Use C++17 [[fallthrough]] attribute

This changes gdb to use the C++17 [[fallthrough]] attribute rather
than special comments.

This was mostly done by script, but I neglected a few spellings and so
also fixed it up by hand.

I suspect this fixes the bug mentioned below, by switching to a
standard approach that, presumably, clang supports.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=23159
Approved-By: John Baldwin <jhb@FreeBSD.org>
Approved-By: Luis Machado <luis.machado@arm.com>
Approved-By: Pedro Alves <pedro@palves.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/gdb/eval.c b/gdb/eval.c
index 3358b0d..8192aeb 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -172,7 +172,7 @@ fetch_subexp_value (struct expression *exp,
 	case MEMORY_ERROR:
 	  if (!preserve_errors)
 	    break;
-	  /* Fall through.  */
+	  [[fallthrough]];
 	default:
 	  throw;
 	  break;