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

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"