Port to gcc -Wimplicit-fallthrough=5

* src/common.h (FALLTHROUGH): New macro, for use with gcc
-Wimplicit-fallthrough=5, which is now the default when used with
Gnulib after commit 2017-05-16T16:23:52!eggert@cs.ucla.edu
and with --enable-gcc-warnings

src/buffer.c

@@ -106,7 +106,7 @@ bool write_archive_to_stdout;
 /* When creating a multi-volume archive, each 'bufmap' represents
    a member stored (perhaps partly) in the current record buffer.
    Bufmaps are form a single-linked list in chronological order.
-   
+
    After flushing the record to the output media, all bufmaps that
    represent fully written members are removed from the list, the
    nblocks and sizeleft values in the bufmap_head and start values
@@ -1004,7 +1004,7 @@ void
 flush_archive (void)
 {
   size_t buffer_level;
-  
+
   if (access_mode == ACCESS_READ && time_to_start_writing)
     {
       access_mode = ACCESS_WRITE;
@@ -1296,8 +1296,7 @@ change_tape_menu (FILE *read_file)
               sys_spawn_shell ();
               break;
             }
-          /* FALL THROUGH */
-
+	  FALLTHROUGH;
         default:
           fprintf (stderr, _("Invalid input. Type ? for help.\n"));
         }
@@ -1506,8 +1505,7 @@ try_new_volume (void)
       header = find_next_block ();
       if (header->header.typeflag != GNUTYPE_MULTIVOL)
         break;
-      /* FALL THROUGH */
-
+      FALLTHROUGH;
     case GNUTYPE_MULTIVOL:
       if (!read_header0 (&dummy))
         return false;
@@ -1532,7 +1530,7 @@ try_new_volume (void)
 		 quote (bufmap_head->file_name)));
 	  return false;
 	}
-      
+
       if (strcmp (continued_file_name, bufmap_head->file_name))
         {
           if ((archive_format == GNU_FORMAT || archive_format == OLDGNU_FORMAT)

src/common.h

@@ -44,6 +44,12 @@
 # define GLOBAL extern
 #endif
 
+#if 7 <= __GNUC__
+# define FALLTHROUGH __attribute__ ((__fallthrough__))
+#else
+# define FALLTHROUGH ((void) 0)
+#endif
+
 #define TAREXIT_SUCCESS PAXEXIT_SUCCESS
 #define TAREXIT_DIFFERS PAXEXIT_DIFFERS
 #define TAREXIT_FAILURE PAXEXIT_FAILURE

src/compare.c

@@ -480,8 +480,7 @@ diff_archive (void)
       ERROR ((0, 0, _("%s: Unknown file type '%c', diffed as normal file"),
 	      quotearg_colon (current_stat_info.file_name),
 	      current_header->header.typeflag));
-      /* Fall through.  */
-
+      FALLTHROUGH;
     case AREGTYPE:
     case REGTYPE:
     case GNUTYPE_SPARSE:

src/delete.c

@@ -187,8 +187,7 @@ delete_archive_members (void)
 	      skip_member ();
 	      break;
 	    }
-
-	  /* Fall through.  */
+	  FALLTHROUGH;
 	case HEADER_SUCCESS_EXTENDED:
 	  logical_status = status;
 	  break;
@@ -199,7 +198,7 @@ delete_archive_members (void)
 	      set_next_block_after (current_header);
 	      break;
 	    }
-	  /* Fall through.  */
+	  FALLTHROUGH;
 	case HEADER_END_OF_FILE:
 	  logical_status = HEADER_END_OF_FILE;
 	  break;
@@ -210,14 +209,12 @@ delete_archive_members (void)
 	    {
 	    case HEADER_STILL_UNREAD:
 	      WARN ((0, 0, _("This does not look like a tar archive")));
-	      /* Fall through.  */
-
+	      FALLTHROUGH;
 	    case HEADER_SUCCESS:
 	    case HEADER_SUCCESS_EXTENDED:
 	    case HEADER_ZERO_BLOCK:
 	      ERROR ((0, 0, _("Skipping to next header")));
-	      /* Fall through.  */
-
+	      FALLTHROUGH;
 	    case HEADER_FAILURE:
 	      break;
 

src/extract.c

@@ -394,7 +394,7 @@ set_stat (char const *file_name,
 }
 
 /* Find the direct ancestor of FILE_NAME in the delayed_set_stat list.
- */   
+ */
 static struct delayed_set_stat *
 find_direct_ancestor (char const *file_name)
 {
@@ -758,10 +758,9 @@ maybe_recoverable (char *file_name, bool regular, bool *interdir_made)
 	    break;
 	  stp = &st;
 	}
-
       /* The caller tried to open a symbolic link with O_NOFOLLOW.
 	 Fall through, treating it as an already-existing file.  */
-
+      FALLTHROUGH;
     case EEXIST:
       /* Remove an old file, if the options allow this.  */
 
@@ -778,8 +777,7 @@ maybe_recoverable (char *file_name, bool regular, bool *interdir_made)
 	case KEEP_NEWER_FILES:
 	  if (file_newer_p (file_name, stp, &current_stat_info))
 	    break;
-	  /* FALL THROUGH */
-
+	  FALLTHROUGH;
 	case DEFAULT_OLD_FILES:
 	case NO_OVERWRITE_DIR_OLD_FILES:
 	case OVERWRITE_OLD_FILES:
@@ -939,7 +937,7 @@ is_directory_link (const char *file_name)
   struct stat st;
   int e = errno;
   int res;
-  
+
   res = (fstatat (chdir_fd, file_name, &st, AT_SYMLINK_NOFOLLOW) == 0 &&
 	 S_ISLNK (st.st_mode) &&
 	 fstatat (chdir_fd, file_name, &st, 0) == 0 &&
@@ -1011,7 +1009,7 @@ extract_dir (char *file_name, int typeflag)
 
 	  if (keep_directory_symlink_option && is_directory_link (file_name))
 	    return 0;
-	  
+
 	  if (deref_stat (file_name, &st) == 0)
 	    {
 	      current_mode = st.st_mode;

src/list.c

@@ -120,7 +120,7 @@ enforce_one_top_level (char **pfile_name)
 {
   char *file_name = *pfile_name;
   char *p;
-  
+
   for (p = file_name; *p && (ISSLASH (*p) || *p == '.'); p++)
     ;
 
@@ -132,7 +132,7 @@ enforce_one_top_level (char **pfile_name)
 	  if (ISSLASH (p[pos]) || p[pos] == 0)
 	    return;
 	}
-    
+
       *pfile_name = make_file_name (one_top_level_dir, file_name);
       normalize_filename_x (*pfile_name);
     }
@@ -218,7 +218,7 @@ read_and (void (*do_something) (void))
 		  if (show_omitted_dirs_option)
 		    WARN ((0, 0, _("%s: Omitting"),
 			   quotearg_colon (current_stat_info.file_name)));
-		  /* Fall through.  */
+		  FALLTHROUGH;
 		default:
 		  skip_member ();
 		  continue;
@@ -273,8 +273,7 @@ read_and (void (*do_something) (void))
 	    {
 	    case HEADER_STILL_UNREAD:
 	      ERROR ((0, 0, _("This does not look like a tar archive")));
-	      /* Fall through.  */
-
+	      FALLTHROUGH;
 	    case HEADER_ZERO_BLOCK:
 	    case HEADER_SUCCESS:
 	      if (block_number_option)

src/names.c

@@ -146,7 +146,7 @@ static struct argp_option names_options[] = {
   {"no-wildcards-match-slash", NO_WILDCARDS_MATCH_SLASH_OPTION, 0, 0,
    N_("wildcards do not match '/'"), GRID+1 },
 #undef GRID
-  
+
   {NULL}
 };
 
@@ -160,7 +160,7 @@ file_selection_option (int key)
     if (p->key == key)
       return p;
   return NULL;
-}  
+}
 
 static char const *
 file_selection_option_name (int key)
@@ -173,7 +173,7 @@ static bool
 is_file_selection_option (int key)
 {
   return file_selection_option (key) != NULL;
-}  
+}
 
 /* Either NL or NUL, as decided by the --null option.  */
 static char filename_terminator = '\n';
@@ -221,7 +221,7 @@ static int matching_flags = 0;
   /* exclude_fnmatch options */
 static int include_anchored = EXCLUDE_ANCHORED;
   /* Pattern anchoring options used for file inclusion */
-  
+
 #define EXCLUDE_OPTIONS						\
   (((wildcards != disable_wildcards) ? EXCLUDE_WILDCARDS : 0)	\
   | matching_flags						\
@@ -696,7 +696,7 @@ name_list_adjust (void)
 
    For simplicity, only a tail pointer of the list is maintained.
 */
-   
+
 struct name_elt *unconsumed_option_tail;
 
 /* Push an option to the list */
@@ -729,7 +729,7 @@ unconsumed_option_report (void)
   if (unconsumed_option_tail)
     {
       struct name_elt *elt;
-      
+
       ERROR ((0, 0, _("The following options were used after any non-optional arguments in archive create or update mode.  These options are positional and affect only arguments that follow them.  Please, rearrange them properly.")));
 
       elt = unconsumed_option_tail;
@@ -753,13 +753,13 @@ unconsumed_option_report (void)
 		ERROR ((0, 0, _("--%s has no effect"),
 			file_selection_option_name (elt->v.opt.option)));
 	      break;
-	      
+
 	    default:
 	      break;
 	    }
 	  elt = elt->next;
 	}
-      
+
       unconsumed_option_free ();
     }
 }
@@ -967,7 +967,7 @@ handle_option (const char *str, struct name_elt const *ent)
   struct wordsplit ws;
   int i;
   struct option_locus loc;
-  
+
   while (*str && isspace (*str))
     ++str;
   if (*str != '-')
@@ -1025,7 +1025,7 @@ read_next_name (struct name_elt *ent, struct name_elt *ret)
 		   (0, 0, N_("%s: file name read contains nul character"),
 		    quotearg_colon (ent->v.file.name)));
 	  ent->v.file.term = 0;
-	  /* fall through */
+	  FALLTHROUGH;
 	case file_list_success:
 	  if (!ent->v.file.verbatim)
 	    {
@@ -1110,7 +1110,7 @@ name_next_elt (int change_dirs)
 	      name_list_advance ();
 	      break;
 	    }
-	  /* fall through */
+	  FALLTHROUGH;
 	case NELT_NAME:
 	  copy_name (ep);
 	  if (unquote_option)
@@ -1128,7 +1128,7 @@ name_next_elt (int change_dirs)
     }
 
   unconsumed_option_report ();
-  
+
   return NULL;
 }
 

src/sparse.c

@@ -361,11 +361,12 @@ sparse_scan_file (struct tar_sparse_file *file)
       /* fall back to "raw" for this and all other files */
       hole_detection = HOLE_DETECTION_RAW;
 #endif
+      FALLTHROUGH;
     case HOLE_DETECTION_RAW:
       if (sparse_scan_file_raw (file))
 	return true;
     }
-  
+
   return false;
 }
 

src/tar.c

@@ -1241,7 +1241,7 @@ parse_owner_group (char *arg, uintmax_t field_max, char const **name_option)
 	      u = u1;
 	      break;
 	    }
-	  /* Fall through.  */
+	  FALLTHROUGH;
 	case LONGINT_OVERFLOW:
 	  invalid_num = arg;
 	  break;
@@ -1396,8 +1396,7 @@ parse_opt (int key, char *arg, struct argp_state *state)
       optloc_save (OC_LISTED_INCREMENTAL, args->loc);
       listed_incremental_option = arg;
       after_date_option = true;
-      /* Fall through.  */
-
+      FALLTHROUGH;
     case 'G':
       /* We are making an incremental dump (FIXME: are we?); save
 	 directories at the beginning of the archive, and include in each
@@ -1522,8 +1521,7 @@ parse_opt (int key, char *arg, struct argp_state *state)
 
     case 'N':
       after_date_option = true;
-      /* Fall through.  */
-
+      FALLTHROUGH;
     case NEWER_MTIME_OPTION:
       if (TIME_OPTION_INITIALIZED (newer_mtime_option))
 	USAGE_ERROR ((0, 0, _("More than one threshold date")));
@@ -2066,6 +2064,7 @@ parse_opt (int key, char *arg, struct argp_state *state)
 
       argp_error (state,
 		  _("Options '-[0-7][lmh]' not supported by *this* tar"));
+      exit (EX_USAGE);
 
 #endif /* not DEVICE_PREFIX */
 

src/update.c

@@ -186,13 +186,11 @@ update_archive (void)
 	    {
 	    case HEADER_STILL_UNREAD:
 	      WARN ((0, 0, _("This does not look like a tar archive")));
-	      /* Fall through.  */
-
+	      FALLTHROUGH;
 	    case HEADER_SUCCESS:
 	    case HEADER_ZERO_BLOCK:
 	      ERROR ((0, 0, _("Skipping to next header")));
-	      /* Fall through.  */
-
+	      FALLTHROUGH;
 	    case HEADER_FAILURE:
 	      break;