diff options
Diffstat (limited to 'gcc/cp/typeck2.c')
| -rw-r--r-- | gcc/cp/typeck2.c | 32 |
1 files changed, 30 insertions, 2 deletions
diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c index b91c98d594b..b28044c11dc 100644 --- a/gcc/cp/typeck2.c +++ b/gcc/cp/typeck2.c @@ -1142,8 +1142,29 @@ digest_init_r (tree type, tree init, int nested, int flags, { tree elt = CONSTRUCTOR_ELT (init, 0)->value; if (reference_related_p (type, TREE_TYPE (elt))) - /* We should have fixed this in reshape_init. */ - gcc_unreachable (); + { + /* In C++17, aggregates can have bases, thus participate in + aggregate initialization. In the following case: + + struct B { int c; }; + struct D : B { }; + D d{{D{{42}}}}; + + there's an extra set of braces, so the D temporary initializes + the first element of d, which is the B base subobject. The base + of type B is copy-initialized from the D temporary, causing + object slicing. */ + tree field = next_initializable_field (TYPE_FIELDS (type)); + if (field && DECL_FIELD_IS_BASE (field)) + { + if (warning_at (loc, 0, "initializing a base class of type %qT " + "results in object slicing", TREE_TYPE (field))) + inform (loc, "remove %<{ }%> around initializer"); + } + else + /* We should have fixed this in reshape_init. */ + gcc_unreachable (); + } } if (BRACE_ENCLOSED_INITIALIZER_P (init) @@ -1538,6 +1559,13 @@ process_init_constructor_record (tree type, tree init, int nested, } } + if (DECL_SIZE (field) && integer_zerop (DECL_SIZE (field)) + && !TREE_SIDE_EFFECTS (next)) + /* Don't add trivial initialization of an empty base/field to the + constructor, as they might not be ordered the way the back-end + expects. */ + continue; + /* If this is a bitfield, now convert to the lowered type. */ if (type != TREE_TYPE (field)) next = cp_convert_and_check (TREE_TYPE (field), next, complain); |