可以使用std :: bind1st将void（*）（void *，int）转换为void（*）（int）吗？

Question

I have a function void f (void*, int); , that is used as a callback function. The caller expects void (*)(int) . Can I use std::bind1st to convert one to another? Is there any way to do this without using C++ 11 std::bind , just std::bind1st ?

Answer 1

No. Although std::bind1st() creates a function object with a call operator taking and int , it is not a void(*)(int) . The only way to turn a void(*)(void*, int) into a void(*)(int) is to have a forwarding function which obtains the void* from global resources, eg,

static void* data = 0; // probably needs to be set to a more suitable value
void f_forward(int value) {
    f(data, value);
}

Anybody providing a callback which doesn't take a user-defined context, eg, in the C-like interface a void* which is just passed through, didn't think too hard about the interface.