libiberty: Fix -Wimplicit-fallthrough warnings.

Adjust some comments, add some explicit fall through comments or explicit
returns where necessary to not get implicit-fallthrough warnings.

All fall throughs were deliberate. In one case I added an explicit return
false for clarity instead of falling through a default case (that also
would return false).

libiberty/ChangeLog:

       * cplus-dem.c (demangle_signature): Move fall through comment.
       (demangle_fund_type): Add fall through comment between 'G' and 'I'.
       * hashtab.c (iterative_hash): Add fall through comments.
       * regex.c (regex_compile): Add Fall through comment after '+'/'?'.
       (byte_re_match_2_internal): Add Fall through comment after jump_n.
       Change "Note fall through" to "Fall through".
       (common_op_match_null_string_p): Return false after set_number_at
       instead of fall through.

From-SVN: r241864

libiberty/ChangeLog

+2016-11-02  Mark Wielaard  <mjw@redhat.com>
+
+	* cplus-dem.c (demangle_signature): Move fall through comment.
+	(demangle_fund_type): Add fall through comment between 'G' and 'I'.
+	* hashtab.c (iterative_hash): Add fall through comments.
+	* regex.c (regex_compile): Add Fall through comment after '+'/'?'.
+	(byte_re_match_2_internal): Add Fall through comment after jump_n.
+	Change "Note fall through" to "Fall through".
+	(common_op_match_null_string_p): Return false after set_number_at
+	instead of fall through.
+
 2016-11-01  Jason Merrill  <jason@redhat.com>
 
 	* cp-demangle.c (d_ctor_dtor_name): Handle inheriting constructor.

libiberty/cplus-dem.c

@@ -1657,9 +1657,7 @@ demangle_signature (struct work_stuff *work,
 	      (*mangled)++;
 	      break;
 	    }
-	  else
-	    /* fall through */
-	    {;}
+	  /* fall through */
 
 	default:
 	  if (AUTO_DEMANGLING || GNU_DEMANGLING)
@@ -4024,6 +4022,7 @@ demangle_fund_type (struct work_stuff *work,
 	  success = 0;
 	  break;
 	}
+      /* fall through */
     case 'I':
       (*mangled)++;
       if (**mangled == '_')

libiberty/hashtab.c

@@ -962,17 +962,17 @@ iterative_hash (const PTR k_in /* the key */,
   c += length;
   switch(len)              /* all the case statements fall through */
     {
-    case 11: c+=((hashval_t)k[10]<<24);
-    case 10: c+=((hashval_t)k[9]<<16);
-    case 9 : c+=((hashval_t)k[8]<<8);
+    case 11: c+=((hashval_t)k[10]<<24);	/* fall through */
+    case 10: c+=((hashval_t)k[9]<<16);	/* fall through */
+    case 9 : c+=((hashval_t)k[8]<<8);	/* fall through */
       /* the first byte of c is reserved for the length */
-    case 8 : b+=((hashval_t)k[7]<<24);
-    case 7 : b+=((hashval_t)k[6]<<16);
-    case 6 : b+=((hashval_t)k[5]<<8);
-    case 5 : b+=k[4];
-    case 4 : a+=((hashval_t)k[3]<<24);
-    case 3 : a+=((hashval_t)k[2]<<16);
-    case 2 : a+=((hashval_t)k[1]<<8);
+    case 8 : b+=((hashval_t)k[7]<<24);	/* fall through */
+    case 7 : b+=((hashval_t)k[6]<<16);	/* fall through */
+    case 6 : b+=((hashval_t)k[5]<<8);	/* fall through */
+    case 5 : b+=k[4];			/* fall through */
+    case 4 : a+=((hashval_t)k[3]<<24);	/* fall through */
+    case 3 : a+=((hashval_t)k[2]<<16);	/* fall through */
+    case 2 : a+=((hashval_t)k[1]<<8);	/* fall through */
     case 1 : a+=k[0];
       /* case 0: nothing left to add */
     }

libiberty/regex.c

@@ -2493,6 +2493,7 @@ PREFIX(regex_compile) (const char *ARG_PREFIX(pattern),
           if ((syntax & RE_BK_PLUS_QM)
               || (syntax & RE_LIMITED_OPS))
             goto normal_char;
+	  /* Fall through.  */
         handle_plus:
         case '*':
           /* If there is no previous pattern... */
@@ -6697,6 +6698,7 @@ byte_re_match_2_internal (struct re_pattern_buffer *bufp,
                 {
                   case jump_n:
 		    is_a_jump_n = true;
+		    /* Fall through.  */
                   case pop_failure_jump:
 		  case maybe_pop_jump:
 		  case jump:
@@ -7125,7 +7127,7 @@ byte_re_match_2_internal (struct re_pattern_buffer *bufp,
               DEBUG_PRINT1 ("  Match => jump.\n");
 	      goto unconditional_jump;
 	    }
-        /* Note fall through.  */
+        /* Fall through.  */
 
 
 	/* The end of a simple repeat has a pop_failure_jump back to
@@ -7150,7 +7152,7 @@ byte_re_match_2_internal (struct re_pattern_buffer *bufp,
                                dummy_low_reg, dummy_high_reg,
                                reg_dummy, reg_dummy, reg_info_dummy);
           }
-	  /* Note fall through.  */
+	  /* Fall through.  */
 
 	unconditional_jump:
 #ifdef _LIBC
@@ -7453,6 +7455,7 @@ byte_re_match_2_internal (struct re_pattern_buffer *bufp,
                 {
                 case jump_n:
                   is_a_jump_n = true;
+		  /* Fall through.  */
                 case maybe_pop_jump:
                 case pop_failure_jump:
                 case jump:
@@ -7718,6 +7721,7 @@ PREFIX(common_op_match_null_string_p) (UCHAR_T **p, UCHAR_T *end,
 
     case set_number_at:
       p1 += 2 * OFFSET_ADDRESS_SIZE;
+      return false;
 
     default:
       /* All other opcodes mean we cannot match the empty string.  */