https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79548
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
initialize_local_var has:
/* Compute and store the initial value. */
already_used = TREE_USED (decl) || TREE_USED (type);
if (TREE_USED (type))
DECL_READ_P (decl) = 1;
...
/* Set this to 0 so we can tell whether an aggregate which was
initialized was ever used. Don't do this if it has a
destructor, so we don't complain about the 'resource
allocation is initialization' idiom. Now set
attribute((unused)) on types so decls of that type will be
marked used. (see TREE_USED, above.) */
if (TYPE_NEEDS_CONSTRUCTING (type)
&& ! already_used
&& TYPE_HAS_TRIVIAL_DESTRUCTOR (type)
&& DECL_NAME (decl))
TREE_USED (decl) = 0;
else if (already_used)
TREE_USED (decl) = 1;
And, for u TREE_USED (type) is set.
I'm afraid I have absolutely no idea how the fact whether type is used
(comes from:
#0 0x0000000000b1bf76 in maybe_record_typedef_use (t=<type_decl 0x7fffefc51000
U>) at ../../gcc/c-family/c-warn.c:1928
#1 0x000000000090ca8f in cp_parser_lookup_name (parser=0x7ffff7ff5bd0,
name=<identifier_node 0x7fffefc3ea80 U>, tag_type=none_type,
is_template=false, is_namespace=false, check_dependency=true,
ambiguous_decls=0x7fffffffd418, name_location=299520)
at ../../gcc/cp/parser.c:25718
#2 0x0000000000904ec9 in cp_parser_class_name (parser=0x7ffff7ff5bd0,
typename_keyword_p=false, template_keyword_p=false, tag_type=none_type,
check_dependency_p=true, class_head_p=false, is_declaration=false,
enum_ok=false) at ../../gcc/cp/parser.c:21946
and then various copy_node) can affect whether a decl is used or not.
