48 lines
1.1 KiB
C++
48 lines
1.1 KiB
C++
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#include <cassert>
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#include <memory>
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// From Wikipedia.
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void shared_ptr() {
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std::shared_ptr<int> p1(new int(5));
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std::shared_ptr<int> p2 = p1; // Both now own the memory.
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// Memory still exists, due to p2:
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p1.reset();
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assert(p1.get() == NULL && p2.get() != NULL);
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// Deletes the memory, since no one else owns the memory.
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p2.reset();
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assert(p1.get() == NULL && p2.get() == NULL);
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}
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void weak_ptr() {
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std::shared_ptr<int> p1(new int(5));
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std::weak_ptr<int> wp1 = p1; // p1 owns the memory.
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{
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std::shared_ptr<int> p2 = wp1.lock(); //Now p1 and p2 own the memory.
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assert(p2 != NULL);
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if (p2) { // As p2 is initialized from a weak pointer,
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// you have to check if the memory still exists!
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// Do something with p2
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}
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} // p2 is destroyed. Memory is owned by p1.
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assert(wp1.lock() != NULL);
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p1.reset(); // Memory is deleted.
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assert(wp1.lock() == NULL);
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std::shared_ptr<int> p3 = wp1.lock();
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// Memory is gone, so we get an empty shared_ptr.
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assert(p3 == NULL);
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if (p3) {
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// Will not execute this.
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}
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}
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int main() {
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shared_ptr();
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weak_ptr();
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}
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