feat: support libc/compiler-rt for small places

_embdemo/hello-esp32/main.go

@@ -0,0 +1,16 @@
+package main
+
+import "github.com/goplus/lib/c"
+
+func myprint(s *c.Char) {
+	for i := 0; i < int(c.Strlen(s)); i++ {
+		WriteByte(byte(c.Index(s, i)))
+	}
+}
+
+func main() {
+	for {
+		myprint(c.Str("hello world"))
+		sleep(1)
+	}
+}

_embdemo/hello-esp32/uart.go

@@ -0,0 +1,13 @@
+package main
+
+import (
+	_ "unsafe"
+
+	"github.com/goplus/lib/c"
+)
+
+//go:linkname WriteByte C.board_uart_write_char
+func WriteByte(b byte)
+
+//go:linkname sleep sleep
+func sleep(c c.Int)

_embdemo/write-esp32/main.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	_ "unsafe"
+
+	"github.com/goplus/lib/c"
+)
+
+//go:linkname write C.write
+func write(c.Int, *c.Char, c.SizeT) int
+
+func main() {
+	buf := c.Malloc(6)
+	c.Memset(buf, 0, 6)
+	c.Strncpy((*c.Char)(buf), c.Str("abcde"), 5)
+
+	if c.Strcmp((*c.Char)(buf), c.Str("abcde")) == 0 {
+		write(1, c.Str("pass strcmp"), 11)
+	}
+
+	if byte(c.Index((*c.Char)(buf), 0)) == 'a' {
+		write(1, c.Str("pass index"), 10)
+	}
+
+	c.Memset(buf, c.Int('A'), 5)
+	if c.Strcmp((*c.Char)(buf), c.Str("AAAAA")) == 0 {
+		write(1, c.Str("pass memeset"), 11)
+	}
+
+	write(1, (*c.Char)(buf), 5)
+}

internal/build/build.go

@@ -838,15 +838,16 @@ func isWasmTarget(goos string) bool {
 	return slices.Contains([]string{"wasi", "js", "wasip1"}, goos)
 }
 
-func needStart(conf *Config) bool {
-	if conf.Target == "" {
-		return !isWasmTarget(conf.Goos)
+func needStart(ctx *context) bool {
+	if ctx.buildConf.Target == "" {
+		return !isWasmTarget(ctx.buildConf.Goos)
 	}
-	switch conf.Target {
+	switch ctx.buildConf.Target {
 	case "wasip2":
 		return false
 	default:
-		return true
+		// since newlib-esp32 provides _start, we don't need to provide a fake _start function
+		return ctx.crossCompile.Libc != "newlib-esp32"
 	}
 }
 
@@ -903,10 +904,10 @@ define weak void @_start() {
 }
 `
 	mainDefine := "define i32 @main(i32 noundef %0, ptr nocapture noundef readnone %1) local_unnamed_addr"
-	if !needStart(ctx.buildConf) && isWasmTarget(ctx.buildConf.Goos) {
+	if !needStart(ctx) && isWasmTarget(ctx.buildConf.Goos) {
 		mainDefine = "define hidden noundef i32 @__main_argc_argv(i32 noundef %0, ptr nocapture noundef readnone %1) local_unnamed_addr"
 	}
-	if !needStart(ctx.buildConf) {
+	if !needStart(ctx) {
 		startDefine = ""
 	}
 	mainCode := fmt.Sprintf(`; ModuleID = 'main'

internal/crosscompile/compile/compile.go

@@ -0,0 +1,103 @@
+package compile
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"slices"
+	"strings"
+
+	"github.com/goplus/llgo/internal/clang"
+)
+
+type CompileOptions struct {
+	CC      string // Compiler to use
+	Linker  string
+	CCFLAGS []string
+	CFLAGS  []string
+	LDFLAGS []string
+}
+
+type CompileGroup struct {
+	OutputFileName string
+	Files          []string // List of source files to compile
+	CFlags         []string // C compiler flags
+	CCFlags        []string
+	LDFlags        []string // Linker flags
+}
+
+func (g CompileGroup) IsCompiled(outputDir string) bool {
+	archive := filepath.Join(outputDir, filepath.Base(g.OutputFileName))
+	_, err := os.Stat(archive)
+	return err == nil
+}
+
+func (g CompileGroup) Compile(
+	outputDir string, options CompileOptions,
+) (err error) {
+	if g.IsCompiled(outputDir) {
+		return
+	}
+	tmpCompileDir, err := os.MkdirTemp("", "compile-group*")
+	if err != nil {
+		return
+	}
+	defer os.RemoveAll(tmpCompileDir)
+
+	compileLDFlags := append(slices.Clone(options.LDFLAGS), g.LDFlags...)
+	compileCCFlags := append(slices.Clone(options.CCFLAGS), g.CCFlags...)
+	compileCFFlags := append(slices.Clone(options.CFLAGS), g.CFlags...)
+
+	cfg := clang.NewConfig(options.CC, compileCCFlags, compileCFFlags, compileLDFlags, options.Linker)
+
+	var objFiles []string
+
+	compiler := clang.NewCompiler(cfg)
+
+	compiler.Verbose = true
+
+	archive := filepath.Join(outputDir, filepath.Base(g.OutputFileName))
+	fmt.Fprintf(os.Stderr, "Start to compile group %s to %s...\n", g.OutputFileName, archive)
+
+	for _, file := range g.Files {
+		var tempObjFile *os.File
+		tempObjFile, err = os.CreateTemp(tmpCompileDir, fmt.Sprintf("%s*.o", strings.ReplaceAll(file, string(os.PathSeparator), "-")))
+		if err != nil {
+			return
+		}
+
+		lang := "c"
+		if filepath.Ext(file) == ".S" {
+			lang = "assembler-with-cpp"
+		}
+		err = compiler.Compile("-o", tempObjFile.Name(), "-x", lang, "-c", file)
+		if err != nil {
+			return
+		}
+
+		objFiles = append(objFiles, tempObjFile.Name())
+	}
+
+	args := []string{"rcs", archive}
+	args = append(args, objFiles...)
+
+	ccDir := filepath.Dir(options.CC)
+	llvmAr := filepath.Join(ccDir, "llvm-ar")
+
+	cmd := exec.Command(llvmAr, args...)
+	// TODO(MeteorsLiu): support verbose
+	// cmd.Stdout = os.Stdout
+	// cmd.Stderr = os.Stderr
+	err = cmd.Run()
+	return
+}
+
+// CompileConfig represents compilation configuration
+type CompileConfig struct {
+	Url           string
+	Name          string // compile name (e.g., "picolibc", "musl", "glibc")
+	Groups        []CompileGroup
+	ArchiveSrcDir string
+	LibcCFlags    []string
+}