C++ named requirements: DefaultInsertable (since C++11)

Specifies that an object of the type can be default-constructed in-place by a given allocator.

# Notes

By default, this will value-initialize the object, as by ::new((void*)p) T()(until C++20)std::construct_at(p)(since C++20).

If value-initialization is undesirable, for example, if the object is of non-class type and zeroing out is not needed, it can be avoided by providing a custom Allocator::construct.

Although it is required that customized construct is used when constructing elements of std::basic_string until C++23, all implementations only used the default mechanism. The requirement is corrected by P1072R10 to match existing practice.

# Defect reports

# See also

• DefaultConstructible
• CopyInsertable
• MoveInsertable
• EmplaceConstructible
• Erasable