重载函数的C ++地址

Question

In my project I want to do something like following:

static void test0(void)
{
    printf("%s [%d]\n", __func__, __LINE__);
}

static void test0(int a)
{
    printf("%s [%d] %d\n", __func__, __LINE__, a);
}

static std::map<std::string, void*> initializeAddressMap()
{
    std::map<std::string, void*> addressmap;
    addressmap["test0"] = (void*) &test0;    // ERROR HERE <------
    return addressmap;
}

Basically, the third function returns a mapping of string to function address. However, at this point, I get an error address of overloaded function with no contextual type information , which also makes sense, since I have overloaded the test0 function, and compiler at this point doesn't know the address of which function to take. Is there any way I could address this problem, other than calling my functions different names?

Answer 1

You should define pointer type when getting function address:

#include <iostream>

static void test(void)
{
    printf("%s [%d]\n", __func__, __LINE__);
}

static void test(int a)
{
    printf("%s [%d] %d\n", __func__, __LINE__, a);
}

int main()
{
    using t_pf1 = void (*)(void);
    using t_pf2 = void (*)(int);
    ::std::cout << (uintptr_t) t_pf1{&test} << "\n"
      << (uintptr_t) t_pf2{&test} << ::std::endl;
    return 0;
}

working code online

Answer 2

The easiest solution is to store the pointer to the overloaded function in a pointer, first:

#include <cstdio>

static void test0(void)
{
    printf("%s [%d]\n", __func__, __LINE__);
}

static void test0(int a)
{
    printf("%s [%d] %d\n", __func__, __LINE__, a);
}

int main(void) {
    void (*select1)(void) = test0;  // will match void(void)
    void (*select2)(int) = test0;   // will match void(int)

    select1();
    select2(42);

    return 0;
}

$ ./a.out
test0 [5]
test0 [10] 42

If you want to call the stored void* , then you have to make it a function pointer again. You can do that by eg reinterpret_cast<void(*)(int)>(p) .