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It is useful to get the count of std::weak_ptr that are tracking a
resource just as we have a reference count of std::shared_ptr that tracks a
resource.

Most implementations already have this information but there is no API in
the standards to extract this information.

I can explain why I need this information in one of the scenarios that I
have in my project.

I have built a custom caching mechanism that does caching based on user
request. The cached objects are disposed when the memory consumed by
caching exceeds a pre-defined memory size set by the user. The cached
objects are returned to the user  through  std::weak_ptr. The utility of
the weak_ptr is primarily to avoid dangling pointers once the cache is
cleared. However, the logic of which cache object has to be disposed is not
a trivial decision and having a reference count of the number of weak_ptr
is of immense value.


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<div dir=3D"ltr">It is useful to get the count of std::w<span style=3D"colo=
r: rgb(0, 0, 0); background-color: rgb(250, 250, 250);">eak_ptr&nbsp;</span=
>that are tracking a resource&nbsp;just as we have a reference count of std=
::<span style=3D"color: rgb(0, 0, 0); background-color: rgb(250, 250, 250);=
">shared_ptr&nbsp;</span>that tracks a resource.<div><br></div><div>Most im=
plementations already have this information but there is no API in the stan=
dards to extract this information.</div><div><br></div><div>I can explain w=
hy I need this information in one of the scenarios that I have in my projec=
t.</div><div><br></div><div>I have built a custom caching mechanism that do=
es caching based on user request. The cached objects are disposed when the =
memory consumed by caching exceeds a pre-defined memory size set by the use=
r. The cached objects are returned to the user &nbsp;through &nbsp;<span cl=
ass=3D"styled-by-prettify" style=3D"color: rgb(0, 0, 0); background-color: =
rgb(250, 250, 250);">std</span><span class=3D"styled-by-prettify" style=3D"=
color: rgb(102, 102, 0); background-color: rgb(250, 250, 250);">::</span><s=
pan class=3D"styled-by-prettify" style=3D"color: rgb(0, 0, 0); background-c=
olor: rgb(250, 250, 250);">weak_ptr.&nbsp;</span>The utility of the weak_pt=
r is primarily to avoid dangling pointers once the cache is cleared. Howeve=
r, the logic of which cache object has to be disposed is not a trivial deci=
sion and having a reference count of the number of weak_ptr is of immense v=
alue.</div><div><br></div><div><br></div></div>

<p></p>

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