How do I check the size of a Golang project?

Question

Is there an easy way to check the size of a Golang project? It\'s not an executable, it\'s a package that I\'m importing in my own project.

Answer 1

You can see how big the library binaries are by looking in the $GOPATH/pkg directory (if $GOPATH is not exported go defaults to $HOME/go).

So to check the size of some of the gorilla http pkgs. Install them first:

$ go get -u github.com/gorilla/mux
$ go get -u github.com/gorilla/securecookie
$ go get -u github.com/gorilla/sessions

The KB binary sizes on my 64-bit MacOS (darwin_amd64):

$ cd $GOPATH/pkg/darwin_amd64/github.com/gorilla/
$ du -k *

284 mux.a
128 securecookie.a
128 sessions.a

EDIT:

Library (package) size is one thing, but how much space that takes up in your executable after the link stage can vary wildly. This is because packages have their own dependencies and with that comes extra baggage, but that baggage may be shared by other packages you import.

An example demonstrates this best:

empty.go:

package main

func main() {}

http.go:

package main

import "net/http"

var _ = http.Serve

func main() {}

mux.go:

package main

import "github.com/gorilla/mux"

var _ = mux.NewRouter

func main() {}

All 3 programs are functionally identical - executing zero user code - but their dependencies differ. The resulting binary sizes in KB:

$ du -k *

1028    empty
5812    http
5832    mux

What does this tell us? The core go pkg net/http adds significant size to our executable. The mux pkg is not large by itself, but it has an import dependency on net/http pkg - hence the significant file size for it too. Yet the delta between mux and http is only 20KB, whereas the listed file size of the mux.a library is 284KB. So we can't simply add the library pkg sizes to determine their true footprint.

Conclusion: The go linker will strip out a lot of baggage from individual libraries during the build process, but in order to get a true sense of how much extra weight importing certain packages, one has to look at all of the pkg's sub-dependencies as well.