builtins.c (compute_objsize): Add an argument and set it to offset into destination.

gcc/ChangeLog:

	* builtins.c (compute_objsize): Add an argument and set it to offset
	into destination.
	* builtins.h (compute_objsize): Add an argument.
	* tree-object-size.c (addr_object_size): Add an argument and set it
	to offset into destination.
	(compute_builtin_object_size): Same.
	* tree-object-size.h (compute_builtin_object_size): Add an argument.
	* tree-ssa-strlen.c (get_addr_stridx): Add an argument and set it
	to offset into destination.
	(maybe_warn_overflow): New function.
	(handle_store): Call maybe_warn_overflow to issue warnings.

gcc/testsuite/ChangeLog:

	* c-c++-common/Wstringop-overflow-2.c: Adjust text of expected messages.
	* g++.dg/warn/Wstringop-overflow-3.C: Same.
	* gcc.dg/Wstringop-overflow-17.c: Same.

From-SVN: r279248