Re: [9fans] Golang support for Plan 9

[Pavel Zholkover <paulzhol@gmail.com>]

On Tue, Dec 28, 2010 at 9:24 AM, Skip Tavakkolian
<skip.tavakkolian@gmail.com> wrote:
> sorry for the noise; the -s was mentioned in your original post and i
> missed it.  now hell-o example works. i'll try out a few more things.
>
> i checked out a complete release (fresh copy) earlier today before
> applying the patch; it had the same results (one patch failed to
> apply).
> $ hg identify
> 51c777dbccb9+ tip
>

You were right, I did a clean pull and then tried applying to patch -
it fails on exec.go (not sure what is the cause though).
I'm attaching a diff for the missing file exec_unix.go (it is not
needed for plan9 but all the other os's break without it).

Also if you are brave enough to run "cd src/pkg; make clean;
GOOS=plan9 make -k install" after building the 8g
toolchain you could import "fmt" and friends... fmt.Println should even work :)

diff -r 51c777dbccb9 src/pkg/os/exec_unix.go
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pkg/os/exec_unix.go	Tue Dec 28 22:53:30 2010 +0200
@@ -0,0 +1,148 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os
+
+import (
+	"syscall"
+)
+
+// ForkExec forks the current process and invokes Exec with the
program, arguments,
+// and environment specified by name, argv, and envv.  It returns the process
+// id of the forked process and an Error, if any.  The fd array specifies the
+// file descriptors to be set up in the new process: fd[0] will be Unix file
+// descriptor 0 (standard input), fd[1] descriptor 1, and so on.  A nil entry
+// will cause the child to have no open file descriptor with that index.
+// If dir is not empty, the child chdirs into the directory before
execing the program.
+func ForkExec(name string, argv []string, envv []string, dir string,
fd []*File) (pid int, err Error) {
+	if envv == nil {
+		envv = Environ()
+	}
+	// Create array of integer (system) fds.
+	intfd := make([]int, len(fd))
+	for i, f := range fd {
+		if f == nil {
+			intfd[i] = -1
+		} else {
+			intfd[i] = f.Fd()
+		}
+	}
+
+	p, e := syscall.ForkExec(name, argv, envv, dir, intfd)
+	if e != 0 {
+		return 0, &PathError{"fork/exec", name, Errno(e)}
+	}
+	return p, nil
+}
+
+// Exec replaces the current process with an execution of the
+// named binary, with arguments argv and environment envv.
+// If successful, Exec never returns.  If it fails, it returns an Error.
+// ForkExec is almost always a better way to execute a program.
+func Exec(name string, argv []string, envv []string) Error {
+	if envv == nil {
+		envv = Environ()
+	}
+	e := syscall.Exec(name, argv, envv)
+	if e != 0 {
+		return &PathError{"exec", name, Errno(e)}
+	}
+	return nil
+}
+
+// TODO(rsc): Should os implement its own syscall.WaitStatus
+// wrapper with the methods, or is exposing the underlying one enough?
+//
+// TODO(rsc): Certainly need to have Rusage struct,
+// since syscall one might have different field types across
+// different OS.
+
+// Waitmsg stores the information about an exited process as reported by Wait.
+type Waitmsg struct {
+	Pid                int             // The process's id.
+	syscall.WaitStatus                 // System-dependent status info.
+	Rusage             *syscall.Rusage // System-dependent resource usage info.
+}
+
+// Options for Wait.
+const (
+	WNOHANG   = syscall.WNOHANG  // Don't wait if no process has exited.
+	WSTOPPED  = syscall.WSTOPPED // If set, status of stopped
subprocesses is also reported.
+	WUNTRACED = WSTOPPED
+	WRUSAGE   = 1 << 20 // Record resource usage.
+)
+
+// WRUSAGE must not be too high a bit, to avoid clashing with Linux's
+// WCLONE, WALL, and WNOTHREAD flags, which sit in the top few bits of
+// the options
+
+// Wait waits for process pid to exit or stop, and then returns a
+// Waitmsg describing its status and an Error, if any. The options
+// (WNOHANG etc.) affect the behavior of the Wait call.
+func Wait(pid int, options int) (w *Waitmsg, err Error) {
+	var status syscall.WaitStatus
+	var rusage *syscall.Rusage
+	if options&WRUSAGE != 0 {
+		rusage = new(syscall.Rusage)
+		options ^= WRUSAGE
+	}
+	pid1, e := syscall.Wait4(pid, &status, options, rusage)
+	if e != 0 {
+		return nil, NewSyscallError("wait", e)
+	}
+	w = new(Waitmsg)
+	w.Pid = pid1
+	w.WaitStatus = status
+	w.Rusage = rusage
+	return w, nil
+}
+
+// Convert i to decimal string.
+func itod(i int) string {
+	if i == 0 {
+		return "0"
+	}
+
+	u := uint64(i)
+	if i < 0 {
+		u = -u
+	}
+
+	// Assemble decimal in reverse order.
+	var b [32]byte
+	bp := len(b)
+	for ; u > 0; u /= 10 {
+		bp--
+		b[bp] = byte(u%10) + '0'
+	}
+
+	if i < 0 {
+		bp--
+		b[bp] = '-'
+	}
+
+	return string(b[bp:])
+}
+
+func (w Waitmsg) String() string {
+	// TODO(austin) Use signal names when possible?
+	res := ""
+	switch {
+	case w.Exited():
+		res = "exit status " + itod(w.ExitStatus())
+	case w.Signaled():
+		res = "signal " + itod(w.Signal())
+	case w.Stopped():
+		res = "stop signal " + itod(w.StopSignal())
+		if w.StopSignal() == syscall.SIGTRAP && w.TrapCause() != 0 {
+			res += " (trap " + itod(w.TrapCause()) + ")"
+		}
+	case w.Continued():
+		res = "continued"
+	}
+	if w.CoreDump() {
+		res += " (core dumped)"
+	}
+	return res
+}