Reflect used to communicate to the runtime using interface words,
which is bad for precise GC because sometimes iwords hold a pointer
and sometimes they don't.  This change rewrites channel and select
operations to always pass pointers to the runtime.

reflect.Select gets somewhat more expensive, as we now do an allocation
per receive case instead of one allocation whose size is the max of
all the received types.  This seems unavoidable to get preciseness
(unless we move the allocation into selectgo, which is a much bigger
change).

Fixes #6490

R=golang-codereviews, dvyukov, rsc
CC=golang-codereviews
https://golang.org/cl/52900043

Status codes 204, 304, and 1xx don't allow bodies. We already
had a function for this, but we were hard-coding just 304
(StatusNotModified) in a few places.  Use the function
instead, and flesh out tests for all codes.

Fixes #6685

R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/53290044

R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/8274046

Apparently this is expensive on Windows.

Fixes #7020

R=golang-codereviews, alex.brainman, mattn.jp, dvyukov
CC=golang-codereviews
https://golang.org/cl/52840043

We forgot to include the width of "0x" when computing the crossover
from internal buffer to allocated buffer.
Also add a helper function to the test for formatting large zero-padded
test strings.

Fixes #6777.

R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/50820043

This CL makes the bitmaps a little more precise about variables
that have their address taken but for which the address does not
escape to the heap, so that the variables are kept in the stack frame
rather than allocated on the heap.

The code before this CL handled these variables by treating every
return statement as using every such variable and depending on
liveness analysis to essentially treat the variable as live during the
entire function. That approach has false positives and (worse) false
negatives. That is, it's both sloppy and buggy:

        func f(b1, b2 bool) {	// x live here! (sloppy)
                if b2 {
                        print(0) // x live here! (sloppy)
                        return
                }
                var z **int
                x := new(int)
                *x = 42
                z = &x
                print(**z) // x live here (conservative)
                if b2 {
                        print(1) // x live here (conservative)
                        return
                }
                for {
                        print(**z) // x not live here (buggy)
                }
        }

The first two liveness annotations (marked sloppy) are clearly
wrong: x cannot be live if it has not yet been declared.

The last liveness annotation (marked buggy) is also wrong:
x is live here as *z, but because there is no return statement
reachable from this point in the code, the analysis treats x as dead.

This CL changes the liveness calculation to mark such variables
live exactly at points in the code reachable from the variable
declaration. This keeps the conservative decisions but fixes
the sloppy and buggy ones.

The CL also detects ambiguously live variables, those that are
being marked live but may not actually have been initialized,
such as in this example:

        func f(b1 bool) {
                var z **int
                if b1 {
                        x := new(int)
                        *x = 42
                        z = &x
                } else {
                        y := new(int)
                        *y = 54
                        z = &y
                }
                print(**z) // x, y live here (conservative)
        }

Since the print statement is reachable from the declaration of x,
x must conservatively be marked live. The same goes for y.
Although both x and y are marked live at the print statement,
clearly only one of them has been initialized. They are both
"ambiguously live".

These ambiguously live variables cause problems for garbage
collection: the collector cannot ignore them but also cannot
depend on them to be initialized to valid pointer values.

Ambiguously live variables do not come up too often in real code,
but recent changes to the way map and interface runtime functions
are invoked has created a large number of ambiguously live
compiler-generated temporary variables. The next CL will adjust
the analysis to understand these temporaries better, to make
ambiguously live variables fairly rare.

Once ambiguously live variables are rare enough, another CL will
introduce code at the beginning of a function to zero those
slots on the stack. At that point the garbage collector and the
stack copying routines will be able to depend on the guarantee that
if a slot is marked as live in a liveness bitmap, it is initialized.

R=khr
CC=golang-codereviews, iant
https://golang.org/cl/51810043

Missed this case in CL 51010045.

TBR=khr
CC=golang-codereviews
https://golang.org/cl/53200043

Example of output:

goroutine 4 [sleep for 3 min]:
time.Sleep(0x34630b8a000)
        src/pkg/runtime/time.goc:31 +0x31
main.func·002()
        block.go:16 +0x2c
created by main.main
        block.go:17 +0x33

Full program and output are here:
http://play.golang.org/p/NEZdADI3Td

Fixes #6809.

R=golang-codereviews, khr, kamil.kisiel, bradfitz, rsc
CC=golang-codereviews
https://golang.org/cl/50420043

Use lock-free fixed-size ring for work queues
instead of an unbounded mutex-protected array.
The ring has single producer and multiple consumers.
If the ring overflows, work is put onto global queue.

benchmark              old ns/op    new ns/op    delta
BenchmarkMatmult               7            5  -18.12%
BenchmarkMatmult-4             2            2  -18.98%
BenchmarkMatmult-16            1            0  -12.84%

BenchmarkCreateGoroutines                     105           88  -16.10%
BenchmarkCreateGoroutines-4                   376          219  -41.76%
BenchmarkCreateGoroutines-16                  241          174  -27.80%
BenchmarkCreateGoroutinesParallel             103           87  -14.66%
BenchmarkCreateGoroutinesParallel-4           169          143  -15.38%
BenchmarkCreateGoroutinesParallel-16          158          151   -4.43%

R=golang-codereviews, rsc
CC=ddetlefs, devon.odell, golang-codereviews
https://golang.org/cl/46170044

Give proper types to the argument/return areas
allocated for reflect calls.  Avoid use of iword to
manipulate receivers, which may or may not be pointers.

Update #6490

R=rsc
CC=golang-codereviews
https://golang.org/cl/52110044

Update #7121

R=golang-codereviews, gobot, dsymonds
CC=golang-codereviews
https://golang.org/cl/51750044

Generally improve error messages for escape sequences.

R=adonovan
CC=golang-codereviews
https://golang.org/cl/49430046

Replace the pack command, a C program, with a clean reimplementation in Go.
It does not need to reproduce the full feature set and it is no longer used by
the build chain, but has a role in looking inside archives created by the build
chain directly.

Since it's not in C, it is no longer build by dist, so remove it from cmd/dist and
make it a "tool" in cmd/go terminology.

Fixes #2705

R=rsc, dave, minux.ma, josharian
CC=golang-codereviews
https://golang.org/cl/52310044

Fixes #5139.
Update #7065.

R=golang-codereviews, bradfitz, minux.ma
CC=golang-codereviews
https://golang.org/cl/52090045

Fixes #6564

R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/52420043

See also discussion in CL 51010045.

R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/52230043

R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/52360044

Make it clear that if you do a . import, you cannot use a qualified identifier.

R=gri
CC=golang-codereviews
https://golang.org/cl/52390043

R=rsc, iant
CC=golang-codereviews
https://golang.org/cl/52360043

R=golang-codereviews, minux.ma
CC=golang-codereviews
https://golang.org/cl/52310043

      Previously, filenames containing special characters could:
      1) Escape the <a> tag, with a file called something like: ">foo
      2) Break the links in the index by prematurely ending the path portion
      of the url, with a file called: foo?bar

      In order to avoid a forbidden dependency on the html package, I'm
      using htmlReplacer from net/http/server.go, which is equivalent to
      html.EscapeString.

      This change also expands fakeFile.Readdir to better emulate
os.File.Readdir.

R=golang-codereviews, rsc, gobot, bradfitz, josharian, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/37440043

Map iteration previously started from a random bucket, but walked each
bucket from the beginning. Now, iteration always starts from the first
bucket and walks each bucket starting at a random offset. For
performance, the random offset is selected at the start of iteration
and reused for each bucket.

Iteration over a map with 8 or fewer elements--a single bucket--will
now be non-deterministic. There will now be only 8 different possible
map iterations.

Significant benchmark changes, on my OS X laptop (rough but consistent):

benchmark                              old ns/op     new ns/op     delta
BenchmarkMapIter                       128           121           -5.47%
BenchmarkMapIterEmpty                  4.26          4.45          +4.46%
BenchmarkNewEmptyMap                   114           111           -2.63%

Fixes #6719.

R=khr, bradfitz
CC=golang-codereviews
https://golang.org/cl/47370043

Still work to do. See http://golang.org/issue/7125

««« original CL description
net/http/cookiejar: document format of domain in PublicSuffix

Document what values a PublicSuffixList must accept as
a domain in a call to PublicSuffix.

R=bradfitz, nigeltao
CC=golang-codereviews
https://golang.org/cl/47560044

»»»

R=golang-codereviews, minux.ma
CC=golang-codereviews
https://golang.org/cl/51770044

R=golang-codereviews, iant, mjk
CC=golang-codereviews
https://golang.org/cl/52220043

R=golang-codereviews, minux.ma
CC=golang-codereviews
https://golang.org/cl/52240043

Having these flags misleads people into thinking they're acceptable
for code that "must be gofmt'd".

If an organization wishes to use gofmt internally with
different settings, they can fork gofmt trivially. But "gofmt"
as used by the community with open source Go code should not
support these old knobs.

Also removes the -comments flag.

Fixes #7101

R=r, gri
CC=golang-codereviews
https://golang.org/cl/52170043

Now with more syscall!

R=golang-codereviews, minux.ma
CC=golang-codereviews
https://golang.org/cl/52150043

Fix another issue (similar to Issue 6995) where there was a
data race when sharing a server handler's Request.Body with
another goroutine that out-lived the Handler's goroutine.

In some cases we were not closing the incoming Request.Body
(which would've required reading it until the end) if we
thought it we thought we were going to be forcibly closing the
underlying net.Conn later anyway. But that optimization
largely moved to the transfer.go *body later, and locking was
added to *body which then detected read-after-close, so now
calling the (*body).Close always is both cheap and correct.

No new test because TestTransportAndServerSharedBodyRace caught it,
albeit only sometimes. Running:

while ./http.test -test.cpu=8 -test.run=TestTransportAndServerSharedBodyRace; do true; done

... would reliably cause a race before, but not now.

Update #6995
Fixes #7092

R=golang-codereviews, khr
CC=golang-codereviews
https://golang.org/cl/51700043

For historical reasons, temp was returning a copy
of the created Node*, not the original Node*.
This meant that if analysis recorded information in the
returned node (for example, n->addrtaken = 1), the
analysis would not show up on the original Node*, the
one kept in fn->dcl and consulted during liveness
bitmap creation.

Correct this, and watch for it when setting addrtaken.

Fixes #7083.

R=khr, dave, minux.ma
CC=golang-codereviews
https://golang.org/cl/51010045

R=khr
CC=golang-codereviews
https://golang.org/cl/51820043

R=khr, dvyukov
CC=golang-codereviews
https://golang.org/cl/51830043

Void function can not return false.

R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/52000043

R=golang-codereviews, dave, bradfitz
CC=golang-codereviews
https://golang.org/cl/51000043

It's too sensitive.

Fixes bug 7095

R=golang-codereviews, iant, minux.ma, rsc
CC=golang-codereviews
https://golang.org/cl/50470043

The golden file for link.hello.darwin.amd64
was a little ahead of the checked-in code.

R=iant
TBR=iant
CC=golang-codereviews
https://golang.org/cl/51870043

R=iant
CC=golang-codereviews
https://golang.org/cl/51470043

Related changes included in this CL:

 - Add explicit start symbol to Prog.
 - Add omitRuntime bool to Prog.
 - Introduce p.Packages[""] to hold automatic symbols
 - Add SymOrder to Prog to preserve symbol order.
 - Add layout test (and fix bug that was putting everything in text section).

R=iant
CC=golang-codereviews
https://golang.org/cl/51260045

The hex dumps will diff better, and I hope they will avoid
a repeat of http://bugs.debian.org/716853.

The CL will probably show the testdata diffs as "binary",
but in fact the binary versions are being replaced by
textual hex dumps (output of hexdump -C).

R=iant
CC=golang-codereviews
https://golang.org/cl/51000044

Also fixes a dialgoogle test glitch after issue 6628 fix.

R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/50660044

On Plan 9, we can observe the following open file descriptors:

  0 r  c    0 (000000000000000a   0 00)     0        0 /dev/null
  1 rw |    0 (0000000001df6742   0 00) 65536       54 #|/data1
  2 rw |    0 (0000000001df6782   0 00) 65536        0 #|/data1
  3 rw M 1956 (0000000000d66dd2   0 00)  8192       12 /tmp/333163398
  4 r  c    0 (0000000000000001   0 00)     0      528 /dev/bintime
  5 r  M 1956 (0000000000d66dd1 854 00)  8192        0 /tmp/go-build843954301/os/exec/_test/exec.test
  6 r  M 1956 (0000000000d66dd1 854 00)  8192        0 /tmp/go-build843954301/os/exec/_test/exec.test
  7 r  M 1956 (0000000000d66dd1 854 00)  8192        0 /tmp/go-build843954301/os/exec/_test/exec.test
  8 r  M 1956 (0000000000d66dd1 854 00)  8192        0 /tmp/go-build843954301/os/exec/_test/exec.test
  9 r  M 1956 (0000000000d66dd1 854 00)  8192        0 /tmp/go-build843954301/os/exec/_test/exec.test
 10 r  M 1956 (0000000000d66dd1 854 00)  8192        0 /tmp/go-build843954301/os/exec/_test/exec.test
 11 r  c    0 (000000000000000f   0 00)     0       32 /dev/random
 12 r  M 1956 (0000000000d66dd1 854 00)  8192        0 /tmp/go-build843954301/os/exec/_test/exec.test
 13 r  c    0 (000000000000000a   0 00)     0        0 /dev/null
 14 rw |    0 (0000000001df6801   0 00) 65536        0 #|/data
 15 rw |    0 (0000000001df6802   0 00) 65536     1275 #|/data1

R=rsc, bradfitz, aram
CC=golang-codereviews
https://golang.org/cl/51420044