From: Rob Pike Date: Thu, 25 Jun 2015 06:20:27 +0000 (+1000) Subject: doc: first cut at prose for big changes in go1.5.html X-Git-Tag: go1.5beta1~119 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=751eef83e0c0a28879cdcdc384d6810dad915e90;p=gostls13.git doc: first cut at prose for big changes in go1.5.html Change-Id: Ie2aba3d5069d88548414f7d76b9b6efb9acf0393 Reviewed-on: https://go-review.googlesource.com/11477 Reviewed-by: Brad Fitzpatrick --- diff --git a/doc/go1.5.html b/doc/go1.5.html index 09c0075a30..0f9a6c6493 100644 --- a/doc/go1.5.html +++ b/doc/go1.5.html @@ -4,93 +4,217 @@ "Template": true }--> + +

Introduction to Go 1.5

+ +

+The latest Go release, version 1.5, +is a significant release, including major architectural changes to the implementation. +Despite that, we expect almost all Go programs to continue to compile and run as before, +because the release still maintains the Go 1 promise +of compatibility. +

+ +

+The biggest developments in the implementation are: +

+ + + +

+These and a number of other changes to the implementation and tools +are discussed below. +

+ +

+The release also contains one small language change involving map literals. +

+ +

+Finally, the timing of the release +strays from the usual six-month interval, +both to provide more time to prepare this major release and to shift the schedule thereafter to +time the release dates more conveniently. +

+ +

Changes to the language

+ +

Map literals

+ +

+Due to an oversight, the rule that allowed the element type to be elided from slice literals was not +applied to map keys. +This has been corrected in Go 1.5. +An example will make this clear: as of Go 1.5, 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 be written as follows, without the Point type listed explicitly: +

+ +
+m := map[Point]string{
+    {29.935523, 52.891566}:   "Persepolis",
+    {-25.352594, 131.034361}: "Uluru",
+    {37.422455, -122.084306}: "Googleplex",
+}
+
+ +

The Implementation

+ +

No more C

+ +

+The compiler and runtime are now implemented in Go and assembler, without C. +The only C source left in the tree is related to testing or to cgo. +There was a C compiler in the tree in 1.4 and earlier. +It was used to build the runtime; a custom compiler was necessary in part to +guarantee the C code would work with the stack management of goroutines. +Since the runtime is in Go now, there is no need for this C compiler and it is gone. +Details of the process to eliminate C are discussed elsewhere. +

+ +

+The conversion from C was done with the help of custom tools created for the job. +Most important, the compiler was actually moved by automatic translation of +the C code into Go. +It is in effect the same program in a different language. +It is not a new implementation +of the compiler so we expect the process will not have introduced new compiler +bugs. +An overview of this process is available in the slides for +this presentation. +

+ +

Compiler and tools

+ +

+Independent of but encouraged by the move to Go, the names of the tools have changed. +The old names 6g, 8g and so on are gone; instead there +is just one binary, accessible as go tool compile, +that compiles Go source into binaries suitable for the architecture and operating system +specified by $GOARCH and $GOOS. +Simlarly, there is now one linker (go tool link) +and one assembler (go tool asm). +The linker was translated automatically from the old C implementation, +but the assembler is a new native Go implementation discussed +in more detail below. +

+ +

+Similar to the drop of the names 6g, 8g, and so on, +the output of the compiler and assembler are now given a plain .o suffix +rather than .8, .6, etc. +

+ + +

Garbage collector

+ +

+TODO +

+ +

Runtime

+ +

+In Go 1.5, the order in which goroutines are scheduled has been changed. +The properties of the scheduler were never defined by the language, +but programs that depended on the scheduling order may be broken +by this change. +We have seen a few (erroneous) programs affected by this change. +If you have programs that implicitly depend on the scheduling +order, you will need to update them. +

+ +

+Another potentially breaking change is that the runtime now +sets the default number of threads to run simultaneously, +defined by GOMAXPROCS, to the number +of cores available on the CPU. +In prior releases it defaulted to 1. +Programs that do not expect to run with multiple cores may +break inadvertently. +They can be updated by removing the restriction or by setting +GOMAXPROCS explicitly. +

+ +

Build

+ +

+Now that the Go compiler and runtime are implemented in Go, a Go compiler +must be available to compile the distribution from source. +Thus, to build the Go core, a working Go distribution must already be in place. +(Go programmers who do not work on the core are unaffected by this change.) +Any Go 1.4 or later distribution (including gccgo) will serve. +For details, see the design document. +

+ +

Ports

+ +

+Due mostly to the industry's move away the 32-bit x86 architecture, +the set of binary downloads provided is reduced in 1.5. +A distribution for the OS X operating system is provided only for the +amd64 architecture, not 386. +Similarly, the ports for Snow Leopard (Apple OS X 10.6) still work but are no +longer released as a download or maintained since Apple no longer maintains that version +of the operating system. +Also, the dragonfly/386 port is no longer supported at all +because DragonflyBSD itself no longer supports the 32-bit 386 architecture. +

+ +

+There are however several new ports available to be built from source. +These include darwin/arm and darwin/arm64. +The new port linux/arm64 is mostly in place, but cgo +is only supported using external linking. +

+ 
-Overall:
-- toolchain in Go
-- new GC
-- go tool asm, go tool compile, go tool link
-- default output files changed: now file.o and a.out
-- internal enforced even outside standard library (golang.org/s/go14internal; https://golang.org/cl/9156)
-- gomaxprocs=numcpu (golang.org/s/go15gomaxprocs)
-
-Language:
-- permit omission of key type in map composite literals where key is a composite literal (https://golang.org/cl/2591)
-
-Build:
-- Go 1.4 required to build (https://golang.org/cl/2470, https://golang.org/cl/2993)
-
-New Ports:
-- darwin/arm, a.k.a iOS. (https://golang.org/cl/2118, 2119, 3273, 2121, 2122, ..., 2127)
-- darwin/arm64
-- linux/arm64 (cgo is supported, but only with external linking)
-- openbsd/arm (no cgo or external linking)
-
-Removed Ports:
-- dragonfly/386 (https://golang.org/cl/7543)
-- The port to Snow Leopard (OS X 10.6) is no longer actively maintained.
-
-Runtime:
-- goroutine scheduling order changed; never guaranteed by language,
-  but can break tests that implicitly assume a specific execution
-  order
 
 API additions and behavior changes:
 
-archive/zip: add (*Writer).SetOffset method (https://golang.org/cl/7445)
-bufio: add Reader.Discard (https://golang.org/cl/2260)
-bytes: add Buffer.Cap (https://golang.org/cl/8342)
-bytes, strings: add Reader.Size (https://golang.org/cl/3199)
-bytes, strings: add LastIndexByte (https://golang.org/cl/9500)
-crypto/cipher: clarify what will happen if len(src) != len(dst) for the Stream interface. (https://golang.org/cl/1754)
-crypto/cipher: support non-standard nonce lengths for GCM. (https://golang.org/cl/8946)
-crypto/elliptic: add Name field to CurveParams struct (https://golang.org/cl/2133)
-crypto/elliptic: Unmarshaling points now automatically checks that the point is on the curve (https://golang.org/cl/2421)
-crypto/tls: change default minimum version to TLS 1.0. (https://golang.org/cl/1791)
-crypto/tls: including Certificate Transparency SCTs in the handshake is now supported (https://golang.org/cl/8988)
-crypto/tls: session ticket keys can now be rotated at runtime (https://golang.org/cl/9072)
-crypto/tls: servers will now always call GetCertificate to pick a certificate for a connection when Certificates is empty (https://golang.org/cl/8792)
-crypto/x509: wildcards are now only accepted as the first label (https://golang.org/cl/5691)
-crypto/x509: unknown critical extensions now cause errors in Verify, not when parsing (https://golang.org/cl/9390)
-database/sql: add Stats (https://golang.org/cl/7950)
-encoding/base64: add unpadded encodings (https://golang.org/cl/1511)
 flag: new nicer format for PrintDefaults (https://golang.org/cl/7330)
-fmt: empty slices now print nothing with %x (bug fix) (https://golang.org/cl/8864)
-fmt: reflect.Value now prints what it holds (https://golang.org/cl/8731)
-go/ast: add Implicit field to ast.EmptyStmt; changed meaning of ast.EmptyStmt.Semicolon position (https://golang.org/cl/5720)
-go/build: reserved GOARCHes for common architectures (https://golang.org/cl/9644)
-io: add CopyBuffer, Copy with user-provided buffer (https://golang.org/cl/8730)
-log: add SetOutput functions (https://golang.org/cl/2686, https://golang.org/cl/3023)
-log: add LUTC flag (https://golang.org/cl/8761)
 math/big: add arbitrary precision Floats (many cl's)
-math/big: add Jacobi and Int.ModSqrt (https://golang.org/cl/1886)
-mime: add ExtensionByType (https://golang.org/cl/7444)
 mime/quotedprintable: new package (https://golang.org/cl/5940 + others)
-net: add sequential and RFC 6555-compliant TCP dialing (https://golang.org/cl/8768)
-net: add Source field to OpError (https://go-review.googlesource.com/9231)
-net: fix inconsistent errors (https://golang.org/cl/9236)
-net: add SocketConn, SocketPacketConn (https://golang.org/cl/9275)
-net: use Go's DNS resolver when system configuration permits (https://golang.org/cl/8945)
-net/http: support for setting trailers from a server Handler (https://golang.org/cl/2157)
-net/http: ignore the Unix epoch time in ServeContent (https://golang.org/cl/7915)
-net/http/cgi: fix REMOTE_ADDR, REMOTE_HOST, add REMOTE_PORT (https://golang.org/cl/4933)
-net/mail: adds AddressParser type (https://golang.org/cl/10392)
-net/smtp: add TLSConnectionState accessor (https://golang.org/cl/2151)
-os: add LookupEnv (https://golang.org/cl/9741)
-os/signal: add Ignore and Reset (https://golang.org/cl/3580)
 reflect: add ArrayOf (https://golang.org/cl/4111)
 reflect: add FuncOf (https://golang.org/cl/1996)
-runtime, syscall: use SYSCALL instruction on FreeBSD (Go 1.5 now requires FreeBSD 8-STABLE+) (https://golang.org/cl/3020)
-runtime, syscall: use get_random_bytes syscall for NaCl (Go 1.5 now requires NaCl SDK pepper-39 or above) (https://golang.org/cl/1755)
-runtime/pprof: memory profiles include overall memory statistics by default (https://golang.org/cl/9491)
-strings: add Compare(x, y string) int, for symmetry with bytes.Compare (https://golang.org/cl/2828)
-syscall: Add Foreground and Pgid to SysProcAttr (https://golang.org/cl/5130)
-syscall: add missing Syscall9 for darwin/amd64 (https://golang.org/cl/6555)
-syscall: Add GidMappingsEnableSetgroups to linux SysProcAttr (http://golang.org/cl/10670)
-testing/quick: support generation of arrays (https://golang.org/cl/3865)
-testing/quick: generated pointers can now be nil (https://golang.org/cl/10821)
-text/template: add Options method (https://golang.org/cl/8462)
-text/template: huge integers are now parse errors (https://golang.org/cl/9651)
-time: add time.AppendFormat(https://golang.org/cl/1760)
 
 Tools:
 
@@ -104,6 +228,7 @@ cmd/go: .swig/.swigcxx files now require SWIG 3.0.6 or later
 cmd/go: add -run flag to go generate (https://golang.org/cl/9005)
 cmd/go: add $GOLINE to generate's variables (https://golang.org/cl/9007)
 cmd/go: add go doc (https://golang.org/cl/9227)
+cmd/go: internal enforced even outside standard library (golang.org/s/go14internal; https://golang.org/cl/9156)
 cmd/go, testing: add go test -count (https://golang.org/cl/10669)
 cmd/go: add preliminary support for vendor directories (https://golang.org/cl/10923)
 cmd/vet: better validation of struct tags (https://golang.org/cl/2685)
@@ -115,6 +240,7 @@ cmd/go: add -buildmode build option
 cmd/gc: add -dynlink option (for amd64 only)
 cmd/ld: add -buildmode option
 cmd/trace: new command to view traces (https://golang.org/cl/3601)
+
 Performance:
 
 cmd/gc: evaluate concrete == interface without allocating (https://golang.org/cl/2096)
@@ -167,3 +293,209 @@ were fixed in fmt, archive/zip, archive/tar, encoding/gob, image/jpeg, image/png
 image/gif, compress/flate, text/template, html/template. The fixes harden implementation
 against incorrect and malicious inputs.
+ +

Minor changes to the library

+ +