Reason for huge size of compiled executable of Go

go executable
Karthic Rao picture Karthic Rao · Feb 18, 2015 · Viewed 26.4k times · Source

I complied a hello world Go program which generated native executable on my linux machine. But I was surprised to see the size of the simple Hello world Go program, it was 1.9MB !

Why is it that the executable of such a simple program in Go is so huge?

Answer

icza picture icza · Feb 18, 2015

This exact question appears in the official FAQ: Why is my trivial program such a large binary?

Quoting the answer:

The linkers in the gc tool chain (5l, 6l, and 8l) do static linking. All Go binaries therefore include the Go run-time, along with the run-time type information necessary to support dynamic type checks, reflection, and even panic-time stack traces.

A simple C "hello, world" program compiled and linked statically using gcc on Linux is around 750 kB, including an implementation of printf. An equivalent Go program using fmt.Printf is around 1.9 MB, but that includes more powerful run-time support and type information.

So the native executable of your Hello World is 1.9 MB because it contains a runtime which provides garbage collection, reflection and many other features (which your program might not really use, but it's there). And the implementation of the fmt package which you used to print the "Hello World" text (plus its dependencies).

Now try the following: add another fmt.Println("Hello World! Again") line to your program and compile it again. The result will not be 2x 1.9MB, but still just 1.9 MB! Yes, because all the used libraries (fmt and its dependencies) and the runtime are already added to the executable (and so just a few more bytes will be added to print the 2nd text which you just added).

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