gcc/ChangeLog:
	PR preprocessor/79210
	* input.c (get_substring_ranges_for_loc): Replace line_width
	assertion with error-handling.

gcc/testsuite/ChangeLog:
	PR preprocessor/79210
	* gcc.dg/format/pr79210.c: New test case.
	* gcc.dg/plugin/diagnostic-test-string-literals-2.c (test_pr79210):
	New function.

From-SVN: r245070