When should we use std::enable_shared_from_this

Question

I just knew std::enable_shared_from_this form this link.
But after reading the code below, I don\'t know when to use it.

try {
        G         


        

Answer 1

There're some use case which you can't use the template std::shared_ptr like opaque pointer.

In that case, it's useful to have this:

In some_file.cpp

struct A : std::enable_shared_from_this {};

extern "C" void f_c(A*);
extern "C" void f_cpp(A* a) {
   std::shared_ptr shared_a = a->shared_from_this();
   // work with operation requires shared_ptr
}

int main()
{
    std::shared_ptr a = std::make_shared();
    f_c(a.get());
}

---

In some_other.c

struct A;
void f_cpp(struct A* a);
void f_c(struct A* a) {
    f_cpp(a);
}