277 lines
11 KiB
C++
277 lines
11 KiB
C++
#pragma once
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/*
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tests/constructor_stats.h -- framework for printing and tracking object
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instance lifetimes in example/test code.
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Copyright (c) 2016 Jason Rhinelander <jason@imaginary.ca>
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All rights reserved. Use of this source code is governed by a
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BSD-style license that can be found in the LICENSE file.
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This header provides a few useful tools for writing examples or tests that want to check and/or
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display object instance lifetimes. It requires that you include this header and add the following
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function calls to constructors:
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class MyClass {
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MyClass() { ...; print_default_created(this); }
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~MyClass() { ...; print_destroyed(this); }
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MyClass(const MyClass &c) { ...; print_copy_created(this); }
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MyClass(MyClass &&c) { ...; print_move_created(this); }
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MyClass(int a, int b) { ...; print_created(this, a, b); }
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MyClass &operator=(const MyClass &c) { ...; print_copy_assigned(this); }
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MyClass &operator=(MyClass &&c) { ...; print_move_assigned(this); }
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...
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}
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You can find various examples of these in several of the existing example .cpp files. (Of course
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you don't need to add any of the above constructors/operators that you don't actually have, except
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for the destructor).
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Each of these will print an appropriate message such as:
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### MyClass @ 0x2801910 created via default constructor
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### MyClass @ 0x27fa780 created 100 200
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### MyClass @ 0x2801910 destroyed
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### MyClass @ 0x27fa780 destroyed
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You can also include extra arguments (such as the 100, 200 in the output above, coming from the
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value constructor) for all of the above methods which will be included in the output.
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For testing, each of these also keeps track the created instances and allows you to check how many
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of the various constructors have been invoked from the Python side via code such as:
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from example import ConstructorStats
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cstats = ConstructorStats.get(MyClass)
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print(cstats.alive())
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print(cstats.default_constructions)
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Note that `.alive()` should usually be the first thing you call as it invokes Python's garbage
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collector to actually destroy objects that aren't yet referenced.
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For everything except copy and move constructors and destructors, any extra values given to the
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print_...() function is stored in a class-specific values list which you can retrieve and inspect
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from the ConstructorStats instance `.values()` method.
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In some cases, when you need to track instances of a C++ class not registered with pybind11, you
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need to add a function returning the ConstructorStats for the C++ class; this can be done with:
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m.def("get_special_cstats", &ConstructorStats::get<SpecialClass>, py::return_value_policy::reference)
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Finally, you can suppress the output messages, but keep the constructor tracking (for
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inspection/testing in python) by using the functions with `print_` replaced with `track_` (e.g.
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`track_copy_created(this)`).
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*/
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#include "pybind11_tests.h"
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#include <unordered_map>
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#include <list>
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#include <typeindex>
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#include <sstream>
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class ConstructorStats {
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protected:
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std::unordered_map<void*, int> _instances; // Need a map rather than set because members can shared address with parents
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std::list<std::string> _values; // Used to track values (e.g. of value constructors)
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public:
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int default_constructions = 0;
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int copy_constructions = 0;
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int move_constructions = 0;
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int copy_assignments = 0;
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int move_assignments = 0;
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void copy_created(void *inst) {
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created(inst);
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copy_constructions++;
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}
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void move_created(void *inst) {
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created(inst);
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move_constructions++;
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}
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void default_created(void *inst) {
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created(inst);
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default_constructions++;
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}
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void created(void *inst) {
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++_instances[inst];
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}
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void destroyed(void *inst) {
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if (--_instances[inst] < 0)
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throw std::runtime_error("cstats.destroyed() called with unknown "
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"instance; potential double-destruction "
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"or a missing cstats.created()");
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}
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static void gc() {
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// Force garbage collection to ensure any pending destructors are invoked:
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#if defined(PYPY_VERSION)
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PyObject *globals = PyEval_GetGlobals();
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PyObject *result = PyRun_String(
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"import gc\n"
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"for i in range(2):"
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" gc.collect()\n",
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Py_file_input, globals, globals);
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if (result == nullptr)
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throw py::error_already_set();
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Py_DECREF(result);
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#else
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py::module::import("gc").attr("collect")();
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#endif
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}
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int alive() {
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gc();
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int total = 0;
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for (const auto &p : _instances)
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if (p.second > 0)
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total += p.second;
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return total;
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}
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void value() {} // Recursion terminator
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// Takes one or more values, converts them to strings, then stores them.
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template <typename T, typename... Tmore> void value(const T &v, Tmore &&...args) {
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std::ostringstream oss;
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oss << v;
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_values.push_back(oss.str());
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value(std::forward<Tmore>(args)...);
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}
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// Move out stored values
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py::list values() {
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py::list l;
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for (const auto &v : _values) l.append(py::cast(v));
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_values.clear();
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return l;
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}
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// Gets constructor stats from a C++ type index
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static ConstructorStats& get(std::type_index type) {
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static std::unordered_map<std::type_index, ConstructorStats> all_cstats;
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return all_cstats[type];
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}
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// Gets constructor stats from a C++ type
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template <typename T> static ConstructorStats& get() {
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#if defined(PYPY_VERSION)
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gc();
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#endif
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return get(typeid(T));
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}
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// Gets constructor stats from a Python class
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static ConstructorStats& get(py::object class_) {
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auto &internals = py::detail::get_internals();
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const std::type_index *t1 = nullptr, *t2 = nullptr;
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try {
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auto *type_info = internals.registered_types_py.at(class_.ptr());
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for (auto &p : internals.registered_types_cpp) {
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if (p.second == type_info) {
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if (t1) {
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t2 = &p.first;
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break;
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}
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t1 = &p.first;
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}
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}
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}
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catch (std::out_of_range) {}
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if (!t1) throw std::runtime_error("Unknown class passed to ConstructorStats::get()");
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auto &cs1 = get(*t1);
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// If we have both a t1 and t2 match, one is probably the trampoline class; return whichever
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// has more constructions (typically one or the other will be 0)
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if (t2) {
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auto &cs2 = get(*t2);
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int cs1_total = cs1.default_constructions + cs1.copy_constructions + cs1.move_constructions + (int) cs1._values.size();
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int cs2_total = cs2.default_constructions + cs2.copy_constructions + cs2.move_constructions + (int) cs2._values.size();
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if (cs2_total > cs1_total) return cs2;
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}
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return cs1;
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}
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};
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// To track construction/destruction, you need to call these methods from the various
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// constructors/operators. The ones that take extra values record the given values in the
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// constructor stats values for later inspection.
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template <class T> void track_copy_created(T *inst) { ConstructorStats::get<T>().copy_created(inst); }
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template <class T> void track_move_created(T *inst) { ConstructorStats::get<T>().move_created(inst); }
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template <class T, typename... Values> void track_copy_assigned(T *, Values &&...values) {
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auto &cst = ConstructorStats::get<T>();
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cst.copy_assignments++;
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cst.value(std::forward<Values>(values)...);
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}
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template <class T, typename... Values> void track_move_assigned(T *, Values &&...values) {
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auto &cst = ConstructorStats::get<T>();
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cst.move_assignments++;
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cst.value(std::forward<Values>(values)...);
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}
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template <class T, typename... Values> void track_default_created(T *inst, Values &&...values) {
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auto &cst = ConstructorStats::get<T>();
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cst.default_created(inst);
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cst.value(std::forward<Values>(values)...);
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}
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template <class T, typename... Values> void track_created(T *inst, Values &&...values) {
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auto &cst = ConstructorStats::get<T>();
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cst.created(inst);
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cst.value(std::forward<Values>(values)...);
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}
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template <class T, typename... Values> void track_destroyed(T *inst) {
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ConstructorStats::get<T>().destroyed(inst);
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}
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template <class T, typename... Values> void track_values(T *, Values &&...values) {
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ConstructorStats::get<T>().value(std::forward<Values>(values)...);
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}
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/// Don't cast pointers to Python, print them as strings
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inline const char *format_ptrs(const char *p) { return p; }
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template <typename T>
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py::str format_ptrs(T *p) { return "{:#x}"_s.format(reinterpret_cast<std::uintptr_t>(p)); }
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template <typename T>
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auto format_ptrs(T &&x) -> decltype(std::forward<T>(x)) { return std::forward<T>(x); }
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template <class T, typename... Output>
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void print_constr_details(T *inst, const std::string &action, Output &&...output) {
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py::print("###", py::type_id<T>(), "@", format_ptrs(inst), action,
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format_ptrs(std::forward<Output>(output))...);
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}
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// Verbose versions of the above:
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template <class T, typename... Values> void print_copy_created(T *inst, Values &&...values) { // NB: this prints, but doesn't store, given values
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print_constr_details(inst, "created via copy constructor", values...);
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track_copy_created(inst);
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}
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template <class T, typename... Values> void print_move_created(T *inst, Values &&...values) { // NB: this prints, but doesn't store, given values
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print_constr_details(inst, "created via move constructor", values...);
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track_move_created(inst);
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}
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template <class T, typename... Values> void print_copy_assigned(T *inst, Values &&...values) {
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print_constr_details(inst, "assigned via copy assignment", values...);
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track_copy_assigned(inst, values...);
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}
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template <class T, typename... Values> void print_move_assigned(T *inst, Values &&...values) {
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print_constr_details(inst, "assigned via move assignment", values...);
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track_move_assigned(inst, values...);
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}
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template <class T, typename... Values> void print_default_created(T *inst, Values &&...values) {
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print_constr_details(inst, "created via default constructor", values...);
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track_default_created(inst, values...);
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}
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template <class T, typename... Values> void print_created(T *inst, Values &&...values) {
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print_constr_details(inst, "created", values...);
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track_created(inst, values...);
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}
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template <class T, typename... Values> void print_destroyed(T *inst, Values &&...values) { // Prints but doesn't store given values
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print_constr_details(inst, "destroyed", values...);
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track_destroyed(inst);
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}
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template <class T, typename... Values> void print_values(T *inst, Values &&...values) {
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print_constr_details(inst, ":", values...);
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track_values(inst, values...);
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}
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