You're comparing C+StdLib vs. Rust without StdLib. Disable stdlib for C version and use the following program:

#include <windows.h>

int _start() {

    const char str[] = "Hello world!\n";
    HANDLE stdout = GetStdHandle(STD_OUTPUT_HANDLE);
    DWORD written;

    WriteFile(stdout, str, sizeof(str), &written, NULL);
    ExitProcess(12);

    return 0;

}

https://stackoverflow.com/a/42536990

Which is similar to what the Rust program does. The result should be significantly less than 1k

I tried your program with MSVC using the following command:

    cl small2.c /MD /link /entry:_start /subsystem:CONSOLE kernel32.lib

It's 5kb.

If I remember correctly you need a /nodefaultlib flag to disable stdlibs

https://docs.microsoft.com/en-us/cpp/build/reference/nodefau...

Ok, I've just tried that but I also needed to add `/force` otherwise it complained about missing symbols. So the full compile line is:

    cl small2.c /link /force /nodefaultlib /entry:_start /subsystem:CONSOLE kernel32.lib

This gets it down to 3kb.

I think the thing being measured by GP is "easiest way to get to the 1kb mentioned in the title" not "most complicated way to get as small as possible".

Have you actually tried this on MSVC? This is my program. I created a file called `small.c`

    #include <stdio.h>
    
    int main(void) {
        puts("Hello World!");
        return 0;
    }

I then compiled it using this command:

   cl small.c /MD

The result? 9kb! That's 9 times the size.

Can you, though?

Compiling that source on Windows using visual studio produces a 98K executable.

You just need to add some compiler options; /MD should get the size down quite a bit already, then decrease the file alignment and merge sections together:

    /MD /link /align:4096 /filealign:512 /merge:.rdata=.text /merge:.data=.text

That produced a 1.5K binary, which with a custom stub should reach 1K.

So the point is moot, you can't have a simple 1k C example.

Have you actually tried this? Merging .data into .text doesn't work. The binary doesn't run and there's this link warning:

> LINK : warning LNK4254: section '.data' (C0000040) merged into '.text' (60000020) with different attributes

In order to get that to 1Kb you would probably have to drop the `.idata` section and resolve syscalls from the PEB like I did.

The smallest executable gcc (on Ubuntu) compiles that to is 8296 bytes (tried every -O optimization).

Is that stripped or unstripped?

Hm I only looked at the output of size which gives

   text    data     bss     dec     hex filename
   1566     600       8    2174     87e hello

(no optimisations)

Actually, the equivalent Rust code to this is just the following:

    println!("Hello world!");

Exactly that text. Compile it and it comes in at exactly 13.6% of the C program you have that compiles to 1k.