Context.Alignof/Offsetsof/Sizeof now provide means
to customize the type checker for a given platform.

- provide Context.Offsetsof to specify the
  offsets of struct fields
- use the correct sizes for ints, uint, uintptrs
  in constant computations
- moved all size computations into separate file
  (sizes.go)
- fixed a bug with string constant slicing

R=adonovan, axwalk
CC=golang-dev
https://golang.org/cl/7363054

- imported objects don't have position information
- gc exported data contains non-exported objects at
  the top-level, guard against them
- better error message when dot-imports conflict
  with local declarations

R=adonovan, r
CC=golang-dev
https://golang.org/cl/7379052

R=adonovan, r
CC=golang-dev
https://golang.org/cl/7376055

pkg/go/doc: move BUG notes from Package.Bugs to the general Package.Notes field.
Removing .Bugs would break existing code so it's left in for now.

R=gri, gri, gary.burd, dsymonds, rsc, kevlar
CC=golang-dev
https://golang.org/cl/7341053

Fixes #4760.

R=golang-dev, minux.ma, bradfitz
CC=golang-dev
https://golang.org/cl/7312053

Separates the implementation of nanotime on 64-bit
version of Plan 9 from that on the 32-bit version.
The former uses a syscall.

R=rsc, rminnich, ality
CC=golang-dev
https://golang.org/cl/7379051

R=dr.volker.dobler
CC=golang-dev
https://golang.org/cl/7398049

Also restores the checking of _test.go files, which disappeared
as a result of the package-at-a-time change.
Fixes #4895.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7399051

Functions for representing network connections as files
and vice versa, on Plan 9.

Representing network connections as files is not so
straight-forward, because a network connection on Plan 9
is represented by a host of files rather than a single
file descriptor (as is the case on UNIX). We use the
type system to distinguish between listeners and
connections, returning the control file in the former
case and the data file in the latter case.

R=rsc, rminnich, ality, akumar, bradfitz
CC=golang-dev
https://golang.org/cl/7235068

Then mark them with a build tag so they're not compiled into the binary.
They are called test_*.go rather than *_test.go because they are not
for go test. Use make test to test the command.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/7377052

Fixes #4781.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7365056

Composite literals using the &T{} form were incorrectly
exported, leading to weird errors at import time.

Fixes #4879.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7395054

This avoids an allocation when closures are used
as "macros", in Walk idioms, or as argument to defer.

benchmark                old ns/op    new ns/op    delta
BenchmarkSearchWrappers       1171          354  -69.77%
BenchmarkCallClosure             3            3  -12.54%
BenchmarkCallClosure1          119            7  -93.95%
BenchmarkCallClosure2          183           74  -59.18%
BenchmarkCallClosure3          187           75  -59.57%
BenchmarkCallClosure4          187           76  -58.98%

Compared to Go 1:
benchmark                  old ns/op    new ns/op    delta
BenchmarkSearchWrappers         3208          354  -88.97%

Fixes #3520.

R=daniel.morsing, bradfitz, minux.ma, dave, rsc
CC=golang-dev
https://golang.org/cl/7397056

Fixes #4858.

R=golang-dev, bradfitz, r, rsc
CC=golang-dev
https://golang.org/cl/7387044

Fixes #4903.

R=golang-dev, daniel.morsing, dave, r
CC=golang-dev
https://golang.org/cl/7388056

Fixes #4810.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/7401050

Fixes #3747.

Update #4912
This CL adds gotype into .5 object file.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7376054

Syscalls return `-1' on error and the representation is always
32-bits. The `$-1' literal in 64-bit assembly is always the
64-bit representation. So this change makes sure that we
always do a 32-bit comparison when checking for error.
Also makes sure that in the error case, we return a 64-bit
`-1' from runtime.seek.

Fixes the arithmetic for handling the error-string in
runtime.Syscall6.

R=golang-dev, rminnich, rsc, ality, minux.ma
CC=golang-dev
https://golang.org/cl/7399052

sigprocmask() is process-wide on darwin, so two concurrent
libcgo_sys_thread_start() can result in all signals permanently
blocked, which in particular blocks handling of nil derefs.
Fixes #4833.

R=golang-dev, dave, rsc
CC=golang-dev
https://golang.org/cl/7324058

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/7372048

Don't reference the non-portable syscall.Signal(0).

Maybe they'll pass too. Untested. plan9 bit from
Akshat Kumar.

R=golang-dev, akumar
CC=golang-dev
https://golang.org/cl/7370049

Now that the type information is in TYPE instructions
that are not rewritten by the optimization passes,
we don't have to try to preserve the type information
(no longer) attached to MOV instructions.

R=ken2
CC=golang-dev
https://golang.org/cl/7402054

This changeset adds a mostly-precise garbage collection of channels.
The garbage collection support code in the linker isn't recognizing
channel types yet.

Fixes issue http://stackoverflow.com/questions/14712586/memory-consumption-skyrocket

R=dvyukov, rsc, bradfitz
CC=dave, golang-dev, minux.ma, remyoudompheng
https://golang.org/cl/7307086

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7393059

Regenerate cmd/gc/builtin.c.
Fixes #4908.

R=rsc
CC=golang-dev
https://golang.org/cl/7383053

Now that vet does typechecking, it should use only pkg.gofiles, instead
of pkg.allgofiles. Ignored files should not be checked by vet, because
they wouldn't typecheck.

Fixes #4906.

R=rsc, r
CC=golang-dev
https://golang.org/cl/7401051

R=ken2
CC=golang-dev
https://golang.org/cl/7365057

The type information is (and for years has been) included
as an extra field in the address chunk of an instruction.
Unfortunately, suppose there is a string at a+24(FP) and
we have an instruction reading its length. It will say:

        MOVQ x+32(FP), AX

and the type of *that* argument is int (not slice), because
it is the length being read. This confuses the picture seen
by debuggers and now, worse, by the garbage collector.

Instead of attaching the type information to all uses,
emit an explicit list of TYPE instructions with the information.
The TYPE instructions are no-ops whose only role is to
provide an address to attach type information to.

For example, this function:

        func f(x, y, z int) (a, b string) {
                return
        }

now compiles into:

        --- prog list "f" ---
        0000 (/Users/rsc/x.go:3) TEXT    f+0(SB),$0-56
        0001 (/Users/rsc/x.go:3) LOCALS  ,
        0002 (/Users/rsc/x.go:3) TYPE    x+0(FP){int},$8
        0003 (/Users/rsc/x.go:3) TYPE    y+8(FP){int},$8
        0004 (/Users/rsc/x.go:3) TYPE    z+16(FP){int},$8
        0005 (/Users/rsc/x.go:3) TYPE    a+24(FP){string},$16
        0006 (/Users/rsc/x.go:3) TYPE    b+40(FP){string},$16
        0007 (/Users/rsc/x.go:3) MOVQ    $0,b+40(FP)
        0008 (/Users/rsc/x.go:3) MOVQ    $0,b+48(FP)
        0009 (/Users/rsc/x.go:3) MOVQ    $0,a+24(FP)
        0010 (/Users/rsc/x.go:3) MOVQ    $0,a+32(FP)
        0011 (/Users/rsc/x.go:4) RET     ,

The { } show the formerly hidden type information.
The { } syntax is used when printing from within the gc compiler.
It is not accepted by the assemblers.

The same type information is now included on global variables:

0055 (/Users/rsc/x.go:15) GLOBL   slice+0(SB){[]string},$24(AL*0)

This more accurate type information fixes a bug in the
garbage collector's precise heap collection.

The linker only cares about globals right now, but having the
local information should make things a little nicer for Carl
in the future.

Fixes #4907.

R=ken2
CC=golang-dev
https://golang.org/cl/7395056

See also CL 7383051 for details.

R=adonovan, bradfitz
CC=golang-dev
https://golang.org/cl/7378063

It's accessed without mutex protection
in a different goroutine from the one that
sets it.

Also make sure that Client.Call after Client.Close
will reliably return ErrShutdown, and that clients
see ErrShutdown rather than io.EOF when appropriate.

Suggestions welcome for a way to reliably test
the mutex issue.

R=r, iant
CC=golang-dev
https://golang.org/cl/7338045

This CL addresses the comments on CL 7368046 that I've overlooked.

Update #4866.

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/7369052

Fixes #4888.

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/7383051

Added the command line flag -ex to godoc to print examples in
text output.

Samples from the generated output:

$ godoc -ex strings Index
...
func Index(s, sep string) int
    Index returns the index of the first instance of sep in s, or -1 if sep
    is not present in s.

    Example:
        fmt.Println(strings.Index("chicken", "ken"))
        fmt.Println(strings.Index("chicken", "dmr"))
        // Output:
        // 4
        // -1
...

$ godoc -ex container/heap
...
package heap
    import "container/heap"

    Package heap provides heap operations for any type that implements
    heap.Interface. A heap is a tree with the property that each node is the
    minimum-valued node in its subtree.

    Example:
        // This example demonstrates an integer heap built using the heap interface.
        package heap_test

        import (
            "container/heap"
            "fmt"
        ...

    Example:
        // This example demonstrates a priority queue built using the heap interface.
        package heap_test

        import (
            "container/heap"
            "fmt"
        )
...

Fixes #3587.

R=golang-dev, minux.ma, adg, rsc, gri
CC=golang-dev
https://golang.org/cl/7356043

R=golang-dev, kamil.kisiel, bradfitz
CC=golang-dev
https://golang.org/cl/7369049

Made possible by go/types, as long as the package type-checks OK.

Fixes #4684.

R=golang-dev
CC=golang-dev
https://golang.org/cl/7407045

The heuristics for BitLen of a product of randomly generated primes
are wrong, and the generated candidates never match the required
size for nprimes > 10. This corner case is not expected to be used in
practice.

R=agl
CC=golang-dev
https://golang.org/cl/7397052

Executable heap is gone on Unix!

R=golang-dev, dave, bradfitz
CC=golang-dev
https://golang.org/cl/7405045

Or gcc (-fPIC) will complain:
cmd/dist/unix.c: In function ‘cansse2’
cmd/dist/unix.c:774: error: can't find a register in class ‘BREG’ while reloading ‘asm’
cmd/dist/unix.c:774: error: ‘asm’ operand has impossible constraints

This affects bootstrapping on native Darwin/386 where all code is
compiled with -fPIC.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7394047

This CL allows to receive network interface arrival and depature
notifications through routing sockets on BSD variants. So far
Darwin doesn't support this feature.

Also does small simplification.

Update #4866.

R=golang-dev, lucio.dere, dave
CC=golang-dev
https://golang.org/cl/7365055

Update #4866.

R=golang-dev
CC=golang-dev
https://golang.org/cl/7382053