Switch pc-windows-gnu targets from GCC to Clang

Author: dennisameling

.github/workflows/ci.yml

@@ -366,25 +366,25 @@ jobs:
             env:
               RUST_CONFIGURE_ARGS: "--build=i686-pc-windows-gnu"
               SCRIPT: make ci-mingw-subset-1
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
             os: windows-latest-xl
           - name: i686-mingw-2
             env:
               RUST_CONFIGURE_ARGS: "--build=i686-pc-windows-gnu"
               SCRIPT: make ci-mingw-subset-2
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
             os: windows-latest-xl
           - name: x86_64-mingw-1
             env:
               SCRIPT: make ci-mingw-subset-1
               RUST_CONFIGURE_ARGS: "--build=x86_64-pc-windows-gnu --enable-profiler"
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
             os: windows-latest-xl
           - name: x86_64-mingw-2
             env:
               SCRIPT: make ci-mingw-subset-2
               RUST_CONFIGURE_ARGS: "--build=x86_64-pc-windows-gnu --enable-profiler"
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
             os: windows-latest-xl
           - name: dist-x86_64-msvc
             env:
@@ -409,14 +409,14 @@ jobs:
             env:
               RUST_CONFIGURE_ARGS: "--build=i686-pc-windows-gnu --enable-full-tools --enable-profiler"
               SCRIPT: python x.py dist
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
               DIST_REQUIRE_ALL_TOOLS: 1
             os: windows-latest-xl
           - name: dist-x86_64-mingw
             env:
               SCRIPT: python x.py dist
               RUST_CONFIGURE_ARGS: "--build=x86_64-pc-windows-gnu --enable-full-tools --enable-profiler"
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
               DIST_REQUIRE_ALL_TOOLS: 1
             os: windows-latest-xl
           - name: dist-x86_64-msvc-alt

compiler/rustc_target/src/spec/i686_pc_windows_gnu.rs

@@ -7,7 +7,7 @@ pub fn target() -> Target {
         .insert(LinkerFlavor::Lld(LldFlavor::Ld), vec!["-m".to_string(), "i386pe".to_string()]);
     base.max_atomic_width = Some(64);
     base.frame_pointer = FramePointer::Always; // Required for backtraces
-    base.linker = Some("i686-w64-mingw32-gcc".to_string());
+    base.linker = Some("i686-w64-mingw32-clang".to_string());
 
     // Mark all dynamic libraries and executables as compatible with the larger 4GiB address
     // space available to x86 Windows binaries on x86_64.

compiler/rustc_target/src/spec/windows_gnu_base.rs

@@ -16,34 +16,13 @@ pub fn opts() -> TargetOptions {
         ],
     );
 
-    let mut late_link_args = LinkArgs::new();
     let mut late_link_args_dynamic = LinkArgs::new();
     let mut late_link_args_static = LinkArgs::new();
-    // Order of `late_link_args*` was found through trial and error to work with various
-    // mingw-w64 versions (not tested on the CI). It's expected to change from time to time.
-    let mingw_libs = vec![
-        "-lmsvcrt".to_string(),
-        "-lmingwex".to_string(),
-        "-lmingw32".to_string(),
-        "-lgcc".to_string(), // alas, mingw* libraries above depend on libgcc
-        // mingw's msvcrt is a weird hybrid import library and static library.
-        // And it seems that the linker fails to use import symbols from msvcrt
-        // that are required from functions in msvcrt in certain cases. For example
-        // `_fmode` that is used by an implementation of `__p__fmode` in x86_64.
-        // The library is purposely listed twice to fix that.
-        //
-        // See https://github.com/rust-lang/rust/pull/47483 for some more details.
-        "-lmsvcrt".to_string(),
-        "-luser32".to_string(),
-        "-lkernel32".to_string(),
-    ];
-    late_link_args.insert(LinkerFlavor::Gcc, mingw_libs.clone());
-    late_link_args.insert(LinkerFlavor::Lld(LldFlavor::Ld), mingw_libs);
     let dynamic_unwind_libs = vec![
         // If any of our crates are dynamically linked then we need to use
         // the shared libgcc_s-dw2-1.dll. This is required to support
         // unwinding across DLL boundaries.
-        "-lgcc_s".to_string(),
+        "-l:libunwind.dll.a".to_string(),
     ];
     late_link_args_dynamic.insert(LinkerFlavor::Gcc, dynamic_unwind_libs.clone());
     late_link_args_dynamic.insert(LinkerFlavor::Lld(LldFlavor::Ld), dynamic_unwind_libs);
@@ -53,8 +32,7 @@ pub fn opts() -> TargetOptions {
         // binaries to be redistributed without the libgcc_s-dw2-1.dll
         // dependency, but unfortunately break unwinding across DLL
         // boundaries when unwinding across FFI boundaries.
-        "-lgcc_eh".to_string(),
-        "-l:libpthread.a".to_string(),
+        "-l:libunwind.a".to_string(),
     ];
     late_link_args_static.insert(LinkerFlavor::Gcc, static_unwind_libs.clone());
     late_link_args_static.insert(LinkerFlavor::Lld(LldFlavor::Ld), static_unwind_libs);
@@ -64,7 +42,8 @@ pub fn opts() -> TargetOptions {
         env: "gnu".to_string(),
         vendor: "pc".to_string(),
         // FIXME(#13846) this should be enabled for windows
-        function_sections: false,
+        function_sections: true,
+        no_default_libraries: false,
         linker: Some("gcc".to_string()),
         dynamic_linking: true,
         executables: true,
@@ -80,7 +59,6 @@ pub fn opts() -> TargetOptions {
         pre_link_objects_fallback: crt_objects::pre_mingw_fallback(),
         post_link_objects_fallback: crt_objects::post_mingw_fallback(),
         crt_objects_fallback: Some(CrtObjectsFallback::Mingw),
-        late_link_args,
         late_link_args_dynamic,
         late_link_args_static,
         abi_return_struct_as_int: true,

compiler/rustc_target/src/spec/x86_64_pc_windows_gnu.rs

@@ -10,7 +10,7 @@ pub fn target() -> Target {
     base.pre_link_args
         .insert(LinkerFlavor::Lld(LldFlavor::Ld), vec!["-m".to_string(), "i386pep".to_string()]);
     base.max_atomic_width = Some(64);
-    base.linker = Some("x86_64-w64-mingw32-gcc".to_string());
+    base.linker = Some("x86_64-w64-mingw32-clang".to_string());
 
     Target {
         llvm_target: "x86_64-pc-windows-gnu".to_string(),

src/bootstrap/bootstrap.py

@@ -470,6 +470,15 @@ def download_toolchain(self, stage0=True, rustc_channel=None):
             with output(self.rustc_stamp(stage0)) as rust_stamp:
                 rust_stamp.write(key)
 
+            # FIXME remove this when the Clang Windows GNU toolchain has been published
+            if (os.environ.get('GCC_LIBS_HACK')):
+                gcc_libs_hack = os.environ.get('GCC_LIBS_HACK')
+                gcc_libs_hack_dest = '{}/rustlib/{}/lib'.format(lib_dir, self.build)
+                shutil.copy(gcc_libs_hack + '/libgcc.a', gcc_libs_hack_dest)
+                shutil.copy(gcc_libs_hack + '/libgcc_eh.a', gcc_libs_hack_dest)
+                shutil.copy(gcc_libs_hack + '/libgcc_s.a', gcc_libs_hack_dest)
+                shutil.copy(gcc_libs_hack + '/libstdc++.a', gcc_libs_hack_dest)
+
         if self.rustfmt() and self.rustfmt().startswith(bin_root) and (
             not os.path.exists(self.rustfmt())
             or self.program_out_of_date(

src/bootstrap/dist.rs

@@ -160,31 +160,29 @@ fn make_win_dist(
     }
 
     let compiler = if target == "i686-pc-windows-gnu" {
-        "i686-w64-mingw32-gcc.exe"
+        "i686-w64-mingw32-clang.exe"
     } else if target == "x86_64-pc-windows-gnu" {
-        "x86_64-w64-mingw32-gcc.exe"
+        "x86_64-w64-mingw32-clang.exe"
+    } else if target == "aarch64-pc-windows-gnu" {
+        "aarch64-w64-mingw32-clang.exe"
     } else {
-        "gcc.exe"
+        "clang.exe"
     };
     let target_tools = [compiler, "ld.exe", "dlltool.exe", "libwinpthread-1.dll"];
     let mut rustc_dlls = vec!["libwinpthread-1.dll"];
-    if target.starts_with("i686-") {
-        rustc_dlls.push("libgcc_s_dw2-1.dll");
-    } else {
-        rustc_dlls.push("libgcc_s_seh-1.dll");
-    }
+
+    rustc_dlls.push("libunwind.dll");
+    rustc_dlls.push("libc++.dll");
 
     let target_libs = [
         //MinGW libs
-        "libgcc.a",
-        "libgcc_eh.a",
-        "libgcc_s.a",
+        "libunwind.a",
+        "libunwind.dll.a",
         "libm.a",
         "libmingw32.a",
         "libmingwex.a",
-        "libstdc++.a",
+        "libc++.a",
         "libiconv.a",
-        "libmoldname.a",
         "libpthread.a",
         //Windows import libs
         "libadvapi32.a",

src/bootstrap/native.rs

@@ -163,10 +163,10 @@ impl Step for Llvm {
             }
         };
 
-        let llvm_exp_targets = match builder.config.llvm_experimental_targets {
-            Some(ref s) => s,
-            None => "AVR;M68k",
-        };
+        //let llvm_exp_targets = match builder.config.llvm_experimental_targets {
+        //    Some(ref s) => s,
+        //    None => "AVR;M68k",
+        //};
 
         let assertions = if builder.config.llvm_assertions { "ON" } else { "OFF" };
         let plugins = if builder.config.llvm_plugins { "ON" } else { "OFF" };
@@ -177,7 +177,7 @@ impl Step for Llvm {
             .define("LLVM_ENABLE_ASSERTIONS", assertions)
             .define("LLVM_ENABLE_PLUGINS", plugins)
             .define("LLVM_TARGETS_TO_BUILD", llvm_targets)
-            .define("LLVM_EXPERIMENTAL_TARGETS_TO_BUILD", llvm_exp_targets)
+            // .define("LLVM_EXPERIMENTAL_TARGETS_TO_BUILD", llvm_exp_targets)
             .define("LLVM_INCLUDE_EXAMPLES", "OFF")
             .define("LLVM_INCLUDE_DOCS", "OFF")
             .define("LLVM_INCLUDE_BENCHMARKS", "OFF")

src/ci/github-actions/ci.yml

@@ -577,28 +577,28 @@ jobs:
             env:
               RUST_CONFIGURE_ARGS: --build=i686-pc-windows-gnu
               SCRIPT: make ci-mingw-subset-1
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
             <<: *job-windows-xl
 
           - name: i686-mingw-2
             env:
               RUST_CONFIGURE_ARGS: --build=i686-pc-windows-gnu
               SCRIPT: make ci-mingw-subset-2
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
             <<: *job-windows-xl
 
           - name: x86_64-mingw-1
             env:
               SCRIPT: make ci-mingw-subset-1
               RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-gnu --enable-profiler
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
             <<: *job-windows-xl
 
           - name: x86_64-mingw-2
             env:
               SCRIPT: make ci-mingw-subset-2
               RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-gnu --enable-profiler
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
             <<: *job-windows-xl
 
           - name: dist-x86_64-msvc
@@ -644,15 +644,15 @@ jobs:
             env:
               RUST_CONFIGURE_ARGS: --build=i686-pc-windows-gnu --enable-full-tools --enable-profiler
               SCRIPT: python x.py dist
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
               DIST_REQUIRE_ALL_TOOLS: 1
             <<: *job-windows-xl
 
           - name: dist-x86_64-mingw
             env:
               SCRIPT: python x.py dist
               RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-gnu --enable-full-tools --enable-profiler
-              CUSTOM_MINGW: 1
+              CUSTOM_MINGW: 0
               DIST_REQUIRE_ALL_TOOLS: 1
             <<: *job-windows-xl
 

src/ci/scripts/install-mingw.sh

@@ -57,10 +57,18 @@ if isWindows; then
     esac
 
     if [[ "${CUSTOM_MINGW-0}" -ne 1 ]]; then
-        pacman -S --noconfirm --needed mingw-w64-$arch-toolchain mingw-w64-$arch-cmake \
-            mingw-w64-$arch-gcc \
-            mingw-w64-$arch-python # the python package is actually for python3
-        ciCommandAddPath "$(ciCheckoutPath)/msys2/mingw${bits}/bin"
+        # FIXME remove the GCC_LIBS_HACK when the Clang Windows GNU toolchain has been published
+        export GCC_LIBS_HACK="$(cygpath -am missing-libs-hack)"
+        echo "GCC_LIBS_HACK path is ${GCC_LIBS_HACK}"
+        mkdir -p "${GCC_LIBS_HACK}"
+        cp "$(cygpath -u $(clang -print-libgcc-file-name))" "${GCC_LIBS_HACK}/libgcc.a"
+        cp "/clang64/lib/libunwind.a" "${GCC_LIBS_HACK}/libgcc_eh.a"
+        cp "/clang64/lib/libunwind.dll.a" "${GCC_LIBS_HACK}/libgcc_s.a"
+        export RUSTFLAGS_BOOTSTRAP="-C link-arg=-L$(cygpath -am missing-libs-hack)"
+        pacman -S --noconfirm --needed mingw-w64-clang-$arch-toolchain mingw-w64-clang-$arch-cmake \
+            mingw-w64-clang-$arch-ninja \
+            mingw-w64-clang-$arch-python # the python package is actually for python3
+        ciCommandAddPath "$(ciCheckoutPath)/msys2/clang${bits}/bin"
     else
         mingw_dir="mingw${bits}"