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

Currently it's always zero, but that is inconsistent with math.Pow
and also plain wrong.
This is a proposal for how it should be defined.
Fixes #7583.

LGTM=rsc
R=golang-codereviews, iant, gobot, rsc
CC=golang-codereviews
https://golang.org/cl/76940044

Fixes #7252.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/77990044

Fixes #7488.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/78050043

This rule not existing has been the source of many discussions
on golang-dev and on issues. We have stated publicly that it is
true, but we have never written it down. Write it down.

Fixes #6242.

LGTM=r, dan.kortschak, iant, dvyukov
R=golang-codereviews, r, dominik.honnef, dvyukov, dan.kortschak, iant, 0xjnml
CC=golang-codereviews
https://golang.org/cl/75130045

Fixes #6403

LGTM=rsc
R=iant, rsc
CC=golang-codereviews
https://golang.org/cl/72840044

ReadFrom should not return until it receives a non-nil error
or too many contiguous (0, nil)s from a given reader.
Currently it immediately returns if it receives one (0, nil).
Fixes #7611.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/76400048

Fixes #6902

LGTM=iant
R=iant, rsc
CC=golang-codereviews
https://golang.org/cl/78730049

bi is a slice and not an array, so bi[:] does not make much sense.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/79280043

LGTM=josharian, dan.kortschak
R=golang-codereviews, josharian, dan.kortschak
CC=golang-codereviews
https://golang.org/cl/75080043

It's a little bit waste to check if r is not a surrogate
code point because RuneError is not a surrogate code point.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/79230043

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/79080044

LGTM=dave
R=golang-codereviews, dave
CC=golang-codereviews
https://golang.org/cl/79120043

"min" and "max" in "case '{'" clause are fresh variables.
The variables defined in the outer scope never get value
other than 0.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/78750044

Currently Scan ignores an error returned from source if the number
of bytes source has read is 0.

Fixes #7594.

LGTM=gri
R=golang-codereviews, bradfitz, gri
CC=golang-codereviews
https://golang.org/cl/78120043

warning: src/cmd/ld/macho.c:595 sign-extended character constant
warning: src/cmd/ld/macho.c:595 sign-extended character constant
warning: src/cmd/ld/symtab.c:63 sign-extended character constant
warning: src/cmd/ld/symtab.c:63 sign-extended character constant

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/76580046

LGTM=dvyukov
R=dvyukov
CC=golang-codereviews
https://golang.org/cl/78410043

Fixes issue #6976.

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/72080044

They aren't segmented any more, at least with gc.
Also improve the comparison of goroutines and threads.
Fixes #7373.

LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/77950044

Prose referred to 'b', code used 'buf'.
Fixes #7601.

LGTM=dominik.honnef
R=golang-codereviews, dominik.honnef
CC=golang-codereviews
https://golang.org/cl/78470043

Revision 3ae4607a43ff introduced CONVNOP layers
to fix type checking issues arising from comparisons.
The added complexity made 8g run out of registers
when compiling an equality function in go.net/ipv6.

A similar issue occurred in test/sizeof.go on
amd64p32 with 6g.

Fixes #7405.

LGTM=khr
R=rsc, dave, iant, khr
CC=golang-codereviews
https://golang.org/cl/78100044

Changes adapted from original CL 15680044.

LGTM=iant
R=rsc, iant, dave
CC=golang-codereviews
https://golang.org/cl/76150044

LGTM=dave, iant
R=iant, khr, rsc, dave
CC=golang-codereviews
https://golang.org/cl/77960044

LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/78040043

LGTM=r, agl
R=agl, r
CC=golang-codereviews
https://golang.org/cl/77530044

LGTM=dave
R=dave, rsc
CC=golang-codereviews
https://golang.org/cl/78110043

Encoding.Decode() failed to detect trailing garbages if input contains "==" followed by garbage smaller than 3 bytes (for example, it failed to detect "x" in "AA==x"). This patch fixes the bug and adds a few tests.

LGTM=nigeltao
R=golang-codereviews, bradfitz, nigeltao
CC=golang-codereviews
https://golang.org/cl/75340044

This is a patch to apply the same change as CL 76610045.

LGTM=nigeltao
R=nigeltao
CC=golang-codereviews
https://golang.org/cl/77460044

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/78030043

Removes most uses of the REP prefix, which has a high startup cost.

LGTM=iant
R=golang-codereviews, iant, khr
CC=golang-codereviews
https://golang.org/cl/77920043

Rationale:
        It already is for scanning.
        It is accepted for complexes already, but doesn't work.
        It's analogous to %G and %E.
        C accepts it too, and we try to be roughly compatible.
Fixes #7518.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/77580044

CL 77580046 caused a data race issue with tests that assumes ReadAt
does not mutate receiver. This patch partially revert CL 77580046
to fix it.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/77900043

These test cases are redundant because TestSimpleFold tests
all possible rotations of test data, so no need to add
rotated strings.

Also updated the comment as it's guaranteed that SimpleFold
returns values in increasing order.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/77730043

UnreadRune should return an error if previous operation is not
ReadRune.

Fixes #7579.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/77580046

Also move generated code into a separate file,
because it's difficult to work with the file otherwise.

LGTM=khr
R=golang-codereviews, khr
CC=golang-codereviews
https://golang.org/cl/76080044

If runtime_BeforeFork splits stack, it will unsplit it
with spoiled g->stackguard. It leads to check failure in oldstack:

fatal error: stackfree: bad fixed size

runtime stack:
runtime.throw(0xadf3cd)
runtime.stackfree(0xc208040480, 0xfffffffffffff9dd, 0x1b00fa8)
runtime.oldstack()
runtime.lessstack()

goroutine 311 [stack unsplit]:
syscall.forkAndExecInChild(0xc20802eea0, 0xc208192c00, 0x5, 0x5, 0xc208072a80, ...)
syscall.forkExec(0xc20802ed80, 0x54, 0xc2081ccb40, 0x4, 0x4, ...)

Fixes #7567.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews, khr, rsc
https://golang.org/cl/77340045

A too large float constant is an error.
A too small float constant is rounded to zero.

Fixes #7419
Update #6902

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/76730046

"go doc" has been removed in CL 17799.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/77420045

utf8.RuneLen returns -1 for an invalid rune. In that case we
need to extend the internal buffer at least by 3 for \uFFFD.

Fixes #7577.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/77420044