In syscall.forkAndExecInChild, blocks of code labelled Pass 1
and Pass 2 permute the file descriptors (if necessary) which are
passed to the child process.  If Pass 1 begins with fds = {0,2,1},
nextfd = 4 and pipe = 4, then the statement labelled "don't stomp
on pipe" is too late -- the pipe (which will be needed to pass
exec status back to the parent) will have been closed by the
preceding DUP call.

Moving the "don't stomp" test earlier ensures that the pipe is
protected.

Fixes #14979

Change-Id: I890c311527f6aa255be48b3277c1e84e2049ee22
Reviewed-on: https://go-review.googlesource.com/21184
Run-TryBot: David du Colombier <0intro@gmail.com>
Reviewed-by: David du Colombier <0intro@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The tree's pretty inconsistent about single space vs double space
after a period in documentation. Make it consistently a single space,
per earlier decisions. This means contributors won't be confused by
misleading precedence.

This CL doesn't use go/doc to parse. It only addresses // comments.
It was generated with:

$ perl -i -npe 's,^(\s*// .+[a-z]\.)  +([A-Z]),$1 $2,' $(git grep -l -E '^\s*//(.+\.)  +([A-Z])')
$ go test go/doc -update

Change-Id: Iccdb99c37c797ef1f804a94b22ba5ee4b500c4f7
Reviewed-on: https://go-review.googlesource.com/20022
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Dave Day <djd@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Use a go:norace comment rather than having the compiler know the special
name syscall.forkAndExecInChild.

Change-Id: I69bc6aa6fc40feb2148d23f269ff32453696fb28
Reviewed-on: https://go-review.googlesource.com/16097
Reviewed-by: Minux Ma <minux@golang.org>

On Unix, when placing a child in a new process group, allow that group
to become the foreground process group. Also, allow a child process to
join a specific process group.

When setting the foreground process group, Ctty is used as the file
descriptor of the controlling terminal. Ctty has been added to the BSD
and Solaris SysProcAttr structures and the handling of Setctty changed
to match Linux.

Change-Id: I18d169a6c5ab8a6a90708c4ff52eb4aded50bc8c
Reviewed-on: https://go-review.googlesource.com/5130
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Breaks reading from stdin in parent after exec with SysProcAttr{Setpgid: true}.

package main

import (
        "fmt"
        "os"
        "os/exec"
        "syscall"
)

func main() {
        cmd := exec.Command("true")
        cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
        cmd.Run()

        fmt.Printf("Hit enter:")
        os.Stdin.Read(make([]byte, 100))
        fmt.Printf("Bye\n")
}

In go1.3, I type enter at the prompt and the program exits.
With the CL being rolled back, the program wedges at the
prompt.

««« original CL description
syscall: SysProcAttr job control changes

Making the child's process group the foreground process group and
placing the child in a specific process group involves co-ordination
between the parent and child that must be done post-fork but pre-exec.

LGTM=iant
R=golang-codereviews, gobot, iant, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/131750044

»»»

LGTM=minux, dneil
R=dneil, minux
CC=golang-codereviews, iant, michael.p.macinnis
https://golang.org/cl/174450043

Making the child's process group the foreground process group and
placing the child in a specific process group involves co-ordination
between the parent and child that must be done post-fork but pre-exec.

LGTM=iant
R=golang-codereviews, gobot, iant, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/131750044

Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.