c-family: don't warn for [[maybe_unused]] on data member

The C++17 standard (and C2x) says that [[maybe_unused]] may be applied to a
non-static data member, so we shouldn't warn about it.  And I don't see a
reason not to handle a FIELD_DECL the same as any other decl, by setting
TREE_USED on it.  It doesn't look like anything yet cares about that flag on
a FIELD_DECL, but setting it shouldn't hurt.

gcc/c-family/ChangeLog:

	* c-attribs.c (handle_unused_attribute): Handle FIELD_DECL.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/attrib62.C: No longer warn.
	* g++.dg/diagnostic/maybe_unused1.C: New test.

gcc/ChangeLog:

	* doc/extend.texi (unused variable attribute): Applies to
	structure fields as well.

0 files changed, 0 insertions, 0 deletions