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 0.4.1 version.)

26 files changed, 89 insertions, 89 deletions

diff --git a/src/app/config/confparse.c b/src/app/config/confparse.c
index 729e7a4478..efa0c19fa6 100644
--- a/src/app/config/confparse.c
+++ b/src/app/config/confparse.c
@@ -179,7 +179,7 @@ config_assign_value(const config_format_t *fmt, void *options,
       *(int *)lvalue = CFG_AUTO_PORT;
       break;
     }
-    /* fall through */
+    FALLTHROUGH;
   case CONFIG_TYPE_INT:
   case CONFIG_TYPE_UINT:
     i = (int)tor_parse_long(c->value, 10,
@@ -577,7 +577,7 @@ config_get_assigned_option(const config_format_t *fmt, const void *options,
         escape_val = 0;
         break;
       }
-      /* fall through */
+      FALLTHROUGH;
     case CONFIG_TYPE_CSV_INTERVAL:
     case CONFIG_TYPE_INTERVAL:
     case CONFIG_TYPE_MSEC_INTERVAL:
@@ -588,7 +588,7 @@ config_get_assigned_option(const config_format_t *fmt, const void *options,
       tor_asprintf(&result->value, "%d", *(int*)value);
       escape_val = 0; /* Can't need escape. */
       break;
-    case CONFIG_TYPE_UINT64: /* Fall through */
+    case CONFIG_TYPE_UINT64: FALLTHROUGH;
     case CONFIG_TYPE_MEMUNIT:
       tor_asprintf(&result->value, "%"PRIu64,
                    (*(uint64_t*)value));
@@ -605,7 +605,7 @@ config_get_assigned_option(const config_format_t *fmt, const void *options,
         escape_val = 0;
         break;
       }
-      /* fall through */
+      FALLTHROUGH;
     case CONFIG_TYPE_BOOL:
       result->value = tor_strdup(*(int*)value ? "1" : "0");
       escape_val = 0; /* Can't need escape. */
diff --git a/src/core/or/channeltls.c b/src/core/or/channeltls.c
index 25f3baf924..c82cded797 100644
--- a/src/core/or/channeltls.c
+++ b/src/core/or/channeltls.c
@@ -1236,7 +1236,7 @@ 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 3a4e729429..afa029f00d 100644
--- a/src/core/or/circuitbuild.c
+++ b/src/core/or/circuitbuild.c
@@ -2109,7 +2109,7 @@ 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 ebbe7f0824..f74103c6e2 100644
--- a/src/core/or/circuitlist.c
+++ b/src/core/or/circuitlist.c
@@ -845,7 +845,7 @@ 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 18b419e99d..2b66e478d9 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 369a14e889..6f2ef1efc3 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 9e691a02b5..5d8c60dfdb 100644
--- a/src/core/or/relay.c
+++ b/src/core/or/relay.c
@@ -939,7 +939,7 @@ 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 ee22a38142..00887e0d04 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 47ac95f3cf..1a482b5a57 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 "
diff --git a/src/ext/csiphash.c b/src/ext/csiphash.c
index af8559a476..7282252145 100644
--- a/src/ext/csiphash.c
+++ b/src/ext/csiphash.c
@@ -88,13 +88,13 @@ uint64_t siphash24(const void *src, unsigned long src_sz, const struct sipkey *k
 	}
 
 	switch (src_sz - blocks) {
-		case 7: last7 |= (uint64_t)m[i + 6] << 48; /* Falls through. */
-		case 6: last7 |= (uint64_t)m[i + 5] << 40; /* Falls through. */
-		case 5:	last7 |= (uint64_t)m[i + 4] << 32; /* Falls through. */
-		case 4: last7 |= (uint64_t)m[i + 3] << 24; /* Falls through. */
-		case 3:	last7 |= (uint64_t)m[i + 2] << 16; /* Falls through. */
-		case 2:	last7 |= (uint64_t)m[i + 1] <<  8; /* Falls through. */
-		case 1: last7 |= (uint64_t)m[i + 0]      ; /* Falls through. */
+		case 7: last7 |= (uint64_t)m[i + 6] << 48; FALLTHROUGH;
+		case 6: last7 |= (uint64_t)m[i + 5] << 40; FALLTHROUGH;
+		case 5:	last7 |= (uint64_t)m[i + 4] << 32; FALLTHROUGH;
+		case 4: last7 |= (uint64_t)m[i + 3] << 24; FALLTHROUGH;
+		case 3:	last7 |= (uint64_t)m[i + 2] << 16; FALLTHROUGH;
+		case 2:	last7 |= (uint64_t)m[i + 1] <<  8; FALLTHROUGH;
+		case 1: last7 |= (uint64_t)m[i + 0]      ; FALLTHROUGH;
 		case 0:
 		default:;
 	}
diff --git a/src/ext/ed25519/donna/modm-donna-32bit.h b/src/ext/ed25519/donna/modm-donna-32bit.h
index 0ef9e58fa1..5934d9ca9d 100644
--- a/src/ext/ed25519/donna/modm-donna-32bit.h
+++ b/src/ext/ed25519/donna/modm-donna-32bit.h
@@ -385,14 +385,14 @@ sub256_modm_batch(bignum256modm out, const bignum256modm a, const bignum256modm
 	size_t i = 0;
 	bignum256modm_element_t carry = 0;
 	switch (limbsize) {
-		case 8: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 7: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 6: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 5: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 4: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 3: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 2: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 1: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
+		case 8: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 7: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 6: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 5: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 4: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 3: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 2: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 1: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
 		case 0: 
 		default: out[i] = (a[i] - b[i]) - carry;
 	}
@@ -403,14 +403,14 @@ sub256_modm_batch(bignum256modm out, const bignum256modm a, const bignum256modm
 static int
 lt256_modm_batch(const bignum256modm a, const bignum256modm b, size_t limbsize) {
 	switch (limbsize) {
-		case 8: if (a[8] > b[8]) return 0; if (a[8] < b[8]) return 1; /* Falls through. */
-		case 7: if (a[7] > b[7]) return 0; if (a[7] < b[7]) return 1; /* Falls through. */
-		case 6: if (a[6] > b[6]) return 0; if (a[6] < b[6]) return 1; /* Falls through. */
-		case 5: if (a[5] > b[5]) return 0; if (a[5] < b[5]) return 1; /* Falls through. */
-		case 4: if (a[4] > b[4]) return 0; if (a[4] < b[4]) return 1; /* Falls through. */
-		case 3: if (a[3] > b[3]) return 0; if (a[3] < b[3]) return 1; /* Falls through. */
-		case 2: if (a[2] > b[2]) return 0; if (a[2] < b[2]) return 1; /* Falls through. */
-		case 1: if (a[1] > b[1]) return 0; if (a[1] < b[1]) return 1; /* Falls through. */
+		case 8: if (a[8] > b[8]) return 0; if (a[8] < b[8]) return 1; FALLTHROUGH;
+		case 7: if (a[7] > b[7]) return 0; if (a[7] < b[7]) return 1; FALLTHROUGH;
+		case 6: if (a[6] > b[6]) return 0; if (a[6] < b[6]) return 1; FALLTHROUGH;
+		case 5: if (a[5] > b[5]) return 0; if (a[5] < b[5]) return 1; FALLTHROUGH;
+		case 4: if (a[4] > b[4]) return 0; if (a[4] < b[4]) return 1; FALLTHROUGH;
+		case 3: if (a[3] > b[3]) return 0; if (a[3] < b[3]) return 1; FALLTHROUGH;
+		case 2: if (a[2] > b[2]) return 0; if (a[2] < b[2]) return 1; FALLTHROUGH;
+		case 1: if (a[1] > b[1]) return 0; if (a[1] < b[1]) return 1; FALLTHROUGH;
 		case 0: if (a[0] > b[0]) return 0; if (a[0] < b[0]) return 1;
 	}
 	return 0;
@@ -420,14 +420,14 @@ lt256_modm_batch(const bignum256modm a, const bignum256modm b, size_t limbsize)
 static int
 lte256_modm_batch(const bignum256modm a, const bignum256modm b, size_t limbsize) {
 	switch (limbsize) {
-		case 8: if (a[8] > b[8]) return 0; if (a[8] < b[8]) return 1; /* Falls through. */
-		case 7: if (a[7] > b[7]) return 0; if (a[7] < b[7]) return 1; /* Falls through. */
-		case 6: if (a[6] > b[6]) return 0; if (a[6] < b[6]) return 1; /* Falls through. */
-		case 5: if (a[5] > b[5]) return 0; if (a[5] < b[5]) return 1; /* Falls through. */
-		case 4: if (a[4] > b[4]) return 0; if (a[4] < b[4]) return 1; /* Falls through. */
-		case 3: if (a[3] > b[3]) return 0; if (a[3] < b[3]) return 1; /* Falls through. */
-		case 2: if (a[2] > b[2]) return 0; if (a[2] < b[2]) return 1; /* Falls through. */
-		case 1: if (a[1] > b[1]) return 0; if (a[1] < b[1]) return 1; /* Falls through. */
+		case 8: if (a[8] > b[8]) return 0; if (a[8] < b[8]) return 1; FALLTHROUGH;
+		case 7: if (a[7] > b[7]) return 0; if (a[7] < b[7]) return 1; FALLTHROUGH;
+		case 6: if (a[6] > b[6]) return 0; if (a[6] < b[6]) return 1; FALLTHROUGH;
+		case 5: if (a[5] > b[5]) return 0; if (a[5] < b[5]) return 1; FALLTHROUGH;
+		case 4: if (a[4] > b[4]) return 0; if (a[4] < b[4]) return 1; FALLTHROUGH;
+		case 3: if (a[3] > b[3]) return 0; if (a[3] < b[3]) return 1; FALLTHROUGH;
+		case 2: if (a[2] > b[2]) return 0; if (a[2] < b[2]) return 1; FALLTHROUGH;
+		case 1: if (a[1] > b[1]) return 0; if (a[1] < b[1]) return 1; FALLTHROUGH;
 		case 0: if (a[0] > b[0]) return 0; if (a[0] < b[0]) return 1;
 	}
 	return 1;
diff --git a/src/ext/ed25519/donna/modm-donna-64bit.h b/src/ext/ed25519/donna/modm-donna-64bit.h
index 06c98e3039..aa361afdbc 100644
--- a/src/ext/ed25519/donna/modm-donna-64bit.h
+++ b/src/ext/ed25519/donna/modm-donna-64bit.h
@@ -294,10 +294,10 @@ sub256_modm_batch(bignum256modm out, const bignum256modm a, const bignum256modm
 	size_t i = 0;
 	bignum256modm_element_t carry = 0;
 	switch (limbsize) {
-		case 4: out[i] = (a[i] - b[i])        ; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; /* Falls through. */
-		case 3: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; /* Falls through. */
-		case 2:	out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; /* Falls through. */
-		case 1:	out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; /* Falls through. */
+		case 4: out[i] = (a[i] - b[i])        ; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; FALLTHROUGH;
+		case 3: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; FALLTHROUGH;
+		case 2:	out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; FALLTHROUGH;
+		case 1:	out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; FALLTHROUGH;
 		case 0: 
 		default: out[i] = (a[i] - b[i]) - carry;
 	}
@@ -310,10 +310,10 @@ lt256_modm_batch(const bignum256modm a, const bignum256modm b, size_t limbsize)
 	size_t i = 0;
 	bignum256modm_element_t t, carry = 0;
 	switch (limbsize) {
-		case 4: t = (a[i] - b[i])        ; carry = (t >> 63); i++; /* Falls through. */
-		case 3: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
-		case 2: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
-		case 1: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
+		case 4: t = (a[i] - b[i])        ; carry = (t >> 63); i++; FALLTHROUGH;
+		case 3: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
+		case 2: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
+		case 1: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
 		case 0: t = (a[i] - b[i]) - carry; carry = (t >> 63);
 	}
 	return (int)carry;
@@ -325,10 +325,10 @@ lte256_modm_batch(const bignum256modm a, const bignum256modm b, size_t limbsize)
 	size_t i = 0;
 	bignum256modm_element_t t, carry = 0;
 	switch (limbsize) {
-		case 4: t = (b[i] - a[i])        ; carry = (t >> 63); i++; /* Falls through. */
-		case 3: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
-		case 2: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
-		case 1: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
+		case 4: t = (b[i] - a[i])        ; carry = (t >> 63); i++; FALLTHROUGH;
+		case 3: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
+		case 2: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
+		case 1: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
 		case 0: t = (b[i] - a[i]) - carry; carry = (t >> 63);
 	}
 	return (int)!carry;
diff --git a/src/feature/client/entrynodes.c b/src/feature/client/entrynodes.c
index 5b6216f483..6665d3dae7 100644
--- a/src/feature/client/entrynodes.c
+++ b/src/feature/client/entrynodes.c
@@ -2263,7 +2263,7 @@ entry_guards_note_guard_success(guard_selection_t *gs,
       break;
     default:
       tor_assert_nonfatal_unreached();
-      /* Fall through. */
+      FALLTHROUGH;
     case GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD:
       if (guard->is_primary) {
         /* XXXX #20832 -- I don't actually like this logic. It seems to make
diff --git a/src/feature/control/control_cmd.c b/src/feature/control/control_cmd.c
index e0706ee4c8..0824597aff 100644
--- a/src/feature/control/control_cmd.c
+++ b/src/feature/control/control_cmd.c
@@ -1900,7 +1900,7 @@ handle_control_add_onion(control_connection_t *conn,
   case RSAE_BADAUTH:
     control_write_endreply(conn, 512, "Invalid client authorization");
     break;
-  case RSAE_INTERNAL: /* FALLSTHROUGH */
+  case RSAE_INTERNAL: FALLTHROUGH;
   default:
     control_write_endreply(conn, 551, "Failed to add Onion Service");
   }
diff --git a/src/feature/dirclient/dirclient.c b/src/feature/dirclient/dirclient.c
index 1ea50fd350..fa82bdc1e7 100644
--- a/src/feature/dirclient/dirclient.c
+++ b/src/feature/dirclient/dirclient.c
@@ -1369,7 +1369,7 @@ directory_initiate_request,(directory_request_t *request))
       case 1:
         /* start flushing conn */
         conn->base_.state = DIR_CONN_STATE_CLIENT_SENDING;
-        /* fall through */
+        FALLTHROUGH;
       case 0:
         /* queue the command on the outbuf */
         directory_send_command(conn, 1, request);
diff --git a/src/feature/dirparse/parsecommon.c b/src/feature/dirparse/parsecommon.c
index 6c2c4b06b7..c22ed186b8 100644
--- a/src/feature/dirparse/parsecommon.c
+++ b/src/feature/dirparse/parsecommon.c
@@ -222,7 +222,7 @@ token_check_object(memarea_t *area, const char *kwd,
                      kwd, crypto_pk_num_bits(tok->key));
         RET_ERR(ebuf);
       }
-      /* fall through */
+      FALLTHROUGH;
     case NEED_KEY: /* There must be some kind of key. */
       if (!tok->key) {
         tor_snprintf(ebuf, sizeof(ebuf), "Missing public key for %s", kwd);
diff --git a/src/feature/relay/dns.c b/src/feature/relay/dns.c
index d9662962d2..d62598d46f 100644
--- a/src/feature/relay/dns.c
+++ b/src/feature/relay/dns.c
@@ -548,7 +548,7 @@ send_resolved_cell,(edge_connection_t *conn, uint8_t answer_type,
         answer_type = RESOLVED_TYPE_ERROR;
         /* We let this fall through and treat it as an error. */
       }
-      /* Falls through. */
+      FALLTHROUGH;
     case RESOLVED_TYPE_ERROR_TRANSIENT:
     case RESOLVED_TYPE_ERROR:
       {
diff --git a/src/feature/rend/rendclient.c b/src/feature/rend/rendclient.c
index 5bdd4d453e..056efb7c39 100644
--- a/src/feature/rend/rendclient.c
+++ b/src/feature/rend/rendclient.c
@@ -831,7 +831,7 @@ rend_client_report_intro_point_failure(extend_info_t *failed_intro,
         log_warn(LD_BUG, "Unknown failure type %u. Removing intro point.",
                  failure_type);
         tor_fragile_assert();
-        /* fall through */
+        FALLTHROUGH;
       case INTRO_POINT_FAILURE_GENERIC:
         rend_cache_intro_failure_note(failure_type,
                                       (uint8_t *)failed_intro->identity_digest,
diff --git a/src/lib/crypt_ops/crypto_digest_nss.c b/src/lib/crypt_ops/crypto_digest_nss.c
index bc7a0fab16..afa8f6d5ef 100644
--- a/src/lib/crypt_ops/crypto_digest_nss.c
+++ b/src/lib/crypt_ops/crypto_digest_nss.c
@@ -37,8 +37,8 @@ digest_alg_to_nss_oid(digest_algorithm_t alg)
     case DIGEST_SHA1: return SEC_OID_SHA1;
     case DIGEST_SHA256: return SEC_OID_SHA256;
     case DIGEST_SHA512: return SEC_OID_SHA512;
-    case DIGEST_SHA3_256: /* Fall through */
-    case DIGEST_SHA3_512: /* Fall through */
+    case DIGEST_SHA3_256: FALLTHROUGH;
+    case DIGEST_SHA3_512: FALLTHROUGH;
     default:
       return SEC_OID_UNKNOWN;
   }
@@ -85,12 +85,12 @@ static bool
 library_supports_digest(digest_algorithm_t alg)
 {
   switch (alg) {
-    case DIGEST_SHA1: /* Fall through */
-    case DIGEST_SHA256: /* Fall through */
+    case DIGEST_SHA1: FALLTHROUGH;
+    case DIGEST_SHA256: FALLTHROUGH;
     case DIGEST_SHA512:
       return true;
-    case DIGEST_SHA3_256: /* Fall through */
-    case DIGEST_SHA3_512: /* Fall through */
+    case DIGEST_SHA3_256: FALLTHROUGH;
+    case DIGEST_SHA3_512: FALLTHROUGH;
     default:
       return false;
   }
@@ -197,8 +197,8 @@ crypto_digest_alloc_bytes(digest_algorithm_t alg)
 #define END_OF_FIELD(f) (offsetof(crypto_digest_t, f) + \
                          STRUCT_FIELD_SIZE(crypto_digest_t, f))
   switch (alg) {
-    case DIGEST_SHA1: /* Fall through */
-    case DIGEST_SHA256: /* Fall through */
+    case DIGEST_SHA1: FALLTHROUGH;
+    case DIGEST_SHA256: FALLTHROUGH;
     case DIGEST_SHA512:
       return END_OF_FIELD(d.ctx);
     case DIGEST_SHA3_256:
@@ -224,8 +224,8 @@ crypto_digest_new_internal(digest_algorithm_t algorithm)
 
   switch (algorithm)
     {
-    case DIGEST_SHA1: /* fall through */
-    case DIGEST_SHA256: /* fall through */
+    case DIGEST_SHA1: FALLTHROUGH;
+    case DIGEST_SHA256: FALLTHROUGH;
     case DIGEST_SHA512:
       r->d.ctx = PK11_CreateDigestContext(digest_alg_to_nss_oid(algorithm));
       if (BUG(!r->d.ctx)) {
@@ -312,8 +312,8 @@ crypto_digest_add_bytes(crypto_digest_t *digest, const char *data,
    * just doing it ourselves. Hashes are fast.
    */
   switch (digest->algorithm) {
-    case DIGEST_SHA1: /* fall through */
-    case DIGEST_SHA256: /* fall through */
+    case DIGEST_SHA1: FALLTHROUGH;
+    case DIGEST_SHA256: FALLTHROUGH;
     case DIGEST_SHA512:
       tor_assert(len <= UINT_MAX);
       SECStatus s = PK11_DigestOp(digest->d.ctx,
@@ -321,7 +321,7 @@ crypto_digest_add_bytes(crypto_digest_t *digest, const char *data,
                                   (unsigned int)len);
       tor_assert(s == SECSuccess);
       break;
-    case DIGEST_SHA3_256: /* FALLSTHROUGH */
+    case DIGEST_SHA3_256: FALLTHROUGH;
     case DIGEST_SHA3_512:
       keccak_digest_update(&digest->d.sha3, (const uint8_t *)data, len);
       break;
diff --git a/src/lib/crypt_ops/crypto_digest_openssl.c b/src/lib/crypt_ops/crypto_digest_openssl.c
index c631b0eac0..6422615851 100644
--- a/src/lib/crypt_ops/crypto_digest_openssl.c
+++ b/src/lib/crypt_ops/crypto_digest_openssl.c
@@ -160,11 +160,11 @@ crypto_digest_alloc_bytes(digest_algorithm_t alg)
     case DIGEST_SHA512:
       return END_OF_FIELD(d.sha512);
 #ifdef OPENSSL_HAS_SHA3
-    case DIGEST_SHA3_256: /* Fall through */
+    case DIGEST_SHA3_256: FALLTHROUGH;
     case DIGEST_SHA3_512:
       return END_OF_FIELD(d.md);
 #else
-    case DIGEST_SHA3_256: /* Fall through */
+    case DIGEST_SHA3_256: FALLTHROUGH;
     case DIGEST_SHA3_512:
       return END_OF_FIELD(d.sha3);
 #endif /* defined(OPENSSL_HAS_SHA3) */
@@ -304,14 +304,14 @@ crypto_digest_add_bytes(crypto_digest_t *digest, const char *data,
       SHA512_Update(&digest->d.sha512, (void*)data, len);
       break;
 #ifdef OPENSSL_HAS_SHA3
-    case DIGEST_SHA3_256: /* FALLSTHROUGH */
+    case DIGEST_SHA3_256: FALLTHROUGH;
     case DIGEST_SHA3_512: {
       int r = EVP_DigestUpdate(digest->d.md, data, len);
       tor_assert(r);
   }
       break;
 #else /* !(defined(OPENSSL_HAS_SHA3)) */
-    case DIGEST_SHA3_256: /* FALLSTHROUGH */
+    case DIGEST_SHA3_256: FALLTHROUGH;
     case DIGEST_SHA3_512:
       keccak_digest_update(&digest->d.sha3, (const uint8_t *)data, len);
       break;
@@ -377,7 +377,7 @@ crypto_digest_get_digest(crypto_digest_t *digest,
       SHA512_Final(r, &tmpenv.d.sha512);
       break;
 //LCOV_EXCL_START
-    case DIGEST_SHA3_256: /* FALLSTHROUGH */
+    case DIGEST_SHA3_256: FALLTHROUGH;
     case DIGEST_SHA3_512:
     default:
       log_warn(LD_BUG, "Handling unexpected algorithm %d", digest->algorithm);
diff --git a/src/test/test_socks.c b/src/test/test_socks.c
index a4a768ce84..6d3ebd2320 100644
--- a/src/test/test_socks.c
+++ b/src/test/test_socks.c
@@ -778,7 +778,7 @@ test_socks_truncated(void *ptr)
   for (i = 0; i < ARRAY_LENGTH(commands); ++i) {
     for (j = 0; j < commands[i].len; ++j) {
       switch (commands[i].setup) {
-        default: /* Falls through */
+        default: FALLTHROUGH;
         case NONE:
           /* This test calls for no setup on the socks state. */
           break;