1. On entry to a function, only zero the ambiguously live stack variables.
Before, we were zeroing all stack variables containing pointers.
The zeroing is pretty inefficient right now (issue 7624), but there are also
too many stack variables detected as ambiguously live (issue 7345),
and that must be addressed before deciding how to improve the zeroing code.
(Changes in 5g/ggen.c, 6g/ggen.c, 8g/ggen.c, gc/pgen.c)

Fixes #7647.

2. Make the regopt word-based liveness analysis preserve the
whole-variable liveness property expected by the garbage collection
bitmap liveness analysis. That is, if the regopt liveness decides that
one word in a struct needs to be preserved, make sure it preserves
the entire struct. This is particularly important for multiword values
such as strings, slices, and interfaces, in which all the words need
to be present in order to understand the meaning.
(Changes in 5g/reg.c, 6g/reg.c, 8g/reg.c.)

Fixes #7591.

3. Make the regopt word-based liveness analysis treat a variable
as having its address taken - which makes it preserved across
all future calls - whenever n->addrtaken is set, for consistency
with the gc bitmap liveness analysis, even if there is no machine
instruction actually taking the address. In this case n->addrtaken
is incorrect (a nicer way to put it is overconservative), and ideally
there would be no such cases, but they can happen and the two
analyses need to agree.
(Changes in 5g/reg.c, 6g/reg.c, 8g/reg.c; test in bug484.go.)

Fixes crashes found by turning off "zero everything" in step 1.

4. Remove spurious VARDEF annotations. As the comment in
gc/pgen.c explains, the VARDEF must immediately precede
the initialization. It cannot be too early, and it cannot be too late.
In particular, if a function call sits between the VARDEF and the
actual machine instructions doing the initialization, the variable
will be treated as live during that function call even though it is
uninitialized, leading to problems.
(Changes in gc/gen.c; test in live.go.)

Fixes crashes found by turning off "zero everything" in step 1.

5. Do not treat loading the address of a wide value as a signal
that the value must be initialized. Instead depend on the existence
of a VARDEF or the first actual read/write of a word in the value.
If the load is in order to pass the address to a function that does
the actual initialization, treating the load as an implicit VARDEF
causes the same problems as described in step 4.
The alternative is to arrange to zero every such value before
passing it to the real initialization function, but this is a much
easier and more efficient change.
(Changes in gc/plive.c.)

Fixes crashes found by turning off "zero everything" in step 1.

6. Treat wide input parameters with their address taken as
initialized on entry to the function. Otherwise they look
"ambiguously live" and we will try to emit code to zero them.
(Changes in gc/plive.c.)

Fixes crashes found by turning off "zero everything" in step 1.

7. An array of length 0 has no pointers, even if the element type does.
Without this change, the zeroing code complains when asked to
clear a 0-length array.
(Changes in gc/reflect.c.)

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/80160044

Zeroing the outputs makes sure that during function calls
in those functions we do not let the garbage collector
treat uninitialized values as pointers.

The garbage collector may still see uninitialized values
if a preemption occurs during the function prologue,
before the zeroing has had a chance to run.

This reduces the number of 'bad pointer' messages when
that runtime check is enabled, but it doesn't fix all of them,
so the check is still disabled.

It will also avoid leaks, although I doubt any of these were
particularly serious.

LGTM=iant, khr
R=iant, khr
CC=golang-codereviews
https://golang.org/cl/80850044

This was added by the one-pass CL (post Go 1.2)
so it can still be removed.

Removing because surely there will be new operations
added later, and we can't change the constant value
once we define it, so "last" is a bad concept to expose.

Nothing uses it.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/81160043

Fixes #6402

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/81340044

This patch includes fixes pointed out in CL 52140043, which was
originally written by john.gosset.

LGTM=minux.ma
R=golang-codereviews, minux.ma
CC=golang-codereviews
https://golang.org/cl/80320043

The garbage collector will scan these pointers,
so make sure they are initialized.

LGTM=bradfitz, khr
R=khr, bradfitz
CC=golang-codereviews
https://golang.org/cl/80960047

LGTM=iant, rsc
R=rsc, iant, mtj
CC=golang-codereviews
https://golang.org/cl/80260044

If you compile a program that has cgo LDFLAGS directives, those are exported to an environment variable to be used by subsequent compiler tool invocations. The linking phase when using the gccgo toolchain did not consider the envvar CGO_LDFLAGS's linking directives resulting in undefined references when using cgo+gccgo.

Fixes #7573

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/80780043

Generated by addca.

R=gobot
CC=golang-codereviews
https://golang.org/cl/80920048

GCC on OS X 10.6 doesn't support -Wuninitialized without -O.
Fixes #7492.

LGTM=iant
R=golang-codereviews, dave, iant
CC=golang-codereviews
https://golang.org/cl/72360045

m->moreargp/morebuf were not cleared in case of preemption and stack growing,
it can lead to persistent leaks of large memory blocks.

It seems to fix the sync.Pool finalizer failures. I've run the test 500'000 times
w/o a single failure; previously it would fail dozens of times.

Fixes #7633.
Fixes #7533.

LGTM=rsc
R=golang-codereviews
CC=golang-codereviews, khr, rsc
https://golang.org/cl/80480044

Update channel race annotations to support change in
cl/75130045: doc: allow buffered channel as semaphore without initialization
The new annotations are added only for channels with capacity 1.
Strictly saying it's possible to construct a counter-example that
will produce a false positive with capacity > 1. But it's hardly can
lead to false positives in real programs, at least I would like to see such programs first.
Any additional annotations also increase probability of false negatives,
so I would prefer to add them lazily.

LGTM=rsc
R=golang-codereviews
CC=golang-codereviews, iant, khr, rsc
https://golang.org/cl/76970043

Currently it's possible that bgsweep finishes before all spans
have been swept (we only know that sweeping of all spans has *started*).
In such case bgsweep may fail wake up runfinq goroutine when it needs to.
finq may still be nil at this point, but some finalizers may be queued later.
Make bgsweep to wait for sweeping to *complete*, then it can decide
whether it needs to wake up runfinq for sure.
Update #7533

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/75960043

If we set obj, then it will be enqueued for marking at the end of the scanning loop.
This is not necessary, since we've already marked it.
This can wait for 1.4 if you wish.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/80030043

Fixes #7519.

LGTM=adg, mikioh.mikioh
R=golang-codereviews, adg, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/80370043

Their priority was not documented.

Fixes #7571.

LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://golang.org/cl/80360043

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/80120044

Fixes #7627.

CL 61970044 changed the order in which .a files are passed to gccgo's link phase. However by reversing the order it caused gccgo to complain if both internal (liba.a) and external (liba_test.a) versions of a package were presented as the former would not contain all the necessary symbols, and the latter would duplicate symbols already defined.

This change ensures that all 'fake' targets remain at the top of the final link order which should be fine as a package compiled as an external test is a superset of its internal sibling.

Looking at how gcToolchain links tests I think this change now accurately mirrors those actions which present $WORK/_test before $WORK in the link order.

LGTM=iant
R=rsc, iant
CC=golang-codereviews, michael.hudson
https://golang.org/cl/80300043

Makes gc -x better.

LGTM=r
R=golang-codereviews, bradfitz, r
CC=golang-codereviews
https://golang.org/cl/73090043

LGTM=aram, rsc
R=aram, adg, bradfitz, rsc
CC=golang-codereviews
https://golang.org/cl/74750045

Almost all TODOS, but the structure is there and it has the details
from go1.3.txt, which is hereby deleted.

LGTM=dominik.honnef, adg
R=golang-codereviews, dominik.honnef, adg
CC=golang-codereviews
https://golang.org/cl/80240044

If someone configures a 'textwidth' in go files, vim will by default insert
newlines into long lines as you type, which breaks syntax and doesn't really
make sense for go code. This fixes the default.

LGTM=dsymonds
R=golang-codereviews, gobot, dsymonds
CC=golang-codereviews
https://golang.org/cl/76890046

LGTM=adg
R=adg
CC=golang-codereviews
https://golang.org/cl/80310043

Some platform that implements inp_localgroup-like shared internet
protocol control block group looks a bit sensitive about transport
layer protocol's address:port reuse. Sometimes it rejects a TCP SYN
packet using TCP RST, and sometimes silence.

For now, until test case refactoring, we admit few Dial failures on
TestTCPConcurrentAccept as a workaround.

Update #7400
Update #7541

LGTM=jsing
R=jsing
CC=golang-codereviews
https://golang.org/cl/75920043

The previous fix CL 69340044 still leaves a possibility of it.
This CL prevents the kernel, especially DragonFly BSD, from
performing unpredictable asynchronous connection establishment
on stream-based transport layer protocol sockets.

Update #7541
Update #7474

LGTM=jsing
R=jsing
CC=golang-codereviews
https://golang.org/cl/75930043

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/80250043

LGTM=josharian
R=golang-codereviews, josharian
CC=golang-codereviews
https://golang.org/cl/80220043

Fixes windows/amd64 build.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/79470046

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/79890046

Disable it until it's debugged so it doesn't hide other real
problems on Windows. The test was known to be unreliable
anyway (which is why it only needed 1 of 20 runs to pass), but
apparently it never passes on Windows. Figure out why later.

Update #7634

LGTM=alex.brainman
R=adg, alex.brainman
CC=golang-codereviews
https://golang.org/cl/80110043

See http://golang.org/s/go13heapdump for the file format.

LGTM=rsc
R=rsc, bradfitz, dvyukov, khr
CC=golang-codereviews
https://golang.org/cl/37540043

TBR=rsc
CC=golang-codereviews
https://golang.org/cl/80090043

Change two-bit stack map entries to encode:
0 = dead
1 = scalar
2 = pointer
3 = multiword

If multiword, the two-bit entry for the following word encodes:
0 = string
1 = slice
2 = iface
3 = eface

That way, during stack scanning we can check if a string
is zero length or a slice has zero capacity.  We can avoid
following the contained pointer in those cases.  It is safe
to do so because it can never be dereferenced, and it is
desirable to do so because it may cause false retention
of the following block in memory.

Slice feature turned off until issue 7564 is fixed.

Update #7549

LGTM=rsc
R=golang-codereviews, bradfitz, rsc
CC=golang-codereviews
https://golang.org/cl/76380043

The existing code did not have a clear notion of whether
memory has been actually reserved.  It checked based on
whether in 32-bit mode or 64-bit mode and (on GNU/Linux) the
requested address, but it confused the requested address and
the returned address.

LGTM=rsc
R=rsc, dvyukov
CC=golang-codereviews, michael.hudson
https://golang.org/cl/79610043

This the second part of making persistent HTTPS connections to
certain servers (notably Amazon) robust.

See the story in part 1: https://golang.org/cl/76400046/

This is the http Transport change that notes whether our
net.Conn.Read has ever seen an EOF. If it has, then we use
that as an additional signal to not re-use that connection (in
addition to the HTTP response headers)

Fixes #3514

LGTM=rsc
R=agl, rsc
CC=golang-codereviews
https://golang.org/cl/79240044

Update #3514

An io.Reader is permitted to return either (n, nil)
or (n, io.EOF) on EOF or other error.

The tls package previously always returned (n, nil) for a read
of size n if n bytes were available, not surfacing errors at
the same time.

Amazon's HTTPS frontends like to hang up on clients without
sending the appropriate HTTP headers. (In their defense,
they're allowed to hang up any time, but generally a server
hangs up after a bit of inactivity, not immediately.) In any
case, the Go HTTP client tries to re-use connections by
looking at whether the response headers say to keep the
connection open, and because the connection looks okay, under
heavy load it's possible we'll reuse it immediately, writing
the next request, just as the Transport's always-reading
goroutine returns from tls.Conn.Read and sees (0, io.EOF).

But because Amazon does send an AlertCloseNotify record before
it hangs up on us, and the tls package does its own internal
buffering (up to 1024 bytes) of pending data, we have the
AlertCloseNotify in an unread buffer when our Conn.Read (to
the HTTP Transport code) reads its final bit of data in the
HTTP response body.

This change makes that final Read return (n, io.EOF) when
an AlertCloseNotify record is buffered right after, if we'd
otherwise return (n, nil).

A dependent change in the HTTP code then notes whether a
client connection has seen an io.EOF and uses that as an
additional signal to not reuse a HTTPS connection. With both
changes, the majority of Amazon request failures go
away. Without either one, 10-20 goroutines hitting the S3 API
leads to such an error rate that empirically up to 5 retries
are needed to complete an API call.

LGTM=agl, rsc
R=agl, rsc
CC=golang-codereviews
https://golang.org/cl/76400046

The nproc and ndone fields are uint32.  This makes the type
consistent.

LGTM=minux.ma
R=golang-codereviews, minux.ma
CC=golang-codereviews
https://golang.org/cl/79340044

Strictly speaking, it's not necessary in example_test.go, as the
Rows.Close docs say that "If Next returns false, the Rows are closed
automatically". However, if the for loop breaks or returns early, it's
not obvious that you'll leak unless you explicitly call Rows.Close.

LGTM=bradfitz
R=bradfitz
CC=golang-codereviews, rsc
https://golang.org/cl/79330043

Structured Exception Handling (SEH) was the first way to handle
exceptions (memory faults, divides by zero) on Windows.
The S might as well stand for "stack-based": the implementation
interprets stack addresses in a few different ways, and it gets
subtly confused by Go's management of stacks. It's also something
that requires active maintenance during cgo switches, and we've
had bugs in that maintenance in the past.

We have recently come to believe that SEH cannot work with
Go's stack usage. See http://golang.org/issue/7325 for details.

Vectored Exception Handling (VEH) is more like a Unix signal
handler: you set it once for the whole process and forget about it.

This CL drops all the SEH code and replaces it with VEH code.
Many special cases and 7 #ifdefs disappear.

VEH was introduced in Windows XP, so Go on windows/386 will
now require Windows XP or later. The previous requirement was
Windows 2000 or later. Windows 2000 immediately preceded
Windows XP, so Windows 2000 is the only affected version.
Microsoft stopped supporting Windows 2000 in 2010.
See http://golang.org/s/win2000-golang-nuts for details.

Fixes #7325.

LGTM=alex.brainman, r
R=golang-codereviews, alex.brainman, stephen.gutekanst, dave
CC=golang-codereviews, iant, r
https://golang.org/cl/74790043

This has come up twice now. Redirect future questions
to the explanation in the issue tracker.

LGTM=iant, r
R=r, iant
CC=golang-codereviews
https://golang.org/cl/79550043