std::shared_ptr::shared_ptr - cppreference.com ([original](https://en.cppreference.com/w/cpp/memory/shared%5Fptr/shared%5Fptr.html)) (raw)
If *this owns an object and it is the last shared_ptr owning it, the object is destroyed through the owned deleter.
After the destruction, the smart pointers that shared ownership with *this, if any, will report a use_count() that is one less than its previous value.
[edit] Notes
Unlike std::unique_ptr, the deleter of std::shared_ptr is invoked even if the managed pointer is null.
[edit] Example
#include
#include
struct S
{
S() { std::cout << "S::S()\n"; }
S() { std::cout << "S::S()\n"; }
struct Deleter
{
void operator()(S* s) const
{
std::cout << "S::Deleter()\n";
delete s;
}
};
};
int main()
{
auto sp = std::shared_ptr{new S, S::Deleter{}};
auto use_count = [&sp](char c)
{
std::cout << c << ") use_count(): " << sp.use_count() << '\n';
};
use_count('A');
{
auto sp2 = sp;
use_count('B');
{
auto sp3 = sp;
use_count('C');
}
use_count('D');
}
use_count('E');
// sp.reset();
// use_count('F'); // would print "F) use_count(): 0"
}
Output:
S::S() A) use_count(): 1 B) use_count(): 2 C) use_count(): 3 D) use_count(): 2 E) use_count(): 1 S::Deleter() S::~S()