Before C23, and empty parameter list in a declaration provides no information about the parameter list; this code should not compile after C23

cursed.c

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

void put_in_register(int i);
//int read_from_register(void); // conflicting type with definition
int read_from_register(); // incomplete declaration

int main(int argc, const char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Provide a number as a command line argument\n");
	exit(-1);
    }
    int j = atoi(argv[1]);
    put_in_register(j);
    int k = read_from_register();
    printf("%d\n", k);
}

void put_in_register(int i) {}

int read_from_register(int i) {
    return i;
}