C++14: Default values in tuple when returning {}

Question

Consider:

std::tuple<bool, double, int> getTuple()
{
    return {};
}

What does the standard say about the values in the resulting tuple in this case? Is it guaranteed that e.g. the bool is always false?

I'm going to guess yes, because of [this](https://stackoverflow.com/q/3308028/10957435), but that is assuming tuples use default constructors like this. — , Dec 29 '19 at 22:54

score 10 · Accepted Answer · answered Dec 29 '19 at 23:05

The default constructor of tuple is specified to value-initialize all elements, see case 1 in cppreference link.

In brief, value-initialization is the same as if the element were initialized by {} (there are corner cases I'm omitting). For primitive types this means bool is false, double is 0.0 and int is 0 .

C++14: Default values in tuple when returning {}

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