Wasm file comparisons

hello.c

// Compiler: emcc 4.0.23 (Emscripten)
//
// Build commands and resulting WASM sizes:
//
// Default (debug):
//   emcc hello.c -o hello.wasm
//   Size: 15 KB
//
// Release (optimized):
//   emcc -O3 hello.c -o hello.wasm
//   Size: 2.0 KB

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

hello.go

// Compiler: tinygo 0.33.0 (go 1.23.0, LLVM 18.1.2)
//
// Build commands and resulting WASM sizes:
//
// Default (debug):
//   tinygo build -target wasi -o hello.wasm hello.go
//   Size: 470 KB
//
// Release (optimized):
//   tinygo build -target wasi -opt=2 -o hello.wasm hello.go
//   Size: 446 KB

package main

import "fmt"

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

hello.rs

// Compiler: rustc 1.92.0 (ded5c06cf 2025-12-08)
//
// Build commands and resulting WASM sizes:
//
// Default (debug):
//   rustc --target wasm32-wasip1 hello.rs -o hello.wasm
//   Size: 1.8 MB
//
// Release (optimized):
//   rustc --target wasm32-wasip1 -C opt-level=3 hello.rs -o hello.wasm
//   Size: 1.8 MB

fn main() {
    println!("Hello, World!");
}

hello.zig

// Compiler: zig 0.12.0-dev.2700+d12c8db64
//
// Build commands and resulting WASM sizes:
//
// Default (debug):
//   zig build-exe hello.zig -target wasm32-wasi -femit-bin=hello.wasm
//   Size: 601 KB
//
// Release (optimized):
//   zig build-exe hello.zig -target wasm32-wasi -OReleaseFast -femit-bin=hello.wasm
//   Size: 12 KB

const std = @import("std");

pub fn main() void {
    std.debug.print("Hello, World!\n", .{});
}

hello_minimal.c

// Compiler: zig cc (clang 17.0.6 via zig 0.12.0-dev.2700+d12c8db64)
//
// Build commands and resulting WASM sizes:
//
// Minimal (no libc, direct WASI calls, using zig cc):
//   zig cc --target=wasm32-wasi -O3 -nostdlib \
//          -Wl,--no-entry -Wl,--export=_start \
//          hello_minimal.c -o hello_minimal.wasm
//   Size: 1.3 KB (includes debug metadata)
//
// Minimal + stripped:
//   zig cc --target=wasm32-wasi -O3 -nostdlib \
//          -Wl,--no-entry -Wl,--export=_start -Wl,--strip-all \
//          hello_minimal.c -o hello_minimal.wasm
//   Size: 254 B
//
// Compared to standard hello.c (emscripten):
//   Debug:   15 KB  -> 254 B  (60x smaller)
//   Release: 2.0 KB -> 254 B  (8x smaller)

__attribute__((import_module("wasi_snapshot_preview1"), import_name("fd_write")))
int fd_write(int fd, const void *iovs, int iovs_len, int *nwritten);

typedef struct {
    const char *buf;
    int len;
} iovec_t;

void _start() {
    const char msg[] = "Hello, World!\n";
    iovec_t iov = { msg, sizeof(msg) - 1 };
    int nwritten;
    fd_write(1, &iov, 1, &nwritten);
}

hello_minimal.go

// Compiler: tinygo 0.33.0 (go 1.23.0, LLVM 18.1.2)
//
// Build commands and resulting WASM sizes:
//
// Minimal (direct WASI calls, optimized, no debug):
//   tinygo build -target wasi -opt=2 -no-debug -o hello_minimal.wasm hello_minimal.go
//   Size: 17 KB
//
// Compared to standard hello.go:
//   Debug:   470 KB -> 17 KB  (28x smaller)
//   Release: 446 KB -> 17 KB  (26x smaller)

package main

import "unsafe"

//go:wasmimport wasi_snapshot_preview1 fd_write
func fd_write(fd int32, iovs unsafe.Pointer, iovsLen int32, nwritten unsafe.Pointer) int32

type iovec struct {
	buf *byte
	len uint32
}

func main() {
	msg := "Hello, World!\n"
	msgBytes := unsafe.StringData(msg)
	iov := iovec{buf: msgBytes, len: uint32(len(msg))}
	var nwritten int32
	fd_write(1, unsafe.Pointer(&iov), 1, unsafe.Pointer(&nwritten))
}

hello_minimal.rs

// Compiler: rustc 1.92.0 (ded5c06cf 2025-12-08)
//
// Build commands and resulting WASM sizes:
//
// Minimal (no_std, direct WASI calls, LTO, size-optimized):
//   rustc --target wasm32-unknown-unknown -C opt-level=s -C lto=yes \
//         -C link-arg=--export=_start hello_minimal.rs -o hello_minimal.wasm
//   Size: 605 B
//
// Compared to standard hello.rs:
//   Debug:   1.8 MB -> 605 B  (3000x smaller)
//   Release: 1.8 MB -> 605 B  (3000x smaller)

#![no_std]
#![no_main]

use core::panic::PanicInfo;

#[panic_handler]
fn panic(_info: &PanicInfo) -> ! {
    loop {}
}

#[link(wasm_import_module = "wasi_snapshot_preview1")]
extern "C" {
    fn fd_write(fd: u32, iovs: *const Iovec, iovs_len: u32, nwritten: *mut u32) -> u32;
}

#[repr(C)]
struct Iovec {
    buf: *const u8,
    len: u32,
}

#[no_mangle]
pub extern "C" fn _start() {
    let msg = b"Hello, World!\n";
    let iov = Iovec {
        buf: msg.as_ptr(),
        len: msg.len() as u32,
    };
    let mut nwritten: u32 = 0;
    unsafe {
        fd_write(1, &iov, 1, &mut nwritten);
    }
}

hello_minimal.zig

// Compiler: zig 0.12.0-dev.2700+d12c8db64
//
// Build commands and resulting WASM sizes:
//
// Minimal (direct WASI calls, size-optimized):
//   zig build-exe hello_minimal.zig -target wasm32-wasi -OReleaseSmall \
//       -femit-bin=hello_minimal.wasm
//   Size: 199 B
//
// Compared to standard hello.zig:
//   Debug:   601 KB -> 199 B  (3000x smaller)
//   Release: 12 KB  -> 199 B  (60x smaller)

extern "wasi_snapshot_preview1" fn fd_write(fd: i32, iovs: [*]const Ciovec, iovs_len: usize, nwritten: *usize) i32;

const Ciovec = extern struct {
    base: [*]const u8,
    len: usize,
};

pub export fn _start() void {
    const msg = "Hello, World!\n";
    var nwritten: usize = 0;
    _ = fd_write(1, &[_]Ciovec{.{ .base = msg.ptr, .len = msg.len }}, 1, &nwritten);
}