https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97375
Bug ID: 97375
Summary: Unexpected top-level const retainment when declaring
non-type template paramter with decltype(auto)
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: anders.granlund.0 at gmail dot com
Target Milestone: ---
Consider the following program:
#include <iostream>
#include <type_traits>
template<const int N>
void f1()
{
std::cout << std::is_const_v<decltype(N)> << std::endl;
}
template<decltype(auto) N>
void f2()
{
std::cout << std::is_const_v<decltype(N)> << std::endl;
}
int main()
{
const int i = 0;
f1<i>();
f2<i>();
}
When compiling it with -std=c++17 -pedantic-errors it gives the following
output:
0
1
I expect it to give the following output instead:
0
0
So that the ignoral of top-level const is done in both cases.
Note that clang gives the correct output. Compiler explorer link showing the
difference between clang and gcc behaviour:
https://godbolt.org/z/aefYKd
I tried to report this bug first to clang (with a different example program),
but it turned out from the discussion (comment #3) that the bug was actually in
gcc:
https://bugs.llvm.org/show_bug.cgi?id=47792#c3
