https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93377
Bug ID: 93377
Summary: [10 Regression] ICE in tsubst_pack_expansion, at
cp/pt.c:12852
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc-bugs at marehr dot dialup.fu-berlin.de
Target Milestone: ---
The following code worked in gcc9 and below, but fails with a recent snapshot
of gcc
```c++
struct empty
{};
template <typename c>
c value;
template <typename c>
auto func(value<c>);
template <typename, typename...>
struct alignment_algorithm;
template <typename... args_t>
struct select
{
template <typename algorithm_t, typename... _args_t>
decltype(algorithm_t()(func<_args_t>...)) choose();
template <typename...>
static empty choose();
using type = decltype(choose<alignment_algorithm<int>, args_t...>());
};
template <typename, typename... args_t>
struct select_algorithm : select<args_t...>
{};
template <typename, typename = void> struct maybe_value { int value; };
template <typename cn>
struct maybe_value<cn, typename cn::sfinae>;
struct function
{
template <typename algorithm_t,
typename = decltype(
maybe_value<select_algorithm<algorithm_t, int>>::value)>
function(algorithm_t);
};
template <typename>
struct alignment_configuration_traits
{
static constexpr bool is_vectorised = 0;
};
template <typename config_t, typename...>
struct alignment_algorithm
{
using traits_t = alignment_configuration_traits<config_t>;
template <typename indexed_sequence_pairs_t>
void operator()(indexed_sequence_pairs_t) requires traits_t::is_vectorised;
};
int main()
{
function{alignment_algorithm<int>{}};
}
```
(I couldn't reduce it any more, maybe someone else can help with it)
produces the following ICE (https://godbolt.org/z/6uK11R):
```
> g++-git -std=c++17 -fconcepts -c ice.cpp // or g++-git -std=c++2a -c ice.cp
ice.cpp: In instantiation of ‘void alignment_algorithm<
<template-parameter-1-1>, <template-parameter-1-2>
>::operator()(indexed_sequence_pairs_t) requires traits_t<config_t,
<template-parameter-1-2>...>::is_vectorised [with indexed_sequence_pairs_t =
int; config_t = int; <template-parameter-1-2> = {}]’:
ice.cpp:17:25: required by substitution of ‘template<class algorithm_t, class
... _args_t> decltype (algorithm_t()(func<_args_t>...))
select<int>::choose<algorithm_t, _args_t ...>() [with algorithm_t =
alignment_algorithm<int>; _args_t = {int}]’
ice.cpp:22:68: required from ‘struct select<int>’
ice.cpp:37:13: recursively required by substitution of ‘template<class cn>
struct maybe_value<cn, typename cn::sfinae> [with cn =
select_algorithm<alignment_algorithm<int>, int>]’
ice.cpp:37:13: required by substitution of ‘template<class algorithm_t,
class> function::function(algorithm_t) [with algorithm_t =
alignment_algorithm<int>; <template-parameter-1-2> = <missing>]’
ice.cpp:58:40: required from here
ice.cpp:17:25: internal compiler error: in tsubst_pack_expansion, at
cp/pt.c:12852
17 | decltype(algorithm_t()(func<_args_t>...)) choose();
| ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
0x601131 tsubst_pack_expansion(tree_node*, tree_node*, int, tree_node*)
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/pt.c:12852
0x770121 tsubst_template_args(tree_node*, tree_node*, int, tree_node*)
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/pt.c:13111
0x775368 tsubst_argument_pack(tree_node*, tree_node*, int, tree_node*)
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/pt.c:13073
0x7700f4 tsubst_template_args(tree_node*, tree_node*, int, tree_node*)
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/pt.c:13123
0x76c46a tsubst(tree_node*, tree_node*, int, tree_node*)
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/pt.c:14985
0x777997 tsubst_qualified_id
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/pt.c:16002
0x76742f tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/pt.c:19259
0x760e34 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/pt.c:18932
0x760e34 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/pt.c:18590
0x681222 satisfy_constraint_r
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/constraint.cc:2499
0x681998 satisfy_constraint
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/constraint.cc:2575
0x682c14 satisfy_declaration_constraints
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/constraint.cc:2593
0x682ed8 constraint_satisfaction_value
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/constraint.cc:2708
0x682ed8 constraints_satisfied_p(tree_node*)
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/constraint.cc:2729
0x64f2c1 add_function_candidate
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/call.c:2281
0x65175c add_template_candidate_real
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/call.c:3440
0x651ce6 add_template_candidate
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/call.c:3481
0x651ce6 add_candidates
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/call.c:5827
0x656d14 add_candidates
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/call.c:5742
0x656d14 build_op_call_1
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/call.c:4777
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://bugs.archlinux.org/> for instructions.
```
```
> g++-git --version
g++-git (GCC) 10.0.1 20200119 (experimental)
Copyright (C) 2020 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.
```
