go的编译过程、选项、以及二进制包

binary-only-package

It is possible to distribute packages in binary form without including the source code 
used for compiling the package. To do this, the package must be distributed with a 
source file not excluded by build constraints and containing a "//go:binary-only-package"
comment. Like a build constraint, this comment must appear near the top of the file, 
preceded only by blank lines and other line comments and with a blank line following the 
comment, to separate it from the package documentation. Unlike build constraints, this 
comment is only recognized in non-test Go source files. 

例子

example code:

▾ binary-only-pkg/
  ▸ p/
  ▸ p_bin/
  ▸ p_src/
    main.go
    Makefile

main.go中引用了p:

import (
	"github.com/lijiaocn/study-Golang/study/binary-only-pkg/p"
)

首先用p_src中的源码编译得到.a文件:

WORKDIR=github.com/lijiaocn/study-Golang/study/binary-only-pkg

install: 
	rm -rf p; cp -rf p_src p
	go build -o ${GOPATH}/pkg/${WORKDIR}/p.a -i ${WORKDIR}/p

然后用p_bin中的文件编译:

build: 
	rm -rf p; cp -rf p_bin p
	go build

可以看到在p_bin/package.go是一个空的package的情况，就可以完成编译：

$cat p_bin/package.go
//go:binary-only-package

package p

注意，中间的空行必须存在，否则报错。

禁用CGO

Golang实现了自己的runtime，也支持调用C的runtime，默认启动CGO：

CGO_ENABLED=1

启动用CGO后，编译的程序可能需要连接外部的.so，可以将CGO禁用以得到静态连接的程序:

CGO_ENABLED=0 go build

也谈Go的可移值性中做了很好的介绍。

跨平台编译

Golang适应的平台非常广泛，可以通过go tool dist list查看支持的平台:

$ go tool dist list
android/386
android/amd64
android/arm
android/arm64
darwin/386
darwin/amd64
darwin/arm
darwin/arm64
dragonfly/amd64
freebsd/386
freebsd/amd64
freebsd/arm
linux/386
linux/amd64
linux/arm
linux/arm64
linux/mips
linux/mips64
linux/mips64le
linux/mipsle
linux/ppc64
linux/ppc64le
linux/s390x
nacl/386
nacl/amd64p32
nacl/arm
netbsd/386
netbsd/amd64
netbsd/arm
openbsd/386
openbsd/amd64
openbsd/arm
plan9/386
plan9/amd64
plan9/arm
solaris/amd64
windows/386
windows/amd64

编译的时候通过环境变量GOARCH和GOOS指定目标平台，例如: