operator==, !=, <, <=, >, >=, <=> (std::shared_ptr)

From cppreference.com
< cpp‎ | memory‎ | shared ptr
 
C++
 
Utilities library
Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Library feature-test macros
Date and time
Function objects
Formatting library (C++20)
(C++11)
(C++20)
(C++11)
(C++14)
Relational operators (deprecated in C++20)
Comparisons (C++20)
Common vocabulary types
(C++11)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)

Swap, forward and move
(C++14)
(C++11)
(C++11)
(C++11)
Elementary string conversions
(C++17)
(C++17)
(C++17)
Type operations
(C++11)
(C++17)
(C++17)
 
Dynamic memory management
Uninitialized storage
(until C++20)
(until C++20)
(until C++20)
Garbage collection support
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
Miscellaneous
(C++11)
(C++20)
(C++11)
(C++11)
(C++20)
C Library
Low level memory management
 
std::shared_ptr
Member functions
Modifiers
Observers
(C++17)
(until C++20)
Non-member functions
(C++20)
(C++20)
(C++17)
operator==operator!=operator<operator<=operator>operator>=operator<=>
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
functions (deprecated in C++20)
(C++20)
Deduction guides(C++17)
 
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;
 (1) (since C++11)
template< class T, class U >

bool operator!=( const std::shared_ptr<T>& lhs,

                 const std::shared_ptr<U>& rhs ) noexcept;
 (2) (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;
 (3) (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;
 (4) (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;
 (5) (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;
 (6) (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;
 (7) (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;
 (8) (since C++11)
template< class T >
bool operator==( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
 (9) (since C++11)
(until C++20)
template< class T >
bool operator!=( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
 (10) (since C++11)
(until C++20)
template< class T >
bool operator!=( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
 (11) (since C++11)
(until C++20)
template< class T >
bool operator<( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
 (12) (since C++11)
(until C++20)
template< class T >
bool operator<( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
 (13) (since C++11)
(until C++20)
template< class T >
bool operator>( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
 (14) (since C++11)
(until C++20)
template< class T >
bool operator>( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
 (15) (since C++11)
(until C++20)
template< class T >
bool operator<=( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
 (16) (since C++11)
(until C++20)
template< class T >
bool operator<=( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
 (17) (since C++11)
(until C++20)
template< class T >
bool operator>=( const std::shared_ptr<T>& lhs, std::nullptr_t ) noexcept;
 (18) (since C++11)
(until C++20)
template< class T >
bool operator>=( std::nullptr_t, const std::shared_ptr<T>& rhs ) noexcept;
 (19) (since C++11)
(until C++20)
template< class T >

std::strong_ordering operator<=>( const std::shared_ptr<T>& lhs,

                                  std::nullptr_t ) noexcept;
 (20) (since C++20)

Compares two shared_ptr<T> objects or compares shared_ptr<T> with a null pointer.

Note that the comparison operators for shared_ptr simply compare pointer values; the actual objects pointed to are not compared. Having operator< defined for shared_ptr allows shared_ptrs to be used as keys in associative containers, like std::map and std::set.

Parameters

lhs - the left-hand shared_ptr to compare
rhs - the right-hand shared_ptr to compare

Return value

1) lhs.get() == rhs.get()
2) !(lhs == rhs)
3) std::less<V>()(lhs.get(), rhs.get()), where V is the composite pointer type of std::shared_ptr<T>::element_type* and std::shared_ptr<U>::element_type*
4) rhs < lhs
5) !(rhs < lhs)
6) !(lhs < rhs)
7) std::compare_three_way{}(x.get(), y.get())
8) !lhs
9) !rhs
10) (bool)lhs
11) (bool)rhs
12) std::less<std::shared_ptr<T>::element_type*>()(lhs.get(), nullptr)
13) std::less<std::shared_ptr<T>::element_type*>()(nullptr, rhs.get())
14) nullptr < lhs
15) rhs < nullptr
16) !(nullptr < lhs)
17) !(rhs < nullptr)
18) !(lhs < nullptr)
19) !(nullptr < rhs)
20) std::compare_three_way{}(x.get(), nullptr)

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

This section is incomplete
Reason: no example

See also

 returns the stored pointer
(public member function)
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/memory/shared_ptr/operator_cmp&oldid=115767"