https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103968
Bug ID: 103968
Summary: ICE and segfault when instantiating template with
lvalue ref argument and nested template type
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: aliaume.morel at baracoda dot com
Target Milestone: ---
The following compiles with clang, GCC 10.3, but gives an ICE on GCC 11.1 and
12.0.0 (20220110) - tested on Godbolt (https://godbolt.org/z/db5EjWGWa):
```
template <typename Opt, Opt const& options>
struct trait
{
template <typename T>
struct NonInstantiated{};
};
struct Options {};
template <typename T>
struct Widget
{
static constexpr auto c_options = Options{};
using Trait = trait<decltype(c_options), c_options>;
};
Widget<int>::Trait b{}; // Crashes GCC > 10.3
```
Stack trace:
<source>: In instantiation of 'struct trait<const Options, ((const
Options&)Widget<T>::c_options)>':
<source>:17:20: required from here
<source>:5:12: internal compiler error: Segmentation fault
5 | struct NonInstantiated{};
| ^~~~~~~~~~~~~~~
0x1780bf9 internal_error(char const*, ...)
???:0
0x7f628d instantiate_class_template(tree_node*)
???:0
0x829553 complete_type(tree_node*)
???:0
0x6e6d2b start_decl_1(tree_node*, bool)
???:0
0x6f6587 start_decl(cp_declarator const*, cp_decl_specifier_seq*, int,
tree_node*, tree_node*, tree_node**)
???:0
0x7c0cab c_parse_file()
???:0
0x892aa2 c_common_parse_file()
???:0
- This is reproducible in C++17 and C++20 mode.
- In C++20 mode, removing the lvalue ref from the second template argument in
`struct trait` doesn't trigger the ICE and builds successfully.
- If `Widget` is a non-template type, it doesn't trigger the ICE and builds
succesfully.
