https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120136
Bug ID: 120136
Summary: internal compiler error: tree check: accessed elt 1 of
'tree_vec' with -1 elts in add_to_template_args, at
cp/pt.cc:612
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: ldalessandro at gmail dot com
Target Milestone: ---
Created attachment 61341
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=61341&action=edit
reduced test case
Encountered via cvise while trying to reduce a difference ICE. Compile with
c++20.
```
template <class>
concept car = true;
template <auto... xs>
struct set {
static auto contains(car auto x) {
return ((x == xs) || ...);
}
};
template <auto>
struct foo {
template <car auto c>
friend bool operator==(foo, foo<c>);
};
template <car auto c> foo<c> foobar;
auto a = foobar<1>;
auto b = set<a>{};
auto c = b.contains(a);
```
Live: https://godbolt.org/z/q1b6746vb [May 6th, 2025]
<source>: In substitution of 'template<auto [requires ::car<<placeholder>, >]
c> bool operator==(foo<1>, foo<c>) [with auto [requires ::car<<placeholder>, >]
c = <missing>]':
<source>:7:20: required from 'static auto set<xs>::contains(auto:1) [with
auto:1 = foo<1>; auto ...xs = {foo<1>()}]'
7 | return ((x == xs) || ...);
| ~~~^~~~~~
<source>:21:20: required from here
21 | auto c = b.contains(a);
| ~~~~~~~~~~^~~
<source>:7:20: internal compiler error: tree check: accessed elt 1 of
'tree_vec' with -1 elts in add_to_template_args, at cp/pt.cc:612
7 | return ((x == xs) || ...);
| ~~~^~~~~~
0x293a4f5 diagnostic_context::diagnostic_impl(rich_location*,
diagnostic_metadata const*, diagnostic_option_id, char const*, __va_list_tag
(*) [1], diagnostic_t)
???:0
0x2951766 internal_error(char const*, ...)
???:0
0x9e0ef3 tree_vec_elt_check_failed(int, int, char const*, int, char const*)
???:0
0xd1c098 do_auto_deduction(tree_node*, tree_node*, tree_node*, int,
auto_deduction_context, tree_node*, int, tree_node*)
???:0
0xd5ac0f fn_type_unification(tree_node*, tree_node*, tree_node*, tree_node*
const*, unsigned int, tree_node*, unification_kind_t, int, conversion**, bool,
bool)
???:0
0xb114d6 build_new_op(op_location_t const&, tree_code, int, tree_node*,
tree_node*, tree_node*, tree_node*, tree_node**, int)
???:0
0xdbbcf2 build_x_binary_op(op_location_t const&, tree_code, tree_node*,
tree_code, tree_node*, tree_code, tree_node*, tree_node**, int)
???:0
0xd444e4 tsubst_pack_expansion(tree_node*, tree_node*, int, tree_node*)
???:0
0xd25add instantiate_decl(tree_node*, bool, bool)
???:0
0xbdea93 maybe_instantiate_decl(tree_node*)
???:0
0xbe0787 mark_used(tree_node*, int)
???:0
0xaf7ed3 build_new_method_call(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>**, tree_node*, int, tree_node**, int)
???:0
0xd7c639 finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
bool, int)
???:0
0xcfb063 c_parse_file()
???:0
0xe5db29 c_common_parse_file()
???:0
