examples

commit 82f4a9b73624009ce791477574d386377c74c9b4
parent e745bc260c0b094e692e4dc198797e87fa9d33f6
Author: Henry Wilson <henry@henryandlizzy.uk>
Date:   Mon,  6 Feb 2023 22:00:10 +0000

owning_ptr: Add experiment in avoiding shared_ptr liveleaks

Diffstat:
M
.gitignore
 | 
1
+
A
src/owning_ptr.cpp
 | 
82
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 83 insertions(+), 0 deletions(-)
diff --git a/.gitignore b/.gitignore
@@ -33,6 +33,7 @@
 /model
 /morse
 /mutex_container
+/owning_ptr
 /pulse-async-client
 /pulse-simple-client
 /regex
diff --git a/src/owning_ptr.cpp b/src/owning_ptr.cpp
@@ -0,0 +1,82 @@
+#include <memory>
+#include <cassert>
+#include <iostream>
+#include <set>
+
+using namespace std;
+
+template <typename T>
+struct owning_ptr : shared_ptr<T>
+{
+	owning_ptr() = default;
+	explicit owning_ptr(shared_ptr<T> p)
+	:   shared_ptr<T>(move(p))
+	{
+		assert(this->use_count() <= 1);
+	}
+	~owning_ptr()
+	{
+		if (*this)
+			(*this)->pre_destroy();
+		if (auto n = this->use_count(); n > 1)
+		{
+			cerr << "owning_ptr not outliving " << n - 1 << " references\n";
+			terminate();
+		}
+	}
+	owning_ptr(owning_ptr const&) = delete;
+	owning_ptr& operator =(owning_ptr const&) = delete;
+	owning_ptr(owning_ptr&&) = default;
+	owning_ptr& operator =(owning_ptr&&) = default;
+};
+
+struct node : enable_shared_from_this<node>
+{
+	set<shared_ptr<node>> others = {};
+
+	void pre_destroy()
+	{
+		for (auto& o : others)
+			o->others.erase(shared_from_this());
+	}
+
+	[[nodiscard]] static owning_ptr<node> construct()
+	{
+		return owning_ptr{shared_ptr<node>{new node{}}};
+	}
+
+	~node()
+	{
+		cout << "~node(): " << others.size() << endl;
+	}
+
+private:
+	node() = default;
+};
+
+void join(node& a, node& b)
+{
+	a.others.insert(b.shared_from_this());
+	b.others.insert(a.shared_from_this());
+}
+
+set<owning_ptr<node>> nodes;
+
+int main()
+{
+	nodes.insert(node::construct());
+	auto p1 = node::construct();
+	auto q1 = node::construct();
+	auto r1 = node::construct();
+	join(*p1, *q1);
+	join(*p1, *r1);
+	join(*q1, *r1);
+
+	join(*p1, *p1);
+
+	shared_ptr<node> p2 = p1;
+	weak_ptr<node> p3 = p1;
+
+	owning_ptr<node> p4 = move(p1);
+	p2.reset();
+}