C++: huge errors using clang to compile a map with iterators as values
c++, c++11, dictionary, iterator
Solution
As stated in the link that Jesse provided, the easiest fix is by using std::unique_ptr, which has the downside of extra heap allocations, but I really see no better option.
#include <string>
#include <algorithm>
#include <array>
#include <iostream>
#include <random>
#include <map>
#include <unordered_map>
#include <memory>
struct object {
static int next_id;
int id;
int depth;
std::map<int, std::unique_ptr<object>>::iterator id_it;
std::multimap<int, std::map<int, std::unique_ptr<object>>::iterator>::iterator depth_it;
static std::map<int, std::unique_ptr<object>> by_id;
static std::multimap<int, std::map<int, std::unique_ptr<object>>::iterator> by_depth;
object() = delete;
object(object const &) = delete;
object(object &&) = delete;
object & operator=(object const &) = delete;
object && operator=(object &&) = delete;
~object() = default;
object(int id) : id(id), depth(rand()) {}
void init(std::map<int, std::unique_ptr<object>>::iterator it) {
id_it = it;
depth_it = by_depth.emplace(depth, id_it);
}
static int create() {
auto it = by_id.emplace(next_id, std::unique_ptr<object>(new object(next_id))).first;
it->second->init(it);
++next_id;
return it->second->id;
}
static void set_depth(int o, int d) {
auto it = by_id.find(o);
if (it == by_id.end())
return;
auto & obj = it->second;
obj->depth = d;
by_depth.erase(obj->depth_it);
obj->depth_it = by_depth.emplace(obj->depth, obj->id_it);
}
static int get_depth(int o) {
auto it = by_id.find(o);
if (it == by_id.end())
return 0;
return it->second->depth;
}
static int get_id(int o) {
auto it = by_id.find(o);
if (it == by_id.end())
return 0;
return it->second->id;
}
static void destroy(int o) {
auto it = by_id.find(o);
if (it == by_id.end())
return;
by_depth.erase(it->second->depth_it);
by_id.erase(it->first);
}
template <typename T>
static void with(T f) {
for (auto it : by_depth) {
f(it.second->second->id);
}
}
};
int object::next_id = 10000;
std::map<int, std::unique_ptr<object>> object::by_id;
std::multimap<int, std::map<int, std::unique_ptr<object>>::iterator> object::by_depth;
int main() {
for (int i = 0; i < 100; ++i) {
object::create();
}
for (int i = 0; i < 100; ++i) {
object::set_depth(rand() % 100 + 10000, rand());
}
object::with([](int obj) {
std::cout << object::get_id(obj) << "->" << object::get_depth(obj) << std::endl;
});
for (int i = 0; i < 100; ++i) {
object::destroy(10000 + i);
}
object::with([](int obj) {
std::cout << "Object was not deleted!" << std::endl;
});
}
In contrast to what Jesse claims regarding the move constructor and copy constructor, while many containers, such as std::vector, do require MoveConstructible or CopyConstructible, std::map does not.
Problem
I'm trying to use iterators as values in a `std::map` so that I can efficiently lookup an object by either its `id` or iterate it efficiently by its `depth`. Consider the following code: ``` #include <string> #include <algorithm> #include <array> #include <iostream> #include <random> #include <map> #include <unordered_map> struct object { static int next_id; int id; int depth; std::map<int, object>::iterator id_it; std::multimap<int, std::map<int, object>::iterator>::iterator depth_it; static std::map<int, object> by_id; static std::multimap<int, std::map<int, object>::iterator> by_depth; object() = delete; object(object const &) = delete; object(object &&) = delete; object & operator=(object const &) = delete; object && operator=(object &&) = delete; ~object() = default; object(int id) : id(id), depth(rand()) {} void init(std::map<int, object>::iterator it) { id_it = it; depth_it = by_depth.emplace(depth, id_it); } static int create() { auto it = by_id.emplace(next_id, next_id).first; it->second.init(it); ++next_id; return it->second.id; } static void set_depth(int o, int d) { auto it = by_id.find(o); if (it == by_id.end()) return; auto & obj = it->second; obj.depth = d; by_depth.erase(obj.depth_it); obj.depth_it = by_depth.emplace(obj.depth, obj.id_it); } static int get_depth(int o) { auto it = by_id.find(o); if (it == by_id.end()) return 0; return it->second.depth; } static int get_id(int o) { auto it = by_id.find(o); if (it == by_id.end()) return 0; return it->second.id; } static void destroy(int o) { auto it = by_id.find(o); if (it == by_id.end()) return; by_depth.erase(it->second.depth_it); by_id.erase(it->first); } template <typename T> static void with(T f) { for (auto it : by_depth) { f(it.second->second.id); } } }; int object::next_id = 10000; std::map<int, object> object::by_id; std::multimap<int, std::map<int, object>::iterator> object::by_depth; int main() { for (int i = 0; i < 100; ++i) { object::create(); } for (int i = 0; i < 100; ++i) { object::set_depth(rand() % 100 + 10000, rand()); } object::with([](int obj) { std::cout << object::get_id(obj) << "->" << object::get_depth(obj) << std::endl; }); for (int i = 0; i < 100; ++i) { object::destroy(10000 + i); } object::with([](int obj) { std::cout << "Object was not deleted!" << std::endl; }); } ``` Clang gives off huge errors, but MSVC compiles it fine in STRICT mode. Errors here: ``` In file included from error.cpp:1: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:434: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/algorithm:593: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/utility:221:9: error: field has incomplete type 'object' _T2 second; ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:602:16: note: in instantiation of template class 'std::__1::pair<int, object>' requested here value_type __value_; ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:624:22: note: in instantiation of template class 'std::__1::__tree_node<std::__1::pair<int, object>, void *>' requested here typedef typename __node::base __node_base; ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:541:19: note: in instantiation of template class 'std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long>' requested here _TreeIterator __i_; ^ error.cpp:13:37: note: in instantiation of template class 'std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long> >' requested here std::map<int, object>::iterator id_it; ^ error.cpp:9:8: note: definition of 'object' is not complete until the closing '}' struct object { ^ In file included from error.cpp:6: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:834:44: error: no viable conversion from 'iterator' (aka '__tree_iterator<value_type, __node_pointer, difference_type>') to 'iterator' (aka '__map_iterator<typename __base::iterator>') iterator end() _NOEXCEPT {return __tree_.end();} ^~~~~~~~~~~~~ error.cpp:36:25: note: in instantiation of member function 'std::__1::map<int, object, std::__1::less<int>, std::__1::allocator<std::__1::pair<const int, object> > >::end' requested here if (it == by_id.end()) ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:539:24: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from 'iterator' (aka '__tree_iterator<value_type, __node_pointer, difference_type>') to 'const std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long> > &' for 1st argument class _LIBCPP_TYPE_VIS __map_iterator ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:539:24: note: candidate constructor (the implicit move constructor) not viable: no known conversion from 'iterator' (aka '__tree_iterator<value_type, __node_pointer, difference_type>') to 'std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long> > &&' for 1st argument class _LIBCPP_TYPE_VIS __map_iterator ^ In file included from error.cpp:6: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:371: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:1968:19: error: static_cast from '__node_pointer' (aka 'std::__1::__tree_node<std::__1::pair<int, object>, void *> *') to '__node_base_pointer' (aka 'std::__1::__tree_node_base<void *> *') is not allowed static_cast<__node_base_pointer>(__np)); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:1990:5: note: in instantiation of member function 'std::__1::__tree<std::__1::pair<int, object>, std::__1::__map_value_compare<int, object, std::__1::less<int>, true>, std::__1::allocator<std::__1::pair<int, object> > >::erase' requested here erase(__i); ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:937:25: note: in instantiation of function template specialization 'std::__1::__tree<std::__1::pair<int, object>, std::__1::__map_value_compare<int, object, std::__1::less<int>, true>, std::__1::allocator<std::__1::pair<int, object> > >::__erase_unique<int>' requested here {return __tree_.__erase_unique(__k);} ^ error.cpp:60:15: note: in instantiation of member function 'std::__1::map<int, object, std::__1::less<int>, std::__1::allocator<std::__1::pair<const int, object> > >::erase' requested here by_id.erase(it->first); ^ In file included from error.cpp:6: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:371: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:650:59: error: static_cast from '__node_pointer' (aka 'std::__1::__tree_node<std::__1::pair<int, object>, void *> *') to '__node_base_pointer' (aka 'int') is not allowed ...= static_cast<__node_pointer>(__tree_next(static_cast<__node_base_pointer>(__ptr_))); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:1961:5: note: in instantiation of member function 'std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long>::operator++' requested here ++__r; ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:1990:5: note: in instantiation of member function 'std::__1::__tree<std::__1::pair<int, object>, std::__1::__map_value_compare<int, object, std::__1::less<int>, true>, std::__1::allocator<std::__1::pair<int, object> > >::erase' requested here erase(__i); ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:937:25: note: in instantiation of function template specialization 'std::__1::__tree<std::__1::pair<int, object>, std::__1::__map_value_compare<int, object, std::__1::less<int>, true>, std::__1::allocator<std::__1::pair<int, object> > >::__erase_unique<int>' requested here {return __tree_.__erase_unique(__k);} ^ error.cpp:60:15: note: in instantiation of member function 'std::__1::map<int, object, std::__1::less<int>, std::__1::allocator<std::__1::pair<const int, object> > >::erase' requested here by_id.erase(it->first); ^ In file included from error.cpp:6: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:371: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:650:19: error: cannot cast from type 'int' to pointer type '__node_pointer' (aka 'std::__1::__tree_node<std::__1::pair<int, object>, void *> *') ...= static_cast<__node_pointer>(__tree_next(static_cast<__node_base_pointer>(__ptr_))); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:156:14: error: member reference type 'int' is not a pointer if (__x->__right_ != nullptr) ~~~ ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:650:47: note: in instantiation of function template specialization 'std::__1::__tree_next<int>' requested here {__ptr_ = static_cast<__node_pointer>(__tree_next(static_cast<__node_base_pointe... ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:1961:5: note: in instantiation of member function 'std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long>::operator++' requested here ++__r; ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:1990:5: note: in instantiation of member function 'std::__1::__tree<std::__1::pair<int, object>, std::__1::__map_value_compare<int, object, std::__1::less<int>, true>, std::__1::allocator<std::__1::pair<int, object> > >::erase' requested here erase(__i); ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:937:25: note: in instantiation of function template specialization 'std::__1::__tree<std::__1::pair<int, object>, std::__1::__map_value_compare<int, object, std::__1::less<int>, true>, std::__1::allocator<std::__1::pair<int, object> > >::__erase_unique<int>' requested here {return __tree_.__erase_unique(__k);} ^ error.cpp:60:15: note: in instantiation of member function 'std::__1::map<int, object, std::__1::less<int>, std::__1::allocator<std::__1::pair<const int, object> > >::erase' requested here by_id.erase(it->first); ^ In file included from error.cpp:6: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:371: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:159:20: error: member reference type 'int' is not a pointer __x = __x->__parent_; ~~~ ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:160:17: error: member reference type 'int' is not a pointer return __x->__parent_; ~~~ ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:67:24: error: member reference type 'int' is not a pointer return __x == __x->__parent_->__left_; ~~~ ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:158:13: note: in instantiation of function template specialization 'std::__1::__tree_is_left_child<int>' requested here while (!__tree_is_left_child(__x)) ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:650:47: note: in instantiation of function template specialization 'std::__1::__tree_next<int>' requested here {__ptr_ = static_cast<__node_pointer>(__tree_next(static_cast<__node_base_pointe... ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:1961:5: note: in instantiation of member function 'std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long>::operator++' requested here ++__r; ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__tree:1990:5: note: in instantiation of member function 'std::__1::__tree<std::__1::pair<int, object>, std::__1::__map_value_compare<int, object, std::__1::less<int>, true>, std::__1::allocator<std::__1::pair<int, object> > >::erase' requested here erase(__i); ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:937:25: note: in instantiation of function template specialization 'std::__1::__tree<std::__1::pair<int, object>, std::__1::__map_value_compare<int, object, std::__1::less<int>, true>, std::__1::allocator<std::__1::pair<int, object> > >::__erase_unique<int>' requested here {return __tree_.__erase_unique(__k);} ^ error.cpp:60:15: note: in instantiation of member function 'std::__1::map<int, object, std::__1::less<int>, std::__1::allocator<std::__1::pair<const int, object> > >::erase' requested here by_id.erase(it->first); ^ In file included from error.cpp:6: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:1586:44: error: no viable conversion from 'iterator' (aka '__tree_iterator<value_type, __node_pointer, difference_type>') to 'iterator' (aka '__map_iterator<typename __base::iterator>') iterator end() _NOEXCEPT {return __tree_.end();} ^~~~~~~~~~~~~ error.cpp:64:22: note: in instantiation of member function 'std::__1::multimap<int, std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long> >, std::__1::less<int>, std::__1::allocator<std::__1::pair<const int, std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long> > > > >::end' requested here for (auto it : by_depth) { ^ error.cpp:81:5: note: in instantiation of function template specialization 'object::with<<lambda at error.cpp:81:18> >' requested here object::with([](int obj) { ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:539:24: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from 'iterator' (aka '__tree_iterator<value_type, __node_pointer, difference_type>') to 'const std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long> > >, std::__1::__tree_node<std::__1::pair<int, std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long> > >, void *> *, long> > &' for 1st argument class _LIBCPP_TYPE_VIS __map_iterator ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/map:539:24: note: candidate constructor (the implicit move constructor) not viable: no known conversion from 'iterator' (aka '__tree_iterator<value_type, __node_pointer, difference_type>') to 'std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long> > >, std::__1::__tree_node<std::__1::pair<int, std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int, object>, std::__1::__tree_node<std::__1::pair<int, object>, void *> *, long> > >, void *> *, long> > &&' for 1st argument class _LIBCPP_TYPE_VIS __map_iterator ^ 10 errors generated. ``` Invocation: `g++ -std=c++11 file.cpp` where g++ is clang. What's going on?