Merge pull request #324 from jagerman/example-constructor-tracking

Improve constructor/destructor tracking

example/CMakeLists.txt

@@ -60,9 +60,6 @@ foreach(CompilerFlag ${CompilerFlags})
 endforeach()
 
 set(RUN_TEST ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/run_test.py)
-if(MSVC OR CMAKE_CXX_COMPILER_ID MATCHES "Intel")
-  set(RUN_TEST ${RUN_TEST} --relaxed)
-endif()
 
 foreach(VALUE ${PYBIND11_EXAMPLES})
   string(REGEX REPLACE "^(.+).cpp$" "\\1" EXAMPLE_NAME "${VALUE}")

example/constructor-stats.h

+#pragma once
+/*
+    example/constructor-stats.h -- framework for printing and tracking object
+    instance lifetimes in example/test code.
+
+    Copyright (c) 2016 Jason Rhinelander <jason@imaginary.ca>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+
+This header provides a few useful tools for writing examples or tests that want to check and/or
+display object instance lifetimes.  It requires that you include this header and add the following
+function calls to constructors:
+
+    class MyClass {
+        MyClass() { ...; print_default_created(this); }
+        ~MyClass() { ...; print_destroyed(this); }
+        MyClass(const MyClass &c) { ...; print_copy_created(this); }
+        MyClass(MyClass &&c) { ...; print_move_created(this); }
+        MyClass(int a, int b) { ...; print_created(this, a, b); }
+        MyClass &operator=(const MyClass &c) { ...; print_copy_assigned(this); }
+        MyClass &operator=(MyClass &&c) { ...; print_move_assigned(this); }
+
+        ...
+    }
+
+You can find various examples of these in several of the existing example .cpp files.  (Of course
+you don't need to add any of the above constructors/operators that you don't actually have, except
+for the destructor).
+
+Each of these will print an appropriate message such as:
+
+    ### MyClass @ 0x2801910 created via default constructor
+    ### MyClass @ 0x27fa780 created 100 200
+    ### MyClass @ 0x2801910 destroyed
+    ### MyClass @ 0x27fa780 destroyed
+
+You can also include extra arguments (such as the 100, 200 in the output above, coming from the
+value constructor) for all of the above methods which will be included in the output.
+
+For testing, each of these also keeps track the created instances and allows you to check how many
+of the various constructors have been invoked from the Python side via code such as:
+
+    from example import ConstructorStats
+    cstats = ConstructorStats.get(MyClass)
+    print(cstats.alive())
+    print(cstats.default_constructions)
+
+Note that `.alive()` should usually be the first thing you call as it invokes Python's garbage
+collector to actually destroy objects that aren't yet referenced.
+
+For everything except copy and move constructors and destructors, any extra values given to the
+print_...() function is stored in a class-specific values list which you can retrieve and inspect
+from the ConstructorStats instance `.values()` method.
+
+In some cases, when you need to track instances of a C++ class not registered with pybind11, you
+need to add a function returning the ConstructorStats for the C++ class; this can be done with:
+
+    m.def("get_special_cstats", &ConstructorStats::get<SpecialClass>, py::return_value_policy::reference_internal)
+
+Finally, you can suppress the output messages, but keep the constructor tracking (for
+inspection/testing in python) by using the functions with `print_` replaced with `track_` (e.g.
+`track_copy_created(this)`).
+
+*/
+
+#include "example.h"
+#include <unordered_map>
+#include <list>
+#include <typeindex>
+#include <sstream>
+
+class ConstructorStats {
+protected:
+    std::unordered_map<void*, int> _instances; // Need a map rather than set because members can shared address with parents
+    std::list<std::string> _values; // Used to track values (e.g. of value constructors)
+public:
+    int default_constructions = 0;
+    int copy_constructions = 0;
+    int move_constructions = 0;
+    int copy_assignments = 0;
+    int move_assignments = 0;
+
+    void copy_created(void *inst) {
+        created(inst);
+        copy_constructions++;
+    }
+    void move_created(void *inst) {
+        created(inst);
+        move_constructions++;
+    }
+    void default_created(void *inst) {
+        created(inst);
+        default_constructions++;
+    }
+    void created(void *inst) {
+        ++_instances[inst];
+    };
+    void destroyed(void *inst) {
+        if (--_instances[inst] < 0)
+            throw std::runtime_error("cstats.destroyed() called with unknown instance; potential double-destruction or a missing cstats.created()");
+    }
+
+    int alive() {
+        // Force garbage collection to ensure any pending destructors are invoked:
+        py::module::import("gc").attr("collect").operator py::object()();
+        int total = 0;
+        for (const auto &p : _instances) if (p.second > 0) total += p.second;
+        return total;
+    }
+
+    void value() {} // Recursion terminator
+    // Takes one or more values, converts them to strings, then stores them.
+    template <typename T, typename... Tmore> void value(const T &v, Tmore &&...args) {
+        std::ostringstream oss;
+        oss << v;
+        _values.push_back(oss.str());
+        value(std::forward<Tmore>(args)...);
+    }
+    py::list values() {
+        py::list l;
+        for (const auto &v : _values) l.append(py::cast(v));
+        return l;
+    }
+
+    // Gets constructor stats from a C++ type index
+    static ConstructorStats& get(std::type_index type) {
+        static std::unordered_map<std::type_index, ConstructorStats> all_cstats;
+        return all_cstats[type];
+    }
+
+    // Gets constructor stats from a C++ type
+    template <typename T> static ConstructorStats& get() {
+        return get(typeid(T));
+    }
+
+    // Gets constructor stats from a Python class
+    static ConstructorStats& get(py::object class_) {
+        auto &internals = py::detail::get_internals();
+        const std::type_index *t1 = nullptr, *t2 = nullptr;
+        try {
+            auto *type_info = internals.registered_types_py.at(class_.ptr());
+            for (auto &p : internals.registered_types_cpp) {
+                if (p.second == type_info) {
+                    if (t1) {
+                        t2 = &p.first;
+                        break;
+                    }
+                    t1 = &p.first;
+                }
+            }
+        }
+        catch (std::out_of_range) {}
+        if (!t1) throw std::runtime_error("Unknown class passed to ConstructorStats::get()");
+        auto &cs1 = get(*t1);
+        // If we have both a t1 and t2 match, one is probably the trampoline class; return whichever
+        // has more constructions (typically one or the other will be 0)
+        if (t2) {
+            auto &cs2 = get(*t2);
+            int cs1_total = cs1.default_constructions + cs1.copy_constructions + cs1.move_constructions + (int) cs1._values.size();
+            int cs2_total = cs2.default_constructions + cs2.copy_constructions + cs2.move_constructions + (int) cs2._values.size();
+            if (cs2_total > cs1_total) return cs2;
+        }
+        return cs1;
+    }
+};
+
+// To track construction/destruction, you need to call these methods from the various
+// constructors/operators.  The ones that take extra values record the given values in the
+// constructor stats values for later inspection.
+template <class T> void track_copy_created(T *inst) { ConstructorStats::get<T>().copy_created(inst); }
+template <class T> void track_move_created(T *inst) { ConstructorStats::get<T>().move_created(inst); }
+template <class T, typename... Values> void track_copy_assigned(T *, Values &&...values) {
+    auto &cst = ConstructorStats::get<T>();
+    cst.copy_assignments++;
+    cst.value(std::forward<Values>(values)...);
+}
+template <class T, typename... Values> void track_move_assigned(T *, Values &&...values) {
+    auto &cst = ConstructorStats::get<T>();
+    cst.move_assignments++;
+    cst.value(std::forward<Values>(values)...);
+}
+template <class T, typename... Values> void track_default_created(T *inst, Values &&...values) {
+    auto &cst = ConstructorStats::get<T>();
+    cst.default_created(inst);
+    cst.value(std::forward<Values>(values)...);
+}
+template <class T, typename... Values> void track_created(T *inst, Values &&...values) {
+    auto &cst = ConstructorStats::get<T>();
+    cst.created(inst);
+    cst.value(std::forward<Values>(values)...);
+}
+template <class T, typename... Values> void track_destroyed(T *inst) {
+    ConstructorStats::get<T>().destroyed(inst);
+}
+template <class T, typename... Values> void track_values(T *, Values &&...values) {
+    ConstructorStats::get<T>().value(std::forward<Values>(values)...);
+}
+
+inline void print_constr_details_more() { std::cout << std::endl; }
+template <typename Head, typename... Tail> void print_constr_details_more(const Head &head, Tail &&...tail) {
+    std::cout << " " << head;
+    print_constr_details_more(std::forward<Tail>(tail)...);
+}
+template <class T, typename... Output> void print_constr_details(T *inst, const std::string &action, Output &&...output) {
+    std::cout << "### " << py::type_id<T>() << " @ " << inst << " " << action;
+    print_constr_details_more(std::forward<Output>(output)...);
+}
+
+// Verbose versions of the above:
+template <class T, typename... Values> void print_copy_created(T *inst, Values &&...values) { // NB: this prints, but doesn't store, given values
+    print_constr_details(inst, "created via copy constructor", values...);
+    track_copy_created(inst);
+}
+template <class T, typename... Values> void print_move_created(T *inst, Values &&...values) { // NB: this prints, but doesn't store, given values
+    print_constr_details(inst, "created via move constructor", values...);
+    track_move_created(inst);
+}
+template <class T, typename... Values> void print_copy_assigned(T *inst, Values &&...values) {
+    print_constr_details(inst, "assigned via copy assignment", values...);
+    track_copy_assigned(inst, values...);
+}
+template <class T, typename... Values> void print_move_assigned(T *inst, Values &&...values) {
+    print_constr_details(inst, "assigned via move assignment", values...);
+    track_move_assigned(inst, values...);
+}
+template <class T, typename... Values> void print_default_created(T *inst, Values &&...values) {
+    print_constr_details(inst, "created via default constructor", values...);
+    track_default_created(inst, values...);
+}
+template <class T, typename... Values> void print_created(T *inst, Values &&...values) {
+    print_constr_details(inst, "created", values...);
+    track_created(inst, values...);
+}
+template <class T, typename... Values> void print_destroyed(T *inst, Values &&...values) { // Prints but doesn't store given values
+    print_constr_details(inst, "destroyed", values...);
+    track_destroyed(inst);
+}
+template <class T, typename... Values> void print_values(T *inst, Values &&...values) {
+    print_constr_details(inst, ":", values...);
+    track_values(inst, values...);
+}
+

example/example-buffers.cpp

@@ -8,35 +8,36 @@
 */
 
 #include "example.h"
+#include "constructor-stats.h"
 
 class Matrix {
 public:
     Matrix(size_t rows, size_t cols) : m_rows(rows), m_cols(cols) {
-        std::cout << "Value constructor: Creating a " << rows << "x" << cols << " matrix " << std::endl;
+        print_created(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
         m_data = new float[rows*cols];
         memset(m_data, 0, sizeof(float) * rows * cols);
     }
 
     Matrix(const Matrix &s) : m_rows(s.m_rows), m_cols(s.m_cols) {
-        std::cout << "Copy constructor: Creating a " << m_rows << "x" << m_cols << " matrix " << std::endl;
+        print_copy_created(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
         m_data = new float[m_rows * m_cols];
         memcpy(m_data, s.m_data, sizeof(float) * m_rows * m_cols);
     }
 
     Matrix(Matrix &&s) : m_rows(s.m_rows), m_cols(s.m_cols), m_data(s.m_data) {
-        std::cout << "Move constructor: Creating a " << m_rows << "x" << m_cols << " matrix " << std::endl;
+        print_move_created(this);
         s.m_rows = 0;
         s.m_cols = 0;
         s.m_data = nullptr;
     }
 
     ~Matrix() {
-        std::cout << "Freeing a " << m_rows << "x" << m_cols << " matrix " << std::endl;
+        print_destroyed(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
         delete[] m_data;
     }
 
     Matrix &operator=(const Matrix &s) {
-        std::cout << "Assignment operator : Creating a " << s.m_rows << "x" << s.m_cols << " matrix " << std::endl;
+        print_copy_assigned(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
         delete[] m_data;
         m_rows = s.m_rows;
         m_cols = s.m_cols;
@@ -46,7 +47,7 @@ public:
     }
 
     Matrix &operator=(Matrix &&s) {
-        std::cout << "Move assignment operator : Creating a " << s.m_rows << "x" << s.m_cols << " matrix " << std::endl;
+        print_move_assigned(this, std::to_string(m_rows) + "x" + std::to_string(m_cols) + " matrix");
         if (&s != this) {
             delete[] m_data;
             m_rows = s.m_rows; m_cols = s.m_cols; m_data = s.m_data;
@@ -111,5 +112,6 @@ void init_ex_buffers(py::module &m) {
                 { sizeof(float) * m.rows(),          /* Strides (in bytes) for each index */
                   sizeof(float) }
             );
-        });
+        })
+        ;
 }

example/example-buffers.py

@@ -30,3 +30,16 @@ for i in range(m4.rows()):
     for j in range(m4.cols()):
         print(m4[i, j], end = ' ')
     print()
+
+from example import ConstructorStats
+cstats = ConstructorStats.get(Matrix)
+print("Instances not destroyed:", cstats.alive())
+m = m4 = None
+print("Instances not destroyed:", cstats.alive())
+m2 = None # m2 holds an m reference
+print("Instances not destroyed:", cstats.alive())
+print("Constructor values:", cstats.values())
+print("Copy constructions:", cstats.copy_constructions)
+#print("Move constructions:", cstats.move_constructions >= 0) # Don't invoke any
+print("Copy assignments:", cstats.copy_assignments)
+print("Move assignments:", cstats.move_assignments)

example/example-buffers.ref

-Value constructor: Creating a 5x5 matrix 
+### Matrix @ 0x1df1920 created 5x5 matrix
 0.0
 4.0
 [[ 0.  0.  0.  0.  0.]
@@ -10,8 +10,15 @@ Value constructor: Creating a 5x5 matrix
 5.0
 [[ 1.  2.  3.]
  [ 4.  5.  6.]]
-Value constructor: Creating a 2x3 matrix 
+### Matrix @ 0x1fa8cf0 created 2x3 matrix
 1.0 2.0 3.0 
 4.0 5.0 6.0 
-Freeing a 2x3 matrix 
-Freeing a 5x5 matrix 
+Instances not destroyed: 2
+### Matrix @ 0x1fa8cf0 destroyed 2x3 matrix
+Instances not destroyed: 1
+### Matrix @ 0x1df1920 destroyed 5x5 matrix
+Instances not destroyed: 0
+Constructor values: ['5x5 matrix', '2x3 matrix']
+Copy constructions: 0
+Copy assignments: 0
+Move assignments: 0

example/example-callbacks.cpp

@@ -8,6 +8,7 @@
 */
 
 #include "example.h"
+#include "constructor-stats.h"
 #include <pybind11/functional.h>
 
 
@@ -57,29 +58,29 @@ void test_dummy_function(const std::function<int(int)> &f) {
     }
 }
 
-void init_ex_callbacks(py::module &m) {
-    m.def("test_callback1", &test_callback1);
-    m.def("test_callback2", &test_callback2);
-    m.def("test_callback3", &test_callback3);
-    m.def("test_callback4", &test_callback4);
-    m.def("test_callback5", &test_callback5);
-
-    /* Test cleanup of lambda closure */
-
-    struct Payload {
+struct Payload {
     Payload() {
-            std::cout << "Payload constructor" << std::endl;
+        print_default_created(this);
     }
     ~Payload() {
-            std::cout << "Payload destructor" << std::endl;
+        print_destroyed(this);
     }
     Payload(const Payload &) {
-            std::cout << "Payload copy constructor" << std::endl;
+        print_copy_created(this);
     }
     Payload(Payload &&) {
-            std::cout << "Payload move constructor" << std::endl;
+        print_move_created(this);
     }
-    };
+};
+
+void init_ex_callbacks(py::module &m) {
+    m.def("test_callback1", &test_callback1);
+    m.def("test_callback2", &test_callback2);
+    m.def("test_callback3", &test_callback3);
+    m.def("test_callback4", &test_callback4);
+    m.def("test_callback5", &test_callback5);
+
+    /* Test cleanup of lambda closure */
 
     m.def("test_cleanup", []() -> std::function<void(void)> { 
         Payload p;
@@ -94,4 +95,6 @@ void init_ex_callbacks(py::module &m) {
     m.def("dummy_function2", &dummy_function2);
     m.def("roundtrip", &roundtrip);
     m.def("test_dummy_function", &test_dummy_function);
+    // Export the payload constructor statistics for testing purposes:
+    m.def("payload_cstats", &ConstructorStats::get<Payload>);
 }

example/example-callbacks.py

@@ -55,6 +55,12 @@ print("func(number=43) = %i" % f(number=43))
 
 test_cleanup()
 
+from example import payload_cstats
+cstats = payload_cstats()
+print("Payload instances not destroyed:", cstats.alive())
+print("Copy constructions:", cstats.copy_constructions)
+print("Move constructions:", cstats.move_constructions >= 1)
+
 from example import dummy_function
 from example import dummy_function2
 from example import test_dummy_function

example/example-callbacks.ref

@@ -7,7 +7,7 @@ Molly is a dog
 Woof!
 The following error is expected: Incompatible function arguments. The following argument types are supported:
     1. (arg0: example.Dog) -> None
-    Invoked with: <example.Pet object at 0>
+    Invoked with: <example.Pet object at 0x7ffaf4b00db0>
 Callback function 1 called!
 False
 Callback function 2 called : Hello, x, True, 5
@@ -19,12 +19,15 @@ False
 func(43) = 44
 func(43) = 44
 func(number=43) = 44
-Payload constructor
-Payload copy constructor
-Payload move constructor
-Payload destructor
-Payload destructor
-Payload destructor
+### Payload @ 0x7ffdcee09c80 created via default constructor
+### Payload @ 0x7ffdcee09c88 created via copy constructor
+### Payload @ 0xb54500 created via move constructor
+### Payload @ 0x7ffdcee09c88 destroyed
+### Payload @ 0x7ffdcee09c80 destroyed
+### Payload @ 0xb54500 destroyed
+Payload instances not destroyed: 0
+Copy constructions: 1
+Move constructions: True
 argument matches dummy_function
 eval(1) = 2
 roundtrip..
@@ -36,6 +39,7 @@ could not convert to a function pointer.
 All OK!
 could not convert to a function pointer.
 All OK!
-
 test_callback3(arg0: Callable[[int], int]) -> None
+
 test_callback4() -> Callable[[int], int]
+

example/example-methods-and-attributes.cpp

@@ -8,32 +8,25 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include <unordered_map>
+#include <list>
 #include "example.h"
+#include "constructor-stats.h"
 
 class ExampleMandA {
 public:
-    ExampleMandA() {
-        cout << "Called ExampleMandA default constructor.." << endl;
-    }
-    ExampleMandA(int value) : value(value) {
-        cout << "Called ExampleMandA constructor with value " << value << ".." << endl;
-    }
-    ExampleMandA(const ExampleMandA &e) : value(e.value) {
-        cout << "Called ExampleMandA copy constructor with value " << value << ".." << endl;
-    }
-    ExampleMandA(ExampleMandA &&e) : value(e.value) {
-        cout << "Called ExampleMandA move constructor with value " << value << ".." << endl;
-        e.value = 0;
-    }
-    ~ExampleMandA() {
-        cout << "Called ExampleMandA destructor (" << value << ")" << endl;
-    }
+    ExampleMandA() { print_default_created(this); }
+    ExampleMandA(int value) : value(value) { print_created(this, value); }
+    ExampleMandA(const ExampleMandA &e) : value(e.value) { print_copy_created(this); }
+    ExampleMandA(ExampleMandA &&e) : value(e.value) { print_move_created(this); }
+    ~ExampleMandA() { print_destroyed(this); }
+
     std::string toString() {
         return "ExampleMandA[value=" + std::to_string(value) + "]";
     }
 
-    void operator=(const ExampleMandA &e) { cout << "Assignment operator" << endl; value = e.value; }
-    void operator=(ExampleMandA &&e) { cout << "Move assignment operator" << endl; value = e.value; e.value = 0;}
+    void operator=(const ExampleMandA &e) { print_copy_assigned(this); value = e.value; }
+    void operator=(ExampleMandA &&e) { print_move_assigned(this); value = e.value; }
 
     void add1(ExampleMandA other) { value += other.value; }           // passing by value
     void add2(ExampleMandA &other) { value += other.value; }          // passing by reference
@@ -88,5 +81,6 @@ void init_ex_methods_and_attributes(py::module &m) {
         .def("internal4", &ExampleMandA::internal4)
         .def("internal5", &ExampleMandA::internal5)
         .def("__str__", &ExampleMandA::toString)
-        .def_readwrite("value", &ExampleMandA::value);
+        .def_readwrite("value", &ExampleMandA::value)
+        ;
 }

example/example-methods-and-attributes.py

@@ -35,3 +35,16 @@ print(instance1.internal5())
 print("Instance 1, direct access = %i" % instance1.value)
 instance1.value = 100
 print("Instance 1: " + str(instance1))
+
+from example import ConstructorStats
+
+cstats = ConstructorStats.get(ExampleMandA)
+print("Instances not destroyed:", cstats.alive())
+instance1 = instance2 = None
+print("Instances not destroyed:", cstats.alive())
+print("Constructor values:", cstats.values())
+print("Default constructions:", cstats.default_constructions)
+print("Copy constructions:", cstats.copy_constructions)
+print("Move constructions:", cstats.move_constructions >= 1)
+print("Copy assignments:", cstats.copy_assignments)
+print("Move assignments:", cstats.move_assignments)

example/example-methods-and-attributes.ref

-Called ExampleMandA default constructor..
-Called ExampleMandA constructor with value 32..
-Called ExampleMandA copy constructor with value 32..
-Called ExampleMandA copy constructor with value 32..
-Called ExampleMandA destructor (32)
-Called ExampleMandA destructor (32)
+### ExampleMandA @ 0x2801910 created via default constructor
+### ExampleMandA @ 0x27fa780 created 32
+### ExampleMandA @ 0x7fff80a98a74 created via copy constructor
+### ExampleMandA @ 0x7fff80a98a78 created via copy constructor
+### ExampleMandA @ 0x7fff80a98a78 destroyed
+### ExampleMandA @ 0x7fff80a98a74 destroyed
 Instance 1: ExampleMandA[value=320]
 Instance 2: ExampleMandA[value=32]
-Called ExampleMandA copy constructor with value 320..
-Called ExampleMandA move constructor with value 320..
-Called ExampleMandA destructor (0)
+### ExampleMandA @ 0x7fff80a98a84 created via copy constructor
+### ExampleMandA @ 0x2801fd0 created via move constructor
+### ExampleMandA @ 0x7fff80a98a84 destroyed
 ExampleMandA[value=320]
-Called ExampleMandA destructor (320)
+### ExampleMandA @ 0x2801fd0 destroyed
 ExampleMandA[value=320]
 ExampleMandA[value=320]
 ExampleMandA[value=320]
@@ -22,5 +22,13 @@ ExampleMandA[value=320]
 320
 Instance 1, direct access = 320
 Instance 1: ExampleMandA[value=100]
-Called ExampleMandA destructor (32)
-Called ExampleMandA destructor (100)
+Instances not destroyed: 2
+### ExampleMandA @ 0x2801910 destroyed
+### ExampleMandA @ 0x27fa780 destroyed
+Instances not destroyed: 0
+Constructor values: ['32']
+Default constructions: 1
+Copy constructions: 3
+Move constructions: True
+Copy assignments: 0
+Move assignments: 0

example/example-modules.cpp

@@ -9,6 +9,7 @@
 */
 
 #include "example.h"
+#include "constructor-stats.h"
 
 void submodule_func() {
     std::cout << "submodule_func()" << std::endl;
@@ -16,9 +17,10 @@ void submodule_func() {
 
 class A {
 public:
-    A(int v) : v(v) { std::cout << "A constructor" << std::endl; }
-    ~A() { std::cout << "A destructor" << std::endl; }
-    A(const A&) { std::cout << "A copy constructor" << std::endl; }
+    A(int v) : v(v) { print_created(this, v); }
+    ~A() { print_destroyed(this); }
+    A(const A&) { print_copy_created(this); }
+    A& operator=(const A &copy) { print_copy_assigned(this); v = copy.v; return *this; }
     std::string toString() { return "A[" + std::to_string(v) + "]"; }
 private:
     int v;
@@ -26,9 +28,10 @@ private:
 
 class B {
 public:
-    B() { std::cout << "B constructor" << std::endl; }
-    ~B() { std::cout << "B destructor" << std::endl; }
-    B(const B&) { std::cout << "B copy constructor" << std::endl; }
+    B() { print_default_created(this); }
+    ~B() { print_destroyed(this); }
+    B(const B&) { print_copy_created(this); }
+    B& operator=(const B &copy) { print_copy_assigned(this); a1 = copy.a1; a2 = copy.a2; return *this; }
     A &get_a1() { return a1; }
     A &get_a2() { return a2; }
 

example/example-modules.py

@@ -28,3 +28,16 @@ print(b.get_a2())
 print(b.a2)
 
 print(OD([(1, 'a'), (2, 'b')]))
+
+from example import ConstructorStats
+
+cstats = [ConstructorStats.get(A), ConstructorStats.get(B)]
+print("Instances not destroyed:", [x.alive() for x in cstats])
+b = None
+print("Instances not destroyed:", [x.alive() for x in cstats])
+print("Constructor values:", [x.values() for x in cstats])
+print("Default constructions:", [x.default_constructions for x in cstats])
+print("Copy constructions:", [x.copy_constructions for x in cstats])
+#print("Move constructions:", [x.move_constructions >= 0 for x in cstats]) # Don't invoke any
+print("Copy assignments:", [x.copy_assignments for x in cstats])
+print("Move assignments:", [x.move_assignments for x in cstats])

example/example-modules.ref

 example
 example.submodule
 submodule_func()
-A constructor
-A constructor
-B constructor
+### A @ 0x21a5bc0 created 1
+### A @ 0x21a5bc4 created 2
+### B @ 0x21a5bc0 created via default constructor
 A[1]
 A[1]
 A[2]
 A[2]
-A constructor
-A destructor
-A constructor
-A destructor
+### A @ 0x20f93b0 created 42
+### A @ 0x21a5bc0 assigned via copy assignment
+### A @ 0x20f93b0 destroyed
+### A @ 0x20f93d0 created 43
+### A @ 0x21a5bc4 assigned via copy assignment
+### A @ 0x20f93d0 destroyed
 A[42]
 A[42]
 A[43]
 A[43]
 OrderedDict([(1, 'a'), (2, 'b')])
-B destructor
-A destructor
-A destructor
+Instances not destroyed: [2, 1]
+### B @ 0x21a5bc0 destroyed
+### A @ 0x21a5bc4 destroyed
+### A @ 0x21a5bc0 destroyed
+Instances not destroyed: [0, 0]
+Constructor values: [['1', '2', '42', '43'], []]
+Default constructions: [0, 1]
+Copy constructions: [0, 0]
+Copy assignments: [2, 0]
+Move assignments: [0, 0]

example/example-opaque-types.py

@@ -34,6 +34,8 @@ print_opaque_list(cvp.stringList)
 
 print_void_ptr(return_void_ptr())
 print_void_ptr(ExampleMandA())  # Should also work for other C++ types
+from example import ConstructorStats
+print("ExampleMandA still alive:", ConstructorStats.get(ExampleMandA).alive())
 
 try:
     print_void_ptr([1, 2, 3])  # This should not work

example/example-opaque-types.ref

@@ -6,13 +6,14 @@ Opaque list: [Element 1]
 Opaque list: []
 Opaque list: [Element 1, Element 3]
 Got void ptr : 0x1234
-Called ExampleMandA default constructor..
-Got void ptr : 0x7f9ba0f3c430
-Called ExampleMandA destructor (0)
+### ExampleMandA @ 0x2ac5370 created via default constructor
+Got void ptr : 0x2ac5370
+### ExampleMandA @ 0x2ac5370 destroyed
+ExampleMandA still alive: 0
 Caught expected exception: Incompatible function arguments. The following argument types are supported:
     1. (arg0: capsule) -> None
     Invoked with: [1, 2, 3]
 None
 Got null str : 0x0
-<example.StringList object at 0x10d3277a0>
+<example.StringList object at 0x7f7ecde6fc00>
 Opaque list: [some value]

example/example-operator-overloading.cpp

@@ -8,27 +8,28 @@
 */
 
 #include "example.h"
+#include "constructor-stats.h"
 #include <pybind11/operators.h>
 
 class Vector2 {
 public:
-    Vector2(float x, float y) : x(x), y(y) { std::cout << "Value constructor" << std::endl; }
-    Vector2(const Vector2 &v) : x(v.x), y(v.y) { std::cout << "Copy constructor" << std::endl; }
-    Vector2(Vector2 &&v) : x(v.x), y(v.y) { std::cout << "Move constructor" << std::endl; v.x = v.y = 0; }
-    ~Vector2() { std::cout << "Destructor." << std::endl; }
+    Vector2(float x, float y) : x(x), y(y) { print_created(this, toString()); }
+    Vector2(const Vector2 &v) : x(v.x), y(v.y) { print_copy_created(this); }
+    Vector2(Vector2 &&v) : x(v.x), y(v.y) { print_move_created(this); v.x = v.y = 0; }
+    ~Vector2() { print_destroyed(this); }
 
     std::string toString() const {
         return "[" + std::to_string(x) + ", " + std::to_string(y) + "]";
     }
 
     void operator=(const Vector2 &v) {
-        cout << "Assignment operator" << endl;
+        print_copy_assigned(this);
         x = v.x;
         y = v.y;
     }
 
     void operator=(Vector2 &&v) {
-        cout << "Move assignment operator" << endl;
+        print_move_assigned(this);
         x = v.x; y = v.y; v.x = v.y = 0;
     }
 
@@ -51,7 +52,6 @@ private:
     float x, y;
 };
 
-
 void init_ex_operator_overloading(py::module &m) {
     py::class_<Vector2>(m, "Vector2")
         .def(py::init<float, float>())
@@ -69,7 +69,8 @@ void init_ex_operator_overloading(py::module &m) {
         .def(float() - py::self)
         .def(float() * py::self)
         .def(float() / py::self)
-        .def("__str__", &Vector2::toString);
+        .def("__str__", &Vector2::toString)
+        ;
 
     m.attr("Vector") = m.attr("Vector2");
 }

example/example-operator-overloading.py

@@ -25,3 +25,17 @@ v1 += v2
 v1 *= 2
 
 print("(v1+v2)*2 = " + str(v1))
+
+from example import ConstructorStats
+cstats = ConstructorStats.get(Vector2)
+print("Instances not destroyed:", cstats.alive())
+v1 = None
+print("Instances not destroyed:", cstats.alive())
+v2 = None
+print("Instances not destroyed:", cstats.alive())
+print("Constructor values:", cstats.values())
+print("Default constructions:", cstats.default_constructions)
+print("Copy constructions:", cstats.copy_constructions)
+print("Move constructions:", cstats.move_constructions >= 10)
+print("Copy assignments:", cstats.copy_assignments)
+print("Move assignments:", cstats.move_assignments)

example/example-operator-overloading.ref

-Value constructor
-Value constructor
+### Vector2 @ 0x11f7830 created [1.000000, 2.000000]
+### Vector2 @ 0x11427c0 created [3.000000, -1.000000]
 v1    = [1.000000, 2.000000]
 v2    = [3.000000, -1.000000]
-Value constructor
-Move constructor
-Destructor.
-Destructor.
+### Vector2 @ 0x7ffef6b144b8 created [4.000000, 1.000000]
+### Vector2 @ 0x11f7e90 created via move constructor
+### Vector2 @ 0x7ffef6b144b8 destroyed
+### Vector2 @ 0x11f7e90 destroyed
 v1+v2 = [4.000000, 1.000000]
-Value constructor
-Move constructor
-Destructor.
-Destructor.
+### Vector2 @ 0x7ffef6b144b8 created [-2.000000, 3.000000]
+### Vector2 @ 0x11f7e90 created via move constructor
+### Vector2 @ 0x7ffef6b144b8 destroyed
+### Vector2 @ 0x11f7e90 destroyed
 v1-v2 = [-2.000000, 3.000000]
-Value constructor
-Move constructor
-Destructor.
-Destructor.
+### Vector2 @ 0x7ffef6b144c8 created [-7.000000, -6.000000]
+### Vector2 @ 0x1115760 created via move constructor
+### Vector2 @ 0x7ffef6b144c8 destroyed
+### Vector2 @ 0x1115760 destroyed
 v1-8  = [-7.000000, -6.000000]
-Value constructor
-Move constructor
-Destructor.
-Destructor.
+### Vector2 @ 0x7ffef6b144c8 created [9.000000, 10.000000]
+### Vector2 @ 0x1115760 created via move constructor
+### Vector2 @ 0x7ffef6b144c8 destroyed
+### Vector2 @ 0x1115760 destroyed
 v1+8  = [9.000000, 10.000000]
-Value constructor
-Move constructor
-Destructor.
-Destructor.
+### Vector2 @ 0x7ffef6b144b8 created [8.000000, 16.000000]
+### Vector2 @ 0x1115760 created via move constructor
+### Vector2 @ 0x7ffef6b144b8 destroyed
+### Vector2 @ 0x1115760 destroyed
 v1*8  = [8.000000, 16.000000]
-Value constructor
-Move constructor
-Destructor.
-Destructor.
+### Vector2 @ 0x7ffef6b144a8 created [0.125000, 0.250000]
+### Vector2 @ 0x112f150 created via move constructor
+### Vector2 @ 0x7ffef6b144a8 destroyed
+### Vector2 @ 0x112f150 destroyed
 v1/8  = [0.125000, 0.250000]
-Value constructor
-Move constructor
-Destructor.
-Destructor.
+### Vector2 @ 0x7ffef6b144f8 created [7.000000, 6.000000]
+### Vector2 @ 0x112f1b0 created via move constructor
+### Vector2 @ 0x7ffef6b144f8 destroyed
+### Vector2 @ 0x112f1b0 destroyed
 8-v1  = [7.000000, 6.000000]
-Value constructor
-Move constructor
-Destructor.
-Destructor.
+### Vector2 @ 0x7ffef6b144f8 created [9.000000, 10.000000]
+### Vector2 @ 0x112f1b0 created via move constructor
+### Vector2 @ 0x7ffef6b144f8 destroyed
+### Vector2 @ 0x112f1b0 destroyed
 8+v1  = [9.000000, 10.000000]
-Value constructor
-Move constructor
-Destructor.
-Destructor.
+### Vector2 @ 0x7ffef6b144e8 created [8.000000, 16.000000]
+### Vector2 @ 0x112f230 created via move constructor
+### Vector2 @ 0x7ffef6b144e8 destroyed
+### Vector2 @ 0x112f230 destroyed
 8*v1  = [8.000000, 16.000000]
-Value constructor
-Move constructor
-Destructor.
-Destructor.
+### Vector2 @ 0x7ffef6b144d8 created [8.000000, 4.000000]
+### Vector2 @ 0x11fb360 created via move constructor
+### Vector2 @ 0x7ffef6b144d8 destroyed
+### Vector2 @ 0x11fb360 destroyed
 8/v1  = [8.000000, 4.000000]
 (v1+v2)*2 = [8.000000, 2.000000]
-Destructor.
-Destructor.
+Instances not destroyed: 2
+### Vector2 @ 0x11f7830 destroyed
+Instances not destroyed: 1
+### Vector2 @ 0x11427c0 destroyed
+Instances not destroyed: 0
+Constructor values: ['[1.000000, 2.000000]', '[3.000000, -1.000000]', '[4.000000, 1.000000]', '[-2.000000, 3.000000]', '[-7.000000, -6.000000]', '[9.000000, 10.000000]', '[8.000000, 16.000000]', '[0.125000, 0.250000]', '[7.000000, 6.000000]', '[9.000000, 10.000000]', '[8.000000, 16.000000]', '[8.000000, 4.000000]']
+Default constructions: 0
+Copy constructions: 0
+Move constructions: True
+Copy assignments: 0
+Move assignments: 0

example/example-python-types.cpp

@@ -9,6 +9,7 @@
 */
 
 #include "example.h"
+#include "constructor-stats.h"
 #include <pybind11/stl.h>
 
 #ifdef _WIN32
@@ -19,11 +20,11 @@
 class ExamplePythonTypes {
 public:
     static ExamplePythonTypes *new_instance() {
-        return new ExamplePythonTypes();
-    }
-    ~ExamplePythonTypes() {
-        std::cout << "Destructing ExamplePythonTypes" << std::endl;
+        auto *ptr = new ExamplePythonTypes();
+        print_created(ptr, "via new_instance");
+        return ptr;
     }
+    ~ExamplePythonTypes() { print_destroyed(this); }
 
     /* Create and return a Python dictionary */
     py::dict get_dict() {
@@ -168,5 +169,6 @@ void init_ex_python_types(py::module &m) {
         .def("throw_exception", &ExamplePythonTypes::throw_exception, "Throw an exception")
         .def_static("new_instance", &ExamplePythonTypes::new_instance, "Return an instance")
         .def_readwrite_static("value", &ExamplePythonTypes::value, "Static value member")
-        .def_readonly_static("value2", &ExamplePythonTypes::value2, "Static value member (readonly)");
+        .def_readonly_static("value2", &ExamplePythonTypes::value2, "Static value member (readonly)")
+        ;
 }