re PR tree-optimization/86853 (sprintf optimization for wide strings doesn't account for conversion failure)

gcc/ChangeLog:

	PR tree-optimization/86853
	* gimple-ssa-sprintf.c (struct format_result): Rename member.
	(struct fmtresult): Add member and initialize it in ctors.
	(format_character): Handle %C.  Extend range to NUL.  Set MAYFAIL.
	(format_string): Handle %S the same as %ls.  Set MAYFAIL.
	(format_directive): Set POSUNDER4K when MAYFAIL is set.
	(parse_directive): Handle %C same as %c.
	(sprintf_dom_walker::compute_format_length): Adjust.
	(is_call_safe): Adjust.

gcc/testsuite/ChangeLog:

	PR tree-optimization/86853
	* gcc.dg/tree-ssa/builtin-sprintf-10.c: New test.
	* gcc.dg/tree-ssa/builtin-sprintf-11.c: New test.
	* gcc.dg/tree-ssa/builtin-sprintf-warn-18.c: Adjust.

From-SVN: r263612