Auto merge of #60260 - videolabs:rust_uwp2, r=alexcrichton

Add support for UWP targets

Hi,

This pull request aims at adding support for UWP (Universal Windows Apps) platform.
A few notes:
- This requires a very recent mingw-w64 version (containing this commit and the previous related ones: mirror/mingw-w64@e8c433c#diff-eefdfbfe9cec5f4ebab88c9a64d423a9)
- This was tested using LLVM/clang rather than gcc, and so far it assumes that LLVM/clang will be the native compiler. This is mostly due to the fact that the support for exceptions/stack unwinding for UWP got much more attention in libunwind
- The "uwp" part of the target needs support for it in the `cc-rs` & `backtrace-rs` crates. I'll create the MR there right after I submit this one and will link everything together, but I'm not sure what's the correct way of dealing with external dependencies in the context of rust
- Enabling import libraries and copying them across stages requires a change in cargo, for which I'll open a MR right after I submit this one as well
- The i686 stack unwinding is unsupported for now, because LLVM assumes SjLj, while rust seems to assume SEH will be used. I'm unsure how to fix this

Also, this is my first encounter with rust, so please bear with my code, it might not feel so idiomatic or even correct :)

I'm pretty sure there's a way of doing things in a cleaner way when it comes to win/c.rs, maybe having a UWP & desktop specific modules, and import those conditionally? It doesn't feel right to sprinkle `#[cfg(...)]` all over the place

Off course, I'll gladly update anything you see fit (to the extent of my abilities/knowledge :) )!

Thanks,

src/bootstrap/compile.rs

@@ -325,7 +325,7 @@ impl Step for StartupObjects {
     fn run(self, builder: &Builder<'_>) {
         let for_compiler = self.compiler;
         let target = self.target;
-        if !target.contains("pc-windows-gnu") {
+        if !target.contains("windows-gnu") {
             return
         }
 
@@ -1126,6 +1126,7 @@ pub fn run_cargo(builder: &Builder<'_>,
             // Skip files like executables
             if !filename.ends_with(".rlib") &&
                !filename.ends_with(".lib") &&
+               !filename.ends_with(".a") &&
                !is_dylib(&filename) &&
                !(is_check && filename.ends_with(".rmeta")) {
                 continue;

src/librustc_codegen_ssa/back/linker.rs

@@ -368,6 +368,26 @@ impl<'a> Linker for GccLinker<'a> {
             }
         } else {
             self.cmd.arg("-shared");
+            if self.sess.target.target.options.is_like_windows {
+                // The output filename already contains `dll_suffix` so
+                // the resulting import library will have a name in the
+                // form of libfoo.dll.a
+                let implib_name = out_filename
+                    .file_name()
+                    .and_then(|file| file.to_str())
+                    .map(|file| format!("{}{}{}",
+                         self.sess.target.target.options.staticlib_prefix,
+                         file,
+                         self.sess.target.target.options.staticlib_suffix));
+                if let Some(implib_name) = implib_name {
+                    let implib = out_filename
+                        .parent()
+                        .map(|dir| dir.join(&implib_name));
+                    if let Some(implib) = implib {
+                        self.linker_arg(&format!("--out-implib,{}", (*implib).to_str().unwrap()));
+                    }
+                }
+            }
         }
     }
 

src/librustc_target/spec/i686_uwp_windows_gnu.rs

@@ -0,0 +1,27 @@
+use crate::spec::{LinkerFlavor, Target, TargetResult};
+
+pub fn target() -> TargetResult {
+    let mut base = super::windows_uwp_base::opts();
+    base.cpu = "pentium4".to_string();
+    base.max_atomic_width = Some(64);
+    base.eliminate_frame_pointer = false; // Required for backtraces
+
+    // Mark all dynamic libraries and executables as compatible with the larger 4GiB address
+    // space available to x86 Windows binaries on x86_64.
+    base.pre_link_args
+        .get_mut(&LinkerFlavor::Gcc).unwrap().push("-Wl,--large-address-aware".to_string());
+
+    Ok(Target {
+        llvm_target: "i686-pc-windows-gnu".to_string(),
+        target_endian: "little".to_string(),
+        target_pointer_width: "32".to_string(),
+        target_c_int_width: "32".to_string(),
+        data_layout: "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32".to_string(),
+        arch: "x86".to_string(),
+        target_os: "windows".to_string(),
+        target_env: "gnu".to_string(),
+        target_vendor: "uwp".to_string(),
+        linker_flavor: LinkerFlavor::Gcc,
+        options: base,
+    })
+}

src/librustc_target/spec/mod.rs

@@ -60,6 +60,7 @@ mod solaris_base;
 mod uefi_base;
 mod windows_base;
 mod windows_msvc_base;
+mod windows_uwp_base;
 mod thumb_base;
 mod l4re_base;
 mod fuchsia_base;
@@ -434,6 +435,8 @@ supported_targets! {
 
     ("x86_64-pc-windows-gnu", x86_64_pc_windows_gnu),
     ("i686-pc-windows-gnu", i686_pc_windows_gnu),
+    ("i686-uwp-windows-gnu", i686_uwp_windows_gnu),
+    ("x86_64-uwp-windows-gnu", x86_64_uwp_windows_gnu),
 
     ("aarch64-pc-windows-msvc", aarch64_pc_windows_msvc),
     ("x86_64-pc-windows-msvc", x86_64_pc_windows_msvc),

src/librustc_target/spec/windows_uwp_base.rs

@@ -0,0 +1,64 @@
+use crate::spec::{LinkArgs, LinkerFlavor, TargetOptions};
+use std::default::Default;
+
+pub fn opts() -> TargetOptions {
+    let mut pre_link_args = LinkArgs::new();
+    pre_link_args.insert(LinkerFlavor::Gcc, vec![
+            // Tell GCC to avoid linker plugins, because we are not bundling
+            // them with Windows installer, and Rust does its own LTO anyways.
+            "-fno-use-linker-plugin".to_string(),
+
+            // Always enable DEP (NX bit) when it is available
+            "-Wl,--nxcompat".to_string(),
+        ]);
+
+    let mut late_link_args = LinkArgs::new();
+    late_link_args.insert(LinkerFlavor::Gcc, vec![
+        //"-lwinstorecompat".to_string(),
+        //"-lmingwex".to_string(),
+        //"-lwinstorecompat".to_string(),
+        "-lwinstorecompat".to_string(),
+        "-lruntimeobject".to_string(),
+        "-lsynchronization".to_string(),
+        "-lvcruntime140_app".to_string(),
+        "-lucrt".to_string(),
+        "-lwindowsapp".to_string(),
+        "-lmingwex".to_string(),
+        "-lmingw32".to_string(),
+    ]);
+
+    TargetOptions {
+        // FIXME(#13846) this should be enabled for windows
+        function_sections: false,
+        linker: Some("gcc".to_string()),
+        dynamic_linking: true,
+        executables: false,
+        dll_prefix: String::new(),
+        dll_suffix: ".dll".to_string(),
+        exe_suffix: ".exe".to_string(),
+        staticlib_prefix: "lib".to_string(),
+        staticlib_suffix: ".a".to_string(),
+        no_default_libraries: true,
+        target_family: Some("windows".to_string()),
+        is_like_windows: true,
+        allows_weak_linkage: false,
+        pre_link_args,
+        pre_link_objects_exe: vec![
+            "rsbegin.o".to_string(), // Rust compiler runtime initialization, see rsbegin.rs
+        ],
+        pre_link_objects_dll: vec![
+            "rsbegin.o".to_string(),
+        ],
+        late_link_args,
+        post_link_objects: vec![
+            "rsend.o".to_string(),
+        ],
+        custom_unwind_resume: true,
+        abi_return_struct_as_int: true,
+        emit_debug_gdb_scripts: false,
+        requires_uwtable: true,
+        limit_rdylib_exports: false,
+
+        .. Default::default()
+    }
+}

src/librustc_target/spec/x86_64_uwp_windows_gnu.rs

@@ -0,0 +1,22 @@
+use crate::spec::{LinkerFlavor, Target, TargetResult};
+
+pub fn target() -> TargetResult {
+    let mut base = super::windows_uwp_base::opts();
+    base.cpu = "x86-64".to_string();
+    base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m64".to_string());
+    base.max_atomic_width = Some(64);
+
+    Ok(Target {
+        llvm_target: "x86_64-pc-windows-gnu".to_string(),
+        target_endian: "little".to_string(),
+        target_pointer_width: "64".to_string(),
+        target_c_int_width: "32".to_string(),
+        data_layout: "e-m:w-i64:64-f80:128-n8:16:32:64-S128".to_string(),
+        arch: "x86_64".to_string(),
+        target_os: "windows".to_string(),
+        target_env: "gnu".to_string(),
+        target_vendor: "uwp".to_string(),
+        linker_flavor: LinkerFlavor::Gcc,
+        options: base,
+    })
+}

src/libstd/build.rs

@@ -39,6 +39,10 @@ fn main() {
         println!("cargo:rustc-link-lib=framework=Security");
         println!("cargo:rustc-link-lib=framework=Foundation");
         println!("cargo:rustc-link-lib=resolv");
+    } else if target.contains("uwp") {
+        println!("cargo:rustc-link-lib=ws2_32");
+        // For BCryptGenRandom
+        println!("cargo:rustc-link-lib=bcrypt");
     } else if target.contains("windows") {
         println!("cargo:rustc-link-lib=advapi32");
         println!("cargo:rustc-link-lib=ws2_32");