Use __attribute__((fallthrough)) rather than magic GCC comments.

GCC added an implicit-fallthrough warning a while back, where it
would complain if you had a nontrivial "case:" block that didn't end
with break, return, or something like that.  Clang recently added
the same thing.

GCC, however, would let you annotate a fall-through as intended by
any of various magic "/* fall through */" comments.  Clang, however,
only seems to like "__attribute__((fallthrough))".  Fortunately, GCC
accepts that too.

A previous commit in this branch defined a FALLTHROUGH macro to do
the right thing if GNUC is defined; here we replace all of our "fall
through" comments with uses of that macro.

This is an automated commit, made with the following perl one-liner:

  #!/usr/bin/perl -i -p
  s#/\* *falls? ?thr.*?\*/#FALLTHROUGH;#i;

(In order to avoid conflicts, I'm applying this script separately to
each maint branch. This is the 0.4.2 version.)

13 files changed, 17 insertions, 17 deletions

diff --git a/src/core/or/channeltls.c b/src/core/or/channeltls.c
index e9497651ef..d6c9e21631 100644
--- a/src/core/or/channeltls.c
+++ b/src/core/or/channeltls.c
@@ -1237,7 +1237,7 @@ channel_tls_handle_var_cell(var_cell_t *var_cell, or_connection_t *conn)
       /* But that should be happening any longer've disabled bufferevents. */
       tor_assert_nonfatal_unreached_once();
 
-      /* fall through */
+      FALLTHROUGH;
     case OR_CONN_STATE_TLS_SERVER_RENEGOTIATING:
       if (!(command_allowed_before_handshake(var_cell->command))) {
         log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
diff --git a/src/core/or/circuitbuild.c b/src/core/or/circuitbuild.c
index 1daf468715..16bb7e7d79 100644
--- a/src/core/or/circuitbuild.c
+++ b/src/core/or/circuitbuild.c
@@ -2108,7 +2108,7 @@ choose_good_exit_server(origin_circuit_t *circ,
       /* For these three, we want to pick the exit like a middle hop,
        * since it should be random. */
       tor_assert_nonfatal(is_internal);
-      /* Falls through */
+      FALLTHROUGH;
     case CIRCUIT_PURPOSE_C_GENERAL:
       if (is_internal) /* pick it like a middle hop */
         return router_choose_random_node(NULL, options->ExcludeNodes, flags);
diff --git a/src/core/or/circuitlist.c b/src/core/or/circuitlist.c
index 9ee9f93c99..61bcfa9039 100644
--- a/src/core/or/circuitlist.c
+++ b/src/core/or/circuitlist.c
@@ -844,7 +844,7 @@ circuit_purpose_to_controller_hs_state_string(uint8_t purpose)
              "Unrecognized circuit purpose: %d",
              (int)purpose);
       tor_fragile_assert();
-      /* fall through */
+      FALLTHROUGH;
 
     case CIRCUIT_PURPOSE_OR:
     case CIRCUIT_PURPOSE_C_GENERAL:
diff --git a/src/core/or/circuituse.c b/src/core/or/circuituse.c
index 606c5e2dd2..284e315f9c 100644
--- a/src/core/or/circuituse.c
+++ b/src/core/or/circuituse.c
@@ -784,7 +784,7 @@ circuit_expire_building(void)
             TO_ORIGIN_CIRCUIT(victim)->build_state->pending_final_cpath ==
             NULL)
           break;
-        /* fallthrough! */
+        FALLTHROUGH;
       case CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT:
       case CIRCUIT_PURPOSE_C_REND_READY_INTRO_ACKED:
         /* If we have reached this line, we want to spare the circ for now. */
diff --git a/src/core/or/connection_edge.c b/src/core/or/connection_edge.c
index 5f1664d286..4f5f038e6c 100644
--- a/src/core/or/connection_edge.c
+++ b/src/core/or/connection_edge.c
@@ -307,7 +307,7 @@ connection_edge_process_inbuf(edge_connection_t *conn, int package_partial)
         note_user_activity(approx_time());
       }
 
-      /* falls through. */
+      FALLTHROUGH;
     case EXIT_CONN_STATE_OPEN:
       if (connection_edge_package_raw_inbuf(conn, package_partial, NULL) < 0) {
         /* (We already sent an end cell if possible) */
@@ -332,7 +332,7 @@ connection_edge_process_inbuf(edge_connection_t *conn, int package_partial)
       }
       /* Fall through if the connection is on a circuit without optimistic
        * data support. */
-      /* Falls through. */
+      FALLTHROUGH;
     case EXIT_CONN_STATE_CONNECTING:
     case AP_CONN_STATE_RENDDESC_WAIT:
     case AP_CONN_STATE_CIRCUIT_WAIT:
@@ -766,7 +766,7 @@ connection_edge_flushed_some(edge_connection_t *conn)
         note_user_activity(approx_time());
       }
 
-      /* falls through. */
+      FALLTHROUGH;
     case EXIT_CONN_STATE_OPEN:
       sendme_connection_edge_consider_sending(conn);
       break;
diff --git a/src/core/or/crypt_path.c b/src/core/or/crypt_path.c
index 6d5245510f..9b7efc28bf 100644
--- a/src/core/or/crypt_path.c
+++ b/src/core/or/crypt_path.c
@@ -113,7 +113,7 @@ cpath_assert_layer_ok(const crypt_path_t *cp)
     {
     case CPATH_STATE_OPEN:
       relay_crypto_assert_ok(&cp->pvt_crypto);
-      /* fall through */
+      FALLTHROUGH;
     case CPATH_STATE_CLOSED:
       /*XXXX Assert that there's no handshake_state either. */
       tor_assert(!cp->rend_dh_handshake_state);
diff --git a/src/core/or/onion.c b/src/core/or/onion.c
index aa77465b96..aeddedd807 100644
--- a/src/core/or/onion.c
+++ b/src/core/or/onion.c
@@ -509,7 +509,7 @@ create_cell_format_impl(cell_t *cell_out, const create_cell_t *cell_in,
       p += 16;
       space -= 16;
     }
-    /* Fall through */
+    FALLTHROUGH;
   case CELL_CREATE_FAST:
     tor_assert(cell_in->handshake_len <= space);
     memcpy(p, cell_in->onionskin, cell_in->handshake_len);
diff --git a/src/core/or/policies.c b/src/core/or/policies.c
index 83d9a53fc0..39a0817c85 100644
--- a/src/core/or/policies.c
+++ b/src/core/or/policies.c
@@ -2842,7 +2842,7 @@ parse_short_policy(const char *summary)
     switch (*next) {
       case ',':
         ++next;
-        /* fall through */
+        FALLTHROUGH;
       case '\0':
         high = low;
         break;
diff --git a/src/core/or/reasons.c b/src/core/or/reasons.c
index a7952279ba..e21bfa670a 100644
--- a/src/core/or/reasons.c
+++ b/src/core/or/reasons.c
@@ -489,7 +489,7 @@ end_reason_to_http_connect_response_line(int endreason)
       return "HTTP/1.0 502 Bad Gateway (tor protocol violation)\r\n\r\n";
     case END_STREAM_REASON_ENTRYPOLICY:
       return "HTTP/1.0 403 Forbidden (entry policy violation)\r\n\r\n";
-    case END_STREAM_REASON_NOTDIRECTORY: /* Fall Through */
+    case END_STREAM_REASON_NOTDIRECTORY: FALLTHROUGH;
     default:
       tor_assert_nonfatal_unreached();
       return "HTTP/1.0 500 Internal Server Error (weird end reason)\r\n\r\n";
diff --git a/src/core/or/relay.c b/src/core/or/relay.c
index a437b54792..f83d2365e4 100644
--- a/src/core/or/relay.c
+++ b/src/core/or/relay.c
@@ -940,7 +940,7 @@ connection_ap_process_end_not_open(
           break; /* break means it'll close, below */
         /* Else fall through: expire this circuit, clear the
          * chosen_exit_name field, and try again. */
-        /* Falls through. */
+        FALLTHROUGH;
       case END_STREAM_REASON_RESOLVEFAILED:
       case END_STREAM_REASON_TIMEOUT:
       case END_STREAM_REASON_MISC:
diff --git a/src/core/or/scheduler.c b/src/core/or/scheduler.c
index 063342480a..0e3f0fe815 100644
--- a/src/core/or/scheduler.c
+++ b/src/core/or/scheduler.c
@@ -192,7 +192,7 @@ get_scheduler_type_string(scheduler_types_t type)
   case SCHEDULER_KIST_LITE:
     return "KISTLite";
   case SCHEDULER_NONE:
-    /* fallthrough */
+    FALLTHROUGH;
   default:
     tor_assert_unreached();
     return "(N/A)";
@@ -288,7 +288,7 @@ select_scheduler(void)
       scheduler_kist_set_lite_mode();
       goto end;
     case SCHEDULER_NONE:
-      /* fallthrough */
+      FALLTHROUGH;
     default:
       /* Our option validation should have caught this. */
       tor_assert_unreached();
diff --git a/src/core/or/sendme.c b/src/core/or/sendme.c
index 0757ce3d52..e61cf0c0f8 100644
--- a/src/core/or/sendme.c
+++ b/src/core/or/sendme.c
@@ -293,7 +293,7 @@ send_circuit_level_sendme(circuit_t *circ, crypt_path_t *layer_hint,
     log_debug(LD_PROTOCOL, "Emitting SENDME version 1 cell.");
     break;
   case 0x00:
-    /* Fallthrough because default is to use v0. */
+    FALLTHROUGH;
   default:
     /* Unknown version, fallback to version 0 meaning no payload. */
     payload_len = 0;
diff --git a/src/core/proto/proto_socks.c b/src/core/proto/proto_socks.c
index f9f8c8afc0..c06e6b1a41 100644
--- a/src/core/proto/proto_socks.c
+++ b/src/core/proto/proto_socks.c
@@ -856,7 +856,7 @@ fetch_from_buf_socks(buf_t *buf, socks_request_t *req,
       case SOCKS_RESULT_TRUNCATED:
         if (datalen == n_pullup)
           return 0;
-        /* FALLTHRU */
+        FALLTHROUGH;
       case SOCKS_RESULT_MORE_EXPECTED:
         res = 0;
         break;
@@ -962,7 +962,7 @@ parse_socks(const char *data, size_t datalen, socks_request_t *req,
       strlcpy((char*)req->reply, SOCKS_PROXY_IS_NOT_AN_HTTP_PROXY_MSG,
               MAX_SOCKS_REPLY_LEN);
       req->replylen = strlen((char*)req->reply)+1;
-      /* fall through */
+      FALLTHROUGH;
     default: /* version is not socks4 or socks5 */
       log_warn(LD_APP,
                "Socks version %d not recognized. (This port is not an "