预处理器宏中的typedef

Question

I have a macro definition like this, to easily create a shared_ptr for a class:

#define create_ptr(__TYPE__) typedef std::shared_ptr<__TYPE__>

What I want to now is to append "Ptr" to the class name, so that

create_ptr(MyClass)

would result in a typedef named MyClassPtr as std::shared_ptr<MyClass> How would I accomplish this?

Answer 1

You need token concatenation ##

#define create_ptr(__TYPE__) typedef std::shared_ptr<__TYPE__> __TYPE__ ## Ptr;

class Foo{
public:
};

create_ptr(Foo)

FooPtr foo;

For detailed explanation have a look here https://gcc.gnu.org/onlinedocs/cpp/Concatenation.html

Answer 2

An alternative route is a using declaration:

template <typename T>
using sp = std::shared_ptr<T>;

sp<int> my_shared_int_pointer ....