If we don't know whether a path is a module path or a package path,
previously we would first try a module query for it, then fall back to
a package query.

If we are using a sequence of proxies with fallback (as will be the
default in Go 1.13), and the path is not actually a module path, that
initial module query will fail against the first proxy, then
immediately fall back to the next proxy in the sequence — even if the
query could have been satisfied by some other (prefix) module
available from the first proxy.

Instead, we now query the requested path as only one kind of path.
If we query it as a package path but it turns out to only exist as a
module, we can detect that as a PackageNotInModuleError with an
appropriate module path — we do not need to issue a second query to
classify it.

Fixes #31785

Change-Id: I581d44279196e41d1fed27ec25489e75d62654e3
Reviewed-on: https://go-review.googlesource.com/c/go/+/189517
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

modload.ListModules now wraps errors as module.ModuleError as
appropriate. The resulting errors always include the module path and
will include the version, if known.

'go mod download' no longer ignores errors reported by ListModules.
Previously, it started requesting module info, go.mod, and zip. Those
requests would fail, overwriting the original failure. They were
usually less descriptive.

'go mod download' with a module not in the build list (and no version
query) is now an error. Previously, this was silently ignored.

Fixes #30743

Change-Id: Icee8c1c6c5240de135a8b6ba42d6bbcdb757cdac
Reviewed-on: https://go-review.googlesource.com/c/go/+/189323
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

This reverts CL 162337.

Reason for revert: this introduces a regression

Fixes #33538
Updates #18929

Change-Id: Ib2320a840c6d3ec7912e8f414e933d04fbf11ab4
Reviewed-on: https://go-review.googlesource.com/c/go/+/189379Reviewed-by: Robert Griesemer <gri@golang.org>

These will need auditing per #32813 like a few others in go1.13.txt, but
in the meantime they break the API check for beta/RC releases.

Updates #32813
Updates #31912

Change-Id: I3b0501b46324ee6fc0985f84971b99b772c7e4a4
Reviewed-on: https://go-review.googlesource.com/c/go/+/189458Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

Change-Id: Id0a55674a16671aaee99182d9096a9263f7a80b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/189357Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: Ib0ae6e3e678dc7ace21b891e946ffc6bc2a78835
GitHub-Last-Rev: 8c6704ea8c032072ac339dc9d1c6ec78aec15b2a
GitHub-Pull-Request: golang/go#33534
Reviewed-on: https://go-review.googlesource.com/c/go/+/189378
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Document goroutine label inheritance. Goroutine labels are copied upon
goroutine creation and there is a test enforcing this, but it was not
mentioned in the docstrings for `Do` or `SetGoroutineLabels`.

Add notes to both of those functions' docstrings so it's clear that one
does not need to set labels as soon as a new goroutine is spawned if
they want to propagate tags.

Updates #32223
Updates #23458

Change-Id: Idfa33031af0104b884b03ca855ac82b98500c8b4
Reviewed-on: https://go-review.googlesource.com/c/go/+/189317Reviewed-by: Ian Lance Taylor <iant@golang.org>

In modload.Import, confirm that the import path does not start with
"cmd/" before calling QueryPackage, which returns a less helpful
error.

In load.loadPackageData, don't wrap errors with "unknown import path".
The wrapped error should always include the import path, and it's also
repeated in the PackageError wrapper.

Fixes #31031

Change-Id: I071efa22e3842c62831d096f888a8006811fe724
Reviewed-on: https://go-review.googlesource.com/c/go/+/189157
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

Fixes #33472

Change-Id: Iab69e69589f2e017f4cf9770858884b1a570c89e
Reviewed-on: https://go-review.googlesource.com/c/go/+/188799Reviewed-by: Andrew Bonventre <andybons@golang.org>

This mirrors the ELF fix in CL 188957. TestScript/version failed on
darwin after that change.

Fixes #31861

Change-Id: I4ce953ebec8dd5fa47e26d373c59d7e290b75a34
Reviewed-on: https://go-review.googlesource.com/c/go/+/189159
Run-TryBot: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #33433
Change-Id: Idb3961685a3cfd13ba26155a1d64fc24cc418fdb
Reviewed-on: https://go-review.googlesource.com/c/go/+/189117Reviewed-by: Ian Lance Taylor <iant@golang.org>

Explain wrapping and how to use Is and As in the package doc.

Explain "chain" in Is and As.

Updates #33364.

Change-Id: Ic06362106dbd129e33dd47e63176ee5355492086
Reviewed-on: https://go-review.googlesource.com/c/go/+/188737Reviewed-by: Rob Pike <r@golang.org>

A brief description at the top the Standard Library section of the
changes to support error wrapping.

Fixes #33365.

Change-Id: Id5a3b2fe148d9bfb949f2cfc9e5d8a1613a0e219
Reviewed-on: https://go-review.googlesource.com/c/go/+/188798Reviewed-by: Ian Lance Taylor <iant@golang.org>

The prototypes were truncated because they were on multiple lines
of the source file.

Copied from the STD lines for these functions in
https://svn.freebsd.org/base/stable/12/sys/kern/syscalls.master

Change-Id: I618a5444f1353aabee2758c06f86ad726185d19c
Reviewed-on: https://go-review.googlesource.com/c/go/+/188077Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

CL 188817 improved the error message for a nonexistent version in a dependency.
This CL locks in that improvement in a regression test.

Fixes #33474

Change-Id: I6246b4995adee966f24eaebe491d35830aea8370
Reviewed-on: https://go-review.googlesource.com/c/go/+/188977Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

Based on original fix from Mark Glines in golang.org/cl/186737

Fixes #31861

Change-Id: Ibd583a3aa8f8b8eefade998aa2ac757b55140937
Reviewed-on: https://go-review.googlesource.com/c/go/+/188957
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Fixes #33453.

Change-Id: If0aa48f953633690884ddcff033b3be6d1d66443
Reviewed-on: https://go-review.googlesource.com/c/go/+/188541Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

Change-Id: I103a21ae0be8feb9447fa277483b7c2a8b5807e7
Reviewed-on: https://go-review.googlesource.com/c/go/+/188540Reviewed-by: Andrew Bonventre <andybons@golang.org>
Reviewed-by: Richard Musiol <neelance@gmail.com>

The two methods act the same, so make their documentation similar so
that people don't think they act differently.

Change-Id: If224692ef50870faf855d789380a614d1e724132
Reviewed-on: https://go-review.googlesource.com/c/go/+/188137Reviewed-by: Rob Pike <r@golang.org>

CL #163058 moves interpretation of platform-specific errors to the
syscall package. Package syscall errors implement an Is method which
os.IsPermission etc. consult. This results in an unintended semantic
change to the os package predicate functions: The following program
now prints 'true' where it used to print 'false':

	package main
	import "os"
	type myError struct{ error }
	func (e myError) Is(target error) bool { return target == os.ErrPermission }
	func main() { println(os.IsPermission(myError{})) }

Change the os package error predicate functions to only examine syscall
errors, avoiding this semantic change.

This CL does retain one minor semantic change: On Plan9, os.IsPermission
used to return true for any error with text containing the string
"permission denied". It now only returns true for a syscall.ErrorString
containing that text.

Change-Id: I6b512b1de6ced46c2f1cc8d264fa2495ae7bf9f5
Reviewed-on: https://go-review.googlesource.com/c/go/+/188817
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

Updates #31449

Change-Id: I4d7075b20cd8171bc792e40b388f4215264a3317
Reviewed-on: https://go-review.googlesource.com/c/go/+/188819Reviewed-by: Filippo Valsorda <filippo@golang.org>

Fixes #27063

Change-Id: Iedd14fd614a3d79d1387b923a0f123c2bc9e0b33
Reviewed-on: https://go-review.googlesource.com/c/go/+/188763
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The compiler can crash if the compiled code tries to
unconditionally read from a nil pointer. This should cause
the generated binary to panic, not the compiler.

Fixes #33438

Change-Id: Ic8fa89646d6968e2cc4e27da0ad9286662f8bc49
Reviewed-on: https://go-review.googlesource.com/c/go/+/188760Reviewed-by: Austin Clements <austin@google.com>

Documents the work from:
* CL 163599
* CL 163737

which now uses the Request.Body's io.ReaderFrom implementation,
if available, and permits system level optimizations such as
"sendfile" to be used to transmit/upload the Body, which greatly
speeds up file uploads.

Updates #33396

Change-Id: I7b8315c4b3e57ad47bb9be2b0c838857875d4bd5
Reviewed-on: https://go-review.googlesource.com/c/go/+/188457Reviewed-by: Andrew Bonventre <andybons@golang.org>

It is unclear whether the current definition of os.IsTimeout is
desirable or not. Drop ErrTimeout for now so we can consider adding it
(or some other error) in a future release with a corrected definition.

Fixes #33411

Change-Id: I8b880da7d22afc343a08339eb5f0efd1075ecafe
Reviewed-on: https://go-review.googlesource.com/c/go/+/188758Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The Effective Go document references the crypto/cipher Block
interface, but the parameters' names are swapped. This change
alignes them to the crypto definition, to avoid confusion.

Fixes #33432

Change-Id: I8b9aac4dc6af3eec968bbc8f3ee5366b99016fcc
Reviewed-on: https://go-review.googlesource.com/c/go/+/188797Reviewed-by: Ian Lance Taylor <iant@golang.org>

There's a race here with fork/exec, enable the close-on-exec flag
for the new file descriptor.

Fixes #33405

Change-Id: If95bae97a52b7026a930bb3427e47bae3b0032ac
Reviewed-on: https://go-review.googlesource.com/c/go/+/188537
Run-TryBot: Baokun Lee <nototon@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: I33a5313ef10e8c88d9c12507573b385fa0843afe
GitHub-Last-Rev: 844d4351583e3f2e94d6420dcd50d50845d1b4cb
GitHub-Pull-Request: golang/go#33412
Reviewed-on: https://go-review.googlesource.com/c/go/+/188498Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

Fixes #33396

Change-Id: Id975a23b8d6555a3f19ef283fccbbe122f10acfe
Reviewed-on: https://go-review.googlesource.com/c/go/+/188477Reviewed-by: Andrew Bonventre <andybons@golang.org>

As discussed in
https://github.com/golang/go/issues/32463#issuecomment-506833421
the classification of deadline-based timeouts as "temporary" errors is a
historical accident. I/O timeouts used to be duration-based, so they
really were temporary--retrying a timed-out operation could succeed. Now
that they're deadline-based, timeouts aren't temporary unless you reset
the deadline.

Drop ErrTemporary from Go 1.13, since its definition is wrong. We'll
consider putting it back in Go 1.14 with a clear definition and
deprecate net.OpError.Temporary.

Fixes #32463

Change-Id: I70cda664590d8872541e17409a5780da76920891
Reviewed-on: https://go-review.googlesource.com/c/go/+/188398Reviewed-by: Jonathan Amsterdam <jba@google.com>

We shouldn't mask to desired registers if we haven't masked out all the
forbidden registers yet.  In this path we haven't masked out the nospill
registers yet. If the resulting mask contains only nospill registers, then
allocReg fails.

This can only happen on resultNotInArgs-marked instructions, which exist
only on the ARM64, MIPS, MIPS64, and PPC64 ports.

Maybe there's a better way to handle resultNotInArgs instructions.
But for 1.13, this is a low-risk fix.

Fixes #33355

Change-Id: I1082f78f798d1371bde65c58cc265540480e4fa4
Reviewed-on: https://go-review.googlesource.com/c/go/+/188178
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Also add other gccgo options.

This ports CL 45695 and CL 48592 from the gofrontend repo to the gc repo.

CL 45695 (partial entry, other parts out of date and not ported):

    cmd/go: gccgo: consistent results

    Pass the -fdebug-prefix-map and -gno-record-gcc-switches compiler
    options to gccgo to generate consistent results.

CL 48592:

    cmd/go: use gccSupportsFlag for -fsplit-stack

    Don't assume that all (or only) 386/amd64 compilers support
    -fsplit-stack.

Fixes #33108

Change-Id: I61f9e5a67e4fb059f26750e97621d27afa566ec2
Reviewed-on: https://go-review.googlesource.com/c/go/+/187824
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

This is a documentation-only change.

Fixes #28827

Change-Id: Ife9ab997809048784f35872b09905bc209a05eff
Reviewed-on: https://go-review.googlesource.com/c/go/+/188417Reviewed-by: Ian Lance Taylor <iant@golang.org>

Fixes #30401

Change-Id: I7b5035ffc7333c746d4e31563df26ff4f934dfc6
Reviewed-on: https://go-review.googlesource.com/c/go/+/188237Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>

Fixes #33141

Change-Id: I84a8b3496fc9396fd1c09ba9505697c34bdf7105
Reviewed-on: https://go-review.googlesource.com/c/go/+/188022
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

In preparation for the forthcoming spec changes for #6977.
While at it, modernize existing File example that dates
back all the way to commit 18c5b488.

Change-Id: Id10e4df0513e3de15bd58867222923eefa9473ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/187978Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Request.PostForm gets populated with form data for PATCH, POST, or PUT
http verbs.

Change-Id: I33065aa78a8470c4e9490aac830aa6f5963c61cb
Reviewed-on: https://go-review.googlesource.com/c/go/+/187821Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

An apparent typo caused us to re-check size instead.

Updates #29667

Change-Id: Icc1fb9cef1ba77b8490c8fbe6c343be06ff48d8d
Reviewed-on: https://go-review.googlesource.com/c/go/+/188020
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

ioutil.WriteFile always truncates the destination file to 0 before
writing, which is inappropriate for unsynchronized, idempotent,
fixed-size files such as the cache entry files here.

Instead, truncate the file only after writing it, so that a second
write will never (even temporarily!) remove the contents of a
preceding write.

Fixes #29667

Change-Id: I16a53ce79d8a23d23580511cb6abd062f54b65ef
Reviewed-on: https://go-review.googlesource.com/c/go/+/188157
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

Currently when we coalesce memory we make a sysHugePage call
(MADV_HUGEPAGE) to ensure freed and coalesced huge pages are treated as
such so the scavenger's assumptions about performance are more in line
with reality.

Unfortunately we do it way too often because we do it if there was any
change to the huge page count for the span we're coalescing into, not
taking into account that it could coalesce with its neighbors and not
actually create a new huge page.

This change makes it so that it only calls sysHugePage if the original
huge page counts between the span to be coalesced into and its neighbors
do not add up (i.e. a new huge page was created due to alignment). Calls
to sysHugePage will now happen much less frequently, as intended.

Updates #32828.

Change-Id: Ia175919cb79b730a658250425f97189e27d7fda3
Reviewed-on: https://go-review.googlesource.com/c/go/+/186926
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>