#include <iostream>
#include <unordered_map>
#include <string>
struct tree_node {
// tree_node() : attrib_val{"null"} {}
std::unordered_map<std::string, tree_node> child;
};
int main(int argc, char const *argv[])
{
return 0;
}
Этот код прекрасно компилируется на моей ма c с помощью clang:
$ g++ --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/c++/4.2.1
Apple LLVM version 10.0.1 (clang-1001.0.46.4)
Target: x86_64-apple-darwin18.7.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
$ g++ -std=c++11 test.cpp
$
На моей linux машине с g cc 9.1.0 я получаю следующую ошибку :
In file included from /usr/um/gcc-9.1.0/include/c++/9.1.0/bits/stl_algobase.h:64,
from /usr/um/gcc-9.1.0/include/c++/9.1.0/bits/char_traits.h:39,
from /usr/um/gcc-9.1.0/include/c++/9.1.0/ios:40,
from /usr/um/gcc-9.1.0/include/c++/9.1.0/ostream:38,
from /usr/um/gcc-9.1.0/include/c++/9.1.0/iostream:39,
from test.cpp:1:
/usr/um/gcc-9.1.0/include/c++/9.1.0/bits/stl_pair.h: In instantiation of ‘struct std::pair<const std::__cxx11::basic_string<char>, tree_node>’:
/usr/um/gcc-9.1.0/include/c++/9.1.0/ext/aligned_buffer.h:91:28: required from ‘struct __gnu_cxx::__aligned_buffer<std::pair<const std::__cxx11::basic_string<char>, tree_node> >’
/usr/um/gcc-9.1.0/include/c++/9.1.0/bits/hashtable_policy.h:233:43: required from ‘struct std::__detail::_Hash_node_value_base<std::pair<const std::__cxx11::basic_string<char>, tree_node> >’
/usr/um/gcc-9.1.0/include/c++/9.1.0/bits/hashtable_policy.h:264:12: required from ‘struct std::__detail::_Hash_node<std::pair<const std::__cxx11::basic_string<char>, tree_node>, true>’
/usr/um/gcc-9.1.0/include/c++/9.1.0/bits/hashtable_policy.h:2016:13: required from ‘struct std::__detail::_Hashtable_alloc<std::allocator<std::__detail::_Hash_node<std::pair<const std::__cxx11::basic_string<char>, tree_node>, true> > >’
/usr/um/gcc-9.1.0/include/c++/9.1.0/bits/hashtable.h:173:11: required from ‘class std::_Hashtable<std::__cxx11::basic_string<char>, std::pair<const std::__cxx11::basic_string<char>, tree_node>, std::allocator<std::pair<const std::__cxx11::basic_string<char>, tree_node> >, std::__detail::_Select1st, std::equal_to<std::__cxx11::basic_string<char> >, std::hash<std::__cxx11::basic_string<char> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<true, false, true> >’
/usr/um/gcc-9.1.0/include/c++/9.1.0/bits/unordered_map.h:105:18: required from ‘class std::unordered_map<std::__cxx11::basic_string<char>, tree_node>’
test.cpp:7:46: required from here
/usr/um/gcc-9.1.0/include/c++/9.1.0/bits/stl_pair.h:215:11: error: ‘std::pair<_T1, _T2>::second’ has incomplete type
215 | _T2 second; /// @c second is a copy of the second object
| ^~~~~~
test.cpp:5:8: note: forward declaration of ‘struct tree_node’
5 | struct tree_node {
Не нравится tree_node
как значение в unordered_map
по некоторым причинам.