How to set a kernel entry point: error: pointers cannot be cast to integers during const eval

help
1

I'd like to create a struct (e.g. multiboot2) in a binary (i.e. a kernel) where the struct includes a pointer to the kernel entry point. But the compiler won't let me do it, giving me the pointers cannot be cast to integers during const eval error.

How can I achieve this?

Thanks

#![no_std]
#![no_main]

#[repr(C)]
struct Multiboot2 {
    entry_point: u32,
}

static _multiboot_header: Multiboot2 = Multiboot2{
    entry_point: main as usize as u32,
};

fn main() {
    loop{};
}

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

I'm aware this address isn't available until the linker runs. Maybe there is some incantation of extern that will let the compiler leave that unfilled until link time?

2

The type of the field has to be a pointer type.

#[repr(C)]
struct Multiboot2 {
    entry_point: fn(),
}

static _multiboot_header: Multiboot2 = Multiboot2{
    entry_point: main,
};
2 Likes
3

Nice, TY