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pybind11/tests/test_sequences_and_iterators.cpp
Bruce Merry 8a7c266d26
Fix make_key_iterator/make_value_iterator for prvalue iterators (#3348) 
* Add a test showing a flaw in make_key_iterator/make_value_iterator

If the iterator dereference operator returns a value rather than a
reference (and that pair also does not *contain* references),
make_key_iterator and make_value_iterator will return a reference to a
temporary, causing a segfault.

* Fix make_key_iterator/make_value_iterator for prvalue iterators

If an iterator returns a pair<T1, T2> rather than a reference to a pair
or a pair of references, make_key_iterator and make_value_iterator would
return a reference to a temporary, typically leading to a segfault. This
is because the value category of member access to a prvalue is an
xvalue, not a prvalue, so decltype produces an rvalue reference type.
Fix the type calculation to handle this case.

I also removed some decltype parentheses that weren't needed, either
because the expression isn't one of the special cases for decltype or
because decltype was only used for SFINAE. Hopefully that makes the code
a bit more readable.

Closes #3347

* Attempt a workaround for nvcc
2021-10-11 08:35:39 -07:00

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/*
tests/test_sequences_and_iterators.cpp -- supporting Pythons' sequence protocol, iterators,
etc.
Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
All rights reserved. Use of this source code is governed by a
BSD-style license that can be found in the LICENSE file.
*/
#include "pybind11_tests.h"
#include "constructor_stats.h"
#include <pybind11/operators.h>
#include <pybind11/stl.h>
#include <algorithm>
#include <utility>
#include <vector>
#ifdef PYBIND11_HAS_OPTIONAL
#include <optional>
#endif // PYBIND11_HAS_OPTIONAL
template<typename T>
class NonZeroIterator {
const T* ptr_;
public:
explicit NonZeroIterator(const T *ptr) : ptr_(ptr) {}
const T& operator*() const { return *ptr_; }
NonZeroIterator& operator++() { ++ptr_; return *this; }
};
class NonZeroSentinel {};
template<typename A, typename B>
bool operator==(const NonZeroIterator<std::pair<A, B>>& it, const NonZeroSentinel&) {
return !(*it).first || !(*it).second;
}
/* Iterator where dereferencing returns prvalues instead of references. */
template<typename T>
class NonRefIterator {
const T* ptr_;
public:
explicit NonRefIterator(const T *ptr) : ptr_(ptr) {}
T operator*() const { return T(*ptr_); }
NonRefIterator& operator++() { ++ptr_; return *this; }
bool operator==(const NonRefIterator &other) const { return ptr_ == other.ptr_; }
};
class NonCopyableInt {
public:
explicit NonCopyableInt(int value) : value_(value) {}
NonCopyableInt(const NonCopyableInt &) = delete;
NonCopyableInt(NonCopyableInt &&other) noexcept : value_(other.value_) {
other.value_ = -1; // detect when an unwanted move occurs
}
NonCopyableInt &operator=(const NonCopyableInt &) = delete;
NonCopyableInt &operator=(NonCopyableInt &&other) noexcept {
value_ = other.value_;
other.value_ = -1; // detect when an unwanted move occurs
return *this;
}
int get() const { return value_; }
void set(int value) { value_ = value; }
~NonCopyableInt() = default;
private:
int value_;
};
using NonCopyableIntPair = std::pair<NonCopyableInt, NonCopyableInt>;
PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableInt>);
PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableIntPair>);
template <typename PythonType>
py::list test_random_access_iterator(PythonType x) {
if (x.size() < 5)
throw py::value_error("Please provide at least 5 elements for testing.");
auto checks = py::list();
auto assert_equal = [&checks](py::handle a, py::handle b) {
auto result = PyObject_RichCompareBool(a.ptr(), b.ptr(), Py_EQ);
if (result == -1) { throw py::error_already_set(); }
checks.append(result != 0);
};
auto it = x.begin();
assert_equal(x[0], *it);
assert_equal(x[0], it[0]);
assert_equal(x[1], it[1]);
assert_equal(x[1], *(++it));
assert_equal(x[1], *(it++));
assert_equal(x[2], *it);
assert_equal(x[3], *(it += 1));
assert_equal(x[2], *(--it));
assert_equal(x[2], *(it--));
assert_equal(x[1], *it);
assert_equal(x[0], *(it -= 1));
assert_equal(it->attr("real"), x[0].attr("real"));
assert_equal((it + 1)->attr("real"), x[1].attr("real"));
assert_equal(x[1], *(it + 1));
assert_equal(x[1], *(1 + it));
it += 3;
assert_equal(x[1], *(it - 2));
checks.append(static_cast<std::size_t>(x.end() - x.begin()) == x.size());
checks.append((x.begin() + static_cast<std::ptrdiff_t>(x.size())) == x.end());
checks.append(x.begin() < x.end());
return checks;
}
TEST_SUBMODULE(sequences_and_iterators, m) {
// test_sliceable
class Sliceable{
public:
explicit Sliceable(int n) : size(n) {}
int start, stop, step;
int size;
};
py::class_<Sliceable>(m, "Sliceable")
.def(py::init<int>())
.def("__getitem__", [](const Sliceable &s, const py::slice &slice) {
py::ssize_t start = 0, stop = 0, step = 0, slicelength = 0;
if (!slice.compute(s.size, &start, &stop, &step, &slicelength))
throw py::error_already_set();
int istart = static_cast<int>(start);
int istop = static_cast<int>(stop);
int istep = static_cast<int>(step);
return std::make_tuple(istart, istop, istep);
});
m.def("make_forward_slice_size_t", []() { return py::slice(0, -1, 1); });
m.def("make_reversed_slice_object", []() { return py::slice(py::none(), py::none(), py::int_(-1)); });
#ifdef PYBIND11_HAS_OPTIONAL
m.attr("has_optional") = true;
m.def("make_reversed_slice_size_t_optional_verbose", []() { return py::slice(std::nullopt, std::nullopt, -1); });
// Warning: The following spelling may still compile if optional<> is not present and give wrong answers.
// Please use with caution.
m.def("make_reversed_slice_size_t_optional", []() { return py::slice({}, {}, -1); });
#else
m.attr("has_optional") = false;
#endif
// test_sequence
class Sequence {
public:
explicit Sequence(size_t size) : m_size(size) {
print_created(this, "of size", m_size);
m_data = new float[size];
memset(m_data, 0, sizeof(float) * size);
}
explicit Sequence(const std::vector<float> &value) : m_size(value.size()) {
print_created(this, "of size", m_size, "from std::vector");
m_data = new float[m_size];
memcpy(m_data, &value[0], sizeof(float) * m_size);
}
Sequence(const Sequence &s) : m_size(s.m_size) {
print_copy_created(this);
m_data = new float[m_size];
memcpy(m_data, s.m_data, sizeof(float)*m_size);
}
Sequence(Sequence &&s) noexcept : m_size(s.m_size), m_data(s.m_data) {
print_move_created(this);
s.m_size = 0;
s.m_data = nullptr;
}
~Sequence() { print_destroyed(this); delete[] m_data; }
Sequence &operator=(const Sequence &s) {
if (&s != this) {
delete[] m_data;
m_size = s.m_size;
m_data = new float[m_size];
memcpy(m_data, s.m_data, sizeof(float)*m_size);
}
print_copy_assigned(this);
return *this;
}
Sequence &operator=(Sequence &&s) noexcept {
if (&s != this) {
delete[] m_data;
m_size = s.m_size;
m_data = s.m_data;
s.m_size = 0;
s.m_data = nullptr;
}
print_move_assigned(this);
return *this;
}
bool operator==(const Sequence &s) const {
if (m_size != s.size()) return false;
for (size_t i = 0; i < m_size; ++i)
if (m_data[i] != s[i])
return false;
return true;
}
bool operator!=(const Sequence &s) const { return !operator==(s); }
float operator[](size_t index) const { return m_data[index]; }
float &operator[](size_t index) { return m_data[index]; }
bool contains(float v) const {
for (size_t i = 0; i < m_size; ++i)
if (v == m_data[i])
return true;
return false;
}
Sequence reversed() const {
Sequence result(m_size);
for (size_t i = 0; i < m_size; ++i)
result[m_size - i - 1] = m_data[i];
return result;
}
size_t size() const { return m_size; }
const float *begin() const { return m_data; }
const float *end() const { return m_data+m_size; }
private:
size_t m_size;
float *m_data;
};
py::class_<Sequence>(m, "Sequence")
.def(py::init<size_t>())
.def(py::init<const std::vector<float> &>())
/// Bare bones interface
.def("__getitem__",
[](const Sequence &s, size_t i) {
if (i >= s.size())
throw py::index_error();
return s[i];
})
.def("__setitem__",
[](Sequence &s, size_t i, float v) {
if (i >= s.size())
throw py::index_error();
s[i] = v;
})
.def("__len__", &Sequence::size)
/// Optional sequence protocol operations
.def(
"__iter__",
[](const Sequence &s) { return py::make_iterator(s.begin(), s.end()); },
py::keep_alive<0, 1>() /* Essential: keep object alive while iterator exists */)
.def("__contains__", [](const Sequence &s, float v) { return s.contains(v); })
.def("__reversed__", [](const Sequence &s) -> Sequence { return s.reversed(); })
/// Slicing protocol (optional)
.def("__getitem__",
[](const Sequence &s, const py::slice &slice) -> Sequence * {
size_t start = 0, stop = 0, step = 0, slicelength = 0;
if (!slice.compute(s.size(), &start, &stop, &step, &slicelength))
throw py::error_already_set();
auto *seq = new Sequence(slicelength);
for (size_t i = 0; i < slicelength; ++i) {
(*seq)[i] = s[start];
start += step;
}
return seq;
})
.def("__setitem__",
[](Sequence &s, const py::slice &slice, const Sequence &value) {
size_t start = 0, stop = 0, step = 0, slicelength = 0;
if (!slice.compute(s.size(), &start, &stop, &step, &slicelength))
throw py::error_already_set();
if (slicelength != value.size())
throw std::runtime_error(
"Left and right hand size of slice assignment have different sizes!");
for (size_t i = 0; i < slicelength; ++i) {
s[start] = value[i];
start += step;
}
})
/// Comparisons
.def(py::self == py::self)
.def(py::self != py::self)
// Could also define py::self + py::self for concatenation, etc.
;
// test_map_iterator
// Interface of a map-like object that isn't (directly) an unordered_map, but provides some basic
// map-like functionality.
class StringMap {
public:
StringMap() = default;
explicit StringMap(std::unordered_map<std::string, std::string> init)
: map(std::move(init)) {}
void set(const std::string &key, std::string val) { map[key] = std::move(val); }
std::string get(const std::string &key) const { return map.at(key); }
size_t size() const { return map.size(); }
private:
std::unordered_map<std::string, std::string> map;
public:
decltype(map.cbegin()) begin() const { return map.cbegin(); }
decltype(map.cend()) end() const { return map.cend(); }
};
py::class_<StringMap>(m, "StringMap")
.def(py::init<>())
.def(py::init<std::unordered_map<std::string, std::string>>())
.def("__getitem__",
[](const StringMap &map, const std::string &key) {
try {
return map.get(key);
} catch (const std::out_of_range &) {
throw py::key_error("key '" + key + "' does not exist");
}
})
.def("__setitem__", &StringMap::set)
.def("__len__", &StringMap::size)
.def(
"__iter__",
[](const StringMap &map) { return py::make_key_iterator(map.begin(), map.end()); },
py::keep_alive<0, 1>())
.def(
"items",
[](const StringMap &map) { return py::make_iterator(map.begin(), map.end()); },
py::keep_alive<0, 1>())
.def(
"values",
[](const StringMap &map) { return py::make_value_iterator(map.begin(), map.end()); },
py::keep_alive<0, 1>());
// test_generalized_iterators
class IntPairs {
public:
explicit IntPairs(std::vector<std::pair<int, int>> data) : data_(std::move(data)) {}
const std::pair<int, int>* begin() const { return data_.data(); }
// .end() only required for py::make_iterator(self) overload
const std::pair<int, int>* end() const { return data_.data() + data_.size(); }
private:
std::vector<std::pair<int, int>> data_;
};
py::class_<IntPairs>(m, "IntPairs")
.def(py::init<std::vector<std::pair<int, int>>>())
.def("nonzero", [](const IntPairs& s) {
return py::make_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
}, py::keep_alive<0, 1>())
.def("nonzero_keys", [](const IntPairs& s) {
return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
}, py::keep_alive<0, 1>())
.def("nonzero_values", [](const IntPairs& s) {
return py::make_value_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
}, py::keep_alive<0, 1>())
// test iterator that returns values instead of references
.def("nonref", [](const IntPairs& s) {
return py::make_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
NonRefIterator<std::pair<int, int>>(s.end()));
}, py::keep_alive<0, 1>())
.def("nonref_keys", [](const IntPairs& s) {
return py::make_key_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
NonRefIterator<std::pair<int, int>>(s.end()));
}, py::keep_alive<0, 1>())
.def("nonref_values", [](const IntPairs& s) {
return py::make_value_iterator(NonRefIterator<std::pair<int, int>>(s.begin()),
NonRefIterator<std::pair<int, int>>(s.end()));
}, py::keep_alive<0, 1>())
// test single-argument make_iterator
.def("simple_iterator", [](IntPairs& self) {
return py::make_iterator(self);
}, py::keep_alive<0, 1>())
.def("simple_keys", [](IntPairs& self) {
return py::make_key_iterator(self);
}, py::keep_alive<0, 1>())
.def("simple_values", [](IntPairs& self) {
return py::make_value_iterator(self);
}, py::keep_alive<0, 1>())
// Test iterator with an Extra (doesn't do anything useful, so not used
// at runtime, but tests need to be able to compile with the correct
// overload. See PR #3293.
.def("_make_iterator_extras", [](IntPairs& self) {
return py::make_iterator(self, py::call_guard<int>());
}, py::keep_alive<0, 1>())
.def("_make_key_extras", [](IntPairs& self) {
return py::make_key_iterator(self, py::call_guard<int>());
}, py::keep_alive<0, 1>())
.def("_make_value_extras", [](IntPairs& self) {
return py::make_value_iterator(self, py::call_guard<int>());
}, py::keep_alive<0, 1>())
;
// test_iterater_referencing
py::class_<NonCopyableInt>(m, "NonCopyableInt")
.def(py::init<int>())
.def("set", &NonCopyableInt::set)
.def("__int__", &NonCopyableInt::get)
;
py::class_<std::vector<NonCopyableInt>>(m, "VectorNonCopyableInt")
.def(py::init<>())
.def("append", [](std::vector<NonCopyableInt> &vec, int value) {
vec.emplace_back(value);
})
.def("__iter__", [](std::vector<NonCopyableInt> &vec) {
return py::make_iterator(vec.begin(), vec.end());
})
;
py::class_<std::vector<NonCopyableIntPair>>(m, "VectorNonCopyableIntPair")
.def(py::init<>())
.def("append", [](std::vector<NonCopyableIntPair> &vec, const std::pair<int, int> &value) {
vec.emplace_back(NonCopyableInt(value.first), NonCopyableInt(value.second));
})
.def("keys", [](std::vector<NonCopyableIntPair> &vec) {
return py::make_key_iterator(vec.begin(), vec.end());
})
.def("values", [](std::vector<NonCopyableIntPair> &vec) {
return py::make_value_iterator(vec.begin(), vec.end());
})
;
#if 0
// Obsolete: special data structure for exposing custom iterator types to python
// kept here for illustrative purposes because there might be some use cases which
// are not covered by the much simpler py::make_iterator
struct PySequenceIterator {
PySequenceIterator(const Sequence &seq, py::object ref) : seq(seq), ref(ref) { }
float next() {
if (index == seq.size())
throw py::stop_iteration();
return seq[index++];
}
const Sequence &seq;
py::object ref; // keep a reference
size_t index = 0;
};
py::class_<PySequenceIterator>(seq, "Iterator")
.def("__iter__", [](PySequenceIterator &it) -> PySequenceIterator& { return it; })
.def("__next__", &PySequenceIterator::next);
On the actual Sequence object, the iterator would be constructed as follows:
.def("__iter__", [](py::object s) { return PySequenceIterator(s.cast<const Sequence &>(), s); })
#endif
// test_python_iterator_in_cpp
m.def("object_to_list", [](const py::object &o) {
auto l = py::list();
for (auto item : o) {
l.append(item);
}
return l;
});
m.def("iterator_to_list", [](py::iterator it) {
auto l = py::list();
while (it != py::iterator::sentinel()) {
l.append(*it);
++it;
}
return l;
});
// test_sequence_length: check that Python sequences can be converted to py::sequence.
m.def("sequence_length", [](const py::sequence &seq) { return seq.size(); });
// Make sure that py::iterator works with std algorithms
m.def("count_none", [](const py::object &o) {
return std::count_if(o.begin(), o.end(), [](py::handle h) { return h.is_none(); });
});
m.def("find_none", [](const py::object &o) {
auto it = std::find_if(o.begin(), o.end(), [](py::handle h) { return h.is_none(); });
return it->is_none();
});
m.def("count_nonzeros", [](const py::dict &d) {
return std::count_if(d.begin(), d.end(), [](std::pair<py::handle, py::handle> p) {
return p.second.cast<int>() != 0;
});
});
m.def("tuple_iterator", &test_random_access_iterator<py::tuple>);
m.def("list_iterator", &test_random_access_iterator<py::list>);
m.def("sequence_iterator", &test_random_access_iterator<py::sequence>);
// test_iterator_passthrough
// #181: iterator passthrough did not compile
m.def("iterator_passthrough", [](py::iterator s) -> py::iterator {
return py::make_iterator(std::begin(s), std::end(s));
});
// test_iterator_rvp
// #388: Can't make iterators via make_iterator() with different r/v policies
static std::vector<int> list = { 1, 2, 3 };
m.def("make_iterator_1", []() { return py::make_iterator<py::return_value_policy::copy>(list); });
m.def("make_iterator_2", []() { return py::make_iterator<py::return_value_policy::automatic>(list); });
}
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