https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113349
Bug ID: 113349
Summary: internal compiler error: in tsubst
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: federico at kircheis dot it
Target Milestone: ---
While trying to destructure a tuple, I got this internal compiler error
----
<source>: In substitution of 'template<class T> template<long unsigned int N>
using types<T, decltype ((<lambda>(), void()))>::el = std::tuple_element_t<N,
decltype (<lambda>())> [with long unsigned int N = 1; T = s]':
<source>:36:50: required from here
36 | static_assert(std::is_same_v<char*, types<s>::el<1>>);
| ^
<source>:7:28: internal compiler error: in tsubst, at cp/pt.cc:16312
7 | #define MAKE_TUPLE(V, ...) []{\
| ^~~~
8 | auto [ __VA_ARGS__ ] = makeV<V>(); \
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
9 | return std::make_tuple( __VA_ARGS__);\
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
10 | }()
| ~
<source>:19:26: note: in expansion of macro 'MAKE_TUPLE'
19 | struct types<T, decltype(MAKE_TUPLE(T, e0, e1, e2), void())> {
| ^~~~~~~~~~
0x2640f8c internal_error(char const*, ...)
???:0
0xa502dd fancy_abort(char const*, int, char const*)
???:0
0xc92c62 tsubst(tree_node*, tree_node*, int, tree_node*)
???:0
0xca446c tsubst_lambda_expr(tree_node*, tree_node*, int, tree_node*)
???:0
0xc93417 tsubst(tree_node*, tree_node*, int, tree_node*)
???:0
0xc99729 tsubst_template_args(tree_node*, tree_node*, int, tree_node*)
???:0
0xc7c365 instantiate_template(tree_node*, tree_node*, int)
???:0
0xc9420c tsubst(tree_node*, tree_node*, int, tree_node*)
???:0
0xc914dc lookup_template_class(tree_node*, tree_node*, tree_node*, tree_node*,
int, int)
???:0
0xccd98f finish_template_type(tree_node*, tree_node*, int)
???:0
0xc51fda c_parse_file()
???:0
0xda59d9 c_common_parse_file()
???:0
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1
----
The code looks like
----
#include <tuple>
#include <utility>
template <class V>
V makeV();
#define MAKE_TUPLE(V, ...) []{\
auto [ __VA_ARGS__ ] = makeV<V>(); \
return std::make_tuple( __VA_ARGS__);\
}()
template <typename T, typename = void>
struct types{
using type = void;
};
template <typename T>
struct types<T, decltype(MAKE_TUPLE(T, e0, e1, e2), void())> {
template<std::size_t N>
using el = std::tuple_element_t<N, decltype(MAKE_TUPLE(T, e0, e1, e2))>;
};
/*
template <typename T>
struct types<T, decltype(MAKE_TUPLE(T, e1), void())> {
template<std::size_t N>
using el = std::tuple_element_t<N, decltype(MAKE_TUPLE(T, e1))>;
};
*/
struct s{
int& i;
char* b;
float f;
};
//static_assert(std::is_same_v<int&, types<s>::el<0>>); // fails
static_assert(std::is_same_v<char*, types<s>::el<1>>);
static_assert(std::is_same_v<float, types<s>::el<2>>);
----
This code compiles fine with clang and MSVC, and is, to the best of my
knowledge, valid C++
Online example with latest gcc (and clang msvc too)
https://godbolt.org/z/sPxK5avEW
