os: stub out support for some more features

This is necessary for the following:

  - to make sure os/exec can be imported
  - to make sure internal/testenv can be imported

The internal/testenv package (which imports os/exec) is used by a lot of
tests. By adding support for it, more tests can be run.

This commit adds a bunch of new packages that now pass all tests.

src/os/env.go

@@ -12,3 +12,7 @@ func Getenv(key string) string {
 func LookupEnv(key string) (string, bool) {
 	return syscall.Getenv(key)
 }
+
+func Environ() []string {
+	return syscall.Environ()
+}

src/os/exec.go

@@ -16,3 +16,36 @@ func Getpid() int {
 func Getppid() int {
 	return syscall.Getppid()
 }
+
+type ProcAttr struct {
+	Dir   string
+	Env   []string
+	Files []*File
+	Sys   *syscall.SysProcAttr
+}
+
+type ProcessState struct {
+}
+
+func (p *ProcessState) String() string {
+	return "" // TODO
+}
+func (p *ProcessState) Success() bool {
+	return false // TODO
+}
+
+type Process struct {
+	Pid int
+}
+
+func StartProcess(name string, argv []string, attr *ProcAttr) (*Process, error) {
+	return nil, &PathError{"fork/exec", name, ErrNotImplemented}
+}
+
+func (p *Process) Wait() (*ProcessState, error) {
+	return nil, ErrNotImplemented
+}
+
+func (p *Process) Kill() error {
+	return ErrNotImplemented
+}

src/os/file.go

@@ -52,6 +52,16 @@ func Remove(path string) error {
 	return nil
 }
 
+// Symlink is a stub, it is not implemented.
+func Symlink(oldname, newname string) error {
+	return ErrNotImplemented
+}
+
+// RemoveAll is a stub, it is not implemented.
+func RemoveAll(path string) error {
+	return ErrNotImplemented
+}
+
 // File represents an open file descriptor.
 type File struct {
 	handle FileHandle
@@ -187,6 +197,27 @@ func (e *PathError) Error() string {
 	return e.Op + " " + e.Path + ": " + e.Err.Error()
 }
 
+func (e *PathError) Unwrap() error {
+	return e.Err
+}
+
+// LinkError records an error during a link or symlink or rename system call and
+// the paths that caused it.
+type LinkError struct {
+	Op  string
+	Old string
+	New string
+	Err error
+}
+
+func (e *LinkError) Error() string {
+	return e.Op + " " + e.Old + " " + e.New + ": " + e.Err.Error()
+}
+
+func (e *LinkError) Unwrap() error {
+	return e.Err
+}
+
 const (
 	O_RDONLY int = syscall.O_RDONLY
 	O_WRONLY int = syscall.O_WRONLY

src/os/file_anyos.go

@@ -21,6 +21,8 @@ var (
 	Stderr = &File{unixFileHandle(syscall.Stderr), "/dev/stderr"}
 )
 
+const DevNull = "/dev/null"
+
 // isOS indicates whether we're running on a real operating system with
 // filesystem support.
 const isOS = true

src/os/file_other.go

@@ -48,3 +48,7 @@ func (f stdioFileHandle) Close() error {
 
 //go:linkname putchar runtime.putchar
 func putchar(c byte)
+
+func Pipe() (r *File, w *File, err error) {
+	return nil, nil, ErrNotImplemented
+}

src/os/file_unix.go

@@ -2,4 +2,23 @@
 
 package os
 
+import "syscall"
+
 type syscallFd = int
+
+func Pipe() (r *File, w *File, err error) {
+	var p [2]int
+	err = handleSyscallError(syscall.Pipe2(p[:], syscall.O_CLOEXEC))
+	if err != nil {
+		return
+	}
+	r = &File{
+		handle: unixFileHandle(p[0]),
+		name:   "|0",
+	}
+	w = &File{
+		handle: unixFileHandle(p[1]),
+		name:   "|1",
+	}
+	return
+}

src/os/file_windows.go

@@ -5,3 +5,20 @@ package os
 import "syscall"
 
 type syscallFd = syscall.Handle
+
+func Pipe() (r *File, w *File, err error) {
+	var p [2]syscall.Handle
+	e := handleSyscallError(syscall.Pipe(p[:]))
+	if e != nil {
+		return nil, nil, err
+	}
+	r = &File{
+		handle: unixFileHandle(p[0]),
+		name:   "|0",
+	}
+	w = &File{
+		handle: unixFileHandle(p[1]),
+		name:   "|1",
+	}
+	return
+}