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shrink-binary.md

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Shrink Golang binary

Source: https://github.com/xaionaro/documentation/blob/master/golang/reduce-binary-size.md

Table of contents:

0. Prepare

$ go version
go version go1.20.2 linux/amd64

$ mkdir /tmp/helloworld

$ cd /tmp/helloworld

$ cat > hello.go <<EOF
package main

import "fmt"

func main() {
   fmt.Println("hello-world")
}
EOF
  • Default build:
$ go build -o default ./hello.go; stat -c %s default
1845890

$ export CGO_ENABLED=0

$ go build -o default ./hello.go; stat -c %s default
1845882

1. Go build flags

$ go build -ldflags="-s -w" -o stripped hello.go; stat -c %s stripped
1228800
  • Disable function inlining:
$ go build -ldflags="-w -s" -gcflags=all=-l -o disinlining hello.go; stat -c %s disinlining
1208320

# It's not helpful on hello-world example, but it's helpful on big projects. It could save ~10%
  • Disable bound checks:
$ go build -a -gcflags=all="-l -B" -ldflags="-w -s" -o disbound hello.go; stat -c %s disbound
1179648

2. Compress the binary

  • You can compress the binary using UPX.
  • But, just keep in mind:
    • The binary will be much slower
    • It will consume more RAM
    • It will be almost useless if you already store your binary in a compressed state (for example in initrd, compressed by xz).
  • Let's go:
$ upx disbound -o disbound-upx
                       Ultimate Packer for eXecutables
                          Copyright (C) 1996 - 2020
UPX 3.96        Markus Oberhumer, Laszlo Molnar & John Reiser   Jan 23rd 2020

        File size         Ratio      Format      Name
   --------------------   ------   -----------   -----------
   1179648 ->    479572   40.65%   linux/amd64   disbound-upx

Packed 1 file.
479572

$ upx --best --ultra-brute disbound -o disbound-upx-brute; stat -c %s disbound-upx-brute
                       Ultimate Packer for eXecutables
                          Copyright (C) 1996 - 2020
UPX 3.96        Markus Oberhumer, Laszlo Molnar & John Reiser   Jan 23rd 2020

        File size         Ratio      Format      Name
   --------------------   ------   -----------   -----------
   1179648 ->    386044   32.73%   linux/amd64   disbound-upx-brute

Packed 1 file.
386044

3. Illegal: It works but ...

  • 32bits instead of 64bits: It has obvious limitations:
    • 32bit address space
    • 32bit integers
    • Less registers (less performance in some cases)
    • 32bit syscalls (for example there's no kexec_file_load)
$ go env GOARCH
amd64

$ GOARCH=386 go build -a -gcflags=all="-l -B" -ldflags="-w -s" -o disbound-32 hello.go; stat -c %s disbound-32
1122304
  • You can find more in the Source link but I don't think that we should follow it,...

4. Result

$ ls -la
total 9.0M
drwxrwxr-x  2 kiennt kiennt 4.0K Apr 24 16:47 ./
drwxrwxrwt 25 kiennt kiennt  20K Apr 24 16:53 ../
-rwxrwxr-x  1 kiennt kiennt 1.8M Apr 24 15:48 default*
-rwxrwxr-x  1 kiennt kiennt 1.2M Apr 24 15:52 disbound*
-rwxrwxr-x  1 kiennt kiennt 1.1M Apr 24 16:47 disbound-32*
-rwxrwxr-x  1 kiennt kiennt 469K Apr 24 15:52 disbound-upx*
-rwxrwxr-x  1 kiennt kiennt 377K Apr 24 15:52 disbound-upx-brute*
-rwxrwxr-x  1 kiennt kiennt 1.2M Apr 24 15:51 disinlining*
-rwxrwxr-x  1 kiennt kiennt 1.8M Apr 24 15:47 hello*
-rw-rw-r--  1 kiennt kiennt   74 Apr 24 15:46 hello.go
-rwxrwxr-x  1 kiennt kiennt 1.2M Apr 24 15:50 stripped*