How to pass any int to *anyopaque?

Help
1

For example here’s a function in C.

void foo(void *arg) { ... }

I want to pass a number to the function like this

foo((void *)(37));

How do I do it in zig? This is that function when translated to zig

fn foo(arg: ?*anyopaque) void { ... }
2

For runtime, start with @ptrFromInt and then go from there: Documentation - The Zig Programming Language

3

This works:

src/main.c

#include <stdio.h>

void foo(void* arg) {
	int* int_ptr = (int*)arg;
	printf("%d\n", *int_ptr);
}

src/main.zig

extern fn foo(arg: ?*const i32) void;

pub fn main() !void {
    const n: i32 = 42;
    foo(&n);
}

In build.zig

    exe.addCSourceFiles(.{
        .files = &.{"src/main.c"},
    });

Edit: And this too:

foo(&42);

Edit 2: And this:

extern fn foo(arg: *const i32) void;

From what I’ve experienced in this type of C interop, you can really be strict with your types on the Zig side and the compiler will make it work.