CODEWITHSUNDEEP
c++function-pointersinline
Matteo Monti
Matteo Monti

Reputation: 9000

Can I get a function table inlined?

Consider the following example:

#include <iostream>
#include <type_traits>

inline void f()
{
    std :: cout << "Welcome to f!" << std :: endl;
}

inline void g()
{
    std :: cout << "Welcome to g!" << std :: endl;
}

inline void h()
{
    std :: cout << "Welcome to h!" << std :: endl;
}

typedef void (*function)();
const function table[] = {f, g, h};

int main()
{
    int idx;
    std :: cin >> idx;
    table[idx]();
}

Here I have three functions, f, g and h. I put their pointers into a const array. Then, at runtime, I ask my user to provide a number and the corresponding function in the table is called.

I guess this is not going to get inlined, am I correct? I tried to inspect the assembly code but I really suck at reading assembly.

So I wonder, do I have better options to get the call to either f, g and h inlined? I mean, if I were to just make a switch this would work flawlessly.

Note: this is just an example, in a real-world scenario I will have a set of functions, known at compile time but determined by a kinda lengthy procedure. So I am not able to just, e.g., write the code in a switch statement.

Upvotes: 0

Views: 65

Answers (1)

Lanting
Lanting

Reputation: 3068

Provided you make use of proper const expressions, it is guaranteed that the code will be inlined at compile time. Have a look at the conditionals for that in this thread: When does a constexpr function get evaluated at compile time?

Upvotes: 0

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