How to reduce compiled file size?

问题:

Lets compare c and go: Hello_world.c :

#include<stdio.h>
int main(){
    printf("Hello world!");
}

Hello_world.go:

package main
import "fmt"
func main(){
    fmt.Printf("Hello world!")
}

Compile both:

$gcc Hello_world.c -o Hello_c 
$8g Hello_world.go -o Hello_go.8
$8l Hello_go.8 -o Hello_go

and ... what is it?

$ls -ls
... 5,4K 2010-10-05 11:09 Hello_c
... 991K 2010-10-05 11:17 Hello_go

About 1Mb Hello world. Are you kidding me? What I do wrong?

(strip Hello_go -> 893K only)

回答1:

Is it a problem that the file is larger? I don't know Go but I would assume that it statically links some runtime lib which is not the case for the C program. But probably that is nothing to worry about as soon as your program gets larger.

As described here, statically linking the Go runtime is the default. That page also tells you how to set up for dynamic linking.

回答2:

If you are using a Unix-based system (e.g. Linux or Mac OSX) you could try removing the debugging information included in the executable by building it with the -w flag:

go build -ldflags "-w" prog.go

The file sizes are reduced dramatically.

For more details visit the GDB's page: http://golang.org/doc/gdb

回答3:

The 2016 answer:

1. Use Go 1.7

2. Compile with go build -ldflags "-s -w"

➜ ls -lh hello
-rwxr-xr-x 1 oneofone oneofone 976K May 26 20:49 hello*

3. Then use upx, goupx is no longer needed since 1.6.

➜ ls -lh hello
-rwxr-xr-x 1 oneofone oneofone 367K May 26 20:49 hello*

回答4:

Go binaries are large because they are statically linked (except for library bindings using cgo). Try statically linking a C program and you'll see it grow to a comparable size.

If this is really a problem for you (which I have a hard time believing), you can compile with gccgo and dynamically link.

回答5:

You should get goupx, it will "fix" Golang ELF executables to work with upx. I've already got around 78% file size shrink in some cases ~16MB >> ~3MB.

Compression ratio usually tends to 25%, so it's worth a try:

$ go get github.com/pwaller/goupx
$ go build -o filename
$ goupx filename

>>

2014/12/25 10:10:54 File fixed!

        File size         Ratio      Format      Name
   --------------------   ------   -----------   -----------
  16271132 ->   3647116   22.41%  linux/ElfAMD   filename                            

Packed 1 file.

EXTRA: -s flag (strip) can shrink bin file even more goupx -s filename

回答6:

More compact hello-world example:

package main

func main() {
  print("Hello world!")
}

We are skiped large fmt package and noticeably reduced binary:

  $ go build hello.go
  $ ls -lh hello
  ... 259K ... hello2
  $ strip hello
  $ ls -lh hello
  ... 162K ... hello2

Not so compact as C, but though measured in K not M :) Ok, it is not general way just shows some ways to optimize a size: use strip and try to use minimum packages. Anyway Go is not language for making tiny sized binaries.

回答7:

create a file named main.go, let's try with simple hello world program.

package main

import "fmt"

func main(){
    fmt.Println("Hello World!")
}

I use go version 1.9.1

$ go version
 go version go1.9.1 linux/amd64

Compile with standard go build command.

$ go build main.go
$ ls -lh
-rwxr-xr-x-x 1 nil nil 1.8M Oct 27 07:47 main

Let's compile once again with go build but with ldflags as suggested above,

$ go build -ldflags "-s -w" main.go
$ ls -lh
-rwxr-xr-x-x 1 nil nil 1.2M Oct 27 08:15 main

File size is reduced by 30%.

Now, lets use gccgo,

$ go version
 go version go1.8.1 gccgo (GCC) 7.2.0 linux/amd64

Building go with gccgo,

$ go build main.go
$ ls -lh
-rwxr-xr-x 1 nil nil 34K Oct 27 12:18 main

Binary size is reduced by almost 100%. Let's once again try building our main.go with gccgo but with build flags,

$ go build -gccgoflags "-s -w" main.go
-rwxr-xr-x 1 nil nil 23K Oct 27 13:02 main

Warning: As gccgo binaries were dynamically linked. If you have a binary which is very big in size, your binary when compiled with gccgo will not be decreased by 100%, but it will be reduced in size by considerable amount.

Compared to gc, gccgo is slower to compile code but supports more powerful optimizations, so a CPU-bound program built by gccgo will usually run faster. All the optimizations implemented in GCC over the years are available, including inlining, loop optimizations, vectorization, instruction scheduling, and more. While it does not always produce better code, in some cases programs compiled with gccgo can run 30% faster.

The GCC 7 releases are expected to include a complete implementation of the Go 1.8 user libraries. As with earlier releases, the Go 1.8 runtime is not fully merged, but that should not be visible to Go programs.

Pros:

1. Reduced size
2. Optimized.

Cons

1. Slow
2. Cannot use the latest version of go.

You can see over here and here.

回答8:

The binary contains by default the garbage collector, the schedulding system that manage the go routines, and all the libraries you import.

The result is a minimal size of about 1 Mb.

回答9:

From Go 1.8 you can also use the new plugin system to split up your binary into something that resembles shared libraries. For this release it only works on Linux, but other platforms will probably be supported in the future.

https://tip.golang.org/pkg/plugin/

回答10:

2018 answer for the next Go 1.11, as tweeted by Brad Fitzpatrick (mid-June 2018):

As of a few minutes ago, DWARF sections in #golang ELF binaries are now compressed, so at tip binaries are now smaller than Go 1.10, even with all the extra debug stuff at tip.

Cf. Golang issue 11799:

Compressing our debug info might offer a significant, cheap file size win.

See more in commit 594eae5

cmd/link: compress DWARF sections in ELF binaries

The trickiest part of this is that the binary layout code (blk, elfshbits, and various other things) assumes a constant offset between symbols' and sections' file locations and their virtual addresses.

Compression, of course, breaks this constant offset.
But we need to assign virtual addresses to everything before compression in order to resolve relocations before compression.

As a result, compression needs to re-compute the "address" of the DWARF sections and symbols based on their compressed size.
Luckily, these are at the end of the file, so this doesn't perturb any other sections or symbols. (And there is, of course, a surprising amount of code that assumes the DWARF segment comes last, so what's one more place?)

name        old exe-bytes   new exe-bytes   delta
HelloSize      1.60MB ± 0%     1.05MB ± 0%  -34.39%  (p=0.000 n=30+30)
CmdGoSize      16.5MB ± 0%     11.3MB ± 0%  -31.76%  (p=0.000 n=30+30)
[Geo mean]     5.14MB          3.44MB       -33.08%

Rob Pike mentions:

That only helps on machines that use ELF.
Binaries are still too big, and growing.

Brad replied:

At least it's something. Was about to be much worse.
Stopped the bleeding for one release.

Reasons: Debug info, but also register map for the GC to let any instruction be a savepoint.