Question

struct Foo {
    int data;
    Foo() = default;
    Foo(const Foo& arg) = default;
};

But my compiler doesn’t have defaulted constructors yet.

Can I define a macro like DEFAULTED to stand in for = default? If it just left the line as

    Foo(const Foo& arg);

would the compiler still generate its default, or would it complain?

Answer 1

Of course you can:

#if __cplusplus == 201103L
# define DEFAULTED(func) func = default;
#else
# define DEFAULTED(func)
#endif

struct foo
{
    DEFAULTED(foo())
};

However: Some compilers support parts of C++11, and may set __cplusplus to 201103L even though they don’t support default constructors.