Some machines can be configured (or came/come configured) in such a
state that IPv6 only half works: you can bind on [::]:n but not
connect back to it.

This implements a fallback such that it's guaranteed that this pattern
works:

   ln, err := Listen("tcp", ":0")
   ...
   addr := ln.Addr().String() // "[::]:n"
   c, err := Dial("tcp", addr)

... which is also now tested. It will first try to dial "[::]:n", as
before, but if that dial fails, it will also try "0.0.0.0:n".

Fixes #18806 (contains more details)
Fixes #20611 (I was going to fix nacl later, but it was easy enough)

Change-Id: I1107eb197e902ae8185c781ad1bc4e2bc61d1f4c
Reviewed-on: https://go-review.googlesource.com/45088Reviewed-by: Paul Marks <pmarks@google.com>

Allow the Resolver.Dial func to return instances of Conn other than
*TCPConn and *UDPConn. If the Conn is also a PacketConn, assume DNS
messages transmitted over the Conn adhere to section 4.2.1. "UDP usage".
Otherwise, follow section 4.2.2. "TCP usage".

Provides a hook mechanism so that DNS queries generated by the net
package may be answered or modified before being sent to over the
network.

Updates #19910

Change-Id: Ib089a28ad4a1848bbeaf624ae889f1e82d56655b
Reviewed-on: https://go-review.googlesource.com/45153
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

TestServeTLS was added in CL 44074, merged today.
This cleans up the test a little.

Updates #13228

Change-Id: I6efd798fe5fa015a34addbf60ae26919a1ed283e
Reviewed-on: https://go-review.googlesource.com/45152
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Fixes #15731

Change-Id: I6f4da0cbb3b6c93e175f5e384ffa118f383b7c3b
Reviewed-on: https://go-review.googlesource.com/45089Reviewed-by: Ian Lance Taylor <iant@golang.org>

This adds diagnostics so we can tell if the finalizer has started, in
addition to whether or not it has finished.

Updates #19381.

Change-Id: Icb7b1b0380c9ad1128b17074828945511a6cca5d
Reviewed-on: https://go-review.googlesource.com/45138
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Fixes #11945.
Fixes #17446.

Change-Id: Ic674f6ebc0533ab0f97c650689125994941b72e1
Reviewed-on: https://go-review.googlesource.com/45081
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

runtime.GC no longer triggers a STW GC. This fixes the description of
GODEBUG=gctrace=1 so it doesn't claim otherwise.

Change-Id: Ibd34a55c5ae7b5eda5c2393b9a6674bdf1d51eb3
Reviewed-on: https://go-review.googlesource.com/45131Reviewed-by: Rick Hudson <rlh@golang.org>

Server.ServeTLS wraps Server.Serve with added TLS support. This is
particularly useful for serving on manually initialized listeners.
Example use-case includes ability to serve with TLS on listener
provided by systemd's socket activation.

A matching test heavily based on TestAutomaticHTTP2_ListenAndServe
is also included.

Original code by Gurpartap Singh as
https://go-review.googlesource.com/c/38114/

Fixes #13228

Change-Id: I73bb703f501574a84d261c2d7b9243a89fa52d62
Reviewed-on: https://go-review.googlesource.com/44074
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The test is passing on a 64bit RFS.

Fixes #18008

Change-Id: Ia4c4f4dde0392c7f6bbe5dbffc97cf848ec5a107
Reviewed-on: https://go-review.googlesource.com/44953Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #19092

Change-Id: I7c0fde6a4cf460017619dbcce1c1ddaa7af1022a
Reviewed-on: https://go-review.googlesource.com/44811Reviewed-by: Ian Lance Taylor <iant@golang.org>

For #14822.

Change-Id: Ia3f5558f3e0dcb8ee2dab54a6e9588eecc22511f
Reviewed-on: https://go-review.googlesource.com/45074Reviewed-by: Alan Donovan <adonovan@google.com>

For non-constant shifts with an untyped constant shift count, the
spec only said that it must "be converted to unsigned integer type".
go/types accepts any (arbitrarily large) integer value. Both cmd/compile
and gccgo require that the shift count be representable as a uint value
in that case (if the shift count is typed, it may be any unsigned integer
type).

This change adjusts the spec to state what the compilers have been doing
all along. The new wording matches similar rules elsewhere (e.g., for
untyped array and slice indices). Also, while technically this is a
restriction (we could permit arbitrarily large shift counts), in practice
this is irrelevant.

Fixes #14822.

Change-Id: Ia75834c67483cf761c10025c8df758f225ef67c2
Reviewed-on: https://go-review.googlesource.com/45072Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: I78c6198eb909e679cf0f776b77dda52211bfd347
Reviewed-on: https://go-review.googlesource.com/45133
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The current implementation of "goroutine N cmd" assumes it can get
goroutine N's state from the goroutine's sched buffer. But this only
works if the goroutine is blocked. Extend find_goroutine so that, if
there is no saved scheduler state for a goorutine, it tries to find
the thread the goroutine is running on and use the thread's current
register state. We also extend find_goroutine to understand saved
syscall register state.

Fixes #13887.

Change-Id: I739008a8987471deaa4a9da918655e4042cf969b
Reviewed-on: https://go-review.googlesource.com/45031
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: I94aa87fe951701413b479c05b0bc8810255eb01c
Reviewed-on: https://go-review.googlesource.com/45085
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

TestBuildIDContainsArchModeEnv fails on arm64 because defaultGO386 has
different value from x86 (amd64/386). On arm64 defaultGO386 = '387' but
on x86 defaultGO386 = 'sse2'. The difference will make the test succeed
on x86 while fail on arm64 since it generates the same build ID.
Fix it by explicitly setting GO386 instead of using default value

Fixes #20608

Change-Id: I864b0e47325942d9513516bdf47f60391d18c0d0
Reviewed-on: https://go-review.googlesource.com/45112Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #20597.

Change-Id: Iaa059277c02e80a2fbef59cf8bb3c58d2b90fda0
Reviewed-on: https://go-review.googlesource.com/45111Reviewed-by: David Symonds <dsymonds@golang.org>

Fixes #20541.

Change-Id: Ifdfdf3616482b71761daf6d114b779a8ec532051
Reviewed-on: https://go-review.googlesource.com/44495
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

Fixes #19850

Change-Id: I8c86e288159408c687c2a85f458ade282adae450
Reviewed-on: https://go-review.googlesource.com/45077
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Remove note that sync.Cond, sync.Mutex, sync.RWMutex and atomic.Value
can be created as part of other data structures. Structs can be embedded
by default, and default should not be repeated.

Fixes #20471.

Change-Id: If3f5703d3f60abd96482b58ca43450d02a9e645a
Reviewed-on: https://go-review.googlesource.com/44071Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Prep work for issues mentioned below. No semantic or functionality change.

For #11945.
For #17446.

Change-Id: Ia1bb2b87647a6daa47f7863c0eb42cf5e1d35a7c
Reviewed-on: https://go-review.googlesource.com/45076Reviewed-by: Matthew Dempsky <mdempsky@google.com>

This change updates the vendored tzdata database to version 2017b
(released 2017-03-20).

The TestFirstZone test (which always uses the vendored database) is
updated to make it work with the new timezones database. (The Tokelau
abbreviation was changed from 'TKT' to the numeric abbreviation in
tzdata-2017a)

Fixes #19376

Change-Id: I0dea93e8703992de5c92c7840b8bacad9d02c50d
Reviewed-on: https://go-review.googlesource.com/44832
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #20602.

Change-Id: Iac1589484dec626c018314e0cea7efce091fd87d
Reviewed-on: https://go-review.googlesource.com/45075Reviewed-by: Matthew Dempsky <mdempsky@google.com>

The Tx methods Query and Exec uses context.Background()
even Tx was created by context.
This patch enables using Tx.ctx in all Tx methods
which do not has context arg.
Backward compatibility:
- If Tx has created without context, nothing changes.
- If Tx has created with context and non-context method is called:
  - If context is expired, the execution fails,
    but it can fail on Commit or Rollback as well,
    so in terms of whole transaction - nothing changes.
  - If context is not expired, nothing changes too.

Fixes #20098
Change-Id: I9570a2deaace5875bb4c5dcf7b3a084a6bcd0d00
Reviewed-on: https://go-review.googlesource.com/44956Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Daniel Theophanes <kardianos@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: Ib5efe172c55ff624b6771c2f02c466e35ba6cc50
Reviewed-on: https://go-review.googlesource.com/45090Reviewed-by: Rob Pike <r@golang.org>

Updates #20587

Change-Id: I39f7c43a13c887d9d563c108d3575db7f2dffe0e
Reviewed-on: https://go-review.googlesource.com/45050Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #20601

Change-Id: I296d50dc5210a735a2a65d64bfef05d14c93057b
Reviewed-on: https://go-review.googlesource.com/45073
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rhys Hiltner <rhys@justin.tv>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

We insert guard instructions after each "dangerous" instruction
to make NaCl's validator happy. This happens before asmout. If
in asmout an instruction is split to two dangerous instructions,
but only one guard instruction is inserted, the validation fails.
Therefore don't split instructions on NaCl.

Fixes #20595.

Change-Id: Ie34f209bc7d907d6d16ecef6721f88420981ac01
Reviewed-on: https://go-review.googlesource.com/45021
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The new math/bits package has a section for itself, and should not be
mentioned in the 'Minor changes to the library' section of the release
notes.

Updates #20587

Change-Id: I13ecd35f5cee4324e50b2d31800e399c00159126
Reviewed-on: https://go-review.googlesource.com/45051Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Updates #20587

Change-Id: I5df603505ae1d4b65687bec1e973a4ab318b34f1
Reviewed-on: https://go-review.googlesource.com/45014Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

Currently the extra Ms created for cgo callbacks have a corresponding
G that's kept in syscall state with only a call to goexit on its
stack. This leads to confusing output from runtime.NumGoroutines and
in tracebacks:

goroutine 17 [syscall, locked to thread]:
runtime.goexit()
	.../src/runtime/asm_amd64.s:2197 +0x1

Fix this by putting this goroutine into state _Gdead when it's not in
use instead of _Gsyscall. To keep the goroutine counts correct, we
also add one to sched.ngsys while the goroutine is in _Gdead. The
effect of this is as if the goroutine simply doesn't exist when it's
not in use.

Fixes #16631.
Fixes #16714.

Change-Id: Ieae08a2febd4b3d00bef5c23fd6ca88fb2bb0087
Reviewed-on: https://go-review.googlesource.com/45030
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

The test is inherently racy, and for me fails about 0.05% of the time.
So only fail the test if it fails ten times in a row.

Fixes #20594

Change-Id: I3b3f7598f2196f7406f1a3937f38f21ff0c0e4b5
Reviewed-on: https://go-review.googlesource.com/45020
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

As motivated by https://golang.org/design/18130-type-alias which says:

https://github.com/golang/proposal/blob/master/design/18130-type-alias.md#relationship-to-byte-and-rune

> The language specification already defines byte as an alias for
> uint8 and similarly rune as an alias for int32, using the word alias
> as an informal term. It is a goal that the new type declaration
> semantics not introduce a different meaning for alias. That is, it
> should be possible to describe the existing meanings of byte and
> uint8 by saying that they behave as if predefined by:
>
>     type byte = uint8
>     type rune = int32

So, do that. Seems to work.

Updates #18130

Change-Id: I0740bab3f8fb23e946f3542fdbe819007a99465a
Reviewed-on: https://go-review.googlesource.com/45017Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Update #20178

Change-Id: I603f77268ed38afdd84228c775efe006f08f14a7
Reviewed-on: https://go-review.googlesource.com/45018
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

For cgo programs on linux-amd64 we call the C function mmap.
This supports programs such as the C memory sanitizer that need to
intercept all calls to mmap. It turns out that there are programs that
intercept both mmap and munmap, or that at least expect that if they
intercept mmap, they also intercept munmap. So, if we permit mmap
to be intercepted, also permit munmap to be intercepted.

No test, as it requires two odd things: a C program that intercepts
mmap and munmap, and a Go program that calls munmap.

Change-Id: Iec33f47d59f70dbb7463fd12d30728c24cd4face
Reviewed-on: https://go-review.googlesource.com/45016Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

Fixes #20591

Change-Id: I2a4674a3430c5a4d3c569f3ea654c6ff4d9bf7ee
Reviewed-on: https://go-review.googlesource.com/45015Reviewed-by: Ian Lance Taylor <iant@golang.org>

Updates #18354.

Change-Id: I76bc4a73d8dc99eeda14b395e451d75a65184191
Reviewed-on: https://go-review.googlesource.com/45013Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

Fixes #18331

Change-Id: Ie5c6685be3002533b84604ff1f13f2f0850f29e2
Reviewed-on: https://go-review.googlesource.com/45010
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Many TODOs remain.

Updates #20587

Change-Id: If49854ae4d36346d9e072a386f413cc85c66b62a
Reviewed-on: https://go-review.googlesource.com/45012Reviewed-by: Ian Lance Taylor <iant@golang.org>

Go doesn't guarantee that the result of floating point operations will
be the same on different architectures. It was not stated in the
documentation, that can lead to confusion.

Fixes #18354

Change-Id: Idb1b4c256fb9a7158a74256136eca3b8ce44476f
Reviewed-on: https://go-review.googlesource.com/34938Reviewed-by: Ian Lance Taylor <iant@golang.org>