CODEWITHSUNDEEP
c++referencealias
coolgod
coolgod

Reputation: 539

Are alias and reference the same thing in C++?

I'm not asking the difference between pointer and reference. Just a bit confused about the difference between reference and alias.

As far as I'm concerned, reference is a data type while alias is just a word describing the utility of this data type?

Thanks!

Upvotes: 2

Views: 4982

Answers (4)

Davislor
Davislor

Reputation: 15144

Sorry, you said you were not asking the difference between a pointer and a reference.

To answer what you’re asking, the word reference means that a variable is pointing to a location in memory. Alias has a few different meanings, but the one I’ve seen most often in this context is that more than one variable are referencing the same location in memory, such as when you try to call memcpy(p, p, n);. One way to make this happen is with a C++ reference, which is a term of art for a language feature similar but not identical to pointers. Not every reference in C++ necessarily refers to something which ever has another name. You can also do aliasing with pointers, the address operator, a call by reference, or the compiler merging constants so that "Hello" and "Hello" in two places point to the same bytes in memory, or unions. Probably not exhaustive.

If people want to call a reference to something an “alias” even when there isn't any other variable referencing the same memory at the same time, I’m not strongly motivated to argue.

As several others have pointed out, C++14 uses the term “alias” to refer to template types declared with using. (http://en.cppreference.com/w/cpp/language/type_alias)

Upvotes: 2

Some programmer dude
Some programmer dude

Reputation: 409166

No, a reference is not a data-type, a reference references some other variable. Using a reference is the same as using the variable it references. It's very similar to a pointer (and it's not unlikely that the compiler treats references as pointers under the hood).

I've never heard of "alias" by itself in the context of C++, but there are type-aliases, created by e.g. typedef or using. There's also aliasing which is unrelated to both references and type-aliases.

Upvotes: 2

Seth Kitchen
Seth Kitchen

Reputation: 1566

A type alias declaration introduces a name which can be used as a synonym for the type denoted by type-id. It does not introduce a new type and it cannot change the meaning of an existing type name. There is no difference between a type alias declaration and typedef declaration. This declaration may appear in block scope, class scope, or namespace scope.

From http://en.cppreference.com/w/cpp/language/type_alias

Upvotes: 0

Barmar
Barmar

Reputation: 780929

Aliasing refers to any way to refer to the same data through different names. References and pointers are two ways of achieving this behavior.

Upvotes: 2

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