how to change typedef struct declaration into a using alias struct?

Question

my struct is defined like this:

typedef struct
{
  int foo;
  char key;
} myStruct;

and I would like to change it to

using struct myStruct = {
      int foo;
      char key;
    } myStruct;

but it seems that something is wrong with it

That's the simple implementation but I need the using keyword in my app — Alex Butane, Jan 27 '23 at 13:32
`struct actualStruct{ int foo; char key; }; using myStruct = actualStruct;` — Eljay, Jan 27 '23 at 13:33
Why? Is it an assignment requirement? Unlike C, in C++ the name of class does not need to be decorated with `struct` in order to use it so your class name is the type name. — NathanOliver, Jan 27 '23 at 13:33
You could have `using myStruct = struct {...};` but why would you want to do that? — Adrian Mole, Jan 27 '23 at 13:35
@AlexButane It's a requirement that doesn't make any sense. At least in this case. — Daniel Langr, Jan 27 '23 at 13:35
The "newer method" in C++ is just to drop the `typedef` from the declaration of the `struct`. — Adrian Mole, Jan 27 '23 at 13:37
@AlexButane in C++ if you have `struct X {...}`. `X` is already a type. No need for typedef like you do in C. — wohlstad, Jan 27 '23 at 13:37
@AdrianMole Newer is relative, it has been the C++ way almost as long as I can remember. I associate that style with 100% "C" — Pepijn Kramer, Jan 27 '23 at 13:39
Does this answer your question? https://stackoverflow.com/questions/612328/difference-between-struct-and-typedef-struct-in-c — 463035818_is_not_an_ai, Jan 27 '23 at 13:40
@AlexButane So, you want to replace something that doesn't make sense with something else that doesn't make sense as well? This doesn't make sense at all ;) — Daniel Langr, Jan 27 '23 at 13:42
@everyone you are right but if I was requested to change the typedef's to using's I need to find a way to do it. — Alex Butane, Jan 27 '23 at 13:47
@NathanOliver you want to turn that into an actual answer, so people can vote for it? — Chronial, Jan 27 '23 at 13:47
@AlexButane Maybe, you should ask the people who asked you why they insist on using `using`. — Daniel Langr, Jan 27 '23 at 13:49
@Alex - When you were asked to replace `typedef` by `using`, perhaps your manager didn't think anyone would ever have used `typedef struct` in C++? — BoP, Jan 27 '23 at 15:01
OP is confusing the spirit of the task with the actual way people write C++. And this shouldn't be a manual task anyway. I'm pretty sure clang-tidy has checks for both of these situations. — sweenish, Jan 27 '23 at 18:23

Daniel Langr · Accepted Answer · 2023-01-27T13:50:47.877

3

Yes, you can replace

typedef struct
{
  int foo;
  char key;
} myStruct;

by

using myStruct = struct
{
  int foo;
  char key;
};

But it doesn't make any sense, and you will just confuse readers or possible maintainers of the code.

The established way to go is:

struct myStruct
{
  int foo;
  char key;
};

edited Jan 27 '23 at 13:50

answered Jan 27 '23 at 13:48

Daniel Langr

22,196
3
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using myStruct = struct _myStruct { int foo; char key; }; what does this decleration mean? – Alex Butane Jan 27 '23 at 13:56
@AlexButane Type alias declaration; see https://en.cppreference.com/w/cpp/language/type_alias. – Daniel Langr Jan 27 '23 at 15:25

how to change typedef struct declaration into a using alias struct?

1 Answers1