void* is special in C, C99, C11

voidstar.c

/**
 * Local Variables:
 * compile-command: "cc -Wall -Weverything -std=c11 voidstar.c -o ./voidstar && ./voidstar"
 * End:
 */

#include <stdio.h> // for printf

enum WorkType
{
        WT_INT,
        WT_LSTRING,
};

// prototype (just to satisfy the absurd -Weverything)
void do_work(int work_type, void* work_data);

// implementation
void do_work(int work_type, void* work_data)
{
        switch(work_type)
        {
        case WT_INT: {
                // demonstrates void* is casted automatically to `int*`
                int* pointer_to_int = work_data;
                printf("got an int: %d\n", *pointer_to_int);
        } break;
        case WT_LSTRING: {
                // demonstrates void* is casted automatically to `char const*`
                char const* pointer_to_litteral = work_data;
                printf("got a litteral string: %s\n", pointer_to_litteral);
        } break;
        }
}

int main()
{
        int a_serious_integer = 42;
        do_work(WT_INT, &a_serious_integer);
        do_work(WT_LSTRING, "this is a literal string");
}

Yeah, I mixed this with the __attribute((malloc)) thing, which is used for aliasing optimization.