On Thu, Jul 02, 2026 at 01:33:15PM -0400, Jason Merrill wrote: > > 2026-07-02 Jakub Jelinek <[email protected]> > > > > PR c++/126036 > > * reflect.cc (get_range_elts): Avoid calling finish_compound_literal > > when processing_template_decl, instead set *non_constant_p and > > return NULL_TREE. > > This change is OK. > > > (check_metafn_return_type): Likewise. > > It seems a bit odd to treat this case as a wrong return type; let's either > check METAFN_KIND_RET_VECTOR_INFO in process_metafunction or expand the > comment to justify doing it here.
So like this instead? 2026-07-03 Jakub Jelinek <[email protected]> PR c++/126036 * reflect.cc (get_range_elts): Avoid calling finish_compound_literal when processing_template_decl, instead set *non_constant_p and return NULL_TREE. (process_metafunction): Likewise. * g++.dg/reflect/pr126036.C: New test. --- gcc/cp/reflect.cc.jj 2026-06-30 09:20:44.103805523 +0200 +++ gcc/cp/reflect.cc 2026-07-02 23:14:03.192962977 +0200 @@ -698,6 +698,12 @@ get_range_elts (location_t loc, const co } if (kind == REFLECT_CONSTANT_ARRAY && sz == 0) { + /* Don't call finish_compound_literal in a template. */ + if (processing_template_decl) + { + *non_constant_p = true; + return NULL_TREE; + } /* Return std::array <valuet, 0> {}. */ tree args = make_tree_vec (2); TREE_VEC_ELT (args, 0) = valuet; @@ -7887,6 +7893,14 @@ process_metafunction (const constexpr_ct if (check_metafn_return_type (loc, METAFN_KIND_RET (minfo), rettype, non_constant_p)) return NULL_TREE; + /* Don't call get_vector_of_info_elts (for any metafn which returns + vector<info>) in a template. */ + if (processing_template_decl + && METAFN_KIND_RET (minfo) == METAFN_KIND_RET_VECTOR_INFO) + { + *non_constant_p = true; + return NULL_TREE; + } for (int argno = 0; argno < 3; ++argno) switch (METAFN_KIND_ARG (minfo, argno)) { --- gcc/testsuite/g++.dg/reflect/pr126036.C.jj 2026-06-30 15:41:35.653488520 +0200 +++ gcc/testsuite/g++.dg/reflect/pr126036.C 2026-06-30 15:41:15.899727864 +0200 @@ -0,0 +1,21 @@ +// PR c++/126036 +// { dg-do compile { target c++26 } } +// { dg-additional-options "-freflection" } + +#include <meta> + +namespace A { int a; }; + +template <int N> +void +foo () +{ + constexpr auto m = std::meta::members_of (^^A, std::meta::access_context::unchecked ()); + // { dg-error "is not a constant expression because it refers to a result of 'operator new'" "" { target *-*-* } .-1 } +} + +void +bar () +{ + foo <42> (); +} Jakub
