CL 157910047 introduced code to turn a node representing
a zeroed composite literal into N, the nil Node* pointer
(which represents any zero, not the Go literal nil).

That's great for assignments like x = T{}, but it doesn't work
when T{} is used in a value context like T{}.v or x == T{}.
Fix those.

Should have no effect on performance; confirmed.
The deltas below are noise (compare ns/op):

benchmark                          old ns/op      new ns/op      delta
BenchmarkBinaryTree17              2902919192     2915228424     +0.42%
BenchmarkFannkuch11                2597417605     2630363685     +1.27%
BenchmarkFmtFprintfEmpty           73.7           74.8           +1.49%
BenchmarkFmtFprintfString          196            199            +1.53%
BenchmarkFmtFprintfInt             213            217            +1.88%
BenchmarkFmtFprintfIntInt          336            356            +5.95%
BenchmarkFmtFprintfPrefixedInt     289            294            +1.73%
BenchmarkFmtFprintfFloat           415            416            +0.24%
BenchmarkFmtManyArgs               1281           1271           -0.78%
BenchmarkGobDecode                 10271734       10307978       +0.35%
BenchmarkGobEncode                 8985021        9079442        +1.05%
BenchmarkGzip                      410233227      412266944      +0.50%
BenchmarkGunzip                    102114554      103272443      +1.13%
BenchmarkHTTPClientServer          45297          44993          -0.67%
BenchmarkJSONEncode                19499741       19498489       -0.01%
BenchmarkJSONDecode                76436733       74247497       -2.86%
BenchmarkMandelbrot200             4273814        4307292        +0.78%
BenchmarkGoParse                   4024594        4028937        +0.11%
BenchmarkRegexpMatchEasy0_32       131            135            +3.05%
BenchmarkRegexpMatchEasy0_1K       328            333            +1.52%
BenchmarkRegexpMatchEasy1_32       115            117            +1.74%
BenchmarkRegexpMatchEasy1_1K       931            948            +1.83%
BenchmarkRegexpMatchMedium_32      216            217            +0.46%
BenchmarkRegexpMatchMedium_1K      72669          72857          +0.26%
BenchmarkRegexpMatchHard_32        3818           3809           -0.24%
BenchmarkRegexpMatchHard_1K        121398         121945         +0.45%
BenchmarkRevcomp                   613996550      615145436      +0.19%
BenchmarkTemplate                  93678525       93267391       -0.44%
BenchmarkTimeParse                 414            411            -0.72%
BenchmarkTimeFormat                396            399            +0.76%

Fixes #8947.

LGTM=r
R=r, dave
CC=golang-codereviews
https://golang.org/cl/162130043

CC=golang-codereviews
https://golang.org/cl/162140043

In theory both of these lines encode the same three fields:

        a,,c
        a,"",c

However, Postgres defines that when importing CSV, the unquoted
version is treated as NULL (missing), while the quoted version is
treated as a string value (empty string). If the middle field is supposed to
be an integer value, the first line can be imported (NULL is okay), but
the second line cannot (empty string is not).

Postgres's import command (COPY FROM) has an option to force
the unquoted empty to be interpreted as a string but it does not
have an option to force the quoted empty to be interpreted as a NULL.

From http://www.postgresql.org/docs/9.0/static/sql-copy.html:

        The CSV format has no standard way to distinguish a NULL
        value from an empty string. PostgreSQL's COPY handles this
        by quoting. A NULL is output as the NULL parameter string
        and is not quoted, while a non-NULL value matching the NULL
        parameter string is quoted. For example, with the default
        settings, a NULL is written as an unquoted empty string,
        while an empty string data value is written with double
        quotes (""). Reading values follows similar rules. You can
        use FORCE_NOT_NULL to prevent NULL input comparisons for
        specific columns.

Therefore printing the unquoted empty is more flexible for
imports into Postgres than printing the quoted empty.

In addition to making the output more useful with Postgres, not
quoting empty strings makes the output smaller and easier to read.
It also matches the behavior of Microsoft Excel and Google Drive.

Since we are here and making concessions for Postgres, handle this
case too (again quoting the Postgres docs):

        Because backslash is not a special character in the CSV
        format, \., the end-of-data marker, could also appear as a
        data value. To avoid any misinterpretation, a \. data value
        appearing as a lone entry on a line is automatically quoted
        on output, and on input, if quoted, is not interpreted as
        the end-of-data marker. If you are loading a file created by
        another application that has a single unquoted column and
        might have a value of \., you might need to quote that value
        in the input file.

Fixes #7586.

LGTM=bradfitz
R=bradfitz
CC=golang-codereviews
https://golang.org/cl/164760043

Per suggestion from rsc as a result of the dicussion of
(abandoned) CL 153110044.

Fixes #7192.

LGTM=r, rsc, iant
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/163050043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/163760043

Pool memory was only being released during the first GC after the first Put.

Put assumes that p.local != nil means p is on the allPools list.
poolCleanup (called during each GC) removed each pool from allPools
but did not clear p.local, so each pool was cleared by exactly one GC
and then never cleared again.

This bug was introduced late in the Go 1.3 release cycle.

Fixes #8979.

LGTM=rsc
R=golang-codereviews, bradfitz, r, rsc
CC=golang-codereviews, khr
https://golang.org/cl/162980043

test16 used to fail with gccgo.  The withoutRecoverRecursive
test would have failed in some possible implementations.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/151630043

LGTM=bradfitz, austin
R=austin
CC=bradfitz, golang-codereviews
https://golang.org/cl/158330045

Fixes #8348.

Trying to work around clang's dodgy support for .arch by reverting to the external assembler didn't work out so well. Minux had a much better solution to encode the instructions we need as .word directives which avoids .arch altogether.

I've confirmed with gdb that this form produces the expected machine code

Dump of assembler code for function crosscall_arm1:
   0x00000000 <+0>:	push	{r4, r5, r6, r7, r8, r9, r10, r11, r12, lr}
   0x00000004 <+4>:	mov	r4, r0
   0x00000008 <+8>:	mov	r5, r1
   0x0000000c <+12>:	mov	r0, r2
   0x00000010 <+16>:	blx	r5
   0x00000014 <+20>:	blx	r4
   0x00000018 <+24>:	pop	{r4, r5, r6, r7, r8, r9, r10, r11, r12, pc}

There is another compilation failure that blocks building Go with clang on arm

# ../misc/cgo/test
# _/home/dfc/go/misc/cgo/test
/tmp/--407b12.s: Assembler messages:
/tmp/--407b12.s:59: Error: selected processor does not support ARM mode `blx r0'
clang: error: assembler command failed with exit code 1 (use -v to see invocation)
FAIL	_/home/dfc/go/misc/cgo/test [build failed]

I'll open a new issue for that

LGTM=iant
R=iant, minux
CC=golang-codereviews
https://golang.org/cl/158180047

Set correct version number at Windows installer based on
Go's Mercurial tag.

Name                                     | Version
------------------------------------------------
Go Programming Language amd64 go1.3.3    | 1.3.3
Go Programming Language amd64 go1.2rc3   | 1.2
Go Programming Language amd64 go1.2beta1 | 1.2

Fixes #8239.

LGTM=adg
R=adg, c.emil.hessman, alex.brainman
CC=golang-codereviews
https://golang.org/cl/160950044

Partial undo, changes to ldelf.c retained.

Some platforms are still not working even with the integrated assembler disabled, will have to find another solution.

««« original CL description
cmd/cgo: disable clang's integrated assembler

Fixes #8348.

Clang's internal assembler (introduced by default in clang 3.4) understands the .arch directive, but doesn't change the default value of -march. This causes the build to fail when we use BLX (armv5 and above) when clang is compiled for the default armv4t architecture (which appears to be the default on all the distros I've used).

This is probably a clang bug, so work around it for the time being by disabling the integrated assembler when compiling the cgo assembly shim.

This CL also includes a small change to ldelf.c which was required as clang 3.4 and above generate more weird symtab entries.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/156430044
»»»

LGTM=minux
R=iant, minux
CC=golang-codereviews
https://golang.org/cl/162880044

Get rid of gocputicks(), it is no longer used.

LGTM=bradfitz, dave
R=golang-codereviews, bradfitz, dave, minux
CC=golang-codereviews
https://golang.org/cl/161110044

LGTM=rsc
R=minux, rsc
CC=golang-codereviews
https://golang.org/cl/158280043

Fixes #8721

LGTM=rsc
R=r, rsc
CC=golang-codereviews
https://golang.org/cl/155620045

This brings cmd/gc in line with the spec on this question.
It might break existing code, but that code was not conformant
with the spec.

Credit to Rémy for finding the broken code.

Fixes #6366.

LGTM=r
R=golang-codereviews, r
CC=adonovan, golang-codereviews, gri
https://golang.org/cl/129550043

Allows parsing some file formats that assign special
meaning to which stream data is found in.

Will do the same for compress/bzip2 once this is
reviewed and submitted.

Fixes #6486.

LGTM=nigeltao
R=nigeltao, dan.kortschak
CC=adg, bradfitz, golang-codereviews, r
https://golang.org/cl/159120044

Fixes #8348.

Clang's internal assembler (introduced by default in clang 3.4) understands the .arch directive, but doesn't change the default value of -march. This causes the build to fail when we use BLX (armv5 and above) when clang is compiled for the default armv4t architecture (which appears to be the default on all the distros I've used).

This is probably a clang bug, so work around it for the time being by disabling the integrated assembler when compiling the cgo assembly shim.

This CL also includes a small change to ldelf.c which was required as clang 3.4 and above generate more weird symtab entries.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/156430044

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/157220043

It has been failing periodically on Solaris/x64.
Change blockevent so it always records an event if we called
SetBlockProfileRate(1), even if the time delta is negative or zero.

Hopefully this will fix the test on Solaris.
Caveat: I don't actually know what the Solaris problem is, this
is just an educated guess.

LGTM=dave
R=dvyukov, dave
CC=golang-codereviews
https://golang.org/cl/159150043

Russ Cox pointed out that environment strings are not
required to be nil-terminated on Plan 9.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/159130044

Since CL 104570043 and 112720043, we are using the
nsec system call instead of /dev/bintime on Plan 9.

LGTM=rsc
R=rsc
CC=aram, golang-codereviews
https://golang.org/cl/155590043

Shell scripts depend on the old behavior too often.
It's too late to make this change.

LGTM=bradfitz
R=rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/161890044

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/154360048

This test was failing but did not break the build because it
was not run when -test.short was used.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/157150043

I came across this while debugging a GC problem in gccgo.
There is code in assignTo and cvtT2I that handles assignment
to all interface values.  It allocates an empty interface even
if the real type is a non-empty interface.  The fields are
then set for a non-empty interface, but the memory is recorded
as holding an empty interface.  This means that the GC has
incorrect information.

This is extremely unlikely to fail, because the code in the GC
that handles empty interfaces looks like this:

obj = nil;
typ = eface->type;
if(typ != nil) {
        if(!(typ->kind&KindDirectIface) || !(typ->kind&KindNoPointers))
                obj = eface->data;

In the current runtime the condition is always true--if
KindDirectIface is set, then KindNoPointers is clear--and we
always want to set obj = eface->data.  So the question is what
happens when we incorrectly store a non-empty interface value
in memory marked as an empty interface.  In that case
eface->type will not be a *rtype as we expect, but will
instead be a pointer to an Itab.  We are going to use this
pointer to look at a *rtype kind field.  The *rtype struct
starts out like this:

type rtype struct {
        size          uintptr
        hash          uint32            // hash of type; avoids computation in hash tables
        _             uint8             // unused/padding
        align         uint8             // alignment of variable with this type
        fieldAlign    uint8             // alignment of struct field with this type
        kind          uint8             // enumeration for C

An Itab always has at least two pointers, so on a
little-endian 64-bit system the kind field will be the high
byte of the second pointer.  This will normally be zero, so
the test of typ->kind will succeed, which is what we want.

On a 32-bit system it might be possible to construct a failing
case by somehow getting the Itab for an interface with one
method to be immediately followed by a word that is all ones.
The effect would be that the test would sometimes fail and the
GC would not mark obj, leading to an invalid dangling
pointer.  I have not tried to construct this test.

I noticed this in gccgo, where this error is much more likely
to cause trouble for a rather random reason: gccgo uses a
different layout of rtype, and in gccgo the kind field happens
to be the low byte of a pointer, not the high byte.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/155450044

The stack blowout can no longer happen,
but we can still test that too-complex regexps
are rejected.

Replacement for CL 162770043.

LGTM=iant, r
R=r, iant
CC=bradfitz, golang-codereviews
https://golang.org/cl/162860043

This is already tested by TestRE2Exhaustive, but the build has
not broken because that test is not run when using -test.short.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/155580043

Helps in environments with restricted support for unsafe.

LGTM=bradfitz
R=r, bradfitz
CC=dsymonds, golang-codereviews
https://golang.org/cl/156410044

https://golang.org/cl/152700045/ made it possible for struct literals assigned to globals to use <N> as the RHS. Normally, this is to zero out variables on first use. Because globals are already zero (or their linker initialized value), we just ignored this.

Now that <N> can occur from non-initialization code, we need to emit this code. We don't use <N> for initialization of globals any more, so this shouldn't cause any excessive zeroing.

Fixes #8961.

LGTM=rsc
R=golang-codereviews, rsc
CC=bradfitz, golang-codereviews
https://golang.org/cl/154540044

As we did with encoding, provide a trivial byte reader for
faster decoding. We can also reduce some of the copying
by doing the allocation all at once using a slightly different
interface from byte buffers.

benchmark                            old ns/op     new ns/op     delta
BenchmarkEndToEndPipe                13368         12902         -3.49%
BenchmarkEndToEndByteBuffer          5969          5642          -5.48%
BenchmarkEndToEndSliceByteBuffer     479485        470798        -1.81%
BenchmarkEncodeComplex128Slice       92367         92201         -0.18%
BenchmarkEncodeFloat64Slice          39990         38960         -2.58%
BenchmarkEncodeInt32Slice            30510         27938         -8.43%
BenchmarkEncodeStringSlice           33753         33365         -1.15%
BenchmarkDecodeComplex128Slice       232278        196704        -15.32%
BenchmarkDecodeFloat64Slice          150258        128191        -14.69%
BenchmarkDecodeInt32Slice            133806        115748        -13.50%
BenchmarkDecodeStringSlice           335117        300534        -10.32%

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/154360049

CC=golang-codereviews
https://golang.org/cl/156430043

This adds a Reset() to compress/flate's decompressor and plumbs that through
to compress/zlib and compress/gzip's Readers so callers can avoid large
allocations when performing many inflate operations. In particular this
preserves the allocation of the decompressor.hist buffer, which is 32kb and
overwritten as needed while inflating.

On the benchmark described in issue 6317, produces the following speedup on
my 2.3ghz Intel Core i7 MBP with go version devel +6b696a34e0af Sun Aug 03
15:14:59 2014 -0700 darwin/amd64:

blocked.text w/out patch vs blocked.text w/ patch:
benchmark           old ns/op      new ns/op      delta
BenchmarkGunzip     8371577533     7927917687     -5.30%

benchmark           old allocs     new allocs     delta
BenchmarkGunzip     176818         148519         -16.00%

benchmark           old bytes     new bytes     delta
BenchmarkGunzip     292184936     12739528      -95.64%

flat.text vs blocked.text w/patch:
benchmark           old ns/op      new ns/op      delta
BenchmarkGunzip     7939447827     7927917687     -0.15%

benchmark           old allocs     new allocs     delta
BenchmarkGunzip     90702          148519         +63.74%

benchmark           old bytes     new bytes     delta
BenchmarkGunzip     9959528       12739528      +27.91%

Similar speedups to those bradfitz saw in  https://golang.org/cl/13416045.

Fixes #6317.
Fixes #7950.

LGTM=nigeltao
R=golang-codereviews, bradfitz, dan.kortschak, adg, nigeltao, jamesr
CC=golang-codereviews
https://golang.org/cl/97140043

CC=golang-codereviews
https://golang.org/cl/161820043

This is a day 1 error in the flag package: It did not check
that a flag was set at most once on the command line.
Because user-defined flags may have more general
properties, the check applies only to the standard flag
types in this package: bool, string, etc.

Fixes #8960.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/156390043

Fixes #8959.

LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://golang.org/cl/161790043

Needed a %% to quote a percent in the format.

LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://golang.org/cl/156330043

select {
       case <- c:
       case <- c:
}

In this case, c.recvq lists two SudoGs which have the same G.
So we can't use the G as the key to dequeue the correct SudoG,
as that key is ambiguous.  Dequeueing the wrong SudoG ends up
freeing a SudoG that is still in c.recvq.

The fix is to use the actual SudoG pointer as the key.

LGTM=dvyukov
R=rsc, bradfitz, dvyukov, khr
CC=austin, golang-codereviews
https://golang.org/cl/159040043

Simple bug in argument processing: The final arg may
be the pipeline value, in which case it gets bound to the
fixed argument section. The code got that wrong. Easy
to fix.

Fixes #8950.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/161750043

Bytes buffers have more API and are a little slower. Since appending
is a key part of the path in encode, using a faster implementation
speeds things up measurably.
The couple of positive swings are likely garbage-collection related
since memory allocation looks different in the benchmark now.
I am not concerned by them.

benchmark                            old ns/op     new ns/op     delta
BenchmarkEndToEndPipe                6620          6388          -3.50%
BenchmarkEndToEndByteBuffer          3548          3600          +1.47%
BenchmarkEndToEndSliceByteBuffer     336678        367980        +9.30%
BenchmarkEncodeComplex128Slice       78199         71297         -8.83%
BenchmarkEncodeFloat64Slice          37731         32258         -14.51%
BenchmarkEncodeInt32Slice            26780         22977         -14.20%
BenchmarkEncodeStringSlice           35882         26492         -26.17%
BenchmarkDecodeComplex128Slice       194819        185126        -4.98%
BenchmarkDecodeFloat64Slice          120538        120102        -0.36%
BenchmarkDecodeInt32Slice            106442        107275        +0.78%
BenchmarkDecodeStringSlice           272902        269866        -1.11%

LGTM=ruiu
R=golang-codereviews, ruiu
CC=golang-codereviews
https://golang.org/cl/160990043

Use go generate to write better loops for decoding arrays,
just as we did for encoding. It doesn't help as much,
relatively speaking, but it's still noticeable.

benchmark                          old ns/op     new ns/op     delta
BenchmarkDecodeComplex128Slice     202348        184529        -8.81%
BenchmarkDecodeFloat64Slice        135800        120979        -10.91%
BenchmarkDecodeInt32Slice          121200        105149        -13.24%
BenchmarkDecodeStringSlice         288129        278214        -3.44%

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/154420044