A new node type OSPTR is added to refer to the data pointer of
strings and slices in a simple way during walk(). It will be
useful for future work on simplification of slice arithmetic.

benchmark                  old ns/op    new ns/op    delta
BenchmarkCopy1Byte                 9            8  -13.98%
BenchmarkCopy2Byte                14            8  -40.49%
BenchmarkCopy4Byte                13            8  -35.04%
BenchmarkCopy8Byte                13            8  -37.10%
BenchmarkCopy12Byte               14           12  -15.38%
BenchmarkCopy16Byte               14           12  -17.24%
BenchmarkCopy32Byte               19           14  -27.32%
BenchmarkCopy128Byte              31           26  -15.29%
BenchmarkCopy1024Byte            100           92   -7.50%
BenchmarkCopy1String              10            7  -28.99%
BenchmarkCopy2String              10            7  -28.06%
BenchmarkCopy4String              10            8  -22.69%
BenchmarkCopy8String              10            8  -23.30%
BenchmarkCopy12String             11           11   -5.88%
BenchmarkCopy16String             11           11   -5.08%
BenchmarkCopy32String             15           14   -6.58%
BenchmarkCopy128String            28           25  -10.60%
BenchmarkCopy1024String           95           95   +0.53%

R=golang-dev, bradfitz, cshapiro, dave, daniel.morsing, rsc, khr, khr
CC=golang-dev
https://golang.org/cl/9101048

Simpler version of CL 13084043.

R=ken2
CC=golang-dev
https://golang.org/cl/13602045

There is a cleaner, simpler way.

««« original CL description
cmd/5g, cmd/6g, cmd/8g: faster compilation
Replace linked list walk with memset.
This reduces CPU time taken by 'go install -a std' by ~10%.
Before:
real		user		sys
0m23.561s	0m16.625s	0m5.848s
0m23.766s	0m16.624s	0m5.846s
0m23.742s	0m16.621s	0m5.868s
after:
0m22.714s	0m14.858s	0m6.138s
0m22.644s	0m14.875s	0m6.120s
0m22.604s	0m14.854s	0m6.081s

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/13084043
»»»

TBR=dvyukov
CC=golang-dev
https://golang.org/cl/13352049

R=ken2
CC=golang-dev
https://golang.org/cl/13512053

Asking about runtime/cgo when CgoEnabled=false now correctly
returns an error from build.Import (specifically, NoGoError), because
there are no buildable Go files in that directory.

The API tool was depending on it returning a package with no Go
files instead. Correct that assumption.

Fixes all.bash on local machines.
(Dashboard appears not to be running the api tool at all.)

Update #6124

TBR=golang-dev
CC=golang-dev
https://golang.org/cl/13385046

It was never going to last.

««« original CL description
cmd/api: break the builds

There is some question about whether the api tool is
running on Windows (see issue 6124), and now I'm
starting to question whether it runs on any of the builders,
since both darwin/amd64 and linux/amd64 are crashing for me
in the api tool due to a recent cgo-related change, and yet
the dashboard is happy.

If the dashboard is still happy after this CL, we have a problem.

Update #6124

TBR=golang-dev
CC=golang-dev
https://golang.org/cl/13632053
»»»

TBR=golang-dev
CC=golang-dev
https://golang.org/cl/13474045

There is some question about whether the api tool is
running on Windows (see issue 6124), and now I'm
starting to question whether it runs on any of the builders,
since both darwin/amd64 and linux/amd64 are crashing for me
in the api tool due to a recent cgo-related change, and yet
the dashboard is happy.

If the dashboard is still happy after this CL, we have a problem.

Update #6124

TBR=golang-dev
CC=golang-dev
https://golang.org/cl/13632053

args is useful for printing tracebacks.

frame is not necessary anymore, but we might some day
get back to functions where the frame size does not vary
by program counter, and if so we'll need it. Avoid needing
to introduce a new struct format later by keeping it now.

Fixes #5907.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/13632051

The old test for "no Go files" was p.Name == "", meaning we never
saw a Go package statement. That test fails if there are cgo files
that we parsed (and recorded the package name) but then chose
not to use (because cgo is not available).

Test the actual file lists instead.

Fixes #6078.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/13661043

The units example is nice but is covered by the Lucent
license, which may be a concern for some people making a
commercial source code distribution of Go.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/13283045

The various throwing > 0 finish a change started
in a previous CL, which sets throwing = -1 to mean
"don't show the internals". That gets set during the
"all goroutines are asleep - deadlock!" crash, and it
should also be set during any other expected crash
that does not indicate a problem within the runtime.

Most runtime.throw do indicate a problem within the
runtime, however, so we should be able to enumerate
the ones that should be silent. The goroutine sleeping
deadlock is the only one I can think of.

Update #5139

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/13662043

Otherwise, if panic starts running deferred functions,
the code that panicked appears to be calling those
functions directly, which is not the case and can be
confusing.

For example:

main.Two()
        /Users/rsc/x.go:12 +0x2a
runtime.panic(0x20dc0, 0x2100cc010)
        /Users/rsc/g/go/src/pkg/runtime/panic.c:248 +0x106
main.One()
        /Users/rsc/x.go:8 +0x55

This makes clear(er) that main.Two is being called during
a panic, not as a direct call from main.One.

Fixes #5832.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/13302051

getaddrinfo is supposed to set errno when it returns
EAI_SYSTEM, but sometimes it does not.

Fixes #6232.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/13532045

This allows us to make two changes:

1. Force the argument type to be size_t, even on broken
   systems that declare malloc to take a ulong.

2. Call runtime.throw if malloc fails.
   (That is, the program crashes; it does not panic.)

Fixes #3403.
Fixes #5926.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/13413047

This CL adds minimal support of Happy Eyeballs-like TCP connection
setup to Dialer API. Happy Eyeballs and derivation techniques are
described in the following:

- Happy Eyeballs: Success with Dual-Stack Hosts
  http://tools.ietf.org/html/rfc6555

- Analysing Dual Stack Behaviour and IPv6 Quality
  http://www.potaroo.net/presentations/2012-04-17-dual-stack-quality.pdf

Usually, the techniques consist of three components below.

- DNS query racers, that run A and AAAA queries in parallel or series
- A short list of destination addresses
- TCP SYN racers, that run IPv4 and IPv6 transport in parallel or series

This CL implements only the latter two. The existing DNS query
component gathers together A and AAAA records in series, so we don't
touch it here. This CL just uses extended resolveInternetAddr and makes
it possible to run multiple Dial racers in parallel.

For example, when the given destination is a DNS name and the name has
multiple address family A and AAAA records, and it happens on the TCP
wildcard network "tcp" with DualStack=true like the following:

(&net.Dialer{DualStack: true}).Dial("tcp", "www.example.com:80")

The function will return a first established connection either TCP over
IPv4 or TCP over IPv6, and close the other connection internally.

Fixes #3610.
Fixes #5267.

Benchmark results on freebsd/amd64 virtual machine, tip vs. tip+12416043:

benchmark                           old ns/op    new ns/op    delta
BenchmarkTCP4OneShot                    50696        52141   +2.85%
BenchmarkTCP4OneShotTimeout             65775        66426   +0.99%
BenchmarkTCP4Persistent                 10986        10457   -4.82%
BenchmarkTCP4PersistentTimeout          11207        10445   -6.80%
BenchmarkTCP6OneShot                    62009        63718   +2.76%
BenchmarkTCP6OneShotTimeout             78351        79138   +1.00%
BenchmarkTCP6Persistent                 14695        14659   -0.24%
BenchmarkTCP6PersistentTimeout          15032        14646   -2.57%
BenchmarkTCP4ConcurrentReadWrite         7215         6217  -13.83%
BenchmarkTCP6ConcurrentReadWrite         7528         7493   -0.46%

benchmark                          old allocs   new allocs    delta
BenchmarkTCP4OneShot                       36           36    0.00%
BenchmarkTCP4OneShotTimeout                36           36    0.00%
BenchmarkTCP4Persistent                     0            0     n/a%
BenchmarkTCP4PersistentTimeout              0            0     n/a%
BenchmarkTCP6OneShot                       37           37    0.00%
BenchmarkTCP6OneShotTimeout                37           37    0.00%
BenchmarkTCP6Persistent                     0            0     n/a%
BenchmarkTCP6PersistentTimeout              0            0     n/a%
BenchmarkTCP4ConcurrentReadWrite            0            0     n/a%
BenchmarkTCP6ConcurrentReadWrite            0            0     n/a%

benchmark                           old bytes    new bytes    delta
BenchmarkTCP4OneShot                     2500         2503    0.12%
BenchmarkTCP4OneShotTimeout              2508         2505   -0.12%
BenchmarkTCP4Persistent                     0            0     n/a%
BenchmarkTCP4PersistentTimeout              0            0     n/a%
BenchmarkTCP6OneShot                     2713         2707   -0.22%
BenchmarkTCP6OneShotTimeout              2722         2720   -0.07%
BenchmarkTCP6Persistent                     0            0     n/a%
BenchmarkTCP6PersistentTimeout              0            0     n/a%
BenchmarkTCP4ConcurrentReadWrite            0            0     n/a%
BenchmarkTCP6ConcurrentReadWrite            0            0     n/a%

R=golang-dev, bradfitz, nightlyone, rsc
CC=golang-dev
https://golang.org/cl/12416043

For example, if the pattern is m... there is
no need to look in directories not beginning with m.

Fixes #5214.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/13253049

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/13420048

This is not quite what that issue reports,
because this does not involve a DLL.
But I wanted to make sure this much was working.

Update #4339

R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/13653043

Add coverage for some uncovered bytes methods. The increase in actual coverage is disapointing small.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13651044

Fixes #6353.

R=golang-dev, bradfitz, alex.brainman
CC=golang-dev
https://golang.org/cl/13652043

The scan starts at the directory we care about and works
backward to the GOPATH root. The error should say the
original directory name, not the name of the GOPATH root.

Fixes #6175.

R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/13366050

Fixes #5764.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13441051

The entry for LEAL/LEAQ in these optabs was listed as having
two data bytes in the y array. In fact they had and expect no data
bytes. However, the general loop expects to be able to look at at
least one data byte, to make sure it is not 0x0f. So give them each
a single data byte set to 0 (not 0x0f).

Since the MOV instructions have the largest optab cases, this
requires growing the size of the data array.

Clang found this bug because the general o->op[z] == 0x0f
test was using z == 22, which was out of bounds.

In practice the next byte in memory was probably not 0x0f
so it wasn't truly broken. But might as well be clean.

Update #5764

R=ken2
CC=golang-dev
https://golang.org/cl/13241050

Fixes cpu subtype check when using external linker which sets the CPU_SUBTYPE_LIB64 bit (1<<31).
Fixes #6197.

R=golang-dev, minux.ma, rsc
CC=golang-dev
https://golang.org/cl/13248046

Generated by addca.

R=gobot
CC=golang-dev
https://golang.org/cl/13265044

For example, if an x_test.go file contains a syntax error,
b.test fails with an error message. But it wasn't printing
the same FAIL line that a build failure later would print.
This makes all the test failures that happen (once we
decide to start running tests) consistently say FAIL.

Fixes #4701.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13431044

A package main binary (that is, a command) being installed
does not mean we can skip the build of the package archive
during a test.

Fixes #3417.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13462046

Fixes #5662.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13650043

It was lost when the generic "Notes" support went in.

Had to change the test setup, because it precluded even
being able test multi-line comments, much less multi-paragraph
comments.

Now 'godoc sync/atomic' works correctly again.

Fixes #6135.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13427045

Fixes #6191.
Fixes #5426.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13234052

Fixes #5054.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/13609043

Remove test of whether SWIG shared library is older than
sources--should be covered by test of package file anyhow.

Fixes #5739.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/13352046

Fixes #5774.

R=golang-dev, adg, r, bradfitz
CC=golang-dev
https://golang.org/cl/9164043

If using other gdb python scripts loaded before Go's gdb-runtime.py
and that have a different init prototype:
Traceback (most recent call last):
  File "/usr/lib/go/src/pkg/runtime/runtime-gdb.py", line 446, in <module>
    k()
TypeError: __init__() takes exactly 3 arguments (1 given)

The problem is that gdb keeps all python scripts in the same namespace,
so vars() contains them. To avoid that, load helpers one by one.

R=iant, rsc
CC=gobot, golang-dev
https://golang.org/cl/9752044

R=golang-dev, bradfitz
CC=ail, golang-dev
https://golang.org/cl/13441050

$INTBITS will not be defined, of course, but that's the best we can do.

Fixes #5978.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/13253048

Fixes #5676.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13250047

Fixes #6038.

R=iant
CC=golang-dev
https://golang.org/cl/13649043

Various compilers complain about the macro expansion not
being used. I fixed a few yesterday. More today.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13643044

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/13336046