WASI & darwin: support env variables based on libc

Signed-off-by: Takeshi Yoneda <takeshi@tetrate.io>

main_test.go

@@ -58,6 +58,9 @@ func TestCompiler(t *testing.T) {
 	if runtime.GOOS != "windows" {
 		t.Run("Host", func(t *testing.T) {
 			runPlatTests("", matches, t)
+			if runtime.GOOS == "darwin" {
+				runTest("testdata/libc/env.go", "", t, []string{"ENV1=VALUE1", "ENV2=VALUE2"}...)
+			}
 		})
 	}
 
@@ -104,6 +107,7 @@ func TestCompiler(t *testing.T) {
 
 		t.Run("WASI", func(t *testing.T) {
 			runPlatTests("wasi", matches, t)
+			runTest("testdata/libc/env.go", "wasi", t, []string{"ENV1=VALUE1", "ENV2=VALUE2"}...)
 		})
 	}
 }
@@ -113,7 +117,6 @@ func runPlatTests(target string, matches []string, t *testing.T) {
 
 	for _, path := range matches {
 		path := path // redefine to avoid race condition
-
 		t.Run(filepath.Base(path), func(t *testing.T) {
 			t.Parallel()
 			runTest(path, target, t)
@@ -133,7 +136,7 @@ func runBuild(src, out string, opts *compileopts.Options) error {
 	return Build(src, out, opts)
 }
 
-func runTest(path, target string, t *testing.T) {
+func runTest(path, target string, t *testing.T, environmentVars ...string) {
 	// Get the expected output for this test.
 	txtpath := path[:len(path)-3] + ".txt"
 	if path[len(path)-1] == os.PathSeparator {
@@ -182,6 +185,7 @@ func runTest(path, target string, t *testing.T) {
 	ranTooLong := false
 	if target == "" {
 		cmd = exec.Command(binary)
+		cmd.Env = append(cmd.Env, environmentVars...)
 	} else {
 		spec, err := compileopts.LoadTarget(target)
 		if err != nil {
@@ -193,6 +197,14 @@ func runTest(path, target string, t *testing.T) {
 			args := append(spec.Emulator[1:], binary)
 			cmd = exec.Command(spec.Emulator[0], args...)
 		}
+
+		if len(spec.Emulator) != 0 && spec.Emulator[0] == "wasmtime" {
+			for _, v := range environmentVars {
+				cmd.Args = append(cmd.Args, "--env", v)
+			}
+		} else {
+			cmd.Env = append(cmd.Env, environmentVars...)
+		}
 	}
 	stdout := &bytes.Buffer{}
 	cmd.Stdout = stdout

src/os/env.go

@@ -1,9 +1,14 @@
 package os
 
+import (
+	"syscall"
+)
+
 func Getenv(key string) string {
-	return ""
+	v, _ := syscall.Getenv(key)
+	return v
 }
 
 func LookupEnv(key string) (string, bool) {
-	return "", false
+	return syscall.Getenv(key)
 }

src/syscall/syscall_baremetal.go

@@ -1,4 +1,4 @@
-// +build baremetal wasi
+// +build baremetal
 
 package syscall
 

src/syscall/syscall_libc.go

@@ -1,4 +1,4 @@
-// +build darwin nintendoswitch
+// +build darwin nintendoswitch wasi
 
 package syscall
 
@@ -6,6 +6,12 @@ import (
 	"unsafe"
 )
 
+type sliceHeader struct {
+	buf *byte
+	len uintptr
+	cap uintptr
+}
+
 func Close(fd int) (err error) {
 	return ENOSYS // TODO
 }
@@ -48,18 +54,32 @@ func Getpid() (pid int) {
 }
 
 func Getenv(key string) (value string, found bool) {
-	return "", false // TODO
+	data := append([]byte(key), 0)
+	raw := libc_getenv(&data[0])
+	if raw == nil {
+		return "", false
+	}
+
+	ptr := uintptr(unsafe.Pointer(raw))
+	for size := uintptr(0); ; size++ {
+		v := *(*byte)(unsafe.Pointer(ptr))
+		if v == 0 {
+			src := *(*[]byte)(unsafe.Pointer(&sliceHeader{buf: raw, len: size, cap: size}))
+			return string(src), true
+		}
+		ptr += unsafe.Sizeof(byte(0))
+	}
 }
 
 func splitSlice(p []byte) (buf *byte, len uintptr) {
-	slice := (*struct {
-		buf *byte
-		len uintptr
-		cap uintptr
-	})(unsafe.Pointer(&p))
+	slice := (*sliceHeader)(unsafe.Pointer(&p))
 	return slice.buf, slice.len
 }
 
 // ssize_t write(int fd, const void *buf, size_t count)
 //export write
 func libc_write(fd int32, buf *byte, count uint) int
+
+// char *getenv(const char *name);
+//export getenv
+func libc_getenv(name *byte) *byte

src/syscall/syscall_libc_wasi.go

@@ -0,0 +1,50 @@
+// +build wasi
+
+package syscall
+
+// https://github.com/WebAssembly/wasi-libc/blob/main/expected/wasm32-wasi/predefined-macros.txt
+
+type Signal int
+
+const (
+	SIGCHLD = 16
+	SIGINT  = 2
+	SIGKILL = 9
+	SIGTRAP = 5
+	SIGQUIT = 3
+	SIGTERM = 15
+)
+
+const (
+	Stdin  = 0
+	Stdout = 1
+	Stderr = 2
+)
+
+const (
+	__WASI_OFLAGS_CREAT   = 1
+	__WASI_FDFLAGS_APPEND = 1
+	__WASI_OFLAGS_EXCL    = 4
+	__WASI_OFLAGS_TRUNC   = 8
+	__WASI_FDFLAGS_SYNC   = 16
+
+	O_RDONLY = 0x04000000
+	O_WRONLY = 0x10000000
+	O_RDWR   = O_RDONLY | O_WRONLY
+
+	O_CREAT  = __WASI_OFLAGS_CREAT << 12
+	O_CREATE = O_CREAT
+	O_TRUNC  = __WASI_OFLAGS_TRUNC << 12
+	O_APPEND = __WASI_FDFLAGS_APPEND
+	O_EXCL   = __WASI_OFLAGS_EXCL << 12
+	O_SYNC   = __WASI_FDFLAGS_SYNC
+
+	O_CLOEXEC = 0
+)
+
+//go:extern errno
+var libcErrno uintptr
+
+func getErrno() error {
+	return Errno(libcErrno)
+}

testdata/libc/env.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"os"
+)
+
+func main() {
+	println(os.Getenv("ENV1"))
+	v, ok := os.LookupEnv("ENV2")
+	if !ok {
+		panic("ENV2 not found")
+	}
+	println(v)
+}

testdata/libc/env.txt

@@ -0,0 +1,2 @@
+VALUE1
+VALUE2