None of them need to be called out in the release notes.
Change-Id: I143a1879b25063574e4107c1e89264434d45d1d5
Reviewed-on: https://go-review.googlesource.com/33676
Reviewed-by: Ian Lance Taylor <iant@golang.org>
CL 32796 changes the SIGPIPE behaviour for c-archive and c-shared
programs. Add it to go1.8.txt.
Change-Id: I31200187033349c642965a4bb077bcc77d5329a3
Reviewed-on: https://go-review.googlesource.com/33397
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This matches what we already do for switch statements and makes
this large section more visibly organized. No other changes besides
introducing the titles.
Fixes#4486.
Change-Id: I73f274e4fdd27c6cfeaed79090b4553e57a9c479
Reviewed-on: https://go-review.googlesource.com/33410
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
- organize examples better
- add an example illustrating behavior if element type is a named pointer type
- both compilers and go/types (per https://go-review.googlesource.com/33358)
follow this now
See the issue for detailed discussion.
Fixes#17954.
Change-Id: I8d90507ff2347d9493813f75b73233819880d2b4
Reviewed-on: https://go-review.googlesource.com/33361
Reviewed-by: Rob Pike <r@golang.org>
Both automated updates with a few tweaks.
Change-Id: I24579a8dcc32a84a4fff5c2212681ef30dda61d1
Reviewed-on: https://go-review.googlesource.com/33297
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The tree is inconsistent about single l vs double l in those
words in documentation, test messages, and one error value text.
$ git grep -E '[Mm]arshall(|s|er|ers|ed|ing)' | wc -l
42
$ git grep -E '[Mm]arshal(|s|er|ers|ed|ing)' | wc -l
1694
Make it consistently a single l, per earlier decisions. This means
contributors won't be confused by misleading precedence, and it helps
consistency.
Change the spelling in one error value text in newRawAttributes of
crypto/x509 package to be consistent.
This change was generated with:
perl -i -npe 's,([Mm]arshal)l(|s|er|ers|ed|ing),$1$2,' $(git grep -l -E '[Mm]arshall' | grep -v AUTHORS | grep -v CONTRIBUTORS)
Updates #12431.
Follows https://golang.org/cl/14150.
Change-Id: I85d28a2d7692862ccb02d6a09f5d18538b6049a2
Reviewed-on: https://go-review.googlesource.com/33017
Run-TryBot: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
We thought it would at the time, but then Beta 4 changed the ABI
again, so it wasn't true in practice.
Fixes#17643
Change-Id: I36b747bd69a56adc7291fa30d6bffdf67ab8741b
Reviewed-on: https://go-review.googlesource.com/32238
Reviewed-by: Russ Cox <rsc@golang.org>
As agreed upon by the Code of Conduct working group, "race" may refer to
an attempt to classify people based on "defining characteristics",
regardless of how this people view themselves, while "ethnicity" refers
to how people identify themselves.
The Code of Conduct working group believes that the term "ethnicity"
will be more comprehensive and inclusive, and will better serve the Go
community.
Change-Id: I724b72cadb8cf29b4bac8f83017b0303feae3c94
Reviewed-on: https://go-review.googlesource.com/32133
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
For some reason git won't let me write
doc/effective_go.html: reword confusing sentence
or even
doc/effective_go: reword confusing sentence
as the subject line for this CL, but that's not important. The
actual CL just rewrites one sentence and adds an option to grep in
the associated example.
Fixes#15875
Change-Id: Iee159ea751caf4b73eacf3dfc86e29032646373f
Reviewed-on: https://go-review.googlesource.com/32110
Reviewed-by: Ian Lance Taylor <iant@golang.org>
A 16bit binary exponent permits a constant range covering roughly the range
from 7e-9865 to 7e9863 which is more than enough for any practical and
hypothetical constant arithmetic.
Furthermore, until recently cmd/compile could not handle very large exponents
correctly anyway; i.e., the chance that any real programs (but for tests that
explore corner cases) are affected are close to zero.
Finally, restricting the minimum supported range significantly reduces the
implementation complexity in an area that hardly matters in reality for new
or alternative spec-compliant implementations that don't or cannot rely on
pre-existing arbitratry precision arithmetic packages that support a 32bit
exponent range.
This is technically a language change but for the reasons mentioned above
this is unlikely to affect any real programs, and certainly not programs
compiled with the gc or gccgo compilers as they currently support up to
32bit exponents.
Fixes#13572.
Change-Id: I970f919c57fc82c0175844364cf48ea335f17d39
Reviewed-on: https://go-review.googlesource.com/17711
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
This clarifies some of the titles so they're more "news" friendly and
less implementation-oriented.
Change-Id: Ied02aa1e6824b04db5d32ecdd58e972515b1f588
Reviewed-on: https://go-review.googlesource.com/29830
Reviewed-by: Rick Hudson <rlh@golang.org>
With help of a new interactive commit classifier tool (tool location
TBD, likely x/build/cmd/writenotes), classify all commits from go1.7
up to 56d35d4.
We can selectively cull this list later. When in doubt, I erred on the
side of inclusion for now.
Change-Id: I458945004e1b1a148fb2f294b454a390ef4f92c2
Reviewed-on: https://go-review.googlesource.com/30696
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This simply documents the status quo accepted by cmd/compile, gccgo,
and go/types. The new language matches the language used for indices
of index expressions for arrays and slices.
Fixes#16679.
Change-Id: I65447889fbda9d222f2a9e6c10334d1b38c555f0
Reviewed-on: https://go-review.googlesource.com/30474
Reviewed-by: Rob Pike <r@golang.org>
This is a backwards-compatible language change.
Per the proposal (#16085), the rules for conversions are relaxed
such that struct tags in any of the structs involved in the conversion
are ignored (recursively).
Because this is loosening the existing rules, code that compiled so
far will continue to compile.
For #16085.
Fixes#6858.
Change-Id: I0feef651582db5f23046a2331fc3f179ae577c45
Reviewed-on: https://go-review.googlesource.com/24190
Reviewed-by: Russ Cox <rsc@golang.org>
Effective Go has references to a function call f(c, req) made by ServeHTTP mixed with f(w,
req). c is dropped in favor of w to maintain consistency
Fixes#17128
Change-Id: I6746fd115ed5a58971fd24e54024d29d18ead1fa
Reviewed-on: https://go-review.googlesource.com/29311
Reviewed-by: Rob Pike <r@golang.org>
The download page says "OS X 10.8 or later", but other pages said 10.7.
Say 10.8 everywhere.
Turns out Go doesn't even compile on OS X 10.7 (details in bug) and we
only run builders for OS X 10.8+, which is likely why 10.7
regressed. Until recently we only had OS X 10.10 builders, even.
We could run 10.7 builders, but there's basically no reason to do so,
especially with 10.12 coming out imminently.
Fixes#16625
Change-Id: Ida6e20fb6c54aea0a3757235b708ac1c053b8c04
Reviewed-on: https://go-review.googlesource.com/28870
Reviewed-by: Chris Broadfoot <cbro@golang.org>
We relay this info in a few places, in a few different ways, but not
consistently everywhere. This led one of our users to start googling
and not find https://golang.org/doc/code.html#Workspaces, of which `go
help gopath` is the most equivalent.
Change-Id: I28a94375739f3aa4f200e145293ca2a5f65101e1
Reviewed-on: https://go-review.googlesource.com/28690
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Currently the footnote says "gcc is required only if you plan to use cgo",
but the footnote was referenced from the text:
"use the clang or gcc† that comes with Xcode‡ for cgo support"
That seems to imply that clang doesn't get you cgo support on OS X,
which isn't true. The update text matches what the install-source.html
page says.
Change-Id: Ib88464a0d138227d357033123f6675a77d5d777f
Reviewed-on: https://go-review.googlesource.com/28786
Reviewed-by: Minux Ma <minux@golang.org>
See the issue below for details.
Fixes#16794.
Change-Id: I7e338089fd80ddcb634fa80bfc658dee2772361c
Reviewed-on: https://go-review.googlesource.com/27356
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This truly is a common point of confusion that deserves
explanation in the FAQ.
Change-Id: Ie624e31a2042ca99626fe7570d9c8c075aae6a84
Reviewed-on: https://go-review.googlesource.com/28275
Reviewed-by: Ian Lance Taylor <iant@golang.org>
I was confused by the current wording. This wording
answers the question more clearly.
Thanks to Robert Griesemer for suggestions.
Fixes#16916
Change-Id: I50187c8df2db661b9581f4b3c5d5c279d2f9af41
Reviewed-on: https://go-review.googlesource.com/28052
Reviewed-by: Robert Griesemer <gri@golang.org>
Recreated original favicon with svg. Note, the rasterizations are hand
tweaked for crispness and straight export will not give the same results.
Fixes#6938
Change-Id: I9bf7b59028711361c29365b145932d90af419b69
Reviewed-on: https://go-review.googlesource.com/26850
Reviewed-by: Chris Broadfoot <cbro@golang.org>
The enumerations didn't include the syntactic form where the lhs is
full variable declaration with type specification, as in:
var x, ok T = ...
Fixes#15782.
Change-Id: I0f7bafc37dc9dcf62cdb0894a0d157074ccd4b3e
Reviewed-on: https://go-review.googlesource.com/27670
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
The changes match the existing compilers, and assume an adjusted
spec (per issue #16794).
Fixes#15686.
Change-Id: I72677ce75888c41a8f3c2963117a2f2d5501c42b
Reviewed-on: https://go-review.googlesource.com/27290
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
It is no longer used by Go.
It's now moved to golang.org/x/tools/cmd/goyacc for anybody who needs it.
Fixes#11229
Change-Id: Ia431d5a380c7ff784a2050dee2f5bc8acee015da
Reviewed-on: https://go-review.googlesource.com/27325
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Updates #16396
Change-Id: I7b4f85610e66f2c77c17cf8898cc41d81b2efc8c
Reviewed-on: https://go-review.googlesource.com/25283
Reviewed-by: Chris Broadfoot <cbro@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>
Rather than saying "stop-the-world", say "garbage collection pauses".
Change-Id: Ifb2931781ab3094e04bea93f01f18f1acb889bdc
Reviewed-on: https://go-review.googlesource.com/25018
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Most of the runtime improvements are hard to quantify or summarize,
but it's worth mentioning some of the substantial improvements in STW
time, and that the scavenger now actually works on ARM64, PPC64, and
MIPS.
Change-Id: I0e951038516378cc3f95b364716ef1c183f3445a
Reviewed-on: https://go-review.googlesource.com/24966
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
We decided that ppc64 should maintain power5 compatibility.
ppc64le requires power8.
Fixes#16372.
Change-Id: If5b309a0563f55a3c1fe9c853d29a463f5b71101
Reviewed-on: https://go-review.googlesource.com/24915
Reviewed-by: Minux Ma <minux@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Document that the http.Server is now stricter about rejecting
requests with invalid HTTP versions, and also that it rejects plaintext
HTTP/2 requests, except for `PRI * HTTP/2.0` upgrade requests.
The relevant CL is https://golang.org/cl/24505.
Updates #15810.
Change-Id: Ibbace23e001b5e2eee053bd341de50f9b6d3fde8
Reviewed-on: https://go-review.googlesource.com/24731
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
New Gophers sometimes misconstrue the advice in the "Generality" section
as "export interfaces instead of implementations" and add needless
interfaces to their code as a result. Down the road, they end up
needing to add methods and either break existing callers or have to
resort to unpleasant hacks (e.g. using "magic method" type-switches).
Weaken the first paragraph of this section to only advise leaving types
unexported when they will never need additional methods.
Change-Id: I32a1ae44012b5896faf167c02e192398a4dfc0b8
Reviewed-on: https://go-review.googlesource.com/24892
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>
A follow-on to https://golang.org/cl/24852 that mentions the
documentation clarifications.
Updates #16308.
Change-Id: Ic2a6e1d4938d74352f93a6649021fb610efbfcd0
Reviewed-on: https://go-review.googlesource.com/24857
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
For better or for worse, it's IsExist, not IsExists.
Change-Id: I4503f961486edd459c0c81cf3f32047dff7703a4
Reviewed-on: https://go-review.googlesource.com/24819
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
We had ~30 one way, and these four new occurrences the other way.
Updates #11626
Change-Id: Ic6403dc4905874916ae292ff739d33482ed8e5bf
Reviewed-on: https://go-review.googlesource.com/24683
Reviewed-by: Rob Pike <r@golang.org>
- Mention RFC 2616 conformation in which the server now only sends one
"Transfer-Encoding" header when "chunked" is explicitly set.
- Mention that a timeout handler now sends a 200 status code on
encountering an empty response body instead of sending back 0.
Change-Id: Id45e2867390f7e679ab40d7a66db1f7b9d92ce17
Reviewed-on: https://go-review.googlesource.com/24250
Reviewed-by: Andrew Gerrand <adg@golang.org>
Signed-off-by: Steven Phillips <steve@tryingtobeawesome.com>
Change-Id: Ie7c3253a5e1cd43be8fa12bad340204cc6c5ca76
Reviewed-on: https://go-review.googlesource.com/23677
Reviewed-by: Ian Lance Taylor <iant@golang.org>
We say "cancelation," not "cancellation."
Fixes#15928.
Change-Id: I66d545404665948a27281133cb9050eebf1debbb
Reviewed-on: https://go-review.googlesource.com/23673
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Both compilers and also go/types don't permit duplicate types in
type switches; i.e., this spec change is documenting a status quo
that has existed for some time.
Furthermore, duplicate nils are not accepted by gccgo or go/types;
and more recently started causing a compiler error in gc. Permitting
them is inconsistent with the existing status quo.
Rather than making it an implementation restriction (as we have for
expression switches), this is a hard requirement since it was enforced
from the beginning (except for duplicate nils); it is also a well
specified requirement that does not pose a significant burden for
an implementation.
Fixes#15896.
Change-Id: If12db5bafa87598b323ea84418cb05421e657dd8
Reviewed-on: https://go-review.googlesource.com/23584
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The original draft mentioned support for json.Marshaler, but that's
not the case. JSON supports only string keys (not arbitrary JSON)
so only encoding.TextMarshaller is supported.
Change-Id: I7788fc23ac357da88e92aa0ca17b513260840cee
Reviewed-on: https://go-review.googlesource.com/23529
Reviewed-by: Andrew Gerrand <adg@golang.org>
Document the following:
* That the algorithmic changes are still compliant with RFC 1951. I remember
people having questions regarding this issue, and it would be good to re-assure
them that it is still standards compliant.
* io.EOF can now be returned early (c27efce66b)
* Use the term "decompress" when referred to as an action. The term "uncompressed"
or "decompressed" are both valid as ways to represent the current state of the data.
Change-Id: Ie29ebce709357359e7c36d3e7f3d53b260eaadfa
Reviewed-on: https://go-review.googlesource.com/23552
Reviewed-by: Andrew Gerrand <adg@golang.org>
Document new behavior about signal name printing
in panics as per CL golang.org/cl/22753.
For #15810
Change-Id: I9c677d5dd779b41e82afa25e3c797d8e739600d3
Reviewed-on: https://go-review.googlesource.com/23493
Reviewed-by: Russ Cox <rsc@golang.org>
Mostly complete but a few TODOs remain for future CLs.
For #15810.
Change-Id: I81ee19d1088d192cf709a5f7e6b7bcc44ad892ac
Reviewed-on: https://go-review.googlesource.com/23379
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Current number was out-of-date since adding MIPS.
Change-Id: I565342a92de3893b75cdfb76fa39f7fdf15672da
Reviewed-on: https://go-review.googlesource.com/22952
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Note that the spec already makes that point with a comment in the very first
example for struct field tags. This change is simply stating this explicitly
in the actual spec prose.
- gccgo and go/types already follow this rule
- the current reflect package API doesn't distinguish between absent tags
and empty tags (i.e., there is no discoverable difference)
Fixes#15412.
Change-Id: I92f9c283064137b4c8651630cee0343720717a02
Reviewed-on: https://go-review.googlesource.com/22391
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
A late response to CL 22163.
Change-Id: I5275a22af7081875af0256da296811f4fe9832dc
Reviewed-on: https://go-review.googlesource.com/22296
Reviewed-by: David Symonds <dsymonds@golang.org>
Per a suggestion from mdempsky.
Both gc and gccgo consider a statement list as terminating if the
last _non_empty_ statement is terminating; i.e., trailing semis are
ok. Only gotype followed the current stricter rule in the spec.
This change adjusts the spec to match gc and gccgo behavior. In
support of this change, the spec has a matching rule for fallthrough,
which in valid positions may be followed by trailing semis as well.
For details and examples, see the issue below.
Fixes#14422.
Change-Id: Ie17c282e216fc40ecb54623445c17be111e17ade
Reviewed-on: https://go-review.googlesource.com/19981
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
This will allow us to mechanically substitute these strings
using javascript (in a forthcoming change to x/tools/godoc).
Updates #14371
Change-Id: I96e876283060ffbc9f3eabaf55d6b880685453e1
Reviewed-on: https://go-review.googlesource.com/22055
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Named returned values should only be used on public funcs and methods
when it contributes to the documentation.
Named return values should not be used if they're only saving the
programmer a few lines of code inside the body of the function,
especially if that means there's stutter in the documentation or it
was only there so the programmer could use a naked return
statement. (Naked returns should not be used except in very small
functions)
This change is a manual audit & cleanup of public func signatures.
Signatures were not changed if:
* the func was private (wouldn't be in public godoc)
* the documentation referenced it
* the named return value was an interesting name. (i.e. it wasn't
simply stutter, repeating the name of the type)
There should be no changes in behavior. (At least: none intended)
Change-Id: I3472ef49619678fe786e5e0994bdf2d9de76d109
Reviewed-on: https://go-review.googlesource.com/20024
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>
The () parentheses grouped wrongly. Removed them completely in
favor of separate 2- and 3-index slice alternatives which is
clearer.
Fixes#14477.
Change-Id: I0b7521ac912130d9ea8740b8793b3b88e2609418
Reviewed-on: https://go-review.googlesource.com/19853
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The Go 1.6 release notes say that Go 1.7 will remove support
for the GO15VENDOREXPERIMENT environment variable,
making vendoring always on. Do that.
Change-Id: Iba8b79532455828869c1a8076a82edce84259468
Reviewed-on: https://go-review.googlesource.com/19615
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The Go 1.6 release notes say we'll remove the “-X name value” form
(in favor of the “-X name=value” form) in Go 1.7.
Do that.
Also establish the doc/go1.7.txt file.
Change-Id: Ie4565a6bc5dbcf155181754d8d92bfbb23c75338
Reviewed-on: https://go-review.googlesource.com/19614
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Go 1.6 is soon (but not yet).
Fixes#14301.
Change-Id: I85e329b643adcb5d4fa680c5333fbc1f928d4d9d
Reviewed-on: https://go-review.googlesource.com/19550
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
Fixes#13651.
Change-Id: I1d21b49e2b5bc6c507eb084d6d2553e5a9c607cf
Reviewed-on: https://go-review.googlesource.com/19552
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
Go 1.6 significantly improves pause times for large heaps, but it
improves them in many other situations as well, such as when goroutine
churn is high, allocation rate is high, or when there are many
finalizers. Hence, make the statement about pause times a bit more
general.
Change-Id: Ic034b1c904c39dd1d966ee7fa96ca8bbb3614e53
Reviewed-on: https://go-review.googlesource.com/19504
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Currently we use "Section's" as the plural of the debug/elf Section
struct. Change this to "Sections" because it's not possessive and
doesn't seem to fall in to any special cases were the apostrophe is
acceptable.
Change-Id: Id5d3abbd748502a67ead3f483182ee7729db94a2
Reviewed-on: https://go-review.googlesource.com/19505
Reviewed-by: Russ Cox <rsc@golang.org>
The plan9.bell-labs.com site has fallen into disrepair.
We'll instead use the site maintained by contributor David du Colombier.
Fixes#14233
Change-Id: I0c702e5d3b091cccd42b288ea32f34d507a4733d
Reviewed-on: https://go-review.googlesource.com/19240
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: David du Colombier <0intro@gmail.com>
Also fix a few bad links.
Change-Id: If04cdd312db24a827a3c958a9974c50ab148656c
Reviewed-on: https://go-review.googlesource.com/18979
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Fixes#13954
Change-Id: I4c01e9bb3fb08e8b9fa14d4c59b7ea824ba3f0c9
Reviewed-on: https://go-review.googlesource.com/18937
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Consider this code:
func f(*int)
func g() {
p := new(int)
f(p)
}
where f is an assembly function.
In general liveness analysis assumes that during the call to f, p is dead
in this frame. If f has retained p, p will be found alive in f's frame and keep
the new(int) from being garbage collected. This is all correct and works.
We use the Go func declaration for f to give the assembly function
liveness information (the arguments are assumed live for the entire call).
Now consider this code:
func h1() {
p := new(int)
syscall.Syscall(1, 2, 3, uintptr(unsafe.Pointer(p)))
}
Here syscall.Syscall is taking the place of f, but because its arguments
are uintptr, the liveness analysis and the garbage collector ignore them.
Since p is no longer live in h once the call starts, if the garbage collector
scans the stack while the system call is blocked, it will find no reference
to the new(int) and reclaim it. If the kernel is going to write to *p once
the call finishes, reclaiming the memory is a mistake.
We can't change the arguments or the liveness information for
syscall.Syscall itself, both for compatibility and because sometimes the
arguments really are integers, and the garbage collector will get quite upset
if it finds an integer where it expects a pointer. The problem is that
these arguments are fundamentally untyped.
The solution we have taken in the syscall package's wrappers in past
releases is to insert a call to a dummy function named "use", to make
it look like the argument is live during the call to syscall.Syscall:
func h2() {
p := new(int)
syscall.Syscall(1, 2, 3, uintptr(unsafe.Pointer(p)))
use(unsafe.Pointer(p))
}
Keeping p alive during the call means that if the garbage collector
scans the stack during the system call now, it will find the reference to p.
Unfortunately, this approach is not available to users outside syscall,
because 'use' is unexported, and people also have to realize they need
to use it and do so. There is much existing code using syscall.Syscall
without a 'use'-like function. That code will fail very occasionally in
mysterious ways (see #13372).
This CL fixes all that existing code by making the compiler do the right
thing automatically, without any code modifications. That is, it takes h1
above, which is incorrect code today, and makes it correct code.
Specifically, if the compiler sees a foreign func definition (one
without a body) that has uintptr arguments, it marks those arguments
as "unsafe uintptrs". If it later sees the function being called
with uintptr(unsafe.Pointer(x)) as an argument, it arranges to mark x
as having escaped, and it makes sure to hold x in a live temporary
variable until the call returns, so that the garbage collector cannot
reclaim whatever heap memory x points to.
For now I am leaving the explicit calls to use in package syscall,
but they can be removed early in a future cycle (likely Go 1.7).
The rule has no effect on escape analysis, only on liveness analysis.
Fixes#13372.
Change-Id: I2addb83f70d08db08c64d394f9d06ff0a063c500
Reviewed-on: https://go-review.googlesource.com/18584
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Now there are ARM downloads too.
Change-Id: I236381508c69d56748e672d184b92caa715e81ae
Reviewed-on: https://go-review.googlesource.com/18342
Reviewed-by: Andrew Gerrand <adg@golang.org>
