https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108773
--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> ---
The variable is built from
#0 build_local_temp (type=<record_type 0x7ffff6a6dc78 allocator>)
at /space/rguenther/src/gcc/gcc/cp/tree.cc:559
#1 0x000000000110fdc1 in force_target_expr (
type=<record_type 0x7ffff6a6dc78 allocator>,
init=<constructor 0x7ffff6a827c8>, complain=3)
at /space/rguenther/src/gcc/gcc/cp/tree.cc:932
#2 0x0000000001119933 in bot_manip (tp=0x7fffffffbcb8,
walk_subtrees=0x7fffffffbc54, data_=0x7fffffffbcc0)
at /space/rguenther/src/gcc/gcc/cp/tree.cc:3181
#3 0x0000000001dc81e0 in walk_tree_1 (tp=0x7fffffffbcb8,
func=0x111965a <bot_manip(tree*, int*, void*)>, data=0x7fffffffbcc0,
pset=0x0,
lh=0x1124208 <cp_walk_subtrees(tree_node**, int*, tree_node*
(*)(tree_node**, int*, void*), void*, hash_set<tree_node*, false,
default_hash_traits<tree_node*> >*)>) at
/space/rguenther/src/gcc/gcc/tree.cc:11355
#4 0x000000000111aeaf in break_out_target_exprs (
t=<target_expr 0x7ffff68bf7e0>, clear_location=true)
at /space/rguenther/src/gcc/gcc/cp/tree.cc:3366
#5 0x0000000000d208e9 in convert_default_arg (
type=<record_type 0x7ffff6a6dc78 allocator>,
arg=<target_expr 0x7ffff68bf7e0>, fn=<function_decl 0x7ffff6a6fb00 __ct >,
parmnum=1, complain=3) at /space/rguenther/src/gcc/gcc/cp/call.cc:9198
...
where build_local_temp doesn't add the variable to any BIND
