[英]const_iterator and constness of const_iterator::value_type
[英]const_iterator type of a container of const types
如果我编译下面的代码:
#include <list>
using iter_t = std::list<const unsigned>::const_iterator;
int main(int, char**) {
return 0;
}
我收到以下编译错误:
In file included from /usr/local/Cellar/gcc/4.9.2_1/include/c++/4.9.2/x86_64-apple-darwin13.4.0/bits/c++allocator.h:33:0,
from /usr/local/Cellar/gcc/4.9.2_1/include/c++/4.9.2/bits/allocator.h:46,
from /usr/local/Cellar/gcc/4.9.2_1/include/c++/4.9.2/list:61,
from main.cpp:1:
/usr/local/Cellar/gcc/4.9.2_1/include/c++/4.9.2/ext/new_allocator.h: In instantiation of 'class __gnu_cxx::new_allocator<const unsigned int>':
/usr/local/Cellar/gcc/4.9.2_1/include/c++/4.9.2/bits/allocator.h:92:11: required from 'class std::allocator<const unsigned int>'
/usr/local/Cellar/gcc/4.9.2_1/include/c++/4.9.2/bits/stl_list.h:315:9: required from 'class std::_List_base<const unsigned int, std::allocator<const unsigned int> >'
/usr/local/Cellar/gcc/4.9.2_1/include/c++/4.9.2/bits/stl_list.h:447:11: required from 'class std::list<const unsigned int>'
main.cpp:3:41: required from here
/usr/local/Cellar/gcc/4.9.2_1/include/c++/4.9.2/ext/new_allocator.h:93:7: error: 'const _Tp* __gnu_cxx::new_allocator<_Tp>::address(__gnu_cxx::new_allocator<_Tp>::const_reference) const [with _Tp = const unsigned int; __gnu_cxx::new_allocator<_Tp>::const_pointer = const unsigned int*; __gnu_cxx::new_allocator<_Tp>::const_reference = const unsigned int&]' cannot be overloaded
address(const_reference __x) const _GLIBCXX_NOEXCEPT
^
/usr/local/Cellar/gcc/4.9.2_1/include/c++/4.9.2/ext/new_allocator.h:89:7: error: with '_Tp* __gnu_cxx::new_allocator<_Tp>::address(__gnu_cxx::new_allocator<_Tp>::reference) const [with _Tp = const unsigned int; __gnu_cxx::new_allocator<_Tp>::pointer = const unsigned int*; __gnu_cxx::new_allocator<_Tp>::reference = const unsigned int&]'
address(reference __x) const _GLIBCXX_NOEXCEPT
^
如果将容器类型从std::list
更改为std::vector
, std::deque
或std::forward_list
,我会得到大致相同的错误消息。 如果我将模板参数从const unsigned
更改为unsigned
则可以正常编译。
这里发生了什么? 我不明白为什么它不能编译。
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