smaller binaries when compiled with static ldflag

[sjpotter]

What version of Go are you using (go version)?

go version go1.6.3 linux/amd64

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/spotter/gocode"
GORACE=""
GOROOT="/usr/lib/go-1.6"
GOTOOLDIR="/usr/lib/go-1.6/pkg/tool/linux_amd64"
GO15VENDOREXPERIMENT="1"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0"
CXX="g++"
CGO_ENABLED="1"

What did you do?

compiling a project that includes cgo files, hence would normally make a dynamic linked binary (against C runtime) and then compiles it statically.

i.e.

go build ./path/to/command.go

vs

go build --ldflags '-extldflags "-static"' ./path/to/command.go

What did you expect to see?

I expected the dynamic binary to be smaller than the fully statically linked binary.

What did you see instead?

the statically linked binary was significantly smaller, and I'm not the only one to see this

see this from reddit where someone sees similar behavior

https://www.reddit.com/r/golang/comments/46gbdz/binary_sizes_in_go/d058h1u/

[bradfitz]

For questions about Go, see https://golang.org/wiki/Questions.

It looks like you're not comparing dynamic vs static, but dynamic vs static+stripped.

[sjpotter]

Stripped is even smaller (similar) in both cases.

Full Example

$ go build ./cmd/cmd.go
$ ls -l cmd
-rwxr-xr-x 1 spotter spotter 87322360 Dec 28 11:58 cmd
$ strip cmd
$ ls -l cmd
-rwxr-xr-x 1 spotter spotter 60697704 Dec 28 11:58 cmd

$ go build --ldflags '-extldflags "-static"' ./cmd/cmd.go
$ ls -l cmd
-rwxr-xr-x 1 spotter spotter 70021544 Dec 28 11:59 cmd
$ strip cmd
$ ls -l cmd
-rwxr-xr-x 1 spotter spotter 42909128 Dec 28 12:00 cmd