https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111647
--- Comment #1 from Sergei Trofimovich <slyfox at gcc dot gnu.org> ---
More realistic example extracted from gcc's poly_int:
// $ cat rtl-tests.cc
template<unsigned int N> struct poly_int {
template<typename ...Cs> constexpr poly_int (const Cs &... cs)
: coeffs { cs... } {}
int coeffs[N];
};
#define TARGET_DEFINED_VALUE 1
// this works:
//#define TARGET_DEFINED_VALUE 2
// Is instantiated only for N == 2.
template<unsigned int N> struct const_poly_int_tests {
static void run () {
poly_int<TARGET_DEFINED_VALUE> (1, 1);
}
};
$ g++ -c rtl-tests.cc -fchecking=1
# did not fail, BAD!
$ g++ -c rtl-tests.cc -fchecking=2
rtl-tests.cc: In instantiation of 'constexpr poly_int<N>::poly_int(const Cs&
...) [with Cs = {int, int}; unsigned int N = 1]':
rtl-tests.cc:15:42: required from here
rtl-tests.cc:3:5: error: too many initializers for 'int [1]'
3 | : coeffs { cs... } {}
| ^~~~~~~~~~~~~~~~
# failed, GOOD
$ clang++ -c rtl-tests.cc
rtl-tests.cc:3:14: error: excess elements in array initializer
: coeffs { cs... } {}
^~
rtl-tests.cc:15:5: note: in instantiation of function template specialization
'poly_int<1>::poly_int<int, int>' requested here
poly_int<TARGET_DEFINED_VALUE> (1, 1);
^
1 error generated.
# failed, GOOD
