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>
The old link died; replace with an archive.org copy.
Fixes#13345.
Change-Id: Ic4a7fdcf258e1ff3b4a02ecb4f237ae7db2686c7
Reviewed-on: https://go-review.googlesource.com/18335
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Also reference the new Transport.ExpectContinueTimeout after the
mention of 100-continue.
Fixes#13721
Change-Id: I3445c011ed20f29128092c801c7a4bb4dd2b8351
Reviewed-on: https://go-review.googlesource.com/18281
Reviewed-by: Andrew Gerrand <adg@golang.org>
Slightly rephrased sentence to emphasize the contents of the
Unicode categories w/o repeating the full category name each
time.
Fixes#13414.
Change-Id: Icd32ff1547fa81e866c5937a631c3344bb6087c6
Reviewed-on: https://go-review.googlesource.com/18265
Reviewed-by: Rob Pike <r@golang.org>
The proper term is "untyped boolean".
Change-Id: Id871164190a03c64a8a8987b1ad5d8653a21d96e
Reviewed-on: https://go-review.googlesource.com/16135
Reviewed-by: Robert Griesemer <gri@golang.org>
The spec defines precise numeric constants which do not overflow.
Consequently, +/-Inf and NaN values were excluded. The case was not
clear for -0.0 but they are mostly of interest to determine the sign
of infinities which don't exist.
That said, the conversion rules explicitly say that T(x) (for a numeric
x and floating-point type T) is the value after rounding per IEEE-754.
The result is constant if x is constant. Rounding per IEEE-754 can
produce a -0.0 which we cannot represent as a constant.
Thus, the spec is inconsistent. Attempt to fix the inconsistency by
adjusting the rounding rule rather than letting -0.0 into the language.
For more details, see the issue below.
Open to discussion.
Fixes#12576.
Change-Id: Ibe3c676372ab16d9229f1f9daaf316f761e074ee
Reviewed-on: https://go-review.googlesource.com/14727
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
The prose discussing composite literals referred to the composite
literal type with 'LiteralType', denoting the literal type's EBNF
production explicitly. Changed 'LiteralType' to 'literal type' to
remove the literal (no pun intended) connection and instead mean
the underlying type. Seems a simpler and more readable change
than referring to the underlying type everywhere explicitly.
Fixes#12717.
Change-Id: I225df95f9ece2664b19068525ea8bda5ca05a44a
Reviewed-on: https://go-review.googlesource.com/14851
Reviewed-by: Rob Pike <r@golang.org>
Fixes#12288.
For inclusion in the 1.5.1 release.
Change-Id: I9354b7eaa76000498465c4a5cbab7246de9ecb7c
Reviewed-on: https://go-review.googlesource.com/14382
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Start go1.6.txt with a note that nacl ports are no longer
restricted to pepper_41 and a record of the text/template change.
Change-Id: I21dda64aec113c35caf1d565f29e3aac8171480a
Reviewed-on: https://go-review.googlesource.com/14004
Reviewed-by: Rob Pike <r@golang.org>
This makes sure the release page in the release will mention the release.
Fixes#12102.
Change-Id: I36befd7dba7ba9e70ae3335e21c8841179ac4eff
Reviewed-on: https://go-review.googlesource.com/13490
Reviewed-by: Rob Pike <r@golang.org>
Saying "Power 64" was wrong for reasons I don't remember.
(Those reasons are why we stopped using GOARCH=power64.)
Change-Id: Ifaac78d5733bfc780df01b1a66da766af0b17726
Reviewed-on: https://go-review.googlesource.com/13675
Reviewed-by: Rob Pike <r@golang.org>
Make clear that this list is the list of supported systems
for binary distributions, and that other systems may be
able to build the distribution from source, in addition
to using gccgo.
Drop freebsd/arm from the list on this page.
We have never issued a binary distribution for freebsd/arm,
and we're not going to start in Go 1.5, since we don't even
have a working builder for it.
Drop freebsd/386 from the list on the page,
because we are unable to build binary distributions, per adg.
I think the wording here should probably be revised further,
but not now.
Change-Id: Ib43b6b64f5c438bfb9aa4d3daa43393f1e33b71f
Reviewed-on: https://go-review.googlesource.com/13690
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
The SetOutput function has been there since Go 1.
Fixes#12162.
Change-Id: I66210374877581e42689f9943532141659a55ca7
Reviewed-on: https://go-review.googlesource.com/13637
Reviewed-by: Rob Pike <r@golang.org>
Fixes#12062
Updates #11961
The sRPC nameservice was removed in pepper 42. For Go 1.5 stipulate
that NaCl requires pepper 41 only.
Change-Id: Ic88ba342d41f673391efaa96fb581712fa10a0fd
Reviewed-on: https://go-review.googlesource.com/13341
Reviewed-by: Andrew Gerrand <adg@golang.org>
First step towards cleaning up the operator section - no language
changes. Specifically:
- Grouped arithmetic operations by types (integer, floating-point,
string), with corresponding h4 headings.
- Changed Operator precedence title from h3 to h4.
- Moved Integer Overflow section after integer operations and changed
its title from h3 to h4.
This puts things that belong together closer. No heading id's were
lost (in case of references from outside the spec).
Change-Id: I6b349ba8d86a6ae29b596beb297cc45c81e69399
Reviewed-on: https://go-review.googlesource.com/13143
Reviewed-by: Rob Pike <r@golang.org>
Missed in CL 13074.
Change-Id: Ic0600341abbc423cd8d7b2201bf50e3b0bf398a7
Reviewed-on: https://go-review.googlesource.com/13167
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Tracing functionality was moved from runtime/pprof to runtime/trace.
Change-Id: I694e0f209d043c7ffecb113f1825175bf963dde3
Reviewed-on: https://go-review.googlesource.com/13074
Reviewed-by: Rob Pike <r@golang.org>
Russ Cox
Andrew Gerrand
Adam Langley
Michael Hudson-Doyle
Ian Lance Taylor
Brad Fitzpatrick
Robert Griesemer
Benny Siegert
Shenghou Ma
David Symonds
Emmanuel Odeke
Rob Pike
Dave Cheney
Chris Broadfoot
Alex Brainman
Matthew Dempsky
Marcel van Lohuizen
Katrina Owen
Austin Clements
Joe Shaw
Mikio Hara
Dmitry Vyukov