---
name: "std::weak_ptr"
section: "3cxx"
platform: "linux"
package: "libstdc++-12-doc"
version: "12.4.0-5"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/std::weak_ptr/3cxx"
---

# std::weak\_ptr(3cxx)

A non-owning observer for a pointer owned by a shared\_ptr.

## NAME

std::weak\_ptr\< \_Tp \> - A non-owning observer for a pointer owned by a shared\_ptr.

## SYNOPSIS

`#include <memory>`

Inherits std::\_\_weak\_ptr\< \_Tp, \_Lp \>.

### Public Types

**using** **element\_type** = **typename** **remove\_extent**\< \_Tp \>::type\

### Public Member Functions

template\<**typename** **\_Yp** , **typename**  = \_Constructible\<const shared\_ptr\<\_Yp\>&\>\> **weak\_ptr** (const **shared\_ptr**\< **\_Yp** \> &\_\_r) noexcept\
 **weak\_ptr** (const **weak\_ptr** &) noexcept=**default**\
 template\<**typename** **\_Yp** , **typename**  = \_Constructible\<const weak\_ptr\<\_Yp\>&\>\> **weak\_ptr** (const **weak\_ptr**\< **\_Yp** \> &\_\_r) noexcept\
 **weak\_ptr** (**weak\_ptr** &&) noexcept=**default**\
 template\<**typename** **\_Yp** , **typename**  = \_Constructible\<weak\_ptr\<\_Yp\>\>\> **weak\_ptr** (**weak\_ptr**\< **\_Yp** \> &&\_\_r) noexcept\
 bool **expired** () const noexcept\
 **shared\_ptr**\< \_Tp \> **lock** () const noexcept\
 template\<**typename** **\_Yp** \> \_Assignable\< const **shared\_ptr**\< **\_Yp** \> & \> **operator=** (const **shared\_ptr**\< **\_Yp** \> &\_\_r) noexcept\
 **weak\_ptr** & **operator=** (const **weak\_ptr** &\_\_r) noexcept=**default**\
 template\<**typename** **\_Yp** \> \_Assignable\< const **weak\_ptr**\< **\_Yp** \> & \> **operator=** (const **weak\_ptr**\< **\_Yp** \> &\_\_r) noexcept\
 **weak\_ptr** & **operator=** (**weak\_ptr** &&\_\_r) noexcept=**default**\
 template\<**typename** **\_Yp** \> \_Assignable\< **weak\_ptr**\< **\_Yp** \> \> **operator=** (**weak\_ptr**\< **\_Yp** \> &&\_\_r) noexcept\
 template\<**typename** **\_Tp1** \> bool **owner\_before** (const \_\_shared\_ptr\< **\_Tp1**, **\_Lp** \> &**\_\_rhs**) const noexcept\
 template\<**typename** **\_Tp1** \> bool **owner\_before** (const \_\_weak\_ptr\< **\_Tp1**, **\_Lp** \> &**\_\_rhs**) const noexcept\
 **void** **reset** () noexcept\
 **void** **swap** (\_\_weak\_ptr &**\_\_s**) noexcept\
 long **use\_count** () const noexcept\

### Related Symbols

(Note that these are not member symbols.)  template\<**typename** \_Tp \> **void** **swap** (**weak\_ptr**\< \_Tp \> &\_\_a, **weak\_ptr**\< \_Tp \> &\_\_b) noexcept\
 Swap overload for weak\_ptr.

## Detailed Description

### template\<typename \_Tp\>

class std::weak\_ptr\< \_Tp \>"A non-owning observer for a pointer owned by a shared\_ptr.

**Since**

C++11

A weak\_ptr provides a safe alternative to a raw pointer when you want a non-owning reference to an object that is managed by a shared\_ptr.

Unlike a raw pointer, a weak\_ptr can be converted to a new shared\_ptr that shares ownership with every other shared\_ptr that already owns the pointer. In other words you can upgrade from a non-owning 'weak' reference to an owning shared\_ptr, without having access to any of the existing shared\_ptr objects.

Also unlike a raw pointer, a weak\_ptr does not become 'dangling' after the object it points to has been destroyed. Instead, a weak\_ptr becomes *expired* and can no longer be converted to a shared\_ptr that owns the freed pointer, so you cannot accidentally access the pointed-to object after it has been destroyed.

## Author

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