The compiler runs on Windows (and has seeds for macOS)

Windows: the compiler made from bootstrap/windows-x86_64.ll runs under Wine, compiles itself to the same IR, builds an
exe of itself, and every test program passes through it. It needed: Windows-sized unsigned long for libclang's unsaved
file, no 'cross' when Windows builds for Windows, --target passed to libclang (libclang.dll assumes MSVC), the MinGW
triple always in the IR, FINCH_LDFLAGS, .exe names and FINCH_LLVM_INCLUDE in bootstrap/build.sh, winseed.sh/winbuild.sh.
macOS: seeds for arm64 and x86-64 made with the 11.3 SDK; IR is accepted by clang, nothing has run on a Mac yet.
CI gets a windows and a macos job. UNTESTED on real Windows/macOS runners.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015f73FesGZGYPkmDvUcj6QX

.github/workflows/ci.yml

@@ -1,8 +1,8 @@
 name: CI
 
 # The compiler is written in Finch. It is built from bootstrap/<system>.ll, its own LLVM IR (see bootstrap/README.md),
-# then from itself. Linux x86-64 and ARM64 have seeds; macOS and Windows machines can't build the compiler yet
-# (programs for them are built from Linux with --target, and tested here under Wine and qemu).
+# then from itself. Seeds: Linux x86-64 and ARM64 (tested here), Windows x86-64 (tested under Wine, and here),
+# macOS ARM64 and x86-64 (made with Apple's headers; only checked as IR until the macos job below passes).
 
 on:
   push:
@@ -74,6 +74,49 @@ jobs:
             FINCH_CC=aarch64-linux-gnu-gcc QEMU_LD_PREFIX=/usr/aarch64-linux-gnu tests/cross.sh arm64
           fi
 
+  macos:
+    runs-on: macos-15
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install LLVM 21 (libclang)
+        run: brew install llvm@21 pkg-config
+      - name: Build the compiler
+        run: |
+          export FINCH_CLANG="$(brew --prefix llvm@21)/bin/clang"
+          export FINCH_LIBCLANG="-L$(brew --prefix llvm@21)/lib -lclang"
+          export FINCH_LLVM_INCLUDE="$(brew --prefix llvm@21)/include"
+          bootstrap/build.sh
+          build/finch version
+      - name: Tests
+        run: tests/run.sh
+
+  windows:
+    runs-on: windows-2022
+    defaults:
+      run:
+        shell: bash
+    steps:
+      - uses: actions/checkout@v4
+      - name: Download llvm-mingw (clang with MinGW headers) and LLVM for Windows (libclang.dll)
+        run: |
+          curl -sSL -o mingw.zip https://github.com/mstorsjo/llvm-mingw/releases/download/20251216/llvm-mingw-20251216-ucrt-x86_64.zip
+          7z x -y mingw.zip -o/c/ > /dev/null
+          curl -sSL -o llvm.exe https://github.com/llvm/llvm-project/releases/download/llvmorg-21.1.8/LLVM-21.1.8-win64.exe
+          7z x -y llvm.exe -o/c/llvm > /dev/null
+      - name: Build the compiler
+        run: |
+          export PATH="/c/llvm-mingw-20251216-ucrt-x86_64/bin:$PATH"
+          export FINCH_LIBCLANG="C:/llvm/bin/libclang.dll"
+          export FINCH_LLVM_INCLUDE="C:/llvm/include"
+          export FINCH_LDFLAGS="-LC:/llvm/bin"
+          bootstrap/build.sh
+          build/finch.exe version
+      - name: Tests
+        run: |
+          export PATH="/c/llvm-mingw-20251216-ucrt-x86_64/bin:$PATH"
+          export FINCH_LDFLAGS="-LC:/llvm/bin"
+          FINCH=../build/finch.exe tests/run.sh
+
   vscode:
     runs-on: ubuntu-24.04
     defaults:

.gitignore

@@ -1,2 +1,3 @@
 build/
 *.o
+core.*

bootstrap/README.md

@@ -7,6 +7,8 @@ the compiler's own LLVM IR, one file per system:
 |---|---|---|
 | `linux-x86_64.ll` | Linux x86-64 | built and tested here and in CI |
 | `linux-aarch64.ll` | Linux ARM64 | made with the ARM64 cross compiler; CI builds and tests it on an ARM64 runner |
+| `windows-x86_64.ll` | Windows x86-64 (MinGW: llvm-mingw's clang + libclang.dll) | built and run under Wine: it compiles itself, and every test program runs |
+| `macos-arm64.ll`, `macos-x86_64.ll` | macOS | made on Linux with the macOS 11.3 SDK; checked as IR only (nobody has run them yet) |
 
 `bootstrap/build.sh` compiles the seed with `clang` (and the runtime, and libclang) into `build/finch0`; `finch0` builds
 `src/` into `finch1`; `finch1` builds `src/` again into `build/finch`; the two must make the same IR, or the script stops.
@@ -32,8 +34,12 @@ For another system, from a machine that has that system's headers and a cross co
 FINCH_CC=aarch64-linux-gnu-gcc build/finch ir src/main.fch --target arm64 > bootstrap/linux-aarch64.ll
 ```
 
-## macOS and Windows
+## Windows and macOS
 
-There is no seed for them yet: it needs Apple's or Microsoft's headers, which can't be had on Linux. Until there is one,
-programs for macOS and Windows are built from Linux with `--target macos|windows`, and the compiler's older C++ version
-(branch `before-bootstrap`) is the way to get a compiler that runs there.
+Windows: `windows-x86_64.ll` is made by `bootstrap/winseed.sh` on Linux (llvm-mingw's MinGW headers and the headers of an
+official LLVM for Windows); `bootstrap/winbuild.sh` turns it into `finch.exe` for trying under Wine. On a Windows machine
+`bootstrap/build.sh` does the same from Git Bash: put llvm-mingw's `bin` in PATH and set `FINCH_LIBCLANG` (the path of
+`libclang.dll`), `FINCH_LLVM_INCLUDE` (its `include` folder) and `FINCH_LDFLAGS=-L<folder of libclang.dll>`.
+
+macOS: the seeds were made with the macOS 11.3 SDK; `brew install llvm@21` gives clang and libclang; the CI job sets
+`FINCH_CLANG`, `FINCH_LIBCLANG` and `FINCH_LLVM_INCLUDE`. If the macOS build fails, that job is where it shows first.

bootstrap/build.sh

@@ -20,26 +20,32 @@ case "$(uname -s)-$(uname -m)" in
     MINGW*|MSYS*|CYGWIN*)         seed=windows-x86_64 ;;
     *) echo "bootstrap: no seed for $(uname -s) $(uname -m) (see bootstrap/README.md)" >&2; exit 1 ;;
 esac
+EXE=
+case $seed in windows-*) EXE=.exe ;; esac
 [ -f "bootstrap/$seed.ll" ] || { echo "bootstrap: bootstrap/$seed.ll is missing" >&2; exit 1; }
 
 CLANG=${FINCH_CLANG:-clang}
 LIBS=${FINCH_LIBCLANG:--lclang}
+INC=
+[ -z "${FINCH_LLVM_INCLUDE:-}" ] || INC="-I $FINCH_LLVM_INCLUDE"        # where clang-c/Index.h is, if clang does not find it itself
 export FINCH_RT=$PWD/runtime/finch_rt.c
+# Windows: libclang.dll has to sit next to the programs that use it (FINCH_LIBCLANG is then the path of that dll)
+if [ -n "$EXE" ]; then cp "$LIBS" build/; fi
 
 echo "bootstrap: seed ($seed) -> build/finch0"
-$CLANG -O1 -w "bootstrap/$seed.ll" runtime/finch_rt.c -o build/finch0 -lm $LIBS
-echo "bootstrap: build/finch0 packs the runtime and std into src/embedded.fch"
-bootstrap/pack.sh build/finch0
-echo "bootstrap: build/finch0 builds the compiler -> build/finch1"
-build/finch0 build src/main.fch -o build/finch1
-echo "bootstrap: build/finch1 builds the compiler -> build/finch"
-build/finch1 build src/main.fch -o build/finch
+$CLANG -O1 -w "bootstrap/$seed.ll" runtime/finch_rt.c -o build/finch0$EXE -lm $LIBS
+echo "bootstrap: build/finch0$EXE packs the runtime and std into src/embedded.fch"
+bootstrap/pack.sh build/finch0$EXE
+echo "bootstrap: build/finch0$EXE builds the compiler -> build/finch1"
+build/finch0$EXE build src/main.fch -o build/finch1$EXE $INC
+echo "bootstrap: build/finch1$EXE builds the compiler -> build/finch"
+build/finch1$EXE build src/main.fch -o build/finch$EXE $INC
 
 # a compiler that builds itself must come out the same however many times it does
-build/finch1 ir src/main.fch > build/stage1.ll
-build/finch ir src/main.fch > build/stage2.ll
+build/finch1$EXE ir src/main.fch $INC > build/stage1.ll
+build/finch$EXE ir src/main.fch $INC > build/stage2.ll
 if cmp -s build/stage1.ll build/stage2.ll; then
-    echo "bootstrap: build/finch1 and build/finch make the same IR ($(wc -l < build/stage2.ll) lines): done"
+    echo "bootstrap: build/finch1$EXE and build/finch make the same IR ($(wc -l < build/stage2.ll) lines): done"
 else
     echo "bootstrap: the compiler does not reproduce itself (build/stage1.ll and build/stage2.ll differ)" >&2
     exit 1

bootstrap/winbuild.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+# Builds build/win/finch.exe from bootstrap/windows-x86_64.ll on Linux (to try the Windows compiler under Wine):
+#   bootstrap/winbuild.sh <llvm-mingw dir> <LLVM-for-Windows dir>
+set -eu
+cd "$(dirname "$0")/.."
+mkdir -p build/win
+"$1/bin/x86_64-w64-mingw32-clang" -O1 -w bootstrap/windows-x86_64.ll runtime/finch_rt.c -o build/win/finch.exe "$2/bin/libclang.dll"
+cp "$2/bin/libclang.dll" build/win/

bootstrap/winseed.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+# Makes bootstrap/windows-x86_64.ll from Linux, with a Linux-hosted llvm-mingw (MinGW headers) and the headers of an
+# official LLVM for Windows (clang-c/Index.h):
+#   bootstrap/winseed.sh <finch> <llvm-mingw dir> <LLVM-for-Windows dir>
+set -eu
+cd "$(dirname "$0")/.."
+finch=$1; mingw=$2; llvm=$3
+PATH="$mingw/bin:$PATH" FINCH_CC="$mingw/bin/x86_64-w64-mingw32-clang" "$finch" ir src/main.fch --target windows -I "$llvm/include" > bootstrap/windows-x86_64.ll
+echo "wrote bootstrap/windows-x86_64.ll"

src/cimport.fch

@@ -534,7 +534,7 @@ fn importHeaders([]Header headers, []str dirs, str target, bool windows, str ccF
     index := clang_createIndex(0, 0)
     for h in headers {
         src := "#include \"" + h.path + "\"\n"
-        file := CXUnsavedFile(Filename: "finch_import.c".ptr, Contents: src.ptr, Length: u64(src.len))
+        file := host.unsavedFile("finch_import.c", src)
         ptr tu = null
         flags := CXTranslationUnit_DetailedPreprocessingRecord | CXTranslationUnit_SkipFunctionBodies
         err := clang_parseTranslationUnit2(index, "finch_import.c", argv.ptr, i32(argv.len), addr(file), 1, u32(flags), addr(tu))

src/gen.fch

@@ -5773,7 +5773,7 @@ fn runtimeDecls() -> str {
 
 fn assemble(ptr[Gen] g) -> str {
     text := "; generated by the Finch compiler written in Finch\n\n"
-    if g.tg.cross {
+    if g.tg.cross || g.tg.windows {
         text = text + "target triple = \"" + g.tg.triple + "\"\n\n"
     }
     text = text + g.head.join("\n") + "\n\n" + runtimeDecls() + "\n"

src/host.fch

@@ -3,6 +3,12 @@
 // the Windows one).
 import "stdlib.h"
 import "unistd.h"
+import "clang-c/Index.h"
+
+// libclang's description of a file that isn't on disk: its Length is C's `unsigned long`, which is 64 bits here
+fn unsavedFile(str name, str contents) -> CXUnsavedFile {
+    return CXUnsavedFile(Filename: name.ptr, Contents: contents.ptr, Length: u64(contents.len))
+}
 
 fn quote(str a) -> str {
     return "'" + a.replace("'", "'\\''") + "'"

src/host_windows.fch

@@ -5,8 +5,14 @@ import "stdio.h"
 import "process.h"
 import "direct.h"
 import "io.h"
+import "clang-c/Index.h"
 
 // a Windows argument: in double quotes, with the quotes inside doubled up the way CreateProcess reads them
+// libclang's description of a file that isn't on disk: its Length is C's `unsigned long`, which is 32 bits on Windows
+fn unsavedFile(str name, str contents) -> CXUnsavedFile {
+    return CXUnsavedFile(Filename: name.ptr, Contents: contents.ptr, Length: u32(contents.len))
+}
+
 fn quote(str a) -> str {
     return "\"" + a.replace("\"", "\\\"") + "\""
 }
@@ -78,7 +84,8 @@ fn makeDirs(str path) {
         if part.len == 0 || part.ends_with(":") {
             continue                // "" before a leading / and the drive letter
         }
-        _mkdir(p.sub(0, at).ptr)    // fails when it is there already, which is fine
+        sofar := p.sub(0, at)
+        _mkdir(sofar)               // fails when it is there already, which is fine
     }
 }
 
@@ -93,5 +100,5 @@ fn removeTree(str path) {
 // move a file over another
 fn move(str from, str to) {
     delete_file(to)
-    rename(from.ptr, to.ptr)
+    rename(from, to)
 }

src/linker.fch

@@ -226,7 +226,7 @@ fn build(Build b, platform.Target tg, cimport.CImports ci) -> int {
     obj := b.out + ".o"
     write_file(ll, b.ir)
     target := ""
-    if tg.cross {
+    if tg.cross || tg.windows {
         target = " --target=" + tg.triple
     }
     log := b.out + ".log"
@@ -243,6 +243,9 @@ fn build(Build b, platform.Target tg, cimport.CImports ci) -> int {
     if !tg.msvc {
         cmd = cmd + " -lm"
     }
+    if getenv("FINCH_LDFLAGS").len > 0 {
+        cmd = cmd + " " + getenv("FINCH_LDFLAGS")          // more flags for the linker, like -L/where/libclang/is
+    }
     if b.shared {
         if tg.darwin {
             cmd = cmd + " -dynamiclib"

src/main.fch

@@ -277,8 +277,8 @@ fn main([]str args) -> int {
         }
     }
     triple := ""
-    if tg.cross {
-        triple = tg.triple
+    if tg.cross || tg.windows {
+        triple = tg.triple          // on Windows libclang.dll would otherwise assume MSVC, while clang may be MinGW
     }
     ci := cimport.importHeaders(headers, dirs, triple, tg.windows, tg.cc) or {
         print(err)

src/platform.fch

@@ -52,6 +52,9 @@ fn select(str name) -> Target {
             t = "x86_64-apple-macosx14.0.0"
         }
     }
+    if t == "x86_64-w64-windows-gnu" {
+        t = "x86_64-w64-mingw32"        // what clang calls the same system when it runs on Windows
+    }
     tg := Target(triple: t)
     tg.windows = t.contains("windows") || t.contains("mingw") || t.contains("msvc") || t.contains("win32")
     tg.msvc = t.contains("msvc")
@@ -59,7 +62,8 @@ fn select(str name) -> Target {
     tg.arm64 = t.starts_with("aarch64") || t.starts_with("arm64")
     hostArm := hostName.starts_with("aarch64") || hostName.starts_with("arm64")
     hostDarwin := hostName.contains("apple") || hostName.contains("darwin")
-    tg.cross = tg.windows || tg.darwin != hostDarwin || tg.arm64 != hostArm
+    hostWin := hostName.contains("windows") || hostName.contains("mingw") || hostName.contains("msvc")
+    tg.cross = tg.windows != hostWin || tg.darwin != hostDarwin || tg.arm64 != hostArm
     tg.exe = ""
     if tg.windows {
         tg.exe = ".exe"