Given this array declaration and initialization:
std::array<bool, 20> invalid_params{};
Can I assume that all the elements in the array will always be initialized to false, or is it better to do it explicitly?
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anastaciu
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1If you use the `{}` syntax, it's always initialized with `false`. If you don't use that, it's left uninitialized. – Aykhan Hagverdili May 22 '21 at 11:27
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For built-in types, value-initialization is always similar to `=0` for all elements. (becoming `0`, `false`, `nullptr`, etc) – Aykhan Hagverdili May 22 '21 at 11:46
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It's guaranteed to be filled with false values.
std::array is an aggregate, hence it has no user-defined constructors, hence value-initializing it performs zero-initialization.
But if you remove {} (turning it into default-initialization), the elements will be uninitialized.
HolyBlackCat
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If it's defined in global scope its elements will be zero-initialized even without an explicit initializer. – Pete Becker May 22 '21 at 13:39
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Documentation says: "default initialization may result in indeterminate values for non-class T". So, it seems that you can not assume that it will be initialized.
VillageTech
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3Default-initialization would be `std::array
invalid_params;`. With `{}` it's value-initialziation. – HolyBlackCat May 22 '21 at 11:03 -
@HolyBlackCat To be fair, OP didn't specify in their question whether it is safe to assume that the elements would be false using only this syntax (which it is). – eerorika May 22 '21 at 11:06