The State of Go Where we are in May 2015 27 May 2015 Andrew Gerrand

The State of the State of Go I gave a similar talk at FOSDEM in February 2015. talks.golang.org/2015/state-of-go.slide This talk builds on that talk. 2

Go 1.5 3

Release schedule Go 1.5 is scheduled for release in August 2015. The major work is done.

We are now in the "feature freeze" period. 4

From C to Go The gc tool chain has been converted from C to Go. Machine-translated compile tool replaces 6g , 8g , etc.

Machine-translated link tool replaces 6l , 8l , etc.

New asm tool replaces 6a , 8a , etc. Go 1.5 has no C code in the tool chain or runtime. Rob will talk more about this. 5

Concurrent Garbage Collector Goals: Limit GC latency to less than 10 milliseconds.

Run Go application code for at least 40ms out of every 50ms. golang.org/s/go14gc 6

Concurrent GC trade-offs The new GC spends a little more memory and CPU time

in exchange for significantly shorter GC pause times. 7

Better concurrency performance Setting GOMAXPROCS=N (where N is your number of CPUs) works well in Go 1.5. Better performance executing goroutines in parallel: Better perfomance switching between goroutines in serial: 8

Better concurrency performance (bottom line) Better performance under practical workloads: And our benchmark suite: 9

Go 1.5 overall performance 10

Go 1.5 overall performance (continued) 11

OS/Arch ports Go 1.5 supports some new GOOS/GOARCH combinations: darwin/arm , a.k.a iOS

, a.k.a iOS darwin/arm64 (newer iDevices)

(newer iDevices) linux/arm64 (cgo is supported, but only with external linking)

(cgo is supported, but only with external linking) openbsd/arm (no cgo or external linking) And retires some old ones: DragonflyBSD dropped support for i386; dragonfly/386 was removed from Go. Apple no longer supports OS X 10.6 (no security updates since 2013);

the Go port to OS X 10.6 (Snow Leopard) is no longer actively maintained. 12

Shared libraries Go 1.5 can produce Go shared libraries that can be consumed by Go programs. Build the standard library as shared libraries: $ go install -buildmode=shared std Build a "Hello, world" program that links against the shared libraries: $ go build -linkshared hello.go $ ls -l hello -rwxr-xr-x 1 adg adg 13926 May 26 02:13 hello Go 1.5 can also build Go programs as C archive files (for static linking)

or shared libraries (for dynamic linking) that can be consumed by C programs. golang.org/s/execmodes (Demo) 13

Go programs as C libraries Given a package: package p // import "p" import "C" //export Foo func Foo() int32 { return 42 } And a main package that imports it: package main // import "m" import _ "p" func main() {} // ignored You can build an archive file that can be linked into a C program: $ go build -buildmode=c-archive m $ ls $GOPATH/pkg/linux_amd64 m.a p.a p.h 14

A minor language change You may now omit the key type from a map literal. This map literal m := map[Point]string{ Point{29.935523, 52.891566}: "Persepolis", Point{-25.352594, 131.034361}: "Uluru", Point{37.422455, -122.084306}: "Googleplex", } may now be written as: m := map[Point]string{ {29.935523, 52.891566}: "Persepolis", {-25.352594, 131.034361}: "Uluru", {37.422455, -122.084306}: "Googleplex", } 15

"go doc" The go tool has a new implementation of the old doc subcommand,

with a much improved command-line interface: $ go doc zip.reader package zip // import "archive/zip" type Reader struct { File []*File Comment string // Has unexported fields. } func NewReader(r io.ReaderAt, size int64) (*Reader, error) $ cd $GOROOT/src/archive/zip $ go doc reader # same output as above (Demo) 16

Execution tracing The new execution tracer collects data to produce diagrams of process execution. Front end is the Android/Chrome trace-viewer. (github.com/google/trace-viewer) golang.org/s/go15trace 17

Analysis and Refactoring Tools We have been working on tools for analyzing and manipulating Go source code. Analysis tools: oracle : a tool for answering questions about Go source code (w/ plugins for Sublime Text and Emacs).

: a tool for answering questions about Go source code (w/ plugins for Sublime Text and Emacs). callgraph : display the call graph of a Go program.

: display the call graph of a Go program. godoc -analysis=pointer: see pointer analysis details in godoc. Refactoring tools: eg : a template-based refactoring tool

: a template-based refactoring tool gorename : type-safe renaming of identifiers in Go source code. 18

Builder infrastructure We have been hacking away at our continuous build infrastructure. Now running Linux, Windows, OS X, FreeBSD, OpenBSD, and Plan 9 builders

on Google Compute Engine. Spin up builders to do work, spin up many in parallel.

Gives us results much faster. Sharding of tests on slower platforms (eg, ARM). Trybots test pending changes. (Demo) 19

Mobile Go 1.5 provides support for Android and experimental support for iOS. 20

The gomobile tool The gomobile tool simplifies toolchain installation and app

deployment.

(It only supports Android right now.) To install the Android compiler toolchain: $ gomobile init To build an Android APK and install on a device: $ gomobile install To build a shared library for an Android or iOS app: $ gomobile bind (Demo) 21

Go community events GoCon, Tokyo, June

GopherCon, Denver, July

GolangUK, London, August

GothamGo, New York, October

dotGo, Paris, November And more to be announced. 22