PR tree-optimization/82945 - add warning for passing non-strings to functions that expect string arguments

gcc/ChangeLog:

	PR tree-optimization/82945
	* builtins.c (expand_builtin_strlen): Call maybe_warn_nonstring_arg.
	* calls.h (maybe_warn_nonstring_arg): Declare new function.
	* calls.c (get_attr_nonstring_decl, maybe_warn_nonstring_arg): New
	functions.
	(initialize_argument_information): Call maybe_warn_nonstring_arg.
	* calls.h (get_attr_nonstring_decl): Declare new function.
	* doc/extend.texi (attribute nonstring): Update.
	* gimple-fold.c (gimple_fold_builtin_strncpy): Call
	get_attr_nonstring_decl and handle it.
	* tree-ssa-strlen.c (maybe_diag_stxncpy_trunc): Same.  Improve
	detection of nul-termination.
	(strlen_to_stridx): Change to a pointer.
	(handle_builtin_strlen, handle_builtin_stxncpy): Adjust.
	(pass_strlen::execute): Same.

gcc/testsuite/ChangeLog:

	PR tree-optimization/82945
	* c-c++-common/Wstringop-truncation-2.c: New test.
	* c-c++-common/Wstringop-truncation.c: Adjust.
	* c-c++-common/attr-nonstring-2.c: Adjust.
	* c-c++-common/attr-nonstring-3.c: New test.

From-SVN: r255031