install:
   - ps: Start-FileDownload "https://static.rust-lang.org/dist/rust-nightly-${env:TARGET}.exe"
   - rust-nightly-%TARGET%.exe /VERYSILENT /NORESTART /DIR="C:\Program Files (x86)\Rust"
-  - call "C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat" %ARCH%
+  - if defined VS call "%VS%" %ARCH%
   - SET PATH=%PATH%;C:\Program Files (x86)\Rust\bin
   - SET PATH=%PATH%;C:\MinGW\bin
   - rustc -V

gcc-test/build.rs

@@ -1,6 +1,14 @@
 extern crate gcc;
 
+use std::env;
+use std::fs;
+use std::path::PathBuf;
+
 fn main() {
+    let out = PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    fs::remove_dir_all(&out).unwrap();
+    fs::create_dir(&out).unwrap();
+
     gcc::Config::new()
                 .file("src/foo.c")
                 .define("FOO", None)
@@ -31,4 +39,34 @@ fn main() {
                     .file("src/windows.c")
                     .compile("libwindows.a");
     }
+
+    // Test that the `windows_registry` module will set PATH by looking for
+    // nmake which runs vanilla cl, and then also test it after we remove all
+    // the relevant env vars from our own process.
+    if target.contains("msvc") {
+        let out = out.join("tmp");
+        fs::create_dir(&out).unwrap();
+        let status = gcc::windows_registry::find(&target, "nmake.exe").unwrap()
+                            .arg("/fsrc/NMakefile")
+                            .env("OUT_DIR", &out)
+                            .status()
+                            .unwrap();
+        assert!(status.success());
+
+        fs::remove_dir_all(&out).unwrap();
+        fs::create_dir(&out).unwrap();
+
+        env::remove_var("PATH");
+        env::remove_var("VCINSTALLDIR");
+        env::remove_var("INCLUDE");
+        env::remove_var("LIB");
+        let status = gcc::windows_registry::find(&target, "nmake.exe").unwrap()
+                            .arg("/fsrc/NMakefile")
+                            .env("OUT_DIR", &out)
+                            .status()
+                            .unwrap();
+        assert!(status.success());
+        println!("cargo:rustc-link-lib=msvc");
+        println!("cargo:rustc-link-search={}", out.display());
+    }
 }

gcc-test/src/NMakefile

@@ -0,0 +1,13 @@
+all: $(OUT_DIR)/msvc.lib $(OUT_DIR)/msvc.exe
+
+$(OUT_DIR)/msvc.lib: $(OUT_DIR)/msvc.o
+	lib -nologo -out:$(OUT_DIR)/msvc.lib $(OUT_DIR)/msvc.o
+
+$(OUT_DIR)/msvc.o: src/msvc.c
+	$(CC) -nologo -c -Fo:$@ src/msvc.c
+
+$(OUT_DIR)/msvc.exe: $(OUT_DIR)/msvc2.o
+	$(CC) -nologo -Fo:$@ $(OUT_DIR)/msvc2.o
+
+$(OUT_DIR)/msvc2.o: src/msvc.c
+	$(CC) -nologo -c -Fo:$@ src/msvc.c -DMAIN

gcc-test/src/lib.rs

@@ -10,4 +10,7 @@ extern {
 
     #[cfg(windows)]
     pub fn windows();
+
+    #[cfg(target_env = "msvc")]
+    pub fn msvc();
 }

gcc-test/src/msvc.c

@@ -0,0 +1,7 @@
+#include <windows.h>
+
+void msvc() {}
+
+#ifdef MAIN
+int main() {}
+#endif

gcc-test/tests/all.rs

@@ -38,3 +38,11 @@ fn windows_here() {
         windows();
     }
 }
+
+#[test]
+#[cfg(target_env = "msvc")]
+fn msvc_here() {
+    unsafe {
+        msvc();
+    }
+}

src/windows_registry.rs

@@ -31,8 +31,9 @@ pub fn find(_target: &str, _tool: &str) -> Option<Command> {
 pub fn find(target: &str, tool: &str) -> Option<Command> {
     use std::env;
     use std::ffi::OsString;
+    use std::io;
     use std::fs;
-    use std::path::PathBuf;
+    use std::path::{Path, PathBuf};
     use registry::{RegistryKey, LOCAL_MACHINE};
 
     if !target.contains("msvc") { return None }
@@ -121,6 +122,9 @@ pub fn find(target: &str, tool: &str) -> Option<Command> {
         let mut includes = Vec::new();
         if let Some(ref vs_install_dir) = vs_install_dir {
             includes.push(vs_install_dir.join("VC/include"));
+            if let Some((ucrt_root, vers)) = ucrt_install_dir(vs_install_dir) {
+                includes.push(ucrt_root.join("Include").join(vers).join("ucrt"));
+            }
         }
         if let Some((path, major)) = get_windows_sdk_path() {
             if major >= 8 {
@@ -141,6 +145,12 @@ pub fn find(target: &str, tool: &str) -> Option<Command> {
         let mut libs = Vec::new();
         if let Some(ref vs_install_dir) = vs_install_dir {
             libs.push(vs_install_dir.join("VC/lib").join(extra));
+            if let Some((ucrt_root, vers)) = ucrt_install_dir(vs_install_dir) {
+                if let Some(arch) = windows_sdk_v8_subdir(target) {
+                    libs.push(ucrt_root.join("Lib").join(vers)
+                                       .join("ucrt").join(arch));
+                }
+            }
         }
         if let Some(path) = get_windows_sdk_lib_path(target) {
             libs.push(path);
@@ -294,4 +304,33 @@ pub fn find(target: &str, tool: &str) -> Option<Command> {
             None
         }
     }
+
+    fn ucrt_install_dir(vs_install_dir: &Path) -> Option<(PathBuf, String)> {
+        let is_vs_14 = vs_install_dir.iter().filter_map(|p| p.to_str()).any(|s| {
+            s == "Microsoft Visual Studio 14.0"
+        });
+        if !is_vs_14 {
+            return None
+        }
+        let sdk_dir = match get_windows_sdk_path() {
+            Some((mut root, _)) => { root.pop(); root.push("10"); root }
+            None => return None,
+        };
+        (move || -> io::Result<_> {
+            let mut max = None;
+            let mut max_s = None;
+            for entry in try!(fs::read_dir(&sdk_dir.join("Lib"))) {
+                let entry = try!(entry);
+                if let Ok(s) = entry.file_name().into_string() {
+                    if let Ok(u) = s.replace(".", "").parse::<usize>() {
+                        if Some(u) > max {
+                            max = Some(u);
+                            max_s = Some(s);
+                        }
+                    }
+                }
+            }
+            Ok(max_s.map(|m| (sdk_dir, m)))
+        })().ok().and_then(|x| x)
+    }
 }