On Wed, 4 Feb 2026, Marek Polacek wrote: > On Wed, Feb 04, 2026 at 10:38:42AM -0500, Patrick Palka wrote: > > Bootstrap and regtest running on x86_64-pc-linux-gnu, does this look > > OK for trunk/15? > > > > -- >8 -- > > > > Since type pack indexes can be cv-qualified, we need to propagate its > > qualifiers when substituting into them. > > > > PR c++/122169 > > > > gcc/cp/ChangeLog: > > > > * pt.cc (tsubst_pack_index): Propagate cv-qualifiers of a > > PACK_INDEX_TYPE. > > > > gcc/testsuite/ChangeLog: > > > > * g++.dg/cpp26/pack-indexing19.C: New test. > > --- > > gcc/cp/pt.cc | 9 +++++++-- > > gcc/testsuite/g++.dg/cpp26/pack-indexing19.C | 18 ++++++++++++++++++ > > 2 files changed, 25 insertions(+), 2 deletions(-) > > create mode 100644 gcc/testsuite/g++.dg/cpp26/pack-indexing19.C > > > > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc > > index b8039b731b63..f43bf2ef2d50 100644 > > --- a/gcc/cp/pt.cc > > +++ b/gcc/cp/pt.cc > > @@ -14366,10 +14366,15 @@ tsubst_pack_index (tree t, tree args, > > tsubst_flags_t complain, tree in_decl) > > tree index = tsubst_expr (PACK_INDEX_INDEX (t), args, complain, in_decl); > > const bool parenthesized_p = (TREE_CODE (t) == PACK_INDEX_EXPR > > && PACK_INDEX_PARENTHESIZED_P (t)); > > + tree r; > > if (!value_dependent_expression_p (index) && TREE_CODE (pack) == > > TREE_VEC) > > - return pack_index_element (index, pack, parenthesized_p, complain); > > + r = pack_index_element (index, pack, parenthesized_p, complain); > > else > > - return make_pack_index (pack, index); > > + r = make_pack_index (pack, index); > > + if (TREE_CODE (t) == PACK_INDEX_TYPE) > > No need to check that r is a type, I suppose, since cp_build_qualified_type > can deal with an error_mark_node and it can't be anything else than a type.
That was my thinking too. > > > + r = cp_build_qualified_type (r, cp_type_quals (t) | cp_type_quals (r), > > Won't cp_type_quals (r) always be TYPE_UNQUALIFIED? Yes if it's a PACK_INDEX_TYPE, but if we fully resolve the pack index then r could be arbitrary and cv-qualified, e.g. if in the testcase we instantiate f<volatile int>(). > > Patch LGTM otherwise, thanks! > > Marek > >
