fix implicit fallthrough gcc warnings

This patch addresses implicit fallthrough warnings on the
newer gcc compiler. Proper comment to silence the warning or appropriate comments
have been added in the case statements.

Signed-off-by: Ani Sinha <ani@anisinha.ca>

grub-core/commands/hdparm.c

@@ -328,6 +328,7 @@ grub_cmd_hdparm (grub_extcmd_context_t ctxt, int argc, char **args)
 	  ata = ((struct grub_scsi *) disk->data)->data;
 	  break;
 	}
+      // fall through
     default:
       return grub_error (GRUB_ERR_IO, "not an ATA device");
     }

grub-core/disk/cryptodisk.c

@@ -268,6 +268,7 @@ grub_cryptodisk_endecrypt (struct grub_cryptodisk *dev,
 	  break;
 	case GRUB_CRYPTODISK_MODE_IV_PLAIN64:
 	  iv[1] = grub_cpu_to_le32 (sector >> 32);
+	  // fall through
 	case GRUB_CRYPTODISK_MODE_IV_PLAIN:
 	  iv[0] = grub_cpu_to_le32 (sector & 0xFFFFFFFF);
 	  break;

grub-core/disk/diskfilter.c

@@ -71,6 +71,7 @@ is_lv_readable (struct grub_diskfilter_lv *lv, int easily)
 	case GRUB_DISKFILTER_RAID6:
 	  if (!easily)
 	    need--;
+	  // fall through
 	case GRUB_DISKFILTER_RAID4:
 	case GRUB_DISKFILTER_RAID5:
 	  if (!easily)
@@ -507,6 +508,7 @@ read_segment (struct grub_diskfilter_segment *seg, grub_disk_addr_t sector,
       if (seg->node_count == 1)
 	return grub_diskfilter_read_node (&seg->nodes[0],
 					  sector, size, buf);
+      // fall through
     case GRUB_DISKFILTER_MIRROR:
     case GRUB_DISKFILTER_RAID10:
       {

grub-core/disk/efi/efidisk.c

@@ -262,6 +262,9 @@ name_devices (struct grub_efidisk_data *devices)
 	    {
 	    case GRUB_EFI_HARD_DRIVE_DEVICE_PATH_SUBTYPE:
 	      is_hard_drive = 1;
+#if defined(__GNUC__) && __GNUC__ >= 7
+	      __attribute__ ((fallthrough));
+#endif
 	      /* Fall through by intention.  */
 	    case GRUB_EFI_CDROM_DEVICE_PATH_SUBTYPE:
 	      {

grub-core/efiemu/mm.c

@@ -410,6 +410,7 @@ grub_efiemu_mmap_fill (void)
 	default:
 	  grub_dprintf ("efiemu",
 			"Unknown memory type %d. Assuming unusable\n", type);
+	  // fall through
 	case GRUB_MEMORY_RESERVED:
 	  return grub_efiemu_add_to_mmap (addr, size,
 					  GRUB_EFI_UNUSABLE_MEMORY);

grub-core/font/font.c

@@ -1297,6 +1297,7 @@ blit_comb (const struct grub_unicode_glyph *glyph_id,
 	    - grub_font_get_xheight (combining_glyphs[i]->font) - 1;
 	  if (space <= 0)
 	    space = 1 + (grub_font_get_xheight (main_glyph->font)) / 8;
+	  // fall through
 
 	case GRUB_UNICODE_STACK_ATTACHED_ABOVE:
 	  do_blit (combining_glyphs[i], targetx,
@@ -1338,6 +1339,7 @@ blit_comb (const struct grub_unicode_glyph *glyph_id,
 		    + combining_glyphs[i]->height);
 	  if (space <= 0)
 	    space = 1 + (grub_font_get_xheight (main_glyph->font)) / 8;
+	  // fall through
 
 	case GRUB_UNICODE_STACK_ATTACHED_BELOW:
 	  do_blit (combining_glyphs[i], targetx, -(bounds.y - space));

grub-core/fs/udf.c

@@ -970,6 +970,7 @@ grub_udf_read_symlink (grub_fshelp_node_t node)
 	case 1:
 	  if (ptr[1])
 	    goto fail;
+	  // fall through
 	case 2:
 	  /* in 4 bytes. out: 1 byte.  */
 	  optr = out;

grub-core/gdb/cstub.c

@@ -336,6 +336,7 @@ grub_gdb_trap (int trap_no)
 	/* sAA..AA: Step one instruction from AA..AA(optional).  */
 	case 's':
 	  stepping = 1;
+	  // fall through
 
 	/* cAA..AA: Continue at address AA..AA(optional).  */
 	case 'c':

grub-core/gnulib/regexec.c

@@ -4104,8 +4104,8 @@ check_node_accept (const re_match_context_t *mctx, const re_token_t *node,
     case OP_UTF8_PERIOD:
       if (ch >= ASCII_CHARS)
         return false;
-      /* FALLTHROUGH */
 #endif
+      // fall through
     case OP_PERIOD:
       if ((ch == '\n' && !(mctx->dfa->syntax & RE_DOT_NEWLINE))
 	  || (ch == '\0' && (mctx->dfa->syntax & RE_DOT_NOT_NULL)))

grub-core/lib/legacy_parse.c

@@ -626,6 +626,7 @@ grub_legacy_parse (const char *buf, char **entryname, char **suffix)
 	  {
 	  case TYPE_FILE_NO_CONSUME:
 	    hold_arg = 1;
+	    // fall through
 	  case TYPE_PARTITION:
 	  case TYPE_FILE:
 	    args[i] = adjust_file (curarg, curarglen);

grub-core/lib/xzembed/xz_dec_lzma2.c

@@ -1041,6 +1041,7 @@ enum xz_ret xz_dec_lzma2_run(
 				return XZ_DATA_ERROR;
 
 			s->lzma2.sequence = SEQ_LZMA_PREPARE;
+			//fall through
 
 		case SEQ_LZMA_PREPARE:
 			if (s->lzma2.compressed < RC_INIT_BYTES)
@@ -1051,6 +1052,7 @@ enum xz_ret xz_dec_lzma2_run(
 
 			s->lzma2.compressed -= RC_INIT_BYTES;
 			s->lzma2.sequence = SEQ_LZMA_RUN;
+			// fall through
 
 		case SEQ_LZMA_RUN:
 			/*

grub-core/lib/xzembed/xz_dec_stream.c

@@ -748,6 +748,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 				return ret;
 
 			s->sequence = SEQ_BLOCK_START;
+			// fall through
 
 		case SEQ_BLOCK_START:
 			/* We need one byte of input to continue. */
@@ -771,6 +772,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 			s->temp.size = s->block_header.size;
 			s->temp.pos = 0;
 			s->sequence = SEQ_BLOCK_HEADER;
+			// fall through
 
 		case SEQ_BLOCK_HEADER:
 			if (!fill_temp(s, b))
@@ -781,13 +783,15 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 				return ret;
 
 			s->sequence = SEQ_BLOCK_UNCOMPRESS;
+			// fall through
 
 		case SEQ_BLOCK_UNCOMPRESS:
 			ret = dec_block(s, b);
 			if (ret != XZ_STREAM_END)
 				return ret;
 
 			s->sequence = SEQ_BLOCK_PADDING;
+			// fall through
 
 		case SEQ_BLOCK_PADDING:
 			/*
@@ -808,6 +812,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 			}
 
 			s->sequence = SEQ_BLOCK_CHECK;
+			// fall through
 
 		case SEQ_BLOCK_CHECK:
 			ret = hash_validate(s, b, 0);
@@ -823,6 +828,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 				return ret;
 
 			s->sequence = SEQ_INDEX_PADDING;
+			// fall through
 
 		case SEQ_INDEX_PADDING:
 			while ((s->index.size + (b->in_pos - s->in_start))
@@ -862,6 +868,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 #endif
 
 			s->sequence = SEQ_INDEX_CRC32;
+			// fall through
 
 		case SEQ_INDEX_CRC32:
 			ret = hash_validate(s, b, 1);
@@ -870,6 +877,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 
 			s->temp.size = STREAM_HEADER_SIZE;
 			s->sequence = SEQ_STREAM_FOOTER;
+			// fall through
 
 		case SEQ_STREAM_FOOTER:
 			if (!fill_temp(s, b))

grub-core/loader/i386/linux.c

@@ -977,10 +977,13 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
 	      {
 	      case 'g':
 		shift += 10;
+		// fall through
 	      case 'm':
 		shift += 10;
+		// fall through
 	      case 'k':
 		shift += 10;
+		// fall through
 	      default:
 		break;
 	      }

grub-core/loader/i386/pc/linux.c

@@ -252,10 +252,13 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
 	      {
 	      case 'g':
 		shift += 10;
+		// fall through
 	      case 'm':
 		shift += 10;
+		// fall through
 	      case 'k':
 		shift += 10;
+		// fall through
 	      default:
 		break;
 	      }

grub-core/mmap/efi/mmap.c

@@ -72,6 +72,7 @@ grub_efi_mmap_iterate (grub_memory_hook_t hook, int avoid_efi_boot_services)
 		    GRUB_MEMORY_AVAILABLE);
 	      break;
 	    }
+	  break;
 	case GRUB_EFI_RUNTIME_SERVICES_CODE:
 	  hook (desc->physical_start, desc->num_pages * 4096,
 		GRUB_MEMORY_CODE);
@@ -85,6 +86,7 @@ grub_efi_mmap_iterate (grub_memory_hook_t hook, int avoid_efi_boot_services)
 	default:
 	  grub_printf ("Unknown memory type %d, considering reserved\n",
 		       desc->type);
+	  break;
 
 	case GRUB_EFI_BOOT_SERVICES_DATA:
 	  if (!avoid_efi_boot_services)
@@ -93,6 +95,7 @@ grub_efi_mmap_iterate (grub_memory_hook_t hook, int avoid_efi_boot_services)
 		    GRUB_MEMORY_AVAILABLE);
 	      break;
 	    }
+	  break;
 	case GRUB_EFI_RESERVED_MEMORY_TYPE:
 	case GRUB_EFI_RUNTIME_SERVICES_DATA:
 	case GRUB_EFI_MEMORY_MAPPED_IO:

grub-core/normal/charset.c

@@ -858,6 +858,7 @@ grub_bidi_line_logical_to_visual (const grub_uint32_t *logical,
 	  case GRUB_BIDI_TYPE_R:
 	  case GRUB_BIDI_TYPE_AL:
 	    bidi_needed = 1;
+	    // fall through
 	  default:
 	    {
 	      if (join_state == JOIN_FORCE)

grub-core/video/bochs.c

@@ -351,6 +351,7 @@ grub_video_bochs_setup (unsigned int width, unsigned int height,
     case 32:
       framebuffer.mode_info.reserved_mask_size = 8;
       framebuffer.mode_info.reserved_field_pos = 24;
+      // fall through
 
     case 24:
       framebuffer.mode_info.red_mask_size = 8;

grub-core/video/cirrus.c

@@ -431,6 +431,7 @@ grub_video_cirrus_setup (unsigned int width, unsigned int height,
     case 32:
       framebuffer.mode_info.reserved_mask_size = 8;
       framebuffer.mode_info.reserved_field_pos = 24;
+      // fall through
 
     case 24:
       framebuffer.mode_info.red_mask_size = 8;

grub-core/video/i386/pc/vbe.c

@@ -880,6 +880,7 @@ vbe2videoinfo (grub_uint32_t mode,
       /* CGA is basically 4-bit packed pixel.  */
     case GRUB_VBE_MEMORY_MODEL_CGA:
       mode_info->mode_type |= GRUB_VIDEO_MODE_TYPE_CGA;
+      // fall through
     case GRUB_VBE_MEMORY_MODEL_PACKED_PIXEL:
       mode_info->mode_type |= GRUB_VIDEO_MODE_TYPE_INDEX_COLOR;
       break;
@@ -892,6 +893,7 @@ vbe2videoinfo (grub_uint32_t mode,
       /* Non chain 4 is a special case of planar.  */
     case GRUB_VBE_MEMORY_MODEL_NONCHAIN4_256:
       mode_info->mode_type |= GRUB_VIDEO_MODE_TYPE_NONCHAIN4;
+      // fall through
     case GRUB_VBE_MEMORY_MODEL_PLANAR:
       mode_info->mode_type |= GRUB_VIDEO_MODE_TYPE_PLANAR
 	| GRUB_VIDEO_MODE_TYPE_INDEX_COLOR;

grub-core/video/readers/jpeg.c

@@ -701,6 +701,7 @@ grub_jpeg_decode_jpeg (struct grub_jpeg_data *data)
 	case JPEG_MARKER_SOS:	/* Start Of Scan.  */
 	  if (grub_jpeg_decode_sos (data))
 	    break;
+	  // fall through
 	case JPEG_MARKER_RST0:	/* Restart.  */
 	case JPEG_MARKER_RST1:
 	case JPEG_MARKER_RST2:

util/grub-mkimagexx.c

@@ -486,6 +486,7 @@ SUFFIX (relocate_addresses) (Elf_Ehdr *e, Elf_Shdr *sections,
 									    + sym->st_value
 									    - image_target->vaddr_offset));
 		  }
+		  // fall through
 		case R_IA64_LTOFF_FPTR22:
 		  *gpptr = grub_host_to_target64 (addend + sym_addr);
 		  add_value_to_slot_21 ((grub_addr_t) target,