Fixes #7214

LGTM=rsc
R=golang-codereviews, bradfitz, rsc
CC=golang-codereviews, minux.ma
https://golang.org/cl/82080044

Native Client forbids jumps/calls to arbitrary locations and
enforces a particular alignement, which makes the Duff's device
ineffective.

LGTM=khr
R=rsc, dave, khr
CC=golang-codereviews
https://golang.org/cl/84400043

LGTM=mikioh.mikioh
R=golang-codereviews, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/84340043

Update #7362
Fixes #7377
Fixes #7570

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/83020043

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/83880043

LGTM=minux.ma
R=rsc, minux.ma
CC=golang-codereviews
https://golang.org/cl/84260043

Trying to make GODEBUG=gcdead=1 work with liveness
and in particular ambiguously live variables.

1. In the liveness computation, mark all ambiguously live
variables as live for the entire function, except the entry.
They are zeroed directly after entry, and we need them not
to be poisoned thereafter.

2. In the liveness computation, compute liveness (and deadness)
for all parameters, not just pointer-containing parameters.
Otherwise gcdead poisons untracked scalar parameters and results.

3. Fix liveness debugging print for -live=2 to use correct bitmaps.
(Was not updated for compaction during compaction CL.)

4. Correct varkill during map literal initialization.
Was killing the map itself instead of the inserted value temp.

5. Disable aggressive varkill cleanup for call arguments if
the call appears in a defer or go statement.

6. In the garbage collector, avoid bug scanning empty
strings. An empty string is two zeros. The multiword
code only looked at the first zero and then interpreted
the next two bits in the bitmap as an ordinary word bitmap.
For a string the bits are 11 00, so if a live string was zero
length with a 0 base pointer, the poisoning code treated
the length as an ordinary word with code 00, meaning it
needed poisoning, turning the string into a poison-length
string with base pointer 0. By the same logic I believe that
a live nil slice (bits 11 01 00) will have its cap poisoned.
Always scan full multiword struct.

7. In the runtime, treat both poison words (PoisonGC and
PoisonStack) as invalid pointers that warrant crashes.

Manual testing as follows:

- Create a script called gcdead on your PATH containing:

        #!/bin/bash
        GODEBUG=gcdead=1 GOGC=10 GOTRACEBACK=2 exec "$@"
- Now you can build a test and then run 'gcdead ./foo.test'.
- More importantly, you can run 'go test -short -exec gcdead std'
   to run all the tests.

Fixes #7676.

While here, enable the precise scanning of slices, since that was
disabled due to bugs like these. That now works, both with and
without gcdead.

Fixes #7549.

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/83410044

LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/83910043

runtime.Version() requires a trailing "+" when
tree had local modifications at time of build.

Fixes #7701

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/84040045

The garbage collector poison pointers
(0x6969696969696969 and 0x6868686868686868)
are malformed addresses on amd64.
That is, they are not 48-bit addresses sign extended
to 64 bits. This causes a different kind of hardware fault
than the usual 'unmapped page' when accessing such
an address, and OS X 10.9.2 sends the resulting SIGSEGV
incorrectly, making it look like it was user-generated
rather than kernel-generated and does not include the
faulting address. This means that in GODEBUG=gcdead=1
mode, if there is a bug and something tries to dereference
a poisoned pointer, the runtime delivers the SIGSEGV to
os/signal and returns to the faulting code, which faults
again, causing the process to hang instead of crashing.

Fix by rewriting "user-generated" SIGSEGV on OS X to
look like a kernel-generated SIGSEGV with fault address
0xb01dfacedebac1e.

I chose that address because (1) when printed in hex
during a crash, it is obviously spelling out English text,
(2) there are no current Google hits for that pointer,
which will make its origin easy to find once this CL
is indexed, and (3) it is not an altogether inaccurate
description of the situation.

Add a test. Maybe other systems will break too.

LGTM=khr
R=golang-codereviews, khr
CC=golang-codereviews, iant, ken
https://golang.org/cl/83270049

Delaying the runtime.throw until here will print more information.
In particular it will print the signal and code values, which means
it will show the fault address.

The canpanic checks were added recently, in CL 75320043.
They were just not added in exactly the right place.

LGTM=iant
R=dvyukov, iant
CC=golang-codereviews
https://golang.org/cl/83980043

Brad has been asking for this for a while.
I have resisted because I wanted to find a more general way to
do this, one that would keep the performance of code introducing
variables the same as the performance of code that did not.
(See golang.org/issue/3512#c20).

I have not found the more general way, and recent changes to
remove ambiguously live temporaries have blown away the
property I was trying to preserve, so that's no longer a reason
not to make the change.

Fixes #3512.

LGTM=iant
R=iant
CC=bradfitz, golang-codereviews, khr, r
https://golang.org/cl/83740044

Fixes #7476.

LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/84000043

Fixes #7385.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/84010044

Cuts hello world by 70kB, because we don't write
those names into the symbol table.

Update #6853

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/80370045

Fixes #6769.

LGTM=bradfitz
R=bgarcia, rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/84220044

Fixes #7639.

LGTM=rsc
R=r, adg, rsc
CC=golang-codereviews
https://golang.org/cl/81240043

Fixes #7271.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/84170043

This is just testing the status quo, so that any future attempt
to change it will make the test break and redirect the person
making the change to look at issue 6027.

Fixes #6027.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/83930046

Supports all the current GNU tar sparse formats, including the
old GNU format and the GNU PAX format versions 0.0, 0.1, and 1.0.
Fixes #3864.

LGTM=rsc
R=golang-codereviews, dave, gobot, dsymonds, rsc
CC=golang-codereviews
https://golang.org/cl/64740043

Generated by addca.

R=gobot
CC=golang-codereviews
https://golang.org/cl/81400045

The software floating point runs with m->locks++
to avoid being preempted; recognize this case in panic
and undo it so that m->locks is maintained correctly
when panicking.

Fixes #7553.

LGTM=dvyukov
R=golang-codereviews, dvyukov
CC=golang-codereviews
https://golang.org/cl/84030043

Fixes #7682

LGTM=adg
R=golang-codereviews, adg
CC=dsymonds, golang-codereviews, iant
https://golang.org/cl/83800043

The old limit of 5 was chosen because we didn't actually know how
many bytes of arguments there were; 5 was a halfway point between
printing some useful information and looking ridiculous.

Now we know how many bytes of arguments there are, and we stop
the printing when we reach that point, so the "looking ridiculous" case
doesn't happen anymore: we only print actual argument words.
The cutoff now serves only to truncate very long (but real) argument lists.

In multiple debugging sessions recently (completely unrelated bugs)
I have been frustrated by not seeing more of the long argument lists:
5 words is only 2.5 interface values or strings, and not even 2 slices.
Double the max amount we'll show.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews, iant, r
https://golang.org/cl/83850043

The data field is the generic array that acts as a standin
for the keys and values arrays for the generic runtime code.
We want to substitute the keys and values arrays for the data
array, not just add keys and values in addition to it.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/81160044

Fixes #7550.

LGTM=iant
R=golang-codereviews, iant, josharian
CC=golang-codereviews
https://golang.org/cl/83520043

Darwin 10.6 (gcc 4.2) and some older versions of gcc default to C90 mode, not C99 mode. Silence the warning.

LGTM=aram, iant
R=golang-codereviews, aram, iant
CC=golang-codereviews
https://golang.org/cl/83090050

There is no way to call them from outside the net package.
They are used to implement UCPConn.ReadMsgUDP and similar.

LGTM=mikioh.mikioh
R=golang-codereviews, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/83730044

Fixes #7693.

pack.go:347: possible formatting directive in Fatal call

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/83310045

Fixes #7683

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/83080048

Submitted accidentally in CL 83630044.
Fixes various builds.

TBR=khr
CC=golang-codereviews
https://golang.org/cl/83100047

Reduce footprint of liveness bitmaps by about 5x.

1. Mark all liveness bitmap symbols as 4-byte aligned
(they were aligned to a larger size by default).

2. The bitmap data is a bitmap count n followed by n bitmaps.
Each bitmap begins with its own count m giving the number
of bits. All the m's are the same for the n bitmaps.
Emit this bitmap length once instead of n times.

3. Many bitmaps within a function have the same bit values,
but each call site was given a distinct bitmap. Merge duplicate
bitmaps so that no bitmap is written more than once.

4. Many functions end up with the same aggregate bitmap data.
We used to name the bitmap data funcname.gcargs and funcname.gclocals.
Instead, name it gclocals.<md5 of data> and mark it dupok so
that the linker coalesces duplicate sets. This cut the bitmap
data remaining after step 3 by 40%; I was not expecting it to
be quite so dramatic.

Applied to "go build -ldflags -w code.google.com/p/go.tools/cmd/godoc":

                bitmaps           pclntab           binary on disk
before this CL  1326600           1985854           12738268
4-byte align    1154288 (0.87x)   1985854 (1.00x)   12566236 (0.99x)
one bitmap len   782528 (0.54x)   1985854 (1.00x)   12193500 (0.96x)
dedup bitmap     414748 (0.31x)   1948478 (0.98x)   11787996 (0.93x)
dedup bitmap set 245580 (0.19x)   1948478 (0.98x)   11620060 (0.91x)

While here, remove various dead blocks of code from plive.c.

Fixes #6929.
Fixes #7568.

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/83630044

warning: src/cmd/8g/ggen.c:35 non-interruptable temporary
warning: src/cmd/gc/walk.c:656 set and not used: l
warning: src/cmd/gc/walk.c:658 set and not used: l

LGTM=minux.ma
R=golang-codereviews, minux.ma
CC=golang-codereviews
https://golang.org/cl/83660043

1. Use n->alloc, not n->left, to hold the allocated temp being
passed from orderstmt/orderexpr to walk.

2. Treat method values the same as closures.

3. Use killed temporary for composite literal passed to
non-escaping function argument.

4. Clean temporaries promptly in if and for statements.

5. Clean temporaries promptly in select statements.
As part of this, move all the temporary-generating logic
out of select.c into order.c, so that the temporaries can
be reclaimed.

With the new temporaries, can re-enable the 1-entry
select optimization. Fixes issue 7672.

While we're here, fix a 1-line bug in select processing
turned up by the new liveness test (but unrelated; select.c:72).
Fixes #7686.

6. Clean temporaries (but not particularly promptly) in switch
and range statements.

7. Clean temporary used during convT2E/convT2I.

8. Clean temporaries promptly during && and || expressions.

---

CL 81940043 reduced the number of ambiguously live temps
in the godoc binary from 860 to 711.

CL 83090046 reduced the number from 711 to 121.

This CL reduces the number from 121 to 23.

15 the 23 that remain are in fact ambiguously live.
The final 8 could be fixed but are not trivial and
not common enough to warrant work at this point
in the release cycle.

These numbers only count ambiguously live temps,
not ambiguously live user-declared variables.
There are 18 such variables in the godoc binary after this CL,
so a total of 41 ambiguously live temps or user-declared
variables.

The net effect is that zeroing anything on entry to a function
should now be a rare event, whereas earlier it was the
common case.

This is good enough for Go 1.3, and probably good
enough for future releases too.

Fixes #7345.

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/83000048

Don't merge with the zero range, we may
end up zeroing more than we need.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/83430044

DragonFlyBSD, FreeBSD 9 and beyond, NetBSD 6 and beyond, and
Solaris (illumos) support AF_UNIX+SOCK_SEQPACKET socket.

LGTM=dave
R=golang-codereviews, dave
CC=golang-codereviews
https://golang.org/cl/83390043

net: make WriteTo, WriteToUnix and WriteMsgUnix fail when connectionless-mode UnixConn is already connected

This CL tries to fill the gap between Linux and other Unix-like systems
in the same way UDPConn already did.

Fixes #7677.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/83330045

Update #7656

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://golang.org/cl/82560043

Use Duff's device for zeroing.  Combine adjacent regions.

Update #7680
Update #7624

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/83200045

Botched during CL 83090046.

TBR=khr
CC=golang-codereviews
https://golang.org/cl/83070046