operator==, !=, <, <=, >, >=, <=> (std::shared_ptr)
Header: <memory>
Compares two shared_ptr
# Declarations
Compare two shared_ptr objects.
template< class T, class U >
bool operator==( const std::shared_ptr<T>& lhs,
const std::shared_ptr<U>& rhs ) noexcept;
(since C++11)
template< class T, class U >
bool operator!=( const std::shared_ptr<T>& lhs,
const std::shared_ptr<U>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T, class U >
bool operator<( const std::shared_ptr<T>& lhs,
const std::shared_ptr<U>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T, class U >
bool operator>( const std::shared_ptr<T>& lhs,
const std::shared_ptr<U>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T, class U >
bool operator<=( const std::shared_ptr<T>& lhs,
const std::shared_ptr<U>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T, class U >
bool operator>=( const std::shared_ptr<T>& lhs,
const std::shared_ptr<U>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T, class U >
std::strong_ordering operator<=>( const std::shared_ptr<T>& lhs,
const std::shared_ptr<U>& rhs ) noexcept;
(since C++20)
Compare a shared_ptr with a null pointer.
template< class T >
bool operator==( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
(since C++11)
template< class T >
bool operator==( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T >
bool operator!=( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
(since C++11) (until C++20)
template< class T >
bool operator!=( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T >
bool operator<( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
(since C++11) (until C++20)
template< class T >
bool operator<( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T >
bool operator>( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
(since C++11) (until C++20)
template< class T >
bool operator>( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T >
bool operator<=( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
(since C++11) (until C++20)
template< class T >
bool operator<=( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T >
bool operator>=( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
(since C++11) (until C++20)
template< class T >
bool operator>=( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
(since C++11) (until C++20)
template< class T >
std::strong_ordering operator<=>( const std::shared_ptr<T>& lhs,
std::nullptr_t ) noexcept;
(since C++20)
# Parameters
lhs: the left-hand shared_ptr to comparerhs: the right-hand shared_ptr to compare
# Notes
In all cases, it is the stored pointer (the one returned by get()) that is compared, rather than the managed pointer (the one passed to the deleter when use_count goes to zero). The two pointers may differ in a shared_ptr created using the aliasing constructor.
# Example
#include <iostream>
#include <memory>
int main()
{
std::shared_ptr<int> p1(new int(42));
std::shared_ptr<int> p2(new int(42));
std::cout << std::boolalpha
<< "(p1 == p1) : " << (p1 == p1) << '\n'
<< "(p1 <=> p1) == 0 : " << ((p1 <=> p1) == 0) << '\n' // Since C++20
// p1 and p2 point to different memory locations, so p1 != p2
<< "(p1 == p2) : " << (p1 == p2) << '\n'
<< "(p1 < p2) : " << (p1 < p2) << '\n'
<< "(p1 <=> p2) < 0 : " << ((p1 <=> p2) < 0) << '\n' // Since C++20
<< "(p1 <=> p2) == 0 : " << ((p1 <=> p2) == 0) << '\n'; // Since C++20
}
# Defect reports
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3427 | C++20 | operator<=>(shared_ptr, nullptr_t) was ill-formed | definition fixed |