builtin-attrs.def (ATTR_SENTINEL, [...]): New.

builtin-attrs.def (ATTR_SENTINEL, [...]): New.

gcc:
	* builtin-attrs.def (ATTR_SENTINEL, ATTR_SENTINEL_NOTHROW_LIST):
	New.
	* builtins.def (BUILT_IN_EXECL, BUILT_IN_EXECLP): Add `sentinel'
	attribute.
	* c-common.c (handle_sentinel_attribute, check_function_sentinel):
	New functions.
	(c_common_attribute_table): Add `sentinel' attribute.
	(check_function_arguments): Handle `sentinel' attribute.
	* doc/extend.texi: Document `sentinel' attribute.

gcc/testsuite:
	* gcc.dg/format/sentinel-1.c: New test.

include:
	* ansidecl.h (ATTRIBUTE_SENTINEL): Define.
	* libiberty.h (concat, reconcat, concat_length, concat_copy,
	concat_copy2): Use ATTRIBUTE_SENTINEL.

From-SVN: r87096