如何使用宏在函数中放置代码？

Question

Let's say I have a function

void foo()
{
    foo1();
}

I want to have a macro that I can use in other place like that:

ADD_FUNCTION_TO_FOO(foo2());

So the function foo() will look like that for the compiler:

void foo()
{
    foo1();
    foo2();
}

Is that possible to achieve? Or perhaps is there other way around that?

Answer 1

You can't modify a function. The definition of foo() is exactly what it does, forever.

But you could write foo to be extensible in the first place:

#include <functional>
#include <vector>
#include <iostream>

std::vector<std::function<void()>> extra_callbacks_for_foo;

void foo1();

void foo()
{
    foo1();
    for (auto& cb : extra_callbacks_for_foo)
        cb();
}

#define ADD_FUNCTION_TO_FOO(expr) \
  (extra_callbacks_for_foo.push_back([&]() { (expr); }))

See the working example on coliru .