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caution
  • c-shared
    • musl 环境不支持构建 c-shared golang/go#13492 runtime: c-shared builds fail with musllibc
    • windows 下构建 c-shared 需要使用 TDM-GCC
    • 无法 dlclose, offload c-shared #11100
      • 涉及到 VM
envnotemacOS
GOENV~/Library/Application Support/go/env
GOCACHE~/Library/Caches/go-build
GOMODCACHE~/go/pkg/mod
GOTOOLDIR
GOMODgo.mod 位置
GOWORK
# 所有交叉编译列表
go tool dist list
# 包含 cgo 支持情况
go tool dist list -json

# 移除 mod 缓存
go clean -modcache
buildmodedesc
archivebuild non-main, .a
c-archivemain+imports, cgo //export
c-sharedmain+imports, cgo //export
defaultmain+non-main, exec， .a
exemain+imports,exec, 忽略非 main 包
piemain+imports, exec, pie
pluginmain+imports, plugin, 忽略非 main 包
sharednon-main, for -linkshared - module 出来后 异常
ldflagsdesc
-wdisable DWARF generation
-sdisable symbol table
-X 'wener.me/gou/build.Version=123'add definition
-linkmode=external
-extldflags "$LDFLAGS"
gcflagsdesc
-NDisable optimizations
-lDisable inlining
flagsdesc
-modcacherw新的 mod 缓存 rw - 可以 rm -rf
-trimpath移除环境相关路径，reproduceable
-ldflags "$GOLDFLAGS"
-mod=readonly不动 go.mod
-buildmode=pie
# https://pkg.go.dev/cmd/compile
go tool compile -help
envdefaultdesc
GOMAXPROCSMax Thread
GOGC100off 关闭 GC
GOOS
GOARCH

自定义常量​

package main

var Version = "dev"
var CommitTime = ""
var CommitID = ""
var BuildTime = ""
DEF_FLAGS="
-X 'wener.me/tools/build.Version=$(git describe --tags --abbrev=0)'
-X 'wener.me/tools/build.CommitID=$(git rev-parse --short HEAD)'
-X 'wener.me/tools/build.CommitTime=$(git log -1 --format=%cd --date=iso8601)'
-X 'wener.me/tools/build.BuildTime=$(date --iso-8601=seconds)'
"
go build -o bin/cli -ldflags "$DEF_FLAGS" ./cmd/cli

限定 Build Tag​

  • 内置 Tag
    • 版本 - 例如 go1.18
    • cgo
    • gc, gccgo
    • GOOS
    • GOARCH
//go:build tag
//+build tag1,tag2

// 复杂限定
//go:build (linux && 386) || (darwin && !cgo)

package main
go build -tags "tag1 tag2"

交叉编译​

CC_FOR_TARGET=/path/to/arm-unknown-linux-gnueabi-gcc CXX_FOR_TARGET=/path/to/arm-unknown-linux-gnueabi-g++ RANLIB_FOR_TARGET=/path/to/arm-unknown-linux-gnueabi-ranlib

CC=i586-mingw32-gcc GOOS=windows GOARCH=386 CGO_ENABLED=1 go build -v -o myprogram.exe -ldflags="-extld=$CC"
CC=x86_64-pc-linux-gcc GOOS=linux GOARCH=amd64 CGO_ENABLED=1 go build -v -o myprogram -ldflags="-extld=$CC"
CC=arm-linux-gnueabihf-gcc GOOS=linux GOARCH=arm GOARM=6 CGO_ENABLED=1 go build -v -o myprogram -ldflags="-extld=$CC"

构建缓存​

# macOS $HOME/Library/Caches/go-build
# linux $HOME/.cache/go-build
go env GOCACHE

# CI 的时候可修改 GOPATH 更好利用缓存
export GOPATH="$PWD/.cache"
export PATH="$PWD/.cache/bin:$PATH"
export GO111MODULE=on
export GOPROXY=https://goproxy.io

# 清除缓存
go clean -cache

musl static​

-linkmode external -extldflags "-static"

docker builder​

docker pull quay.io/prometheus/golang-builder:arm
docker run --rm -it --entrypoint bash \
  --name go-builder quay.io/prometheus/golang-builder:arm

Ports

GOAMD64​

go 1.18 新增 GOAMD64 环境变量

  • v1 - 默认
  • v2 - CMPXCHG16B, LAHF, SAHF, POPCNT, SSE3, SSE4.1, SSE4.2, SSSE3
    • 2009: Nehalem, Jaguar, Intel Atom Silvermont, QEMU
    • amdv2
  • v3 - AVX, AVX2, BMI1, BMI2, F16C, FMA, LZCNT, MOVBE, OSXSAVE
    • 2015 - Haswell, Excavator
    • amdv3
  • v4 - AVX512F, AVX512BW, AVX512CD, AVX512DQ, AVX512VL
    • 2017: Skylake-X, Skylake-SP
    • 2022: Zen 4
    • amdv4
  • 参考 
# AMDv3
# avx 可能有，但可能没 avx2
grep -oE 'avx2|bmi1|bmi2|f16|fma' /proc/cpuinfo  | sort -u
# AMDv4
grep -oE 'avx512' /proc/cpuinfo  | sort -u

GOARM​

  • ARM 浮点数逻辑

默认基于构建环境自动监测，监测失败则使用 6

  • GOARM=5: use software floating point; when CPU doesn't have VFP co-processor
  • GOARM=6: use VFPv1 only; default if cross compiling; usually ARM11 or better cores (VFPv2 or better is also supported)
  • GOARM=7: use VFPv3; usually Cortex-A cores

FAQ

unrecognized command-line option '-marm'​

CC=arm-linux-gnueabi-gcc

arm-none-eabi-gcc: error: unrecognized command-line option '-pthread'​

需要 arm-linux-eabi

# musl 不包含 pthread 可创建空包满足
# 空包
# ar -rc /usr/lib/libpthread.a
# 交叉编译环境
arm-none-eabi-ar -rc /usr/arm-none-eabi/lib/libpthread.a
  • gcc-arm-none-eabi
    • Cortex-M0/M0+/M3/M4, Cortex-R4/R5/R7, Cortex-A
    • 不支持线程

loadinternal: cannot find runtime/cgo​

CGO_ENABLED=1

FATAL: kernel too old​

注意 gcc 版本

CC=arm-linux-gnueabi-gcc
echo 'int main(){}' > test.c
# ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), statically linked, for GNU/Linux 3.2.0, BuildID[sha1]=a839e1b10daec5d9c348eef8854bb271f8097d34, not stripped
# 注意 GNU/Linux 3.2.0
$CC -o test test.c
file test

implicit declaration of function '_beginthread'; did you mean 'OpenThread'​

换 C 编译器, 尝试用 TDM-GCC

export PATH=/c/TDM-GCC-64/bin:$PATH
LC_ALL=c gcc -v

c-shared 内存泄漏​

使用 c-shared 的方式很难能保证最后 valgrind 不显示有溢出