https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97938
Bug ID: 97938
Summary: g++ crash when inferring type of auto parameter pack
in lambda capture
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: elel at 3wh dot net
Target Milestone: ---
The following test case:
#include <iostream>
#include <tuple>
template <typename... Args>
int print_args(Args&&... args) {
std::cout << (args << ...);
return sizeof...(args);
}
template <typename T1, typename T2>
auto fwd(const T1& t1, const T2& t2) {
return std::apply([&t2] (auto&&... ts1) {
return std::apply([...ts1 = std::forward<decltype(ts1)>(ts1)] (auto&&...
ts2) {
return print_args(ts1..., std::forward<decltype(ts2)>(ts2)...);
}, t2);
}, t1);
}
int main() {
auto t1 = std::make_tuple(int{1}, float{2});
auto t2 = std::make_tuple(float{3}, int{4});
return fwd(t1, t2);
}
Compiled as:
g++ -std=c++20 -g -O2 gcc_crash.cpp
Crashes g++ with the following message:
gcc_crash.cpp: In instantiation of ‘fwd<std::tuple<int, float>,
std::tuple<float, int> >::<lambda(auto:11&& ...)> [with auto:11 = {const int&,
const float&}]’:
/usr/include/c++/10.2.0/type_traits:2506:26: required by substitution of
‘template<class _Fn, class ... _Args> static std::__result_of_success<decltype
(declval<_Fn>()((declval<_Args>)()...)), std::__invoke_other>
std::__result_of_other_impl::_S_test(int) [with _Fn = fwd<std::tuple<int,
float>, std::tuple<float, int> >::<lambda(auto:11&& ...)>; _Args = {const int&,
const float&}]’
/usr/include/c++/10.2.0/type_traits:2517:55: required from ‘struct
std::__result_of_impl<false, false, fwd<std::tuple<int, float>,
std::tuple<float, int> >::<lambda(auto:11&& ...)>, const int&, const float&>’
/usr/include/c++/10.2.0/type_traits:138:12: recursively required by
substitution of ‘template<class _Result, class _Ret> struct
std::__is_invocable_impl<_Result, _Ret, true, std::__void_t<typename
_CTp::type> > [with _Result = std::__invoke_result<fwd<std::tuple<int, float>,
std::tuple<float, int> >::<lambda(auto:11&& ...)>, const int&, const float&>;
_Ret = void]’
/usr/include/c++/10.2.0/type_traits:138:12: required from ‘struct
std::__and_<std::__is_invocable_impl<std::__invoke_result<fwd<std::tuple<int,
float>, std::tuple<float, int> >::<lambda(auto:11&& ...)>, const int&, const
float&>, void, true, void>,
std::__call_is_nothrow<std::__invoke_result<fwd<std::tuple<int, float>,
std::tuple<float, int> >::<lambda(auto:11&& ...)>, const int&, const float&>,
fwd<std::tuple<int, float>, std::tuple<float, int> >::<lambda(auto:11&& ...)>,
const int&, const float&> >’
/usr/include/c++/10.2.0/type_traits:2979:12: required from ‘struct
std::is_nothrow_invocable<fwd<std::tuple<int, float>, std::tuple<float, int>
>::<lambda(auto:11&& ...)>, const int&, const float&>’
/usr/include/c++/10.2.0/tuple:1715:37: required from ‘constexpr const bool
std::__unpack_std_tuple<template<class _Fn, class ... _ArgTypes> struct
std::is_nothrow_invocable, fwd<std::tuple<int, float>, std::tuple<float, int>
>::<lambda(auto:11&& ...)>, const std::tuple<int, float>&>’
/usr/include/c++/10.2.0/tuple:1730:14: required from ‘constexpr
decltype(auto) std::apply(_Fn&&, _Tuple&&) [with _Fn = fwd<std::tuple<int,
float>, std::tuple<float, int> >::<lambda(auto:11&& ...)>; _Tuple = const
std::tuple<int, float>&]’
gcc_crash.cpp:12:20: required from ‘auto fwd(const T1&, const T2&) [with T1 =
std::tuple<int, float>; T2 = std::tuple<float, int>]’
gcc_crash.cpp:22:20: required from here
gcc_crash.cpp:13:23: internal compiler error: Segmentation fault
13 | return std::apply([...ts1 = std::forward<decltype(ts1)>(ts1)]
(auto&&... ts2) {
|
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
14 | return print_args(ts1..., std::forward<decltype(ts2)>(ts2)...);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
15 | }, t2);
| ~
Please submit a full bug report,
with preprocessed source if appropriate.
In other scenarios (not the minimal test case above) the same bug triggers the
message:
internal compiler error: in cxx_incomplete_type_diagnostic, at cp/typeck2.c:584
