I noticed that format_pieces can create an empty literal piece.
However, there's never a need for one, so this patch removes the
possibility.
gdb/ChangeLog
2019-10-01 Tom Tromey <tom@tromey.com>
* unittests/format_pieces-selftests.c: Update. Add final format.
* gdbsupport/format.c (format_pieces::format_pieces): Don't add
empty literal pieces.