Multiple variable initialization compiler support

Question

Under g++ 7.4 I could declare and initialize multiple variables like so:

std::pair<T, T> foo();

int main ()
{  auto [a, b] = foo();  }

However under Apple clang-703 it gives me an error.

I could not find any information about support for this feature in both compilers. Is it supported by modern compilers or should I not use it? Also what is the name of the feature?

Edit: The error is:

auto [a, b] = foo();
      ^1    ^2

1 => use of undeclared identifier 'a'.

2 => expected unqualified-id.

@bstract_Everything It is called structured binding declarations and is supported by compilers that confirm to C++ 17. — Vlad from Moscow, May 24 '19 at 12:41
@VladfromMoscow Ok so it is standardized. If you post as an answer Ill mark it. — Abstract_Everything, May 24 '19 at 12:44
Please **[edit]** your question with an [mre] or [SSCCE (Short, Self Contained, Correct Example)](http://sscce.org) — NathanOliver, May 24 '19 at 12:51

score 1 · Accepted Answer · answered May 24 '19 at 12:51

1

This is a C++17 feature called a structured binding.

Clang 5 supports them; in fact it did since 4, as do many other compilers.

Trouble is, you're using Apple Clang, which has different version numbers. Possibly your compiler is just too old, or you did not enable C++17 functionality the way you did with your GCC 7.4 (in which C++17 was still experimental and opt-in).

answered May 24 '19 at 12:51

Lightness Races in Orbit

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Thanks did not know about the different versions, I had 17 enabled since I built it from cmake. I cannot upvote the answer due to reputation. – Abstract_Everything May 24 '19 at 13:06
Now you can! ;) – Lightness Races in Orbit May 24 '19 at 13:24

Multiple variable initialization compiler support

1 Answers1