https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101792
Bug ID: 101792
Summary: Compiling access to templated parent object fails with
unrelated message: invalid use of 'auto'
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: serpent7776 at gmail dot com
Target Milestone: ---
Sorry for the title, but I don't know how to describe the issue.
The following code fails to compile with error message:
<source>: In instantiation of 'int fun(Ts ...) [with Ts = {int, int, int}]':
<source>:26:10: required from here
<source>:21:41: error: invalid use of 'auto'
21 | return pack.template Value<0, int>::value;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
Compiler returned: 1
The mentioned line doesn't have `auto`, so it's at best a misleading error
message. `auto` from error message refers to the `auto` on previous line.
Clang compiles the code without issue.
If I remove `template` keyword from offending line, gcc compiles the code
without issue.
gcc 11.2 x86_64
flags: -std=c++17 -Wall -Wextra -pedantic -O2
#include <utility>
template <std::size_t, typename T>
struct Value
{
const T& value;
};
template <class Idxs, class ...Ts>
struct Pack;
template <std::size_t ...Idxs, typename ...Ts>
struct Pack<std::index_sequence<Idxs...>, Ts...> : Value<Idxs, Ts>...
{
};
template <typename ...Ts>
int fun(Ts... ts)
{
auto pack = Pack<std::index_sequence_for<Ts...>, Ts...> {{ts}...};
return pack.template Value<0, int>::value;
}
void f()
{
fun<>(1, 2, 3);
}
link to godbolt to see the issue:
https://godbolt.org/z/z7so93Wq8
