https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111532
Bug ID: 111532
Summary: tuple get accesses through base element type in
constant expression
Product: gcc
Version: 13.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: oliverzlee at gmail dot com
Target Milestone: ---
The following does not compile with GCC trunk/13.2/13.1/12.2/12.1 and
-std=c++14:
#include <tuple>
class A
{};
class B : A
{
public:
constexpr auto base() const -> A
{
return static_cast<const A&>(*this);
}
};
auto main() -> int
{
constexpr auto x =
std::get<0>(std::tuple<B>{}).base();
(void)x;
}
with the following error:
<source>: In function 'int main()':
<source>:18:38: in 'constexpr' expansion of '(& std::get<0,
B>(std::tuple<B>()))->B::base()'
<source>:18:39: error: accessing value of '<anonymous>.std::_Head_base<0, B,
true>::_M_head_impl' through a 'const A' glvalue in a constant expression
18 | std::get<0>(std::tuple<B>{}).base();
| ^
Compiler returned: 1
This compiles with -std=c++17 and -std=c++20, outside of constant expressions,
and with GCC 11.4.
Here is a godbolt link:
https://godbolt.org/z/x9dvherM6
