https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81507
Bug ID: 81507
Summary: map header kills variant of vectors
Product: gcc
Version: 7.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: benni.buch at gmail dot com
Target Milestone: ---
I ran into a very strange bug:
#include <variant>
#include <vector>
#include <map> // must include map to trigger the error!!!
template < typename A, typename B >
void apply(A const&, B const&){}
int main(){
auto value = std::variant< std::vector< int >, std::vector< short > >();
std::visit([](auto const& v){
apply(v, 0ul); // std::tuple_size<long unsigned int> is incomplete
}, value);
}
$ g++-7.1 -std=c++1z -o main gcc_variant_bug.cpp
In file included from
/home/bebuch/media/programme/gcc-7/include/c++/7.1.1/bits/node_handle.h:40:0,
from
/home/bebuch/media/programme/gcc-7/include/c++/7.1.1/bits/stl_tree.h:72,
from
/home/bebuch/media/programme/gcc-7/include/c++/7.1.1/map:60,
from gcc_variant_bug.cpp:4:
/home/bebuch/media/programme/gcc-7/include/c++/7.1.1/tuple: In instantiation of
'constexpr const size_t std::tuple_size_v<long unsigned int>':
/home/bebuch/media/programme/gcc-7/include/c++/7.1.1/tuple:1670:44: required
from 'constexpr decltype(auto) std::apply(_Fn&&, _Tuple&&) [with _Fn = const
std::vector<int>&; _Tuple = long unsigned int]'
gcc_variant_bug.cpp:14:8: required from 'main()::<lambda(const auto:1&)>
[with auto:1 = std::vector<int>]'
/home/bebuch/media/programme/gcc-7/include/c++/7.1.1/variant:1236:44:
required from 'constexpr decltype(auto) std::visit(_Visitor&&, _Variants&& ...)
[with _Visitor = main()::<lambda(const auto:1&)>; _Variants =
{std::variant<std::vector<int, std::allocator<int> >, std::vector<short int,
std::allocator<short int> > >&}]'
gcc_variant_bug.cpp:15:10: required from here
/home/bebuch/media/programme/gcc-7/include/c++/7.1.1/tuple:1271:29: error:
incomplete type 'std::tuple_size<long unsigned int>' used in nested name
specifier
inline constexpr size_t tuple_size_v = tuple_size<_Tp>::value;
^~~~~~~~~~~~
$ g++-7.1 --version
g++-7.1 (GCC) 7.1.1 20170509
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
I'm not quiet sure if it is a bug in the library or in the compiler frontend,
but since the header map is involved, I suppose it's in the library.
