https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78752
Bug ID: 78752
Summary: [concepts] ICE with constrained variadic member
function
Product: gcc
Version: 6.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tcbrindle at gmail dot com
Target Milestone: ---
Created attachment 40287
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40287&action=edit
Short test case causing ICE
Test code:
#include <type_traits>
template <class T, class U>
concept bool Same = std::is_same<T, U>::value;
struct test {
template <Same<int>... Ints>
void func(Ints... ints) {}
};
int main()
{
test t;
t.func(1, 2, 3);
}
Compiling with g++ -fconcepts -std=c++17 gives:
concepts_ice.cpp: In substitution of 'template<class ... Ints> requires
Same<Ints, int>... void test::func(Ints ...) [with Ints = {int, int, int}]':
concepts_ice.cpp:14:19: required from here
concepts_ice.cpp:9:10: internal compiler error: in tsubst_constraint, at
cp/constraint.cc:1957
void func(Ints... ints) {}
^~~~
concepts_ice.cpp:9:10: internal compiler error: Abort trap: 6
g++-6: internal compiler error: Abort trap: 6 (program cc1plus)
Please submit a full bug report,
with preprocessed source if appropriate.
----
If we replace the member function definition with the more verbose
struct test {
template <class... Ints>
requires (Same<Ints, int> && ...)
void func(Ints... ints) {}
};
then this compiles correctly. Replacing it with the abbreviated syntax
struct test {
void func(Same<int>... ints) {}
};
gives "constraints not satisfied" when calling `test{}.func(1, 2, 3);`, but no
ICE.
This seems to be specific to member functions: the free function
template <Same<int>... Ints>
void func(Ints... ints) {}
func(1, 2, 3);
works as expected, but the abbreviated version
void func(Same<int>... ints) {}
still reports constraints not satisfied.
