Following CL 68150047, the goos and goarch
variables are not currently set when the GOOS
and GOARCH environment variables are not set.

This made the content of the build tag to be
ignored in this case.

This CL sets goos and goarch to runtime.GOOS
and runtime.GOARCH when the GOOS and GOARCH
environments variables are not set.

LGTM=aram, bradfitz
R=golang-codereviews, aram, gobot, rsc, dave, bradfitz
CC=golang-codereviews, rsc
https://golang.org/cl/112490043

LGTM=josharian, adg
R=golang-codereviews, josharian, adg
CC=golang-codereviews
https://golang.org/cl/119110043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/117060043

This is bad for 2 reasons:
1. if the code under lock ever grows stack,
it will deadlock as stack growing acquires mheap lock.
2. It currently deadlocks with SetCPUProfileRate:
scavenger locks mheap, receives prof signal and tries to lock prof lock;
meanwhile SetCPUProfileRate locks prof lock and tries to grow stack
(presumably in runtime.unlock->futexwakeup). Boom.
Let's assume that it
Fixes #8407.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews, khr
https://golang.org/cl/112640043

With cl/112640043 TestCgoDeadlockCrash episodically print:
unexpected return pc for runtime.newstackcall
After adding debug output I see the following trace:

runtime: unexpected return pc for runtime.newstackcall called from 0xc208011b00
runtime.throw(0x414da86)
        src/pkg/runtime/panic.c:523 +0x77
runtime.gentraceback(0x40165fc, 0xba440c28, 0x0, 0xc208d15200, 0xc200000000, 0xc208ddfd20, 0x20, 0x0, 0x0, 0x300)
	src/pkg/runtime/traceback_x86.c:185 +0xca4
runtime.callers(0x1, 0xc208ddfd20, 0x20)
	src/pkg/runtime/traceback_x86.c:438 +0x98
mcommoninit(0xc208ddfc00)
	src/pkg/runtime/proc.c:369 +0x5c
runtime.allocm(0xc208052000)
	src/pkg/runtime/proc.c:686 +0xa6
newm(0x4017850, 0xc208052000)
	src/pkg/runtime/proc.c:933 +0x27
startm(0xc208052000, 0x100000001)
	src/pkg/runtime/proc.c:1011 +0xba
wakep()
	src/pkg/runtime/proc.c:1071 +0x57
resetspinning()
	src/pkg/runtime/proc.c:1297 +0xa1
schedule()
	src/pkg/runtime/proc.c:1366 +0x14b
runtime.gosched0(0xc20808e240)
	src/pkg/runtime/proc.c:1465 +0x5b
runtime.newstack()
	src/pkg/runtime/stack.c:891 +0x44d
runtime: unexpected return pc for runtime.newstackcall called from 0xc208011b00
runtime.newstackcall(0x4000cbd, 0x4000b80)
	src/pkg/runtime/asm_amd64.s:278 +0x6f

I suspect that it can happen on any stack split.
So don't unwind g0 stack.
Also, that comment is lying -- we can traceback w/o mcache,
CPU profiler does that.

LGTM=rsc
R=golang-codereviews
CC=golang-codereviews, khr, rsc
https://golang.org/cl/120040043

There are fields in the Addr that do not matter for the
purpose of deciding that the same word is already
in the current literal pool. Copy only the fields that
do matter.

This came up when comparing against the Go version
because the way it is invoked doesn't copy a few fields
(like node) that are never directly used by liblink itself.

Also remove a stray print that is not well-defined in
the new liblink. (Cannot use %D outside of %P, because
%D needs the outer Prog*.)

LGTM=minux
R=minux
CC=golang-codereviews
https://golang.org/cl/119000043

This matches Go's fmt.Printf instead of ANSI C's dumb rules.
It makes the -S output from C liblink match Go's liblink.

LGTM=minux
R=minux
CC=golang-codereviews
https://golang.org/cl/112600043

They do not, but pretend that they do.
The immediate need is that it breaks the new GC because
these are weird symbols as if with pointers but not necessary
pointer aligned.

LGTM=rsc
R=golang-codereviews, dave, josharian, khr, rsc
CC=golang-codereviews, iant, khr, rlh
https://golang.org/cl/116060043

R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/111560043

I've found this very useful for generating
good test case lists for -short mode for
the disassemblers.

Fixes #7959.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/98150043

Fixes #8398.

LGTM=chines
R=golang-codereviews, chines, josharian
CC=golang-codereviews
https://golang.org/cl/114140043

As pointed out by Elias Naur, the convention for Go runtime functions means this function should be named gothrow.

Discussion: https://golang.org/cl/115860045/#msg6

LGTM=dvyukov
R=golang-codereviews, dvyukov
CC=golang-codereviews
https://golang.org/cl/118120043

Currently they are scanned conservatively.
But there is no reason to scan them. C world must not contain
pointers into Go heap. Moreover, we don't have enough information
to emit write barriers nor update pointers there in future.
The immediate need is that it breaks the new GC because
these are weird symbols as if with pointers but not necessary
pointer aligned.

LGTM=rsc
R=golang-codereviews, rlh, rsc
CC=golang-codereviews, iant, khr
https://golang.org/cl/117000043

CL 117950044 updates vet to fix LEA* issue.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/112440043

In the runtime, we want to control where allocations happen.
In particular, we don't want the code implementing malloc to
itself trigger a malloc.  This change prevents the compiler
from inserting mallocs on our behalf (due to escaping declarations).

This check does not trigger on the current runtime code.

Note: Composite literals are still allowed.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/105280047

So we can tell from a binary which version of
Go built it.

LGTM=minux, rsc
R=golang-codereviews, minux, khr, rsc, dave
CC=golang-codereviews
https://golang.org/cl/117040043

LGTM=dave
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/112420044

This is more useful than panicking, since otherwise every caller needs
to do the length check before calling; some will forget, and have a
potential submarine crasher as a result. Other implementations of this
functionality do a length check.

This is backward compatible, except if someone has written code that
relies on this panicking with different length args. However, that was
not the case before Go 1.3 either.

Updates #7304.

LGTM=agl
R=agl, minux, hanwen
CC=golang-codereviews
https://golang.org/cl/118750043

In both cases we lie to malloc about the actual size that we need.
In panic we ask for less memory than we are going to use.
In slice we ask for more memory than we are going to use
(potentially asking for a fractional number of elements).
This breaks the new GC.

LGTM=khr
R=golang-codereviews, dave, khr
CC=golang-codereviews, rsc
https://golang.org/cl/116940043

LGTM=khr
R=golang-codereviews, dave, khr
CC=golang-codereviews, rsc
https://golang.org/cl/116950043

Rewrite gotos that violate Go's stricter rules.
Use uchar* instead of char* in a few places that aren't strings.
Remove dead opcross code from asm5.c.
Declare regstr (in both list6 and list8) static.

LGTM=minux, dave
R=minux, dave
CC=golang-codereviews
https://golang.org/cl/113230043

Even though pointers are 4 bytes the stack frame should be kept
a multiple of 8 bytes so that return addresses pushed on the stack
are properly aligned.

Fixes #8379.

LGTM=dvyukov, minux
R=minux, bradfitz, dvyukov, dave
CC=golang-codereviews
https://golang.org/cl/115840048

LGTM=rsc
R=rsc, dan.kortschak
CC=golang-codereviews, r
https://golang.org/cl/115840046

We might want to add a go/build.IsInternal(pkg string) bool
later, but this works for now.

LGTM=dave, rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/113300044

These correspond to 2 and 3 word fat copies/clears on 8g, which dominate usage in the stdlib. (70% of copies and 46% of clears are for 2 or 3 words.) I missed these in CL 111350043, which added 2 and 3 word benchmarks for 6g. A follow-up CL will optimize these cases.

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/115160043

LGTM=dvyukov
R=golang-codereviews, dvyukov
CC=golang-codereviews
https://golang.org/cl/118020043

I'm improving gccgo's detection of variables that are only set
but not used, and it triggers additional errors on this code.
The new gccgo errors are correct; gc seems to suppress them
due to the other, expected, errors.  This change uses the
variables so that no compiler will complain.

gccgo change is https://golang.org/cl/119920043 .

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/116050043

The gccgo compiler would fail this test.  The fix for gccgo is
https://golang.org/cl/116960043 .

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/118000043

GC thinks that it's an invalid pointer on plan9:
http://build.golang.org/log/f7da638a20544ef7f45e81f23fdbc4875044c296

LGTM=0intro
R=golang-codereviews, 0intro
CC=aram, golang-codereviews
https://golang.org/cl/113350043

benchmark                      old ns/op     new ns/op     delta
BenchmarkSelectUncontended     220           165           -25.00%
BenchmarkSelectContended       209           161           -22.97%
BenchmarkSelectProdCons        1042          904           -13.24%

But more importantly this change will allow
to get rid of free function in runtime.

Fixes #6494.

LGTM=rsc, khr
R=golang-codereviews, rsc, dominik.honnef, khr
CC=golang-codereviews, remyoudompheng
https://golang.org/cl/107670043

Fixes #8389.

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/111320044

This is a temporary change to see how far the
builder gets when it times out.

LGTM=aram, 0intro
R=0intro, aram
CC=golang-codereviews, mischief
https://golang.org/cl/111400043

subtract freed count before span gets merged during free.

LGTM=dvyukov
R=dmitry, dvyukov
CC=golang-codereviews
https://golang.org/cl/112450045

Fix virtual address of the start of the text segment
on amd64 Plan 9.

This issue has been partially fixed in cmd/add2line,
as part of CL 106460044, but we forgot to report the
change to cmd/objdump.

In the meantime, we also fixed the textStart address
in both cmd/add2line and cmd/objdump.

LGTM=aram, ality, mischief
R=rsc, mischief, aram, ality
CC=golang-codereviews, jas
https://golang.org/cl/117920043

LGTM=dvyukov
R=golang-codereviews, dvyukov
CC=golang-codereviews
https://golang.org/cl/111360045

Hook pre-commit runs before 'hg commit' command whereas hook precommit runs
after the user has entered commit message.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/106320043

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/105500043

Fixes #8347.

LGTM=dave
R=golang-codereviews, dave
CC=golang-codereviews
https://golang.org/cl/109600044

The CopyFat benchmarks were changed in CL 92760044. See CL 111350043 for discussion.

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/116000043

These benchmarks are important for performance. When compiling the stdlib:

* 77.1% of the calls to sgen (copyfat) are for 16 bytes; another 8.7% are for 24 bytes. (The next most common is 32 bytes, at 5.7%.)
* Over half the calls to clearfat are for 16 or 24 bytes.

LGTM=khr
R=golang-codereviews, khr
CC=golang-codereviews
https://golang.org/cl/111350043