Go 1.15 is officially released, so let's take a look at some of the changes that deserve attention

Go Team announced the official release of Go 1.15 this morning. Because of the impact of this year's outbreak, so although this version released as scheduled, but the content of the change is not much.

Most of its changes are implemented in toolchains, runtimes, and libraries. A s always, this release retains a promise of Go 1 This guarantees that almost all Go programs will compile and run as normally as before.

Go 1.15 includes significant improvements to the linker, improved allocation of small objects with a large number of cores, and deprecation of X.509 CommonName GOPROXY now supports skipping agents that return errors and adding a new embedded tzdata package.

Let's take a look at the specific changes that deserve attention.

(Recommended course: Go tutorial)

1, the new linker

Official design document address: https://golang.org/s/better-linker, from a naming point of view, is a better linker (this is nonsense).

This version of Go reduces the use (time and memory) of linker resources and improves code robustness/maintainability. F or ELF operating systems Linux FreeBSD OpenBSD Dragonfly and S olaris running on the amd64 architecture, the link speed of a representative large Go assembly is increased by 20% and the average memory requirement is reduced by 30%. NetBSD I mprovements to other /OS combinations. K ey factors in improving link program performance are the target file format of the new design, as well as improvements in the internal phases to improve concurrence (for example, by applying relocation in parallel to symbols). T he target file in Go 1.15 is slightly larger than its 1.14 equivalent. T hese changes are part of a multi-version project to modernize Go Linker, which means that other improvements to the Linker are expected in future releases. The linker now defaults to the internal link mode of -buildmode=pie on linux/amd64 and linux/arm64 so these configurations no longer require C linker.

2, compiler improvements, including slightly smaller binaries

The security rules for package unsafe allow unsafe.Pointer converts to uintptr P reviously, in some cases, the compiler allowed multiple chain conversions (such as syscall.Syscall（…，uintptr（uintptr（ptr）），…） ）。 T he compiler now only needs one conversion. Code that uses multiple conversions should be updated to meet security rules.

Compared to Go 1.14 Go 1.15 reduces the typical binary size by approximately 5% compared to Go 1.14 by eliminating certain types of GC metadata and more aggressively eliminating unused type metadata. T he toolchain now mitigates Intel CPU errata SKX102 on GOARCH=amd64 by aligning the function with the 32-byte boundary and filling the jump instruction. Although this padding increases the binary size, it goes far beyond what the above binary size improvements make up.

Go 1.15 adds -spectre flag to both the compiler and the assembler to allow Spectre mitigations to be enabled. T hese are almost absolutely unnecessary and are provided primarily as "defense-in-depth" mechanisms. For more information, see Spectre Wiki page.

The compiler will now reject //go: compiler instructions, which are meaningless to the declarations it uses, and a "misplaced compiler instruction" error. Such error-using instructions have been corrupted before, but the compiler silently ignores them.

The compiler's -json optimization logging report now has a large copy >= 128 字节 and contains a description of the escape analysis decision.

(Recommended course: Go Web programming)

3, embedded tzdata (time zone data)

Added a new package: time/tzdata when the system can't find time zone data (such as Windows, etc.), by importing the package, embedding time zone data in the program, or by passing -tags timetzdata at compile time to achieve the same effect.

Check out this issue https://github.com/golang/go/issues/38017 and the description of the package time/tzdata https://golang.org/pkg/time/tzdata/.

4, increase testing. T B. TempDir

Test generation of temporary files is quite common, this in order to better solve this problem. See issue for issue https://github.com/golang/go/issues/35998.

5, increase testing. T.Deadline

Introduce context into testing package. See issue https://github.com/golang/go/issues/28135 for details.

6, about the Ports section

darwin/386 darwin/arm are no longer supported; riscv64 is better; linux/arm64 is now supported as Class I port

7, API changes

1. net/url.URL RawFragment and EscapedFragment see issue: https://github.com/golang/go/issues/37776;

1. net/url.URL.Redacted see issue for details: https://github.com/golang/go/issues/34855;

3. time.Ticker.Reset we know that Timer has Reset this time for Ticker also increased, see issue https://github.com/golang/go/issues/33184;

1. regexp.Regexp.SubexpIndex see issue https://github.com/golang/go/issues/32420;

1. sync.Map.LoadAndDelete see issue https://github.com/golang/go/issues/33762 for details;

1. crypto/tls.Dialer.DialContext see issue for details: https://github.com/golang/go/issues/18482;

There are other API changes, not to mention.

8, tool chain

1. Add go env GOMODCACHE https://github.com/golang/go/issues/34527;

1. opt-in fallbacks in GOPROXY ： https://github.com/golang/go/issues/37367 ；

1. vet：warn about string(int) and detect impossible interface assertions https://github.com/golang/go/issues/32479 and https://github.com/golang/go/issues/4483;

1. println allows two values to be printed. println(twoValues()) ；

1. panic Displays printable values instead of addresses. Like what:

type MyString string
panic(MyString("hello"))

Print now:

panic: (main.MyString) (0x48aa00,0x4c0840)

Expect to print:

panic: main.MyString("hello")

Readability is much better.

9, performance

1. Better write masking on amd64

1. On Linux forkAndExec uses dup3

1. sha512 algorithm speed increased by 15%;

1. ReadMemStats delay reduced by 95%;

1. 99% faster channel reception in the off state;

1. Converting a small int value to interface{} does not allocate additional memory;

(Recommended micro-class: Go micro-class)

10, more detailed changes

For more detailed changes, see the official release document https://golang.org/doc/go1.15.

Here's a look at some notable changes in Go 1.15, and I hope it's helpful.