This is a bad interaction between sharing a constructor for an array and stripping its trailing zero-initializers. Here we reuse a ctor and then strip its 0s. This breaks overload resolution in this test: D can be initialized from {} but not from {0}, so if we truncate the constructor not to include the zero, the F(D) overload becomes valid and then we get the ambiguous conversion error.
Bootstrapped/regtested on x86_64-linux, ok for trunk? PR c++/94124 - wrong conversion error with non-viable overload. * decl.c (reshape_init_array_1): Unshare a constructor if we stripped trailing zero-initializers. * g++.dg/cpp0x/initlist-overload1.C: New test. --- gcc/cp/decl.c | 7 +++++++ gcc/testsuite/g++.dg/cpp0x/initlist-overload1.C | 15 +++++++++++++++ 2 files changed, 22 insertions(+) create mode 100644 gcc/testsuite/g++.dg/cpp0x/initlist-overload1.C diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index bb242743074..aa58e5f88ae 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -6062,6 +6062,13 @@ reshape_init_array_1 (tree elt_type, tree max_index, reshape_iter *d, else if (last_nonzero < nelts - 1) nelts = last_nonzero + 1; + /* Sharing a stripped constructor can get in the way of + overload resolution. E.g., initializing a class from + {{0}} might be invalid while initializing the same class + from {{}} might be valid. */ + if (reuse) + new_init = unshare_constructor (new_init); + vec_safe_truncate (CONSTRUCTOR_ELTS (new_init), nelts); } diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-overload1.C b/gcc/testsuite/g++.dg/cpp0x/initlist-overload1.C new file mode 100644 index 00000000000..12bb606ce67 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/initlist-overload1.C @@ -0,0 +1,15 @@ +// PR c++/94124 - wrong conversion error with non-viable overload. +// { dg-do compile { target c++11 } } + +template <int N> struct A { typedef int _Type[N]; }; +template <int N> struct B { typename A<N>::_Type _M_elems; }; +class C { }; +struct D { + D(C); +}; + +struct F { + F(B<2>); + F(D); // This overload should not be viable. +}; +F fn1() { return {{{0}}}; } base-commit: 0b7f1e24316cfc1f85408918d1734d3266d65089 -- Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA