Use fallthrough attribute.

Use __attribute__ ((fallthrough)) to indicate switch case fall through
instead of a comment. This ensures 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>

19 files changed, 48 insertions, 26 deletions

diff --git a/backends/ChangeLog b/backends/ChangeLog
index 190ae968..098bed76 100644
--- a/backends/ChangeLog
+++ b/backends/ChangeLog
@@ -1,3 +1,25 @@
+2018-02-09  Joshua Watt  <JPEWhacker@gmail.com>
+
+	* aarch64_retval.c (aarch64_return_value_location): Use FALLTHROUGH
+	macro instead of comment.
+	* alpha_retval.c (alpha_return_value_location): Likewise.
+	* arm_regs.c (arm_register_info): Likewise.
+	* arm_retval.c (arm_return_value_location): Likewise.
+	* i386_regs.c (i386_register_info): Likewise.
+	* i386_retval.c (i386_return_value_location): Likewise.
+	* ia64_retval.c (ia64_return_value_location): Likewise.
+	* linux-core-note.c (core_note): Likewise.
+	* m68k_retval.c (m68k_return_value_location): Likewise.
+	* ppc64_retval.c (ppc64_return_value_location): Likewise.
+	* ppc_regs.c (ppc_register_info): Likewise.
+	* ppc_retval.c (ppc_return_value_location): Likewise.
+	* s390_retval.c (s390_return_value_location): Likewise.
+	* sh_retval.c (sh_return_value_location): Likewise.
+	* sparc_retval.c (sparc_return_value_location): Likewise.
+	* tilegx_retval.c (tilegx_return_value_location): Likewise.
+	* x86_64_regs.c (x86_64_register_info): Likewise.
+	* x86_64_retval.c (x86_64_return_value_location): Likewise.
+
 2017-10-24  Mark Wielaard  <mark@klomp.org>
 
 	* Makefile.am (m68k_corenote_no_Wpacked_not_aligned): New variable.
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: