Add cygwin target.

compiler/rustc_target/src/spec/base/cygwin.rs

@@ -0,0 +1,51 @@
+use std::borrow::Cow;
+
+use crate::spec::{Cc, DebuginfoKind, LinkerFlavor, Lld, SplitDebuginfo, TargetOptions, cvs};
+
+pub(crate) fn opts() -> TargetOptions {
+    let mut pre_link_args = TargetOptions::link_args(LinkerFlavor::Gnu(Cc::No, Lld::No), &[
+        // FIXME: Disable ASLR for now to fix relocation error
+        "--disable-dynamicbase",
+        "--enable-auto-image-base",
+    ]);
+    crate::spec::add_link_args(&mut pre_link_args, LinkerFlavor::Gnu(Cc::Yes, Lld::No), &[
+        // 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",
+        "-Wl,--disable-dynamicbase",
+        "-Wl,--enable-auto-image-base",
+    ]);
+    let cygwin_libs = &["-lcygwin", "-lgcc", "-lcygwin", "-luser32", "-lkernel32", "-lgcc_s"];
+    let mut late_link_args =
+        TargetOptions::link_args(LinkerFlavor::Gnu(Cc::No, Lld::No), cygwin_libs);
+    crate::spec::add_link_args(
+        &mut late_link_args,
+        LinkerFlavor::Gnu(Cc::Yes, Lld::No),
+        cygwin_libs,
+    );
+    TargetOptions {
+        os: "cygwin".into(),
+        vendor: "pc".into(),
+        // FIXME(#13846) this should be enabled for cygwin
+        function_sections: false,
+        linker: Some("gcc".into()),
+        dynamic_linking: true,
+        dll_prefix: "".into(),
+        dll_suffix: ".dll".into(),
+        exe_suffix: ".exe".into(),
+        families: cvs!["unix"],
+        is_like_windows: true,
+        allows_weak_linkage: false,
+        pre_link_args,
+        late_link_args,
+        abi_return_struct_as_int: true,
+        emit_debug_gdb_scripts: false,
+        requires_uwtable: true,
+        eh_frame_header: false,
+        // FIXME(davidtwco): Support Split DWARF on Cygwin - may require LLVM changes to
+        // output DWO, despite using DWARF, doesn't use ELF..
+        debuginfo_kind: DebuginfoKind::Pdb,
+        supported_split_debuginfo: Cow::Borrowed(&[SplitDebuginfo::Off]),
+        ..Default::default()
+    }
+}

compiler/rustc_target/src/spec/base/mod.rs

@@ -3,6 +3,7 @@ pub(crate) mod android;
 pub(crate) mod apple;
 pub(crate) mod avr_gnu;
 pub(crate) mod bpf;
+pub(crate) mod cygwin;
 pub(crate) mod dragonfly;
 pub(crate) mod freebsd;
 pub(crate) mod fuchsia;

compiler/rustc_target/src/spec/mod.rs

@@ -1992,6 +1992,7 @@ supported_targets! {
     ("riscv64imac-unknown-nuttx-elf", riscv64imac_unknown_nuttx_elf),
     ("riscv64gc-unknown-nuttx-elf", riscv64gc_unknown_nuttx_elf),
 
+    ("x86_64-pc-cygwin", x86_64_pc_cygwin),
 }
 
 /// Cow-Vec-Str: Cow<'static, [Cow<'static, str>]>
@@ -2970,8 +2971,8 @@ impl Target {
         );
         check_eq!(
             self.is_like_windows,
-            self.os == "windows" || self.os == "uefi",
-            "`is_like_windows` must be set if and only if `os` is `windows` or `uefi`"
+            self.os == "windows" || self.os == "uefi" || self.os == "cygwin",
+            "`is_like_windows` must be set if and only if `os` is `windows`, `uefi` or `cygwin`"
         );
         check_eq!(
             self.is_like_wasm,

compiler/rustc_target/src/spec/targets/x86_64_pc_cygwin.rs

@@ -0,0 +1,32 @@
+use crate::spec::{Cc, LinkerFlavor, Lld, Target, base};
+
+pub(crate) fn target() -> Target {
+    let mut base = base::cygwin::opts();
+    base.cpu = "x86-64".into();
+    // FIXME: Disable ASLR for now to fix relocation error
+    base.add_pre_link_args(LinkerFlavor::Gnu(Cc::No, Lld::No), &[
+        "-m",
+        "i386pep",
+        "--disable-high-entropy-va",
+    ]);
+    base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &[
+        "-m64",
+        "-Wl,--disable-high-entropy-va",
+    ]);
+    base.max_atomic_width = Some(64);
+    base.linker = Some("x86_64-pc-cygwin-gcc".into());
+    Target {
+        llvm_target: "x86_64-pc-cygwin".into(),
+        pointer_width: 64,
+        data_layout:
+            "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128".into(),
+        arch: "x86_64".into(),
+        options: base,
+        metadata: crate::spec::TargetMetadata {
+            description: Some("64-bit x86 Cygwin".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: Some(true),
+        },
+    }
+}

src/bootstrap/src/core/builder/cargo.rs

@@ -239,7 +239,11 @@ impl Cargo {
                 // flesh out rpath support more fully in the future.
                 self.rustflags.arg("-Zosx-rpath-install-name");
                 Some(format!("-Wl,-rpath,@loader_path/../{libdir}"))
-            } else if !target.is_windows() && !target.contains("aix") && !target.contains("xous") {
+            } else if !target.is_windows()
+                && !target.contains("cygwin")
+                && !target.contains("aix")
+                && !target.contains("xous")
+            {
                 self.rustflags.arg("-Clink-args=-Wl,-z,origin");
                 Some(format!("-Wl,-rpath,$ORIGIN/../{libdir}"))
             } else {

src/doc/rustc/src/SUMMARY.md

@@ -101,6 +101,7 @@
     - [\*-win7-windows-gnu](platform-support/win7-windows-gnu.md)
     - [\*-win7-windows-msvc](platform-support/win7-windows-msvc.md)
     - [x86_64-fortanix-unknown-sgx](platform-support/x86_64-fortanix-unknown-sgx.md)
+    - [x86_64-pc-cygwin](platform-support/x86_64-pc-cygwin.md)
     - [x86_64-pc-solaris](platform-support/solaris.md)
     - [x86_64-unknown-linux-none.md](platform-support/x86_64-unknown-linux-none.md)
     - [x86_64-unknown-none](platform-support/x86_64-unknown-none.md)

src/doc/rustc/src/platform-support.md

@@ -406,6 +406,7 @@ target | std | host | notes
 [`wasm64-unknown-unknown`](platform-support/wasm64-unknown-unknown.md) | ? |  | WebAssembly
 [`x86_64-apple-tvos`](platform-support/apple-tvos.md) | ✓ |  | x86 64-bit tvOS
 [`x86_64-apple-watchos-sim`](platform-support/apple-watchos.md) | ✓ |  | x86 64-bit Apple WatchOS simulator
+[`x86_64-pc-cygwin`](platform-support/x86_64-pc-cygwin.md) | ? |  | 64-bit x86 Cygwin |
 [`x86_64-pc-nto-qnx710`](platform-support/nto-qnx.md) | ✓ |  | x86 64-bit QNX Neutrino 7.1 RTOS with default network stack (io-pkt) |
 [`x86_64-pc-nto-qnx710_iosock`](platform-support/nto-qnx.md) | ✓ |  | x86 64-bit QNX Neutrino 7.1 RTOS with new network stack (io-sock) |
 [`x86_64-pc-nto-qnx800`](platform-support/nto-qnx.md) | ✓ |  | x86 64-bit QNX Neutrino 8.0 RTOS |

src/doc/rustc/src/platform-support/x86_64-pc-cygwin.md

@@ -0,0 +1,39 @@
+# `x86_64-pc-cygwin`
+
+**Tier: 3**
+
+Windows targets supporting Cygwin.
+The `*-cygwin` targets are **not** intended as native target for applications,
+a developer writing Windows applications should use the `*-pc-windows-*` targets instead, which are *native* Windows.
+
+Cygwin is only intended as an emulation layer for Unix-only programs which do not support the native Windows targets.
+
+## Target maintainers
+
+- [Berrysoft](https://github.com/Berrysoft)
+
+## Requirements
+
+This target is cross compiled. It needs `x86_64-pc-cygwin-gcc` as linker.
+
+The `target_os` of the target is `cygwin`, and it is `unix`.
+
+## Building the target
+
+For cross-compilation you want LLVM with [llvm/llvm-project#121439 (merged)](https://github.com/llvm/llvm-project/pull/121439) applied to fix the LLVM codegen on importing external global variables from DLLs.
+No native builds on Cygwin now. It should be possible theoretically though, but might need a lot of patches.
+
+## Building Rust programs
+
+Rust does not yet ship pre-compiled artifacts for this target. To compile for
+this target, you will either need to build Rust with the target enabled (see
+"Building the target" above), or build your own copy of `core` by using
+`build-std` or similar.
+
+## Testing
+
+Created binaries work fine on Windows with Cygwin.
+
+## Cross-compilation toolchains and C code
+
+Compatible C code can be built with GCC shipped with Cygwin. Clang is untested.

tests/assembly/targets/targets-pe.rs

@@ -84,6 +84,9 @@
 //@ revisions: x86_64_win7_windows_msvc
 //@ [x86_64_win7_windows_msvc] compile-flags: --target x86_64-win7-windows-msvc
 //@ [x86_64_win7_windows_msvc] needs-llvm-components: x86
+//@ revisions: x86_64_pc_cygwin
+//@ [x86_64_pc_cygwin] compile-flags: --target x86_64-pc-cygwin
+//@ [x86_64_pc_cygwin] needs-llvm-components: x86
 
 // Sanity-check that each target can produce assembly code.
 

tests/ui/check-cfg/well-known-values.stderr

@@ -201,7 +201,7 @@ warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
 LL |     target_os = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: expected values for `target_os` are: `aix`, `android`, `cuda`, `dragonfly`, `emscripten`, `espidf`, `freebsd`, `fuchsia`, `haiku`, `hermit`, `horizon`, `hurd`, `illumos`, `ios`, `l4re`, `linux`, `macos`, `netbsd`, `none`, `nto`, `nuttx`, `openbsd`, `psp`, `psx`, `redox`, `rtems`, `solaris`, `solid_asp3`, `teeos`, `trusty`, `tvos`, `uefi`, `unknown`, `visionos`, `vita`, `vxworks`, `wasi`, `watchos`, `windows`, `xous`, and `zkvm`
+   = note: expected values for `target_os` are: `aix`, `android`, `cuda`, `cygwin`, `dragonfly`, `emscripten`, `espidf`, `freebsd`, `fuchsia`, `haiku`, `hermit`, `horizon`, `hurd`, `illumos`, `ios`, `l4re`, `linux`, `macos`, `netbsd`, `none`, `nto`, `nuttx`, `openbsd`, `psp`, `psx`, `redox`, `rtems`, `solaris`, `solid_asp3`, `teeos`, `trusty`, `tvos`, `uefi`, `unknown`, `visionos`, `vita`, `vxworks`, `wasi`, `watchos`, `windows`, `xous`, and `zkvm`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
@@ -274,7 +274,7 @@ LL | #[cfg(target_os = "linuz")] // testing that we suggest `linux`
    |                   |
    |                   help: there is a expected value with a similar name: `"linux"`
    |
-   = note: expected values for `target_os` are: `aix`, `android`, `cuda`, `dragonfly`, `emscripten`, `espidf`, `freebsd`, `fuchsia`, `haiku`, `hermit`, `horizon`, `hurd`, `illumos`, `ios`, `l4re`, `linux`, `macos`, `netbsd`, `none`, `nto`, `nuttx`, `openbsd`, `psp`, `psx`, `redox`, `rtems`, `solaris`, `solid_asp3`, `teeos`, `trusty`, `tvos`, `uefi`, `unknown`, `visionos`, `vita`, `vxworks`, `wasi`, `watchos`, `windows`, `xous`, and `zkvm`
+   = note: expected values for `target_os` are: `aix`, `android`, `cuda`, `cygwin`, `dragonfly`, `emscripten`, `espidf`, `freebsd`, `fuchsia`, `haiku`, `hermit`, `horizon`, `hurd`, `illumos`, `ios`, `l4re`, `linux`, `macos`, `netbsd`, `none`, `nto`, `nuttx`, `openbsd`, `psp`, `psx`, `redox`, `rtems`, `solaris`, `solid_asp3`, `teeos`, `trusty`, `tvos`, `uefi`, `unknown`, `visionos`, `vita`, `vxworks`, `wasi`, `watchos`, `windows`, `xous`, and `zkvm`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: 28 warnings emitted