[PATCH v3] Use fallthrough attribute

[Joshua Watt <jpewhacker at gmail dot com>]

Use __attribute__ ((fallthrough)) to indicate switch case fall through
instead of a comment. This ensure that the fallthrough warning is not
triggered even if the file is pre-processed (hence stripping the
comments) before it is compiled.

The actual fallback implementation is hidden behind a FALLBACK macro in
case the compiler doesn't support it.

Finally, the -Wimplict-fallthrough warning was upgraded to only allow
the attribute to satisfy it; a comment alone is no longer sufficient.

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
---
 backends/aarch64_retval.c    | 2 +-
 backends/alpha_retval.c      | 4 ++--
 backends/arm_regs.c          | 2 +-
 backends/arm_retval.c        | 2 +-
 backends/i386_regs.c         | 2 +-
 backends/i386_retval.c       | 4 ++--
 backends/ia64_retval.c       | 2 +-
 backends/linux-core-note.c   | 2 +-
 backends/m68k_retval.c       | 4 ++--
 backends/ppc64_retval.c      | 6 +++---
 backends/ppc_regs.c          | 2 +-
 backends/ppc_retval.c        | 4 ++--
 backends/s390_retval.c       | 4 ++--
 backends/sh_retval.c         | 2 +-
 backends/sparc_retval.c      | 2 +-
 backends/tilegx_retval.c     | 4 ++--
 backends/x86_64_regs.c       | 2 +-
 backends/x86_64_retval.c     | 2 +-
 config/eu.am                 | 4 +++-
 configure.ac                 | 6 ++++++
 lib/eu-config.h              | 7 +++++++
 libcpu/i386_disasm.c         | 2 +-
 libdw/cfi.c                  | 4 ++--
 libdw/dwarf_frame_register.c | 2 +-
 libdwfl/dwfl_report_elf.c    | 2 +-
 libdwfl/frame_unwind.c       | 2 +-
 libebl/eblobjnote.c          | 2 +-
 libelf/elf32_updatenull.c    | 2 +-
 libelf/elf_begin.c           | 4 ++--
 libelf/elf_cntl.c            | 2 +-
 src/addr2line.c              | 2 +-
 src/elfcompress.c            | 2 +-
 src/elflint.c                | 8 ++++----
 src/objdump.c                | 2 +-
 src/readelf.c                | 8 ++++----
 src/strings.c                | 2 +-
 tests/backtrace.c            | 2 +-
 tests/elfstrmerge.c          | 3 ++-
 38 files changed, 68 insertions(+), 52 deletions(-)

diff --git a/backends/aarch64_retval.c b/backends/aarch64_retval.c
index 68de307e..1308340b 100644
--- a/backends/aarch64_retval.c
+++ b/backends/aarch64_retval.c
@@ -292,7 +292,7 @@ aarch64_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  assert (count > 0);
 	  if (count <= 4)
 	    return pass_hfa (locp, base_size, count);
-	  /* Fall through.  */
+	  FALLTHROUGH;
 
 	case 1:
 	  /* Not a HFA.  */
diff --git a/backends/alpha_retval.c b/backends/alpha_retval.c
index 53dbfa45..d9bae3bc 100644
--- a/backends/alpha_retval.c
+++ b/backends/alpha_retval.c
@@ -85,7 +85,7 @@ alpha_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
@@ -131,7 +131,7 @@ alpha_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  }
       }
 
-      /* Else fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_structure_type:
     case DW_TAG_class_type:
diff --git a/backends/arm_regs.c b/backends/arm_regs.c
index 21c5ad3a..a46a4c99 100644
--- a/backends/arm_regs.c
+++ b/backends/arm_regs.c
@@ -77,7 +77,7 @@ arm_register_info (Ebl *ebl __attribute__ ((unused)),
 
     case 16 + 0 ... 16 + 7:
       regno += 96 - 16;
-      /* Fall through.  */
+      FALLTHROUGH;
     case 96 + 0 ... 96 + 7:
       *setname = "FPA";
       *type = DW_ATE_float;
diff --git a/backends/arm_retval.c b/backends/arm_retval.c
index 7aced742..1c28f016 100644
--- a/backends/arm_retval.c
+++ b/backends/arm_retval.c
@@ -82,7 +82,7 @@ arm_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
diff --git a/backends/i386_regs.c b/backends/i386_regs.c
index fd963a62..7ec93bb9 100644
--- a/backends/i386_regs.c
+++ b/backends/i386_regs.c
@@ -92,7 +92,7 @@ i386_register_info (Ebl *ebl __attribute__ ((unused)),
     case 5:
     case 8:
       *type = DW_ATE_address;
-      /* Fallthrough */
+      FALLTHROUGH;
     case 0 ... 3:
     case 6 ... 7:
       name[0] = 'e';
diff --git a/backends/i386_retval.c b/backends/i386_retval.c
index 4aa646fe..32fec728 100644
--- a/backends/i386_retval.c
+++ b/backends/i386_retval.c
@@ -85,7 +85,7 @@ i386_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
@@ -123,7 +123,7 @@ i386_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	if (size <= 8)
 	  return nloc_intregpair;
       }
-    /* Fallthrough */
+    FALLTHROUGH;
 
     case DW_TAG_structure_type:
     case DW_TAG_class_type:
diff --git a/backends/ia64_retval.c b/backends/ia64_retval.c
index dcd5f28d..03ea4d89 100644
--- a/backends/ia64_retval.c
+++ b/backends/ia64_retval.c
@@ -260,7 +260,7 @@ ia64_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
diff --git a/backends/linux-core-note.c b/backends/linux-core-note.c
index 08282ba4..9faae4c3 100644
--- a/backends/linux-core-note.c
+++ b/backends/linux-core-note.c
@@ -226,7 +226,7 @@ EBLHOOK(core_note) (const GElf_Nhdr *nhdr, const char *name,
       if (memcmp (name, "CORE", nhdr->n_namesz) == 0)
 	break;
       /* Buggy old Linux kernels didn't terminate "LINUX".  */
-      /* Fall through. */
+      FALLTHROUGH;
 
     case sizeof "LINUX":
       if (memcmp (name, "LINUX", nhdr->n_namesz) == 0)
diff --git a/backends/m68k_retval.c b/backends/m68k_retval.c
index c68ed022..a653ba3a 100644
--- a/backends/m68k_retval.c
+++ b/backends/m68k_retval.c
@@ -92,7 +92,7 @@ m68k_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
@@ -135,7 +135,7 @@ m68k_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	if (size <= 8)
 	  return nloc_intregpair;
       }
-      /* Fallthrough */
+      FALLTHROUGH;
     case DW_TAG_structure_type:
     case DW_TAG_class_type:
     case DW_TAG_union_type:
diff --git a/backends/ppc64_retval.c b/backends/ppc64_retval.c
index a2519839..eb1c11ec 100644
--- a/backends/ppc64_retval.c
+++ b/backends/ppc64_retval.c
@@ -96,7 +96,7 @@ ppc64_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
@@ -141,7 +141,7 @@ ppc64_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  return nloc_intreg;
 	}
 
-      /* Else fall through.  */
+      FALLTHROUGH;
     case DW_TAG_structure_type:
     case DW_TAG_class_type:
     case DW_TAG_union_type:
@@ -161,7 +161,7 @@ ppc64_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	    return nloc_vmxreg;
 	  }
       }
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_string_type:
       if (dwarf_aggregate_size (typedie, &size) == 0 && size <= 8)
diff --git a/backends/ppc_regs.c b/backends/ppc_regs.c
index c2d50118..43d2534f 100644
--- a/backends/ppc_regs.c
+++ b/backends/ppc_regs.c
@@ -140,7 +140,7 @@ ppc_register_info (Ebl *ebl __attribute__ ((unused)),
     case 100:
       if (*bits == 32)
 	return stpcpy (name, "mq") + 1 - name;
-      /* Fallthrough */
+      FALLTHROUGH;
     case 102 ... 107:
       name[0] = 's';
       name[1] = 'p';
diff --git a/backends/ppc_retval.c b/backends/ppc_retval.c
index b14a99f1..39b42da1 100644
--- a/backends/ppc_retval.c
+++ b/backends/ppc_retval.c
@@ -108,7 +108,7 @@ ppc_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
@@ -172,7 +172,7 @@ ppc_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	      return nloc_intregquad;
 	    }
       }
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_structure_type:
     case DW_TAG_class_type:
diff --git a/backends/s390_retval.c b/backends/s390_retval.c
index a927d46a..2043f985 100644
--- a/backends/s390_retval.c
+++ b/backends/s390_retval.c
@@ -87,7 +87,7 @@ s390_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
@@ -127,7 +127,7 @@ s390_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	    return size <= asize ? nloc_intreg : nloc_intregpair;
 	  }
       }
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_structure_type:
     case DW_TAG_class_type:
diff --git a/backends/sh_retval.c b/backends/sh_retval.c
index d44f2601..33d7d964 100644
--- a/backends/sh_retval.c
+++ b/backends/sh_retval.c
@@ -84,7 +84,7 @@ sh_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
diff --git a/backends/sparc_retval.c b/backends/sparc_retval.c
index e1b17753..fb81cdce 100644
--- a/backends/sparc_retval.c
+++ b/backends/sparc_retval.c
@@ -91,7 +91,7 @@ sparc_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
diff --git a/backends/tilegx_retval.c b/backends/tilegx_retval.c
index db81a20b..7f7d24b0 100644
--- a/backends/tilegx_retval.c
+++ b/backends/tilegx_retval.c
@@ -79,7 +79,7 @@ tilegx_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
@@ -113,7 +113,7 @@ tilegx_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  return nloc_intreg;
 	}
 
-      /* Else fall through.  */
+      FALLTHROUGH;
     case DW_TAG_structure_type:
     case DW_TAG_class_type:
     case DW_TAG_union_type:
diff --git a/backends/x86_64_regs.c b/backends/x86_64_regs.c
index 84304407..ef987daf 100644
--- a/backends/x86_64_regs.c
+++ b/backends/x86_64_regs.c
@@ -87,7 +87,7 @@ x86_64_register_info (Ebl *ebl __attribute__ ((unused)),
 
     case 6 ... 7:
       *type = DW_ATE_address;
-      /* Fallthrough */
+      FALLTHROUGH;
     case 0 ... 5:
       name[0] = 'r';
       name[1] = baseregs[regno][0];
diff --git a/backends/x86_64_retval.c b/backends/x86_64_retval.c
index b3799ae0..f9114cb1 100644
--- a/backends/x86_64_retval.c
+++ b/backends/x86_64_retval.c
@@ -100,7 +100,7 @@ x86_64_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
 	  typedie = dwarf_formref_die (attr, &die_mem);
 	  tag = DWARF_TAG_OR_RETURN (typedie);
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
 
     case DW_TAG_base_type:
     case DW_TAG_enumeration_type:
diff --git a/config/eu.am b/config/eu.am
index 05c27f02..c2cc349c 100644
--- a/config/eu.am
+++ b/config/eu.am
@@ -62,7 +62,9 @@ NULL_DEREFERENCE_WARNING=
 endif
 
 if HAVE_IMPLICIT_FALLTHROUGH_WARNING
-IMPLICIT_FALLTHROUGH_WARNING=-Wimplicit-fallthrough
+# Use strict fallthrough. Only __attribute__((fallthrough)) will prevent the
+# warning
+IMPLICIT_FALLTHROUGH_WARNING=-Wimplicit-fallthrough=5
 else
 IMPLICIT_FALLTHROUGH_WARNING=
 endif
diff --git a/configure.ac b/configure.ac
index 4ab8816a..4cdb12af 100644
--- a/configure.ac
+++ b/configure.ac
@@ -456,6 +456,12 @@ CFLAGS="$old_CFLAGS"])
 AM_CONDITIONAL(HAVE_IMPLICIT_FALLTHROUGH_WARNING,
 	       [test "x$ac_cv_implicit_fallthrough" != "xno"])
 
+# Assume the fallthrough attribute is supported if -Wimplict-fallthrough is supported
+if test "$ac_cv_implicit_fallthrough" = "yes"; then
+	AC_DEFINE([HAVE_FALLTHROUGH], [1],
+		  [Defined if __attribute__((fallthrough)) is supported])
+fi
+
 dnl Check if we have argp available from our libc
 AC_LINK_IFELSE(
 	[AC_LANG_PROGRAM(
diff --git a/lib/eu-config.h b/lib/eu-config.h
index 135803e7..84b22d7c 100644
--- a/lib/eu-config.h
+++ b/lib/eu-config.h
@@ -198,5 +198,12 @@ asm (".section predict_data, \"aw\"; .previous\n"
 # define COMPAT_VERSION(name, version, prefix) error "should use #ifdef SYMBOL_VERSIONING"
 #endif
 
+#ifndef FALLTHROUGH
+# ifdef HAVE_FALLTHROUGH
+#  define FALLTHROUGH __attribute__ ((fallthrough))
+# else
+#  define FALLTHROUGH ((void) 0)
+# endif
+#endif
 
 #endif	/* eu-config.h */
diff --git a/libcpu/i386_disasm.c b/libcpu/i386_disasm.c
index 831afbe2..a7e03f95 100644
--- a/libcpu/i386_disasm.c
+++ b/libcpu/i386_disasm.c
@@ -819,7 +819,7 @@ i386_disasm (Ebl *ebl __attribute__((unused)),
 			      ++param_start;
 			      break;
 			    }
-			  /* Fallthrough */
+			  FALLTHROUGH;
 			default:
 			  assert (! "INVALID not handled");
 			}
diff --git a/libdw/cfi.c b/libdw/cfi.c
index daa845f3..341e055b 100644
--- a/libdw/cfi.c
+++ b/libdw/cfi.c
@@ -138,7 +138,7 @@ execute_cfi (Dwarf_CFI *cache,
 
 	case DW_CFA_advance_loc1:
 	  operand = *program++;
-	  /* Fallthrough */
+	  FALLTHROUGH;
 	case DW_CFA_advance_loc + 0 ... DW_CFA_advance_loc + CFI_PRIMARY_MAX:
 	advance_loc:
 	  loc += operand * cie->code_alignment_factor;
@@ -301,7 +301,7 @@ execute_cfi (Dwarf_CFI *cache,
 
 	case DW_CFA_restore_extended:
 	  get_uleb128 (operand, program, end);
-	  /* Fallthrough */
+	  FALLTHROUGH;
 	case DW_CFA_restore + 0 ... DW_CFA_restore + CFI_PRIMARY_MAX:
 
 	  if (unlikely (abi_cfi) && likely (opcode == DW_CFA_restore))
diff --git a/libdw/dwarf_frame_register.c b/libdw/dwarf_frame_register.c
index 37e8e917..d0159fb8 100644
--- a/libdw/dwarf_frame_register.c
+++ b/libdw/dwarf_frame_register.c
@@ -62,7 +62,7 @@ dwarf_frame_register (Dwarf_Frame *fs, int regno, Dwarf_Op *ops_mem,
       /* Use the default rule for registers not yet mentioned in CFI.  */
       if (fs->cache->default_same_value)
 	goto same_value;
-      /*FALLTHROUGH*/
+      FALLTHROUGH;
     case reg_undefined:
       /* The value is known to be unavailable.  */
       break;
diff --git a/libdwfl/dwfl_report_elf.c b/libdwfl/dwfl_report_elf.c
index 6950a37b..3fc9384a 100644
--- a/libdwfl/dwfl_report_elf.c
+++ b/libdwfl/dwfl_report_elf.c
@@ -174,7 +174,7 @@ __libdwfl_elf_address_range (Elf *elf, GElf_Addr base, bool add_p_vaddr,
       /* An assigned base address is meaningless for these.  */
       base = 0;
       add_p_vaddr = true;
-      /* Fallthrough. */
+      FALLTHROUGH;
     case ET_DYN:
     default:;
       size_t phnum;
diff --git a/libdwfl/frame_unwind.c b/libdwfl/frame_unwind.c
index 4dc9c432..eaea495f 100644
--- a/libdwfl/frame_unwind.c
+++ b/libdwfl/frame_unwind.c
@@ -442,7 +442,7 @@ expr_eval (Dwfl_Frame *state, Dwarf_Frame *frame, const Dwarf_Op *ops,
 	    }
 	  if (val1 == 0)
 	    break;
-	  /* FALLTHRU */
+	  FALLTHROUGH;
 	case DW_OP_skip:;
 	  Dwarf_Word offset = op->offset + 1 + 2 + (int16_t) op->number;
 	  const Dwarf_Op *found = bsearch ((void *) (uintptr_t) offset, ops, nops,
diff --git a/libebl/eblobjnote.c b/libebl/eblobjnote.c
index f80a1a57..ca4f155d 100644
--- a/libebl/eblobjnote.c
+++ b/libebl/eblobjnote.c
@@ -223,7 +223,7 @@ ebl_object_note (Ebl *ebl, const char *name, uint32_t type,
 		free (buf);
 	      break;
 	    }
-	  /* FALLTHROUGH */
+	  FALLTHROUGH;
 
 	default:
 	  /* Unknown type.  */
diff --git a/libelf/elf32_updatenull.c b/libelf/elf32_updatenull.c
index d83c0b3f..3e9ef61b 100644
--- a/libelf/elf32_updatenull.c
+++ b/libelf/elf32_updatenull.c
@@ -232,7 +232,7 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 		      __libelf_seterrno (ELF_E_GROUP_NOT_REL);
 		      return -1;
 		    }
-		  /* FALLTHROUGH */
+		  FALLTHROUGH;
 		case SHT_SYMTAB_SHNDX:
 		  sh_entsize = elf_typesize (32, ELF_T_WORD, 1);
 		  break;
diff --git a/libelf/elf_begin.c b/libelf/elf_begin.c
index fb3a5b57..b20ab4f3 100644
--- a/libelf/elf_begin.c
+++ b/libelf/elf_begin.c
@@ -611,7 +611,7 @@ read_unmmaped_file (int fildes, off_t offset, size_t maxsize, Elf_Cmd cmd,
 			     ? sizeof (Elf32_Ehdr) : sizeof (Elf64_Ehdr)))
 	return file_read_elf (fildes, NULL, mem.header, offset, maxsize, cmd,
 			      parent);
-      /* FALLTHROUGH */
+      FALLTHROUGH;
 
     default:
       break;
@@ -1126,7 +1126,7 @@ elf_begin (int fildes, Elf_Cmd cmd, Elf *ref)
 	  retval = NULL;
 	  break;
 	}
-      /* FALLTHROUGH */
+      FALLTHROUGH;
 
     case ELF_C_READ:
     case ELF_C_READ_MMAP:
diff --git a/libelf/elf_cntl.c b/libelf/elf_cntl.c
index ab13ffb6..fd681789 100644
--- a/libelf/elf_cntl.c
+++ b/libelf/elf_cntl.c
@@ -62,7 +62,7 @@ elf_cntl (Elf *elf, Elf_Cmd cmd)
 	  result = -1;
 	  break;
 	}
-      /* FALLTHROUGH */
+      FALLTHROUGH;
 
     case ELF_C_FDDONE:
       /* Mark the file descriptor as not usable.  */
diff --git a/src/addr2line.c b/src/addr2line.c
index ba414a74..444ee52c 100644
--- a/src/addr2line.c
+++ b/src/addr2line.c
@@ -618,7 +618,7 @@ handle_address (const char *string, Dwfl *dwfl)
 	case 1:
 	  addr = 0;
 	  j = i;
-	  /* Fallthrough */
+	  FALLTHROUGH;
 	case 2:
 	  if (string[j] != '\0')
 	    break;
diff --git a/src/elfcompress.c b/src/elfcompress.c
index 8e0d5c55..25378a45 100644
--- a/src/elfcompress.c
+++ b/src/elfcompress.c
@@ -149,7 +149,7 @@ parse_opt (int key, char *arg __attribute__ ((unused)),
 		    N_("Only one input file allowed together with '-o'"));
       /* We only use this for checking the number of arguments, we don't
 	 actually want to consume them.  */
-      /* Fallthrough */
+      FALLTHROUGH;
     default:
       return ARGP_ERR_UNKNOWN;
     }
diff --git a/src/elflint.c b/src/elflint.c
index 51e53c23..df1b3a03 100644
--- a/src/elflint.c
+++ b/src/elflint.c
@@ -1764,7 +1764,7 @@ section [%2d] '%s': entry %zu: pointer does not match address of section [%2d] '
 	  if (dyn->d_tag < DT_ADDRRNGLO || dyn->d_tag > DT_ADDRRNGHI)
 	    /* Value is no pointer.  */
 	    break;
-	  /* FALLTHROUGH */
+	  FALLTHROUGH;
 
 	case DT_AUXILIARY:
 	case DT_FILTER:
@@ -3993,7 +3993,7 @@ section [%2zu] '%s': merge flag set but entry size is zero\n"),
 	    case SHT_NOBITS:
 	      if (is_debuginfo)
 		break;
-	      /* Fallthrough */
+	      FALLTHROUGH;
 	    default:
 	      ERROR (gettext ("\
 section [%2zu] '%s' has unexpected type %d for an executable section\n"),
@@ -4137,7 +4137,7 @@ section [%2zu] '%s': ELF header says this is the section header string table but
 	    ERROR (gettext ("\
 section [%2zu] '%s': relocatable files cannot have dynamic symbol tables\n"),
 		   cnt, section_name (ebl, cnt));
-	  /* FALLTHROUGH */
+	  FALLTHROUGH;
 	case SHT_SYMTAB:
 	  check_symtab (ebl, ehdr, shdr, cnt);
 	  break;
@@ -4336,7 +4336,7 @@ section [%2d] '%s': unknown core file note type %" PRIu32
 	    if (nhdr.n_namesz == sizeof "Linux"
 		&& !memcmp (data->d_buf + name_offset, "Linux", sizeof "Linux"))
 	      break;
-	    /* Fallthrough */
+	    FALLTHROUGH;
 	  default:
 	    if (shndx == 0)
 	      ERROR (gettext ("\
diff --git a/src/objdump.c b/src/objdump.c
index 860cfac6..0dd9a6aa 100644
--- a/src/objdump.c
+++ b/src/objdump.c
@@ -223,7 +223,7 @@ parse_opt (int key, char *arg,
 	}
       /* We only use this for checking the number of arguments, we don't
 	 actually want to consume them.  */
-      /* Fallthrough */
+      FALLTHROUGH;
     default:
       return ARGP_ERR_UNKNOWN;
     }
diff --git a/src/readelf.c b/src/readelf.c
index 6c49d305..d606cf5a 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -480,7 +480,7 @@ parse_opt (int key, char *arg,
 	  print_string_sections = true;
 	  break;
 	}
-      /* Fall through.  */
+      FALLTHROUGH;
     case 'x':
       add_dump_section (arg, false);
       any_control_option = true;
@@ -6081,7 +6081,7 @@ attr_callback (Dwarf_Attribute *attrp, void *arg)
 			dwarf_form_name (form), (uintmax_t) num);
 	      return DWARF_CB_OK;
 	    }
-	  /* else fallthrough */
+	  FALLTHROUGH;
 
 	/* These cases always take a loclistptr and no constant. */
 	case DW_AT_location:
@@ -6269,7 +6269,7 @@ attr_callback (Dwarf_Attribute *attrp, void *arg)
 	      print_block (block.length, block.data);
 	      break;
 	    }
-	  /* Fall through.  */
+	  FALLTHROUGH;
 
 	case DW_AT_location:
 	case DW_AT_data_location:
@@ -9326,7 +9326,7 @@ handle_auxv_note (Ebl *ebl, Elf *core, GElf_Word descsz, GElf_Off desc_pos)
 		printf ("    %s\n", name);
 		break;
 	      }
-	    /* Fall through */
+	    FALLTHROUGH;
 	  case 'x':		/* hex */
 	  case 'p':		/* address */
 	  case 's':		/* address of string */
diff --git a/src/strings.c b/src/strings.c
index d214356c..03d0f133 100644
--- a/src/strings.c
+++ b/src/strings.c
@@ -246,7 +246,7 @@ parse_opt (int key, char *arg,
 	case 'b':
 	case 'B':
 	  big_endian = true;
-	  /* FALLTHROUGH */
+	  FALLTHROUGH;
 
 	case 'l':
 	case 'L':
diff --git a/tests/backtrace.c b/tests/backtrace.c
index 21abe8af..f5dd761f 100644
--- a/tests/backtrace.c
+++ b/tests/backtrace.c
@@ -127,7 +127,7 @@ callback_verify (pid_t tid, unsigned frameno, Dwarf_Addr pc,
 	  assert (symname2 == NULL || strcmp (symname2, "jmp") != 0);
 	  break;
 	}
-      /* FALLTHRU */
+      FALLTHROUGH;
     case 4:
       /* Some simple frame unwinders get this wrong and think sigusr2
 	 is calling itself again. Allow it and just pretend there is
diff --git a/tests/elfstrmerge.c b/tests/elfstrmerge.c
index 6924d0e9..3bb90c42 100644
--- a/tests/elfstrmerge.c
+++ b/tests/elfstrmerge.c
@@ -578,7 +578,8 @@ main (int argc, char **argv)
 	      break;
 
 	    case SHT_DYNAMIC:
-	      /* Fallthrough.  There are string indexes in here, but
+	      FALLTHROUGH;
+	      /* There are string indexes in here, but
 		 they (should) point to a allocated string table,
 		 which we don't alter.  */
 	    default:
-- 
2.14.3