rustc: Add knowledge of Windows subsystems.

src/librustc_trans/back/link.rs

@@ -636,7 +636,7 @@ fn link_natively(sess: &Session,
     {
         let mut linker = trans.linker_info.to_linker(&mut cmd, &sess);
         link_args(&mut *linker, sess, crate_type, tmpdir,
-                  objects, out_filename, outputs);
+                  objects, out_filename, outputs, trans);
     }
     cmd.args(&sess.target.target.options.late_link_args);
     for obj in &sess.target.target.options.post_link_objects {
@@ -711,7 +711,8 @@ fn link_args(cmd: &mut Linker,
              tmpdir: &Path,
              objects: &[PathBuf],
              out_filename: &Path,
-             outputs: &OutputFilenames) {
+             outputs: &OutputFilenames,
+             trans: &CrateTranslation) {
 
     // The default library location, we need this to find the runtime.
     // The location of crates will be determined as needed.
@@ -726,6 +727,13 @@ fn link_args(cmd: &mut Linker,
     }
     cmd.output_filename(out_filename);
 
+    if crate_type == config::CrateTypeExecutable &&
+       sess.target.target.options.is_like_windows {
+        if let Some(ref s) = trans.windows_subsystem {
+            cmd.subsystem(s);
+        }
+    }
+
     // If we're building a dynamic library then some platforms need to make sure
     // that all symbols are exported correctly from the dynamic library.
     if crate_type != config::CrateTypeExecutable {

src/librustc_trans/back/linker.rs

@@ -92,6 +92,7 @@ pub trait Linker {
     fn whole_archives(&mut self);
     fn no_whole_archives(&mut self);
     fn export_symbols(&mut self, tmpdir: &Path, crate_type: CrateType);
+    fn subsystem(&mut self, subsystem: &str);
 }
 
 pub struct GnuLinker<'a> {
@@ -294,6 +295,10 @@ impl<'a> Linker for GnuLinker<'a> {
 
         self.cmd.arg(arg);
     }
+
+    fn subsystem(&mut self, subsystem: &str) {
+        self.cmd.arg(&format!("-Wl,--subsystem,{}", subsystem));
+    }
 }
 
 pub struct MsvcLinker<'a> {
@@ -441,6 +446,30 @@ impl<'a> Linker for MsvcLinker<'a> {
         arg.push(path);
         self.cmd.arg(&arg);
     }
+
+    fn subsystem(&mut self, subsystem: &str) {
+        // Note that previous passes of the compiler validated this subsystem,
+        // so we just blindly pass it to the linker.
+        self.cmd.arg(&format!("/SUBSYSTEM:{}", subsystem));
+
+        // Windows has two subsystems we're interested in right now, the console
+        // and windows subsystems. These both implicitly have different entry
+        // points (starting symbols). The console entry point starts with
+        // `mainCRTStartup` and the windows entry point starts with
+        // `WinMainCRTStartup`. These entry points, defined in system libraries,
+        // will then later probe for either `main` or `WinMain`, respectively to
+        // start the application.
+        //
+        // In Rust we just always generate a `main` function so we want control
+        // to always start there, so we force the entry point on the windows
+        // subsystem to be `mainCRTStartup` to get everything booted up
+        // correctly.
+        //
+        // For more information see RFC #1665
+        if subsystem == "windows" {
+            self.cmd.arg("/ENTRY:mainCRTStartup");
+        }
+    }
 }
 
 fn exported_symbols(scx: &SharedCrateContext,

src/librustc_trans/base.rs

@@ -1611,7 +1611,8 @@ pub fn trans_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             metadata: metadata,
             reachable: vec![],
             no_builtins: no_builtins,
-            linker_info: linker_info
+            linker_info: linker_info,
+            windows_subsystem: None,
         };
     }
 
@@ -1747,14 +1748,26 @@ pub fn trans_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
     let linker_info = LinkerInfo::new(&shared_ccx, &reachable_symbols);
 
+    let subsystem = attr::first_attr_value_str_by_name(&krate.attrs,
+                                                       "windows_subsystem");
+    let windows_subsystem = subsystem.map(|subsystem| {
+        if subsystem != "windows" && subsystem != "console" {
+            tcx.sess.fatal(&format!("invalid windows subsystem `{}`, only \
+                                     `windows` and `console` are allowed",
+                                    subsystem));
+        }
+        subsystem.to_string()
+    });
+
     CrateTranslation {
         modules: modules,
         metadata_module: metadata_module,
         link: link_meta,
         metadata: metadata,
         reachable: reachable_symbols,
         no_builtins: no_builtins,
-        linker_info: linker_info
+        linker_info: linker_info,
+        windows_subsystem: windows_subsystem,
     }
 }
 

src/librustc_trans/lib.rs

@@ -169,6 +169,7 @@ pub struct CrateTranslation {
     pub metadata: Vec<u8>,
     pub reachable: Vec<String>,
     pub no_builtins: bool,
+    pub windows_subsystem: Option<String>,
     pub linker_info: back::linker::LinkerInfo
 }
 

src/libsyntax/feature_gate.rs

@@ -309,6 +309,9 @@ declare_features! (
 
     // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
     (active, field_init_shorthand, "1.14.0", Some(37340)),
+
+    // The #![windows_subsystem] attribute
+    (active, windows_subsystem, "1.14.0", Some(37499)),
 );
 
 declare_features! (
@@ -713,6 +716,12 @@ pub const KNOWN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGat
                                               "defining reflective traits is still evolving",
                                               cfg_fn!(reflect))),
 
+    ("windows_subsystem", Whitelisted, Gated(Stability::Unstable,
+                                             "windows_subsystem",
+                                             "the windows subsystem attribute \
+                                              id currently unstable",
+                                             cfg_fn!(windows_subsystem))),
+
     // Crate level attributes
     ("crate_name", CrateLevel, Ungated),
     ("crate_type", CrateLevel, Ungated),

src/test/compile-fail/windows-subsystem-gated.rs

@@ -0,0 +1,14 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![windows_subsystem = "console"]
+//~^ ERROR: the windows subsystem attribute is currently unstable
+
+fn main() {}

src/test/compile-fail/windows-subsystem-invalid.rs

@@ -0,0 +1,15 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(windows_subsystem)]
+#![windows_subsystem = "wrong"]
+//~^ ERROR: invalid subsystem `wrong`, only `windows` and `console` are allowed
+
+fn main() {}

src/test/run-make/windows-subsystem/Makefile

@@ -0,0 +1,5 @@
+-include ../tools.mk
+
+all:
+	$(RUSTC) windows.rs
+	$(RUSTC) console.rs

src/test/run-make/windows-subsystem/console.rs

@@ -0,0 +1,15 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(windows_subsystem)]
+#![windows_subsystem = "console"]
+
+fn main() {}
+

src/test/run-make/windows-subsystem/windows.rs

@@ -0,0 +1,14 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(windows_subsystem)]
+#![windows_subsystem = "windows"]
+
+fn main() {}