Why passing function as &name and name gives different pointers?

I have a function which I want to call another function and print its name and handle its results. It works fine

#include <iostream>
#include <string>
#include <map>

std::map<void *, std::string> ptr_map;
#define IS_API_CALL(fun) ptr_map[fun] = __FUNCTION__;

int api_call_bar(double x) {
    IS_API_CALL(&api_call_bar);
    return 0;
}

std::string getFuncNameByPtr(void * addr) {
    for (auto it = ptr_map.begin(); it != ptr_map.end(); ++it) {
        if (it->first == addr) return it->second;
    }

    return "???";
}

template <typename... Args>
void api_exec(int func(Args...), Args... args) {
    func(args...);
    auto name = getFuncNameByPtr(func); // <-- HERE. &func doesnt work
    std::cout << name << " was called\n";
}

int main() {
    api_exec(&api_call_bar, 2.0);
}

This one prints api_call_bar was called which is fine. The interesting part for me is part marked <-- HERE. If I pass it as &func it doesn't work properly anymore(name is not found by pointer in a map). Why is it so? I think it should be exactly the same.