[英]Self-referential use of unordered_map causes problems for gcc 5.3 but not clang
以下代碼無法在gcc 5.3下編譯 (這是從較大代碼段中獲取的簡化版本):
#include <unordered_map>
#include <string>
class Foo {
std::unordered_map<std::string, Foo> m; //"self-referential"
};
int main()
{
Foo f;
return 0;
}
出現以下錯誤:
g++ --std=c++1y -c rh.cpp
In file included from /usr/local/include/c++/5.3.0/utility:70:0,
from /usr/local/include/c++/5.3.0/unordered_map:38,
from rh.cpp:1:
/usr/local/include/c++/5.3.0/bits/stl_pair.h: In instantiation of ‘struct std::pair<const int, Foo>’:
/usr/local/include/c++/5.3.0/ext/aligned_buffer.h:85:34: required from ‘struct __gnu_cxx::__aligned_buffer<std::pair<const int, Foo> >’
/usr/local/include/c++/5.3.0/bits/hashtable_policy.h:246:43: required from ‘struct std::__detail::_Hash_node_value_base<std::pair<const int, Foo> >’
/usr/local/include/c++/5.3.0/bits/hashtable_policy.h:292:12: required from ‘struct std::__detail::_Hash_node<std::pair<const int, Foo>, false>’
/usr/local/include/c++/5.3.0/bits/hashtable_policy.h:1896:60: required from ‘struct std::__detail::_Hashtable_alloc<std::allocator<std::__detail::_Hash_node<std::pair<const int, Foo>, false> > >’
/usr/local/include/c++/5.3.0/bits/hashtable.h:170:11: required from ‘class std::_Hashtable<int, std::pair<const int, Foo>, std::allocator<std::pair<const int, Foo> >, std::__detail::_Select1st, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, false, true> >’
/usr/local/include/c++/5.3.0/bits/unordered_map.h:101:18: required from ‘class std::unordered_map<int, Foo>’
rh.cpp:4:32: required from here
/usr/local/include/c++/5.3.0/bits/stl_pair.h:102:11: error: ‘std::pair<_T1, _T2>::second’ has incomplete type
_T2 second; /// @c second is a copy of the second object
^
rh.cpp:3:7: note: forward declaration of ‘class Foo’
class Foo {
使用clang的代碼沒有問題(我在Linux上測試了3.8,在OSX上測試了3.9):
clang++ --std=c++1y --stdlib=libc++ -c rh.cpp
在Linux上,使用clang + libstdc ++也會失敗。
問題似乎歸結為在其哈希映射實現中使用__gnu_cxx::__aligned_buffer
libstdc ++ ,它需要完整的類型。
當使用std :: map時,兩個標准庫都可以正常工作,但這不是我可以接受的解決方案。 映射的值類型也不是指向Foo的指針。
為了使代碼在gcc / libstdc ++上運行,我還可以進行其他更改嗎?
謝謝!
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.