Defined in header <memory>
static size_type max_size( const Alloc& a ) noexcept;
(since C++11)
(until C++20)
static constexpr size_type max_size( const Alloc& a ) noexcept;
(since C++20)

If possible, obtains the maximum theoretically possible allocation size from the allocator a, by calling a.max_size().

If the above is not possible (e.g. Alloc does not have the member function max_size()), then returns std::numeric_limits<size_type>::max() / sizeof(value_type).


a - allocator to detect

Return value

Theoretical maximum allocation size.

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2162 C++11 max_size was not requied to be noexcept required
LWG 2466 C++11 theoretical maximum allocation size in bytes was returned as fallback size in elements is returned

See also

(until C++20)
returns the largest supported allocation size
(public member function of std::allocator<T>)

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