all: add support for windows/amd64

This uses Mingw-w64, which seems to be the de facto standard for porting
Unixy programs to Windows.

builder/ar.go

@@ -3,6 +3,7 @@ package builder
 import (
 	"bytes"
 	"debug/elf"
+	"debug/pe"
 	"encoding/binary"
 	"errors"
 	"fmt"
@@ -39,29 +40,42 @@ func makeArchive(arfile *os.File, objs []string) error {
 		}
 
 		// Read the symbols and add them to the symbol table.
-		dbg, err := elf.NewFile(objfile)
-		if err != nil {
-			return fmt.Errorf("failed to open file %s: %w", objpath, err)
-		}
-		symbols, err := dbg.Symbols()
-		if err != nil {
-			return err
-		}
-		for _, symbol := range symbols {
-			bind := elf.ST_BIND(symbol.Info)
-			if bind != elf.STB_GLOBAL && bind != elf.STB_WEAK {
-				// Don't include local symbols (STB_LOCAL).
-				continue
+		if dbg, err := elf.NewFile(objfile); err == nil {
+			symbols, err := dbg.Symbols()
+			if err != nil {
+				return err
 			}
-			if elf.ST_TYPE(symbol.Info) != elf.STT_FUNC && elf.ST_TYPE(symbol.Info) != elf.STT_OBJECT {
-				// Not a function.
-				continue
+			for _, symbol := range symbols {
+				bind := elf.ST_BIND(symbol.Info)
+				if bind != elf.STB_GLOBAL && bind != elf.STB_WEAK {
+					// Don't include local symbols (STB_LOCAL).
+					continue
+				}
+				if elf.ST_TYPE(symbol.Info) != elf.STT_FUNC && elf.ST_TYPE(symbol.Info) != elf.STT_OBJECT {
+					// Not a function.
+					continue
+				}
+				// Include in archive.
+				symbolTable = append(symbolTable, struct {
+					name      string
+					fileIndex int
+				}{symbol.Name, i})
 			}
-			// Include in archive.
-			symbolTable = append(symbolTable, struct {
-				name      string
-				fileIndex int
-			}{symbol.Name, i})
+		} else if dbg, err := pe.NewFile(objfile); err == nil {
+			for _, symbol := range dbg.Symbols {
+				if symbol.StorageClass != 2 {
+					continue
+				}
+				if symbol.SectionNumber == 0 {
+					continue
+				}
+				symbolTable = append(symbolTable, struct {
+					name      string
+					fileIndex int
+				}{symbol.Name, i})
+			}
+		} else {
+			return fmt.Errorf("failed to open file %s as ELF or PE/COFF: %w", objpath, err)
 		}
 
 		// Close file, to avoid issues with too many open files (especially on
@@ -120,11 +134,13 @@ func makeArchive(arfile *os.File, objs []string) error {
 	}
 
 	// Add all object files to the archive.
+	var copyBuf bytes.Buffer
 	for i, objpath := range objs {
 		objfile, err := os.Open(objpath)
 		if err != nil {
 			return err
 		}
+		defer objfile.Close()
 
 		// Store the start index, for when we'll update the symbol table with
 		// the correct file start indices.
@@ -155,13 +171,21 @@ func makeArchive(arfile *os.File, objs []string) error {
 		}
 
 		// Copy the file contents into the archive.
-		n, err := io.Copy(arwriter, objfile)
+		// First load all contents into a buffer, then write it all in one go to
+		// the archive file. This is a bit complicated, but is necessary because
+		// io.Copy can't deal with files that are of an odd size.
+		copyBuf.Reset()
+		n, err := io.Copy(&copyBuf, objfile)
 		if err != nil {
-			return err
+			return fmt.Errorf("could not copy object file into ar file: %w", err)
 		}
 		if n != st.Size() {
 			return errors.New("file modified during ar creation: " + arfile.Name())
 		}
+		_, err = arwriter.Write(copyBuf.Bytes())
+		if err != nil {
+			return fmt.Errorf("could not copy object file into ar file: %w", err)
+		}
 
 		// File is not needed anymore.
 		objfile.Close()

builder/build.go

@@ -115,6 +115,12 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 			return errors.New("could not find wasi-libc, perhaps you need to run `make wasi-libc`?")
 		}
 		libcDependencies = append(libcDependencies, dummyCompileJob(path))
+	case "mingw-w64":
+		_, err := MinGW.load(config, dir)
+		if err != nil {
+			return err
+		}
+		libcDependencies = append(libcDependencies, makeMinGWExtraLibs(dir)...)
 	case "":
 		// no library specified, so nothing to do
 	default:
@@ -518,6 +524,9 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 	// Prepare link command.
 	linkerDependencies := []*compileJob{outputObjectFileJob}
 	executable := filepath.Join(dir, "main")
+	if config.GOOS() == "windows" {
+		executable += ".exe"
+	}
 	tmppath := executable // final file
 	ldflags := append(config.LDFlags(), "-o", executable)
 

builder/builder_test.go

@@ -58,6 +58,7 @@ func TestClangAttributes(t *testing.T) {
 		{GOOS: "linux", GOARCH: "arm64"},
 		{GOOS: "darwin", GOARCH: "amd64"},
 		{GOOS: "darwin", GOARCH: "arm64"},
+		{GOOS: "windows", GOARCH: "amd64"},
 	} {
 		t.Run("GOOS="+options.GOOS+",GOARCH="+options.GOARCH, func(t *testing.T) {
 			testClangAttributes(t, options)

builder/lld.cpp

@@ -11,6 +11,11 @@ bool tinygo_link_elf(int argc, char **argv) {
 	return lld::elf::link(args, false, llvm::outs(), llvm::errs());
 }
 
+bool tinygo_link_mingw(int argc, char **argv) {
+	std::vector<const char*> args(argv, argv + argc);
+	return lld::mingw::link(args, false, llvm::outs(), llvm::errs());
+}
+
 bool tinygo_link_wasm(int argc, char **argv) {
 	std::vector<const char*> args(argv, argv + argc);
 	return lld::wasm::link(args, false, llvm::outs(), llvm::errs());

builder/mingw-w64.go

@@ -0,0 +1,91 @@
+package builder
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/tinygo-org/tinygo/goenv"
+)
+
+var MinGW = Library{
+	name: "mingw-w64",
+	makeHeaders: func(target, includeDir string) error {
+		// copy _mingw.h
+		srcDir := filepath.Join(goenv.Get("TINYGOROOT"), "lib", "mingw-w64")
+		outf, err := os.Create(includeDir + "/_mingw.h")
+		if err != nil {
+			return err
+		}
+		defer outf.Close()
+		inf, err := os.Open(srcDir + "/mingw-w64-headers/crt/_mingw.h.in")
+		if err != nil {
+			return err
+		}
+		_, err = io.Copy(outf, inf)
+		return err
+	},
+	cflags: func(target, headerPath string) []string {
+		// No flags necessary because there are no files to compile.
+		return nil
+	},
+	librarySources: func(target string) []string {
+		// We only use the UCRT DLL file. No source files necessary.
+		return nil
+	},
+}
+
+// makeMinGWExtraLibs returns a slice of jobs to import the correct .dll
+// libraries. This is done by converting input .def files to .lib files which
+// can then be linked as usual.
+//
+// TODO: cache the result. At the moment, it costs a few hundred milliseconds to
+// compile these files.
+func makeMinGWExtraLibs(tmpdir string) []*compileJob {
+	var jobs []*compileJob
+	root := goenv.Get("TINYGOROOT")
+	// Normally all the api-ms-win-crt-*.def files are all compiled to a single
+	// .lib file. But to simplify things, we're going to leave them as separate
+	// files.
+	for _, name := range []string{
+		"kernel32.def.in",
+		"api-ms-win-crt-conio-l1-1-0.def",
+		"api-ms-win-crt-convert-l1-1-0.def",
+		"api-ms-win-crt-environment-l1-1-0.def",
+		"api-ms-win-crt-filesystem-l1-1-0.def",
+		"api-ms-win-crt-heap-l1-1-0.def",
+		"api-ms-win-crt-locale-l1-1-0.def",
+		"api-ms-win-crt-math-l1-1-0.def.in",
+		"api-ms-win-crt-multibyte-l1-1-0.def",
+		"api-ms-win-crt-private-l1-1-0.def.in",
+		"api-ms-win-crt-process-l1-1-0.def",
+		"api-ms-win-crt-runtime-l1-1-0.def.in",
+		"api-ms-win-crt-stdio-l1-1-0.def",
+		"api-ms-win-crt-string-l1-1-0.def",
+		"api-ms-win-crt-time-l1-1-0.def",
+		"api-ms-win-crt-utility-l1-1-0.def",
+	} {
+		outpath := filepath.Join(tmpdir, filepath.Base(name)+".lib")
+		inpath := filepath.Join(root, "lib/mingw-w64/mingw-w64-crt/lib-common/"+name)
+		job := &compileJob{
+			description: "create lib file " + inpath,
+			result:      outpath,
+			run: func(job *compileJob) error {
+				defpath := inpath
+				if strings.HasSuffix(inpath, ".in") {
+					// .in files need to be preprocessed by a preprocessor (-E)
+					// first.
+					defpath = outpath + ".def"
+					err := runCCompiler("-E", "-x", "c", "-Wp,-w", "-P", "-DDEF_X64", "-o", defpath, inpath, "-I"+goenv.Get("TINYGOROOT")+"/lib/mingw-w64/mingw-w64-crt/def-include/")
+					if err != nil {
+						return err
+					}
+				}
+				return link("ld.lld", "-m", "i386pep", "-o", outpath, defpath)
+			},
+		}
+		jobs = append(jobs, job)
+	}
+	return jobs
+}

builder/tools-builtin.go

@@ -13,6 +13,7 @@ import (
 #include <stdlib.h>
 bool tinygo_clang_driver(int argc, char **argv);
 bool tinygo_link_elf(int argc, char **argv);
+bool tinygo_link_mingw(int argc, char **argv);
 bool tinygo_link_wasm(int argc, char **argv);
 */
 import "C"
@@ -24,6 +25,10 @@ const hasBuiltinTools = true
 // This version actually runs the tools because TinyGo was compiled while
 // linking statically with LLVM (with the byollvm build tag).
 func RunTool(tool string, args ...string) error {
+	linker := "elf"
+	if tool == "ld.lld" && len(args) >= 2 && args[0] == "-m" && args[1] == "i386pep" {
+		linker = "mingw"
+	}
 	args = append([]string{"tinygo:" + tool}, args...)
 
 	var cflag *C.char
@@ -41,7 +46,14 @@ func RunTool(tool string, args ...string) error {
 	case "clang":
 		ok = C.tinygo_clang_driver(C.int(len(args)), (**C.char)(buf))
 	case "ld.lld":
-		ok = C.tinygo_link_elf(C.int(len(args)), (**C.char)(buf))
+		switch linker {
+		case "elf":
+			ok = C.tinygo_link_elf(C.int(len(args)), (**C.char)(buf))
+		case "mingw":
+			ok = C.tinygo_link_mingw(C.int(len(args)), (**C.char)(buf))
+		default:
+			return errors.New("unknown linker: " + linker)
+		}
 	case "wasm-ld":
 		ok = C.tinygo_link_wasm(C.int(len(args)), (**C.char)(buf))
 	default: