Comparison of Crystal and C binary sizes

crystal_binary_size_comparison.md

Crystal Source Code:

def factorial(n)
    n < 2 ? 1 : n * factorial(n - 1)
end

if ARGV.size > 0
    n = ARGV.first.to_u64
    puts factorial(n)
else
    puts "No arguments provided"
    exit 1
end

C Source Code:

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h> 

uint64_t factorial(uint64_t n) {
    return (n < 2) ? 1 : n * factorial(n - 1);
}

int main(int argc, char* argv[]) {
    if (argc < 2) {
        printf("No arguments provided\n");
        return 1;
    } else {
        uint64_t n = strtol(argv[1], NULL, 10);
        printf("%lu\n", factorial(n));
        return 0;
    }
}

It can be seen that the binary produced by Crystal is significantly larger than the C binary:

-rwxr-xr-x 1 daniel daniel    7168 Jun 24 19:46 hello_c
-rw-r--r-- 1 daniel daniel     385 Jun 24 19:49 hello.c
-rwxr-xr-x 1 daniel daniel 1270216 Jun 24 20:02 hello_cr
-rw-r--r-- 1 daniel daniel     177 Jun 24 20:01 hello.cr

177x larger in fact.

A lot of data is debug information.

@teaearlgraycold big binaries contains a lot of debug info as @akzhan said. It's intend to use on development environment.

On production, you can compile using: (warning: basic debug info is still very useful on production environments)

>>> crystal build --release --no-debug hello.cr
>>> ls -l
-rwxr-xr-x 1 main main 185600 Jul 21 17:19 hello_cr

185600B is 6.8x smaller that a binary compiled without flags release and no-debug (1270216B)

Optionally you can strip symbols to make the binary even more smaller:

>>> strip -s hello_cr
>>> ls -l
-rwxr-xr-x 1 main main 158344 Jul 21 17:22 hello_cr

strip removes about 30K of unnecessary symbols, then 158344B is about 22X bigger that C binary compared with 177X you got. However Crystal lang is more High level than C and it simplify a lot of things when you code, type inference by example.

Experimenting with smaller binaries

All the above is using standard prelude, you can get even smaller binaries just linking LibC and using empty prelude like:

class String
  def to_unsafe
    pointerof(@c)
  end
end

@[Link("c")]
lib LibC
  fun printf(s : UInt8*, ...) : Int32
end

def factorial(n : UInt64)
  n < 2_u64 ? 1_u64 : n * factorial(n - 1_u64)
end

LibC.printf "%d\n".to_unsafe, factorial(10_u64)

And then:

>>> crystal build fac.cr --prelude="empty" -p --release --no-debug
-rwxr-xr-x 1 main main 8488 Jul 21 17:26 hello_cr

8488B is just 1.2X of C binary and if you strip it is like 0.8X of C binary.

>>> strip -s hello_cr
>>> ls -l
-rwxr-xr-x 1 main main 6216 Jul 21 17:30 hello_cr

You can see a experiment to get an even smaller crystal binary here 👉 https://github.com/kubo39/tinycr (just 146 bytes 😅 )

Thanks for the info, @faustinoaq

@faustinoaq doing god's work 🗡️ ty