If you get a stack of PCs from Callers, it would be expected
that every PC is immediately after a call instruction, so to find
the line of the call, you look up the line for PC-1.
CL 163550043 now explicitly documents that.

The most common exception to this is the top-most return PC
on the stack, which is the entry address of the runtime.goexit
function. Subtracting 1 from that PC will end up in a different
function entirely.

To remove this special case, make the top-most return PC
goexit+PCQuantum and then implement goexit in assembly
so that the first instruction can be skipped.

Fixes #7690.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/170720043

LGTM=rsc
R=golang-codereviews, bradfitz, rsc
CC=golang-codereviews
https://golang.org/cl/163540043

First draft now complete.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/170750043

This removes a bunch of ugly duplicate code.
The end goal is to factor the disassembly code
into cmd/internal/objfile too, so that pprof can use it,
but one step at a time.

LGTM=r, iant
R=r, alex.brainman, iant
CC=golang-codereviews
https://golang.org/cl/149400043

LGTM=iant, cmang
R=cmang, iant, rsc
CC=golang-codereviews
https://golang.org/cl/169760043

Originally traceback was only used for printing the stack
when an unexpected signal came in. In that case, the
initial PC is taken from the signal and should be used
unaltered. For the callers, the PC is the return address,
which might be on the line after the call; we subtract 1
to get to the CALL instruction.

Traceback is now used for a variety of things, and for
almost all of those the initial PC is a return address,
whether from getcallerpc, or gp->sched.pc, or gp->syscallpc.
In those cases, we need to subtract 1 from this initial PC,
but the traceback code had a hard rule "never subtract 1
from the initial PC", left over from the signal handling days.

Change gentraceback to take a flag that specifies whether
we are tracing a trap.

Change traceback to default to "starting with a return PC",
which is the overwhelmingly common case.

Add tracebacktrap, like traceback but starting with a trap PC.

Use tracebacktrap in signal handlers.

Fixes #7690.

LGTM=iant, r
R=r, iant
CC=golang-codereviews
https://golang.org/cl/167810044

Attempt to clear up confusion about how to turn
the PCs reported by Callers into the file and line
number people actually want.

Fixes #7690.

LGTM=r, chris.cs.guy
R=r, chris.cs.guy
CC=golang-codereviews
https://golang.org/cl/163550043

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/165090043

Stupid mistake in previous CL.

TBR=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/166880043

TBR=iant
CC=golang-codereviews
https://golang.org/cl/164180043

TBR=austin
CC=golang-codereviews
https://golang.org/cl/167820043

TBR=austin
CC=golang-codereviews
https://golang.org/cl/162420043

Fixes #8803.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/169720043

Fixes #9006.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/167800043

It now echoes what strconv.FormatFloat says.

Fixes #9012.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/169730043

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/160660046

Fixes #8861.
Fixes #8911.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/165780043

Fixes #8588.

LGTM=austin
R=austin
CC=golang-codereviews, khr
https://golang.org/cl/159700044

goprintf is a printf-like print for Go.
It is used in the code generated by 'defer print(...)' and 'go print(...)'.

Normally print(1, 2, 3) turns into

        printint(1)
        printint(2)
        printint(3)

but defer and go need a single function call to give the runtime;
they give the runtime something like goprintf("%d%d%d", 1, 2, 3).

Variadic functions like goprintf cannot be described in the new
type information world, so we have to replace it.

Replace with a custom function, so that defer print(1, 2, 3) turns
into

        defer func(a1, a2, a3 int) {
                print(a1, a2, a3)
        }(1, 2, 3)

(and then the print becomes three different printints as usual).

Fixes #8614.

LGTM=austin
R=austin
CC=golang-codereviews, r
https://golang.org/cl/159700043

In CL 160670043 the write function was changed
so a zero-length write is now allowed. This leads
the ExampleWriter_Init test to fail.

The reason is that Plan 9 preserves message
boundaries, while the os library expects systems
that don't preserve them. We have to ignore
zero-length writes so they will never turn into EOF.

This issue was previously discussed in CL 7406046.

LGTM=bradfitz
R=rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/163510043

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/166850043

Also a few other minor changes.

Fixes #8712.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/164150043

TBR=crawshaw
CC=golang-codereviews
https://golang.org/cl/162390043

LGTM=rsc, aram, minux
R=golang-codereviews, aram, minux, rsc
CC=golang-codereviews
https://golang.org/cl/162370045

Fixes #9007.

LGTM=iant, r
R=r, iant
CC=golang-codereviews
https://golang.org/cl/160670043

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/165800043

Fixes #8787.

LGTM=rsc
R=rsc, dvyukov
CC=golang-codereviews
https://golang.org/cl/153670043

No easy way to test (would have to actually trigger some routing
events from kernel) but the code is clearly wrong as written.
If the header says there is a submessage, we need to at least
skip over its bytes, not just continue to the next iteration.

Fixes #8203.

LGTM=r
R=r
CC=golang-codereviews, mikioh.mikioh, p
https://golang.org/cl/164140044

get -u now checks that remote repo paths match the
ones predicted by the import paths: if you are get -u'ing
rsc.io/pdf, it has to be checked out from the right location.
This is important in case the rsc.io/pdf redirect changes.

In some cases, people have good reasons to use
non-standard remote repos. Add -f flag to allow that.
The f can stand for force or fork, as you see fit.

Fixes #8850.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/164120043

Just to confirm the fix, by typing the follwing:
go test -run=TestLookupIPDeadline -dnsflood or
go test -run=TestLookupIPDeadline -dnsflood -tags netgo

Update #8602

LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/166740043

still need to do internal and import comments

LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://golang.org/cl/160600043

LGTM=adg, rsc
R=golang-codereviews, adg, bradfitz, dave, rsc
CC=golang-codereviews
https://golang.org/cl/164090044

This leaked into the CL I submitted for Minux,
because I was testing it.

TBR=adg
CC=golang-codereviews
https://golang.org/cl/159600044

NaCl creates /tmp. This lets the zip file populate it.

LGTM=adg
R=adg
CC=golang-codereviews
https://golang.org/cl/159600043

Revived from CL 15690048.

Fixes #5356.

LGTM=rsc
R=adg, dvyukov, rsc
CC=golang-codereviews
https://golang.org/cl/101400043

Add a short introductory section saying what most Go
programmers really need to know, which is that you
shouldn't have to read this document to understand
the behavior of your program.

LGTM=bradfitz, adg, tracey.brendan, iant, rsc, dsymonds
R=golang-codereviews, bradfitz, tracey.brendan, adg, iant, rsc, dsymonds
CC=golang-codereviews
https://golang.org/cl/158500043

Not a language change.

This is simply documenting the status quo which permits
builtin function names to be parenthesized in calls; e.g.,
both

        len(s)
and
        (((len)))(s)

are accepted by all compilers and go/types.

Changed the grammar by merging the details of BuiltinCall
with ordinary Calls. Also renamed the Call production to
Arguments which more clearly identifies that part of the
grammar and also matches better with its counterpart on
the declaration side (Parameters).

The fact that the first argument can be a type (for builtins)
or cannot be a type (for regular function calls) is expressed
in the prose, no need to make the grammar more complicated.

Fixes #9001.

LGTM=iant, r, rsc
R=r, rsc, iant, ken, dave
CC=golang-codereviews
https://golang.org/cl/160570043

TBR=rsc
R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/159590043

The test just doubled a certain number of times
and then gave up. On a mostly fast but occasionally
slow machine this may never make the test run
long enough to see the linear growth.

Change test to keep doubling until the first round
takes at least a full second, to reduce the effect of
occasional scheduling or other jitter.

The failure we saw had a time for the first round
of around 100ms.

Note that this test still passes once it sees a linear
effect, even with a very small total time.
The timeout here only applies to how long the execution
must be to support a reported failure.

LGTM=khr
R=khr
CC=golang-codereviews, rlh
https://golang.org/cl/164070043

Shorter and easier to read form for a common character.

LGTM=bradfitz
R=adg, bradfitz
CC=golang-codereviews, zimmski
https://golang.org/cl/162340043