Some recent failures in gccgo on linux/ppc64 identified
an error in buildmodeInit when buildmode=c-archive.
A fix went into gofrontend, and this is the
corresponding change for master. This change also includes
two other updates related to gccgo in this function that
were in the file from gofrontend but missing from master.
Updates #29046
Change-Id: I9a894e7d728e31fb9e9344cd61d50408df7faf4a
Reviewed-on: https://go-review.googlesource.com/c/152160
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The original value of 65537 consistently caused the test to fail on
Solaris. The new value of 131073 consistently lets the test pass.
Change-Id: If1a76ab89aa8f661ea049113addd04b23a116534
Reviewed-on: https://go-review.googlesource.com/c/152164
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
In CL 129061, a check was added for patterns that reference
nonexistent local directories. While this prevented unnecessary
network lookups (fixing #26874), it caused "go list -e" to exit with
an error instead of listing packages with error messages.
This change avoids the network lookup and does not exit for these
kinds of packages. Errors are still reported by
internal/load.LoadImport for packages that don't exist.
Fixes#28023
Change-Id: I0a648269e437aed3a95bfb05461a397264f3793f
Reviewed-on: https://go-review.googlesource.com/c/151800
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
The type checker may be called incrementally (by repeatedly calling
Checker.Files), for instance when adding _test.go files to a set of
already checked files.
The existing code reset a cache of (already computed) interface
information with each Checker.Files call, causing interfaces to be
recomputed in some cases, albeit with different receiver information
(see comments in this CL for details).
Don't reset the interface cache to avoid this problem.
While adding a test case, also factor out some common testing logic.
Fixes#29029.
Change-Id: I2e2d6d6bb839b3a76522fbc4ba7355c71d3bb80b
Reviewed-on: https://go-review.googlesource.com/c/152259
Reviewed-by: Alan Donovan <adonovan@google.com>
Fix unannounced trailers when body is empty and without announced trailers.
Fixes#29031
Change-Id: If49951a42fe56d4be4436a999627db4c2678659d
GitHub-Last-Rev: 3469adc8f5
GitHub-Pull-Request: golang/go#29032
Reviewed-on: https://go-review.googlesource.com/c/151898
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
To pull in the fix for #28858, which we want to include for Go 1.12.
Fixes#28858.
Change-Id: Id4964cfd38e3d44d6317a2ee124fe2d35038b5fd
Reviewed-on: https://go-review.googlesource.com/c/152277
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
And remove some unnecessary textproto references. (The net/http
package's CanonicalHeaderKey just calls textproto's
CanonicalMIMEHeaderKey)
Fixes#28894
Change-Id: Ibd277893a168368c593147a2677ad6130870cb88
Reviewed-on: https://go-review.googlesource.com/c/152157
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Darwin doesn't support the multiple copies of the runtime package
implied by linking a c-shared library into a Go program.
Updates #29061
Change-Id: I6cf5d00babf82f1de05689c1345aaa5ae0b0659c
Reviewed-on: https://go-review.googlesource.com/c/152159
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
staticcopy of a struct or array should recursively call itself, not
staticassign.
This fixes an issue where a struct with a slice in it is copied during
static initialization. In this case, the backing array for the slice
is duplicated, and each copy of the slice refers to a different
backing array, which is incorrect. That issue has existed since at
least Go 1.2.
I'm not sure why this was never noticed. It seems like a pretty
obvious bug if anyone modifies the resulting slice.
In any case, we started to notice when the optimization in CL 140301
landed. Here is basically what happens in issue29013b.go:
1) The error above happens, so we get two backing stores for what
should be the same slice.
2) The code for initializing those backing stores is reused.
But not duplicated: they are the same Node structure.
3) The order pass allocates temporaries for the map operations.
For the first instance, things work fine and two temporaries are
allocated and stored in the OKEY nodes. For the second instance,
the order pass decides new temporaries aren't needed, because
the OKEY nodes already have temporaries in them.
But the order pass also puts a VARKILL of the temporaries between
the two instance initializations.
4) In this state, the code is technically incorrect. But before
CL 140301 it happens to work because the temporaries are still
correctly initialized when they are used for the second time. But then...
5) The new CL 140301 sees the VARKILLs and decides to reuse the
temporary for instance 1 map 2 to initialize the instance 2 map 1
map. Because the keys aren't re-initialized, instance 2 map 1
gets the wrong key inserted into it.
Fixes#29013
Change-Id: I840ce1b297d119caa706acd90e1517a5e47e9848
Reviewed-on: https://go-review.googlesource.com/c/152081
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
This is just the first step in attempting to make all network connection have
timeouts as a "safe default". TCP keepalives only protect against certain
classes of network and host issues (e.g. server/OS crash), but do nothing
against application-level issues (e.g. an application that accepts connections
but then fails to serve requests).
The actual keep-alive duration (15s) is chosen to cause broken connections
to be closed after 2~3 minutes (depending on the OS, see #23549 for details).
We don't make the actual default value part of the public API for a number of
reasons:
- because it's not very useful by itself: as discussed in #23549 the actual
"timeout" after which the connection is torn down is duration*(KEEPCNT+1),
and we use the OS-wide value for KEEPCNT because there's currently no way
to set it from Go.
- because it may change in the future: if users need to rely on a specific
value they should explicitly set this value instead of relying on the default.
Fixes#23459
Change-Id: I348c03be97588d5001e6de0f377e7a93b51957fd
Reviewed-on: https://go-review.googlesource.com/c/107196
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Before this change, location list construction would extend
from the previous (in linear order) block, even if was not a
flow predecessor. This can cause a debugger to tell lies.
Fix accounts for this in block merging code by (crudely)
"changing" all variables live from a previous block if it
is not also a predecessor.
Fixes#28486.
Change-Id: I11336b0b969f0cd09f40f4e5f2bdfdeb02f377a4
Reviewed-on: https://go-review.googlesource.com/c/146718
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
golang.org/cl/151977 slightly decreased the cost of inlining an extra
call from 60 to 57, since it was a safe change that could help in some
scenarios.
One notable change spotted in that CL is that bytes.Buffer.Grow is now
inlinable, meaning that a fixedbugs test needed updating.
For consistency, add the test case to TestIntendedInlining too,
alongside other commonly used bytes.Buffer methods.
Change-Id: I4fb402fc684ef4c543fc65aea343ca1a4d73a189
Reviewed-on: https://go-review.googlesource.com/c/151979
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
A Go user made a well-documented request for a slightly
lower threshold. I tested against a selection of other
people's benchmarks, and saw a tiny benefit (possibly noise)
at equally tiny cost, and no unpleasant surprises observed
in benchmarking.
I.e., might help, doesn't hurt, low risk, request was
delivered on a silver platter.
It did, however, change the behavior of one test because
now bytes.Buffer.Grow is eligible for inlining.
Updates #19348.
Change-Id: I85e3088a4911290872b8c6bda9601b5354c48695
Reviewed-on: https://go-review.googlesource.com/c/151977
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Avoid redefinition errors when a Go file uses a cgo comment to
There is no particularly good reason to do this, but there is also no
particularly good reason that it should fail.
Fixes#27019
Change-Id: Icd6f8197a89be4ee6b03ddae675667998a8b4189
Reviewed-on: https://go-review.googlesource.com/c/152079
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This CL adds several test cases of arithmetic operations for
386/amd64/arm/arm64.
Change-Id: I362687c06249f31091458a1d8c45fc4d006b616a
Reviewed-on: https://go-review.googlesource.com/c/151897
Run-TryBot: Ben Shi <powerman1st@163.com>
Reviewed-by: Keith Randall <khr@golang.org>
The stat(2) man page contain this comment about the 64-bit versions
of the system file functions:
"Platforms that were released after these updates only have the
newer variants available to them. These platforms have the macro
_DARWIN_FEATURE_ONLY_64_BIT_INODE defined."
It turns out that on iOS the _DARWIN_FEATURE_ONLY_64_BIT_INODE is
defined and that even though the "64"-postfixed versions are
accessible they are deemed private. Apps that refer to private
API are not admissible on App Store, and after the Go runtime
started using libSystem instead of direct syscalls, the App Store
submission checks reject apps built with Go tip.
The fix is simple: use the non-postfixed versions on iOS.
getdirentries(2) is not changed; it is not available at all on iOS
and needs replacement.
Updates #28984
Change-Id: Icb8d44e271456acaa1913ba486fcf5b569722fa9
Reviewed-on: https://go-review.googlesource.com/c/151938
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
While here, rename nonnegintconst to indexconst (because that's
what it is) and add Fatalf calls where we are not expecting the
indexconst call to fail, and fixed wrong comparison in smallintconst.
Fixes#23781.
Change-Id: I86eb13081c450943b1806dfe3ae368872f76639a
Reviewed-on: https://go-review.googlesource.com/c/151599
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This change fixes an error in HACKING.md which claims all pointers
which live in unmanaged memory but point to the heap must be marked
as GC roots explicitly by runtime.markroot. This isn't technically
necessary if the pointer is accessible through a global variable.
Change-Id: I632b25272fdb2f789c5259dd1685d517f45fd435
Reviewed-on: https://go-review.googlesource.com/c/151539
Reviewed-by: Rick Hudson <rlh@golang.org>
In TestObjImporter skip tests that use type aliases when using a
version of gccgo before GCC 7, since that is when type aliases were
added.
Fixes#29006
Change-Id: I676bae9f023931cf95ac9b4d4de893fe8517af9b
Reviewed-on: https://go-review.googlesource.com/c/152078
Reviewed-by: Than McIntosh <thanm@google.com>
TestInstallationImporter checks that it can read the export data for a
list of known standard library packages. It was failing on the SmartOS
builder which has GCC 4.7 installed. Skip packages that did not exist
in GCC 4.7. Most packages are still there and the missing packages are
fairly simple, so this doesn't really affect test quality.
Updates #29006
Change-Id: If7ae6f83d51d40168a9692acb0b99c9bf21f2a4d
Reviewed-on: https://go-review.googlesource.com/c/152077
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Fix a bug in the reading of elderly export data. In such export data
when reading type information it's possible to encounter a named type N1
defined as a typedef of some other named type N2 at a point when the
underying type of N1 has not yet been finalized. Handle this case by
generating a fixup, then process fixups at the end of parsing to
set the correct underlying type.
Fixes#29006.
Change-Id: I6a505c897bd95eb161ee04637bb6eebad9f20d52
Reviewed-on: https://go-review.googlesource.com/c/151997
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
signatureSchemesForCertificate was written to be used with TLS 1.3, but
ended up used for TLS 1.2 client certificates in a refactor. Since it
only supported TLS 1.3 signature algorithms, it would lead to no RSA
client certificates being sent to servers that didn't support RSA-PSS.
TestHandshakeClientCertRSAPKCS1v15 was testing *specifically* for this,
but alas the OpenSSL flag -verify accepts an empty certificates list as
valid, as opposed to -Verify...
Fixes#28925
Change-Id: I61afc02ca501d3d64ab4ad77bbb4cf10931e6f93
Reviewed-on: https://go-review.googlesource.com/c/151660
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>
The call to os.Rename was failing on the darwin builders, despite having passed in the TryBots.
(I tested this change by running 'go test cmd/go' manually on a darwin gomote.)
This fixes the builder failures after CL 146382.
Updates #26794Fixes#29030
Change-Id: I3644773421789f65e56f183d077b4e4fd17b8325
Reviewed-on: https://go-review.googlesource.com/c/151798
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
We don't need a write barrier if:
1) The location we're writing to doesn't hold a heap pointer, and
2) The value we're writing isn't a heap pointer.
The freshly returned value from runtime.newobject satisfies (1).
Pointers to globals, and the contents of the read-only data section satisfy (2).
This is particularly helpful for code like:
p := []string{"abc", "def", "ghi"}
Where the compiler generates:
a := new([3]string)
move(a, statictmp_) // eliminates write barriers here
p := a[:]
For big slice literals, this makes the code a smaller and faster to
compile.
Update #13554. Reduces the compile time by ~10% and RSS by ~30%.
Change-Id: Icab81db7591c8777f68e5d528abd48c7e44c87eb
Reviewed-on: https://go-review.googlesource.com/c/151498
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This adds several new checks to help debug #27993. It adds a mechanism
for freezing write barriers and gcWork puts during the mark completion
algorithm. This way, if we do detect mark completion, we can catch any
puts that happened during the completion algorithm. Based on build
dashboard failures, this seems to be the window of time when these are
happening.
This also double-checks that all work buffers are empty immediately
upon entering mark termination (much earlier than the current check).
This is unlikely to trigger based on the current failures, but is a
good safety net.
Change-Id: I03f56c48c4322069e28c50fbc3c15b2fee2130c2
Reviewed-on: https://go-review.googlesource.com/c/151797
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
The old code ignored the field alignment, and only looked at the field
offset: if the field offset required padding, cgo added padding. But
while that approach works for Go (at least with the gc toolchain) it
doesn't work for C code using packed structs. With a packed struct the
added padding may leave the struct at a misaligned position, and the
inserted alignment, which cgo is not considering, may introduce
additional, unexpected, padding. Padding that ignores alignment is not
a good idea when the struct is not packed, and Go structs are never
packed. So don't ignore alignment.
Fixes#28896
Change-Id: Ie50ea15fa6dc35557497097be9fecfecb11efd8a
Reviewed-on: https://go-review.googlesource.com/c/150602
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
We refactor the conversion of quotes to their unicode equivalent
to a separate function so that it can be called from ToText and Synopsis.
And we introduce a temp buffer to write the escaped HTML and convert
the unicode quotes back to html escaped entities. This simplifies the logic
and gets rid of the need to track the index of the escaped text.
Fixes#27759
Change-Id: I71cf47ddcd4c6794ccdf2898ac25539388b393c1
Reviewed-on: https://go-review.googlesource.com/c/150377
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Adjust mTreap ordering logic to reflect the description of mTreap ordering.
Before it was using unsafe.Pointer in order to gather the base address of
a span. This has been changed to use base, which is the startAddress of a
span as the description is telling us in mgclarge.go.
Fixes: golang/go#28805
Change-Id: Ib3cd94a0757e23d135b5d41830f38fc08bcf16a3
GitHub-Last-Rev: 93f749b670
GitHub-Pull-Request: golang/go#28973
Reviewed-on: https://go-review.googlesource.com/c/151499
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Previously, we were looking for the string go.mod specifically, but
the module-mode-outside-a-module logic added in CL 148517 sets GOMOD
to os.DevNull
Updates #28992
Change-Id: I62a4baaa911a495350294d78bae96be3fe4866cb
Reviewed-on: https://go-review.googlesource.com/c/151617
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
The test that used that module was removed in
https://golang.org/cl/128900.
Change-Id: Id96270a52398c8ccc09821efb2a6a6b4764f44d9
Reviewed-on: https://go-review.googlesource.com/c/151560
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
This assignment became a no-op in CL 36196, where both it and the
preceding assignment were changed to cfg.GOROOTbin (from gorootBin and
gobin respectively).
Change-Id: If74969c4cc3ffc5d8394ff9d8e8bcec9e0a4e3b0
Reviewed-on: https://go-review.googlesource.com/c/151561
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
This is as minimal a change as I could comfortably make to enable 'go
get' outside of a module for 1.12.
In general, commands invoked in module mode while outside of a module
operate as though they are in a module with an initially-empty go.mod
file. ('go env GOMOD' reports os.DevNull.)
Commands that operate on the current directory (such as 'go list' and
'go get -u' without arguments) fail: without a module definition, we
don't know the package path. Likewise, commands whose sole purpose is
to write files within the main module (such as 'go mod edit' and 'go
mod vendor') fail, since we don't know where to write their output.
Since the go.sum file for the main module is authoritative, we do not
check go.sum files when operating outside of a module. I plan to
revisit that when the tree opens for 1.13.
We may also want to revisit the behavior of 'go list': it would be
useful to be able to query individual packages (and dependencies of
those packages) within versioned modules, but today we only allow
versioned paths in conjunction with the '-m' flag.
Fixes#24250
RELNOTE=yes
Change-Id: I028c323ddea27693a92ad0aa4a6a55d5e3f43f2c
Reviewed-on: https://go-review.googlesource.com/c/148517
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
The lockfile guards calls that may change the repo's filesystem contents.
We don't know how robust VCS implementations are to running
simultaneous commands, and this way we don't need to care: only one
'go' command at a time will modify any given repository.
If we can guarantee that particular VCS implementations are robust
enough across all of the VCS tool versions we support, we may be able
to remove some of this locking to improve parallelism.
Updates #26794
Change-Id: I578524974f5015629239cef43d3793aee2b9075c
Reviewed-on: https://go-review.googlesource.com/c/146381
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
Use an arbitrary lockfile to serialize edits, and use atomic renames
to actually write the go.mod file so that we never drop version
requirements due to a command failing partway through a write.
Multiple invocations of the 'go' command may read the go.mod file
concurrently, and will see some consistent version even if some other
invocation changes it concurrently.
Multiple commands may attempt to write the go.mod file concurrently.
One writer will succeed and write a consistent, complete go.mod file.
The others will detect the changed contents and fail explicitly: it is
not, in general, possible to resolve two conflicting changes to module
requirements, so we surface the problem to the user rather than trying
to solve the problem heuristically.
Updates #26794
Change-Id: Ia1a06a01ef93fa9be664f560eb83bb86b0207443
Reviewed-on: https://go-review.googlesource.com/c/146380
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
We employ the following new locking mechanisms:
• Zip files and list files within the module cache are written using
atomic renames of temporary files, so that GOPROXY servers reading
from the cache will never serve incomplete content.
• A lock file for each module version guards downloading and extraction of
(immutable) module contents.
• A lock file alongside each version list (named 'list.lock')
guards updates to the list.
• A single lock file in the module cache guards updates to all go.sum
files. The go.sum files themselves are written using an atomic
rename to ensure that we never accidentally discard existing sums.
Updates #26794
RELNOTE=yes
Change-Id: I16ef8b06ee4bd7b94d0c0a6f5d17e1cecc379076
Reviewed-on: https://go-review.googlesource.com/c/146382
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
This will be used to eliminate a redundant copy in CL 145178.
(It also decouples two design points that were previously coupled: the
destination of the zip output and the program logic to write that
output.)
Updates #26794
Change-Id: I6cfd5a33c162c0016a1b83a278003684560a3772
Reviewed-on: https://go-review.googlesource.com/c/151341
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Also check to make sure we don't overwrite a newer timestamp with an
older one.
testexpire.txt may be written concurrently, and a partially-written
timestamp may appear much older than the actual intended one. We don't
want to re-run tests that should still be cached.
Updates #26794
Change-Id: If56348e799f0e7be3c5bc91b4a336e23ad99f791
Reviewed-on: https://go-review.googlesource.com/c/146379
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
lockedfile.File passes through to os.File, with Open, Create, and OpenFile
functions that mimic the corresponding os functions but acquire locks
automatically, releasing them when the file is closed.
lockedfile.Sentinel is a simplified wrapper around lockedfile.OpenFile for the
common use-case of files that signal the status of idempotent tasks.
lockedfile.Mutex is a Mutex-like synchronization primitive implemented in terms
of file locks.
lockedfile.Read is like ioutil.Read, but obtains a read-lock.
lockedfile.Write is like ioutil.Write, but obtains a write-lock and can be used
for read-only files with idempotent contents.
Updates #26794
Change-Id: I50f7132c71d2727862eed54411f3f27e1af55cad
Reviewed-on: https://go-review.googlesource.com/c/145178
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
