re PR debug/83547 ((statement-frontiers) error: void value not ignored as it ought...

re PR debug/83547 ((statement-frontiers) error: void value not ignored as it ought to be)

	PR debug/83547
	* tree-iterator.c (alloc_stmt_list): Start with cleared
	TREE_SIDE_EFFECTS regardless whether a new STATEMENT_LIST is allocated
	or old one reused.
c/
	* c-typeck.c (c_finish_stmt_expr): Ignore !TREE_SIDE_EFFECTS as
	indicator of ({ }), instead skip all trailing DEBUG_BEGIN_STMTs first,
	and consider empty ones if there are no other stmts.  For
	-Wunused-value walk all statements before the one only followed by
	DEBUG_BEGIN_STMTs.
testsuite/
	* gcc.c-torture/compile/pr83547.c: New test.

From-SVN: r255980