Add Windows/MinGW support

.claude/settings.local.json

@@ -0,0 +1,15 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(make clean:*)",
+      "Bash(make:*)",
+      "Bash(./hemlock.exe:*)",
+      "Bash(./hemlockc.exe:*)",
+      "Bash(timeout 60 bash:*)",
+      "Bash(git pull:*)",
+      "Bash(gcc:*)",
+      "Bash(./hemlockc_debug.exe:*)",
+      "Bash(gdb:*)"
+    ]
+  }
+}

.github/workflows/release.yml

@@ -148,8 +148,69 @@ jobs:
         name: hemlock-macos-arm64
         path: hemlock-macos-arm64.tar.gz
 
+  build-windows:
+    runs-on: windows-latest
+    defaults:
+      run:
+        shell: msys2 {0}
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Setup MSYS2
+      uses: msys2/setup-msys2@v2
+      with:
+        msystem: MINGW64
+        update: true
+        install: >-
+          mingw-w64-x86_64-gcc
+          mingw-w64-x86_64-make
+          mingw-w64-x86_64-libffi
+          mingw-w64-x86_64-openssl
+          mingw-w64-x86_64-zlib
+          make
+          bash
+          coreutils
+          findutils
+          zip
+
+    - name: Build runtime library
+      run: make runtime
+
+    - name: Build release binaries
+      run: make
+
+    - name: Build compiler
+      run: make compiler
+
+    - name: Run basic tests
+      run: |
+        echo 'print("Hello from Hemlock on Windows!");' > /tmp/test.hml
+        ./hemlock.exe /tmp/test.hml
+
+    - name: Package
+      run: |
+        mkdir -p hemlock-windows-x86_64
+        cp hemlock.exe hemlock-windows-x86_64/
+        cp hemlockc.exe hemlock-windows-x86_64/
+        cp libhemlock_runtime.a hemlock-windows-x86_64/
+        cp -r stdlib hemlock-windows-x86_64/
+        mkdir -p hemlock-windows-x86_64/include
+        cp -r runtime/include/* hemlock-windows-x86_64/include/ 2>/dev/null || true
+        cp README.md LICENSE hemlock-windows-x86_64/ 2>/dev/null || cp README.md hemlock-windows-x86_64/
+        # Copy MinGW runtime DLLs that may be needed
+        cp /mingw64/bin/libgcc_s_seh-1.dll hemlock-windows-x86_64/ 2>/dev/null || true
+        cp /mingw64/bin/libwinpthread-1.dll hemlock-windows-x86_64/ 2>/dev/null || true
+        cp /mingw64/bin/libffi-8.dll hemlock-windows-x86_64/ 2>/dev/null || true
+        zip -r hemlock-windows-x86_64.zip hemlock-windows-x86_64
+
+    - name: Upload artifact
+      uses: actions/upload-artifact@v4
+      with:
+        name: hemlock-windows-x86_64
+        path: hemlock-windows-x86_64.zip
+
   release:
-    needs: [build-linux, build-macos-intel, build-macos-arm]
+    needs: [build-linux, build-macos-intel, build-macos-arm, build-windows]
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
@@ -173,6 +234,8 @@ jobs:
           The compiler is a portable code generator that produces native binaries.
 
           ### Quick Start
+
+          **Linux/macOS:**
           ```bash
           # One-line install
           curl -fsSL https://raw.githubusercontent.com/hemlang/hemlock/main/install.sh | bash
@@ -188,12 +251,27 @@ jobs:
           ./hemlockc your_script.hml -o your_program
           ```
 
+          **Windows:**
+          ```powershell
+          # Download and extract
+          Expand-Archive hemlock-windows-x86_64.zip -DestinationPath .
+          cd hemlock-windows-x86_64
+
+          # Run interpreter
+          .\hemlock.exe your_script.hml
+
+          # Compile to native binary
+          .\hemlockc.exe your_script.hml -o your_program.exe
+          ```
+
           ### Platform Notes
           - **Linux x86_64**: Both binaries work on any glibc-based distro (Ubuntu, Debian, Fedora, etc.)
           - **macOS x86_64/arm64**: Both binaries work out of the box
+          - **Windows x86_64**: Built with MinGW-w64, includes required runtime DLLs. Some POSIX features have limited support (see docs/WINDOWS_SUPPORT.md).
         files: |
           artifacts/hemlock-linux-x86_64/hemlock-linux-x86_64.tar.gz
           artifacts/hemlock-macos-x86_64/hemlock-macos-x86_64.tar.gz
           artifacts/hemlock-macos-arm64/hemlock-macos-arm64.tar.gz
+          artifacts/hemlock-windows-x86_64/hemlock-windows-x86_64.zip
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/tests.yml

@@ -236,3 +236,104 @@ jobs:
         name: scan-build-reports
         path: scan-build-reports/
         if-no-files-found: ignore
+
+  # Windows tests using MSYS2/MinGW
+  windows-test:
+    runs-on: windows-latest
+    defaults:
+      run:
+        shell: msys2 {0}
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Setup MSYS2
+      uses: msys2/setup-msys2@v2
+      with:
+        msystem: MINGW64
+        update: true
+        install: >-
+          mingw-w64-x86_64-gcc
+          mingw-w64-x86_64-make
+          mingw-w64-x86_64-libffi
+          mingw-w64-x86_64-openssl
+          mingw-w64-x86_64-zlib
+          make
+          bash
+          coreutils
+          findutils
+
+    - name: Build interpreter
+      run: make clean && make
+
+    - name: Run tests
+      run: |
+        # Run tests with Windows-incompatible tests automatically skipped
+        ./tests/run_tests.sh
+
+  # Windows compiler build test
+  windows-compiler:
+    runs-on: windows-latest
+    defaults:
+      run:
+        shell: msys2 {0}
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Setup MSYS2
+      uses: msys2/setup-msys2@v2
+      with:
+        msystem: MINGW64
+        update: true
+        install: >-
+          mingw-w64-x86_64-gcc
+          mingw-w64-x86_64-make
+          mingw-w64-x86_64-libffi
+          mingw-w64-x86_64-openssl
+          mingw-w64-x86_64-zlib
+          make
+          bash
+          coreutils
+          findutils
+
+    - name: Build compiler
+      run: make compiler
+
+    - name: Run basic compiler test
+      run: |
+        echo 'print("Hello from Windows!");' > /tmp/test.hml
+        ./hemlockc /tmp/test.hml -o /tmp/test.exe
+        /tmp/test.exe
+
+  # Windows parity tests
+  windows-parity:
+    runs-on: windows-latest
+    timeout-minutes: 15
+    defaults:
+      run:
+        shell: msys2 {0}
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Setup MSYS2
+      uses: msys2/setup-msys2@v2
+      with:
+        msystem: MINGW64
+        update: true
+        install: >-
+          mingw-w64-x86_64-gcc
+          mingw-w64-x86_64-make
+          mingw-w64-x86_64-libffi
+          mingw-w64-x86_64-openssl
+          mingw-w64-x86_64-zlib
+          make
+          bash
+          coreutils
+          findutils
+
+    - name: Build interpreter and compiler
+      run: |
+        make clean && make
+        make compiler
+
+    - name: Run parity tests
+      run: make parity

Makefile

@@ -1,15 +1,26 @@
 CC = gcc
-# Use _DARWIN_C_SOURCE on macOS for BSD types, _POSIX_C_SOURCE on Linux
+# Platform detection
+UNAME := $(shell uname 2>/dev/null || echo Windows)
+
+# Use platform-specific flags
 ifeq ($(shell uname),Darwin)
     CFLAGS = -Wall -Wextra -std=c11 -O3 -g -D_DARWIN_C_SOURCE -Iinclude -Isrc -Isrc/frontend -Isrc/backends -Isrc/shared $(EXTRA_CFLAGS)
+    PLATFORM = macos
+else ifeq ($(findstring MINGW,$(UNAME)),MINGW)
+    CFLAGS = -Wall -Wextra -std=c11 -O3 -g -DHML_WINDOWS -Iinclude -Isrc -Isrc/frontend -Isrc/backends -Isrc/shared $(EXTRA_CFLAGS)
+    PLATFORM = windows
+else ifeq ($(findstring MSYS,$(UNAME)),MSYS)
+    CFLAGS = -Wall -Wextra -std=c11 -O3 -g -DHML_WINDOWS -Iinclude -Isrc -Isrc/frontend -Isrc/backends -Isrc/shared $(EXTRA_CFLAGS)
+    PLATFORM = windows
 else
     CFLAGS = -Wall -Wextra -std=c11 -O3 -g -D_POSIX_C_SOURCE=200809L -D_DEFAULT_SOURCE -Iinclude -Isrc -Isrc/frontend -Isrc/backends -Isrc/shared $(EXTRA_CFLAGS)
+    PLATFORM = linux
 endif
 SRC_DIR = src
 BUILD_DIR = build
 
-# Detect libffi, OpenSSL, and libwebsockets (Homebrew on macOS puts them in non-standard locations)
-ifeq ($(shell uname),Darwin)
+# Detect libffi, OpenSSL, and libwebsockets (platform-specific detection)
+ifeq ($(PLATFORM),macos)
     # On macOS, prefer Homebrew's libffi (system pkg-config points to SDK without headers)
     BREW_LIBFFI := $(shell brew --prefix libffi 2>/dev/null)
     ifneq ($(BREW_LIBFFI),)
@@ -35,6 +46,23 @@ ifeq ($(shell uname),Darwin)
     else
         HAS_LIBWEBSOCKETS := 0
     endif
+    # macOS base libraries
+    LDFLAGS_BASE = -lm -lpthread -lffi -ldl -lz -lcrypto
+
+else ifeq ($(PLATFORM),windows)
+    # On Windows/MinGW, use pkg-config if available
+    LIBFFI_CFLAGS := $(shell pkg-config --cflags libffi 2>/dev/null)
+    LIBFFI_LIBS := $(shell pkg-config --libs-only-L libffi 2>/dev/null)
+    ifneq ($(LIBFFI_CFLAGS),)
+        CFLAGS += $(LIBFFI_CFLAGS)
+        LDFLAGS_LIBFFI = $(LIBFFI_LIBS)
+    endif
+    LDFLAGS_OPENSSL =
+    LDFLAGS_LIBWEBSOCKETS =
+    HAS_LIBWEBSOCKETS := 0
+    # Windows base libraries (no -ldl, add -lws2_32 for Winsock)
+    LDFLAGS_BASE = -lm -lpthread -lffi -lz -lcrypto -lws2_32
+
 else
     # On Linux, use pkg-config if available
     LIBFFI_CFLAGS := $(shell pkg-config --cflags libffi 2>/dev/null)
@@ -48,10 +76,12 @@ else
 
     # Check if libwebsockets is available on Linux
     HAS_LIBWEBSOCKETS := $(shell pkg-config --exists libwebsockets 2>/dev/null && echo 1 || (test -f /usr/include/libwebsockets.h && echo 1 || echo 0))
+    # Linux base libraries
+    LDFLAGS_BASE = -lm -lpthread -lffi -ldl -lz -lcrypto
 endif
 
-# Base libraries (always required)
-LDFLAGS = $(LDFLAGS_LIBFFI) $(LDFLAGS_OPENSSL) -lm -lpthread -lffi -ldl -lz -lcrypto $(EXTRA_LDFLAGS)
+# Combine LDFLAGS
+LDFLAGS = $(LDFLAGS_LIBFFI) $(LDFLAGS_OPENSSL) $(LDFLAGS_BASE) $(EXTRA_LDFLAGS)
 
 # Conditionally add libwebsockets
 ifeq ($(HAS_LIBWEBSOCKETS),1)