Add -Wswitch to --enable-gcc-warnings

Make --enable-gcc-warnings a bit pickier, by also using -Wswitch.
* configure.ac (WERROR_CFLAGS): Don’t add -Wno-switch.
* lib-src/etags.c (main, consider_token, C_entries):
* src/coding.c (encode_invocation_designation):
* src/data.c (Ftype_of):
* src/eval.c (Fdefvaralias, default_toplevel_binding)
(Fbacktrace__locals, mark_specpdl):
* src/lisp.h (record_xmalloc):
* src/syntax.c (scan_lists, scan_sexps_forward):
* src/window.c (window_relative_x_coord):
* src/xdisp.c (push_it, pop_it):
* src/xterm.c (xg_scroll_callback, x_check_fullscreen):
Error out or do nothing (as appropriate) if a switch statement
with an enum value does not cover all of the enum.
* src/dispextern.h (struct iterator_stack_entry.u.comp):
Remove unused member discovered by using -Wswitch.
* src/lisp.h (record_xmalloc): Add a ‘+ 0’ to pacify -Wswitch.
* src/vm-limit.c (check_memory_limits):
Simplify warning-diagnostic computation by using a table.

12 files changed, 129 insertions, 31 deletions

diff --git a/configure.ac b/configure.ac
index f86d29ed58b..d537f73c939 100644
--- a/configure.ac
+++ b/configure.ac
@@ -929,9 +929,12 @@ else
   nw="$nw -Wsuggest-attribute=pure"
 
   # This part is merely for shortening the command line,
+  # since -Wall implies -Wswitch.
+  nw="$nw -Wswitch"
+
+  # This part is merely for shortening the command line,
   # since -Wno-FOO needs to be added below regardless.
   nw="$nw -Wmissing-field-initializers"
-  nw="$nw -Wswitch"
   nw="$nw -Wtype-limits"
   nw="$nw -Wunused-parameter"
 
@@ -948,7 +951,6 @@ else
   gl_WARN_ADD([-Wno-missing-field-initializers]) # We need this one
   gl_WARN_ADD([-Wno-sign-compare])     # Too many warnings for now
   gl_WARN_ADD([-Wno-type-limits])      # Too many warnings for now
-  gl_WARN_ADD([-Wno-switch])           # Too many warnings for now
   gl_WARN_ADD([-Wno-unused-parameter]) # Too many warnings for now
   gl_WARN_ADD([-Wno-format-nonliteral])
 
diff --git a/lib-src/etags.c b/lib-src/etags.c
index 7baff8cbfe8..791722d4b66 100644
--- a/lib-src/etags.c
+++ b/lib-src/etags.c
@@ -1268,6 +1268,8 @@ main (int argc, char **argv)
           this_file = argbuffer[i].what;
           process_file (stdin, this_file, lang);
           break;
+	default:
+	  error ("internal error: arg_type");
 	}
     }
 
@@ -2754,6 +2756,9 @@ consider_token (char *str, int len, int c, int *c_extp,
 	 case st_C_struct:
 	 case st_C_enum:
 	   typdef = ttypeseen;
+	   break;
+	 default:
+	   break;
 	 }
        break;
      case ttypeseen:
@@ -2770,8 +2775,11 @@ consider_token (char *str, int len, int c, int *c_extp,
 	 case st_C_struct:
 	 case st_C_enum:
 	   return false;
+	 default:
+	   return true;
 	 }
-       return true;
+     default:
+       break;
      }
 
    switch (toktype)
@@ -2804,6 +2812,8 @@ consider_token (char *str, int len, int c, int *c_extp,
 	     fvdef = fvnone;
 	 }
        return false;
+     default:
+       break;
      }
 
    if (structdef == skeyseen)
@@ -2827,6 +2837,8 @@ consider_token (char *str, int len, int c, int *c_extp,
 	 case st_C_objimpl:
 	   objdef = oimplementation;
 	   return false;
+	 default:
+	   break;
 	 }
        break;
      case oimplementation:
@@ -2888,6 +2900,8 @@ consider_token (char *str, int len, int c, int *c_extp,
 	   objdef = onone;
 	 }
        return false;
+     default:
+       break;
      }
 
    /* A function, variable or enum constant? */
@@ -2943,6 +2957,8 @@ consider_token (char *str, int len, int c, int *c_extp,
 		   return false;
 		 }
 	       break;
+	     default:
+	       break;
 	     }
 	  /* FALLTHRU */
 	  case fvnameseen:
@@ -2959,8 +2975,12 @@ consider_token (char *str, int len, int c, int *c_extp,
 	  fvdef = fvnameseen;	/* function or variable */
 	  *is_func_or_var = true;
 	  return true;
+	 default:
+	   break;
 	}
       break;
+     default:
+       break;
     }
 
   return false;
@@ -3470,6 +3490,8 @@ C_entries (int c_ext, FILE *inf)
 			  fvdef = fignore;
 			}
 		      break;
+		    default:
+		      break;
 		    }
 		  if (structdef == stagseen && !cjava)
 		    {
@@ -3480,6 +3502,8 @@ C_entries (int c_ext, FILE *inf)
 		case dsharpseen:
 		  savetoken = token;
 		  break;
+		default:
+		  break;
 		}
 	      if (!yacc_rules || lp == newlb.buffer + 1)
 		{
@@ -3508,7 +3532,7 @@ C_entries (int c_ext, FILE *inf)
 	    break;
 	  switch (objdef)
 	    {
-	    case  otagseen:
+	    case otagseen:
 	      objdef = oignore;
 	      make_C_tag (true); /* an Objective C class */
 	      break;
@@ -3522,6 +3546,8 @@ C_entries (int c_ext, FILE *inf)
 		  strcpy (token_name.buffer + toklen, ":");
 		}
 	      break;
+	    default:
+	      break;
 	    }
 	  if (structdef == stagseen)
 	    {
@@ -3599,6 +3625,8 @@ C_entries (int c_ext, FILE *inf)
 	      make_C_tag (true); /* an Objective C method */
 	      objdef = oinbody;
 	      break;
+	    default:
+	      break;
 	    }
 	  switch (fvdef)
 	    {
@@ -3672,6 +3700,8 @@ C_entries (int c_ext, FILE *inf)
 		  fvdef = fvnone;
 		}
 	      break;
+	    default:
+	      break;
 	    }
 	  break;
 	case '(':
@@ -3705,6 +3735,8 @@ C_entries (int c_ext, FILE *inf)
 	    case flistseen:
 	      fvdef = finlist;
 	      break;
+	    default:
+	      break;
 	    }
 	  parlev++;
 	  break;
@@ -3730,6 +3762,8 @@ C_entries (int c_ext, FILE *inf)
 		case finlist:
 		  fvdef = flistseen;
 		  break;
+		default:
+		  break;
 		}
 	      if (!instruct
 		  && (typdef == tend
@@ -3801,6 +3835,8 @@ C_entries (int c_ext, FILE *inf)
 		    bracelev = -1;
 		}
 	      break;
+	    default:
+	      break;
 	    }
 	  switch (structdef)
 	    {
@@ -3814,6 +3850,8 @@ C_entries (int c_ext, FILE *inf)
 	      structdef = snone;
 	      make_C_tag (false);  /* a struct or enum */
 	      break;
+	    default:
+	      break;
 	    }
 	  bracelev += 1;
 	  break;
diff --git a/src/coding.c b/src/coding.c
index 1544f319b00..d14e562ce9a 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -4295,6 +4295,9 @@ encode_invocation_designation (struct charset *charset,
 	  else
 	    ENCODE_LOCKING_SHIFT_3;
 	  break;
+
+	default:
+	  break;
 	}
     }
 
@@ -7292,6 +7295,8 @@ produce_annotation (struct coding_system *coding, ptrdiff_t pos)
 	      case CODING_ANNOTATE_CHARSET_MASK:
 		produce_charset (coding, charbuf, pos);
 		break;
+	      default:
+		break;
 	      }
 	  charbuf += len;
 	}
diff --git a/src/data.c b/src/data.c
index 88c5a309859..34265b7ecdc 100644
--- a/src/data.c
+++ b/src/data.c
@@ -226,8 +226,9 @@ for example, (type-of 1) returns `integer'.  */)
           return Qfloat;
         case Lisp_Misc_Finalizer:
           return Qfinalizer;
+	default:
+	  emacs_abort ();
 	}
-      emacs_abort ();
 
     case Lisp_Vectorlike:
       if (WINDOW_CONFIGURATIONP (object))
diff --git a/src/dispextern.h b/src/dispextern.h
index e5adeab0dc0..e44b70bf562 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -2378,10 +2378,6 @@ struct it
 	struct it_slice slice;
 	ptrdiff_t image_id;
       } image;
-      /* method == GET_FROM_COMPOSITION */
-      struct {
-	Lisp_Object object;
-      } comp;
       /* method == GET_FROM_STRETCH */
       struct {
 	Lisp_Object object;
diff --git a/src/eval.c b/src/eval.c
index 77d435acbe6..b42f9047257 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -596,6 +596,11 @@ The return value is BASE-VARIABLE.  */)
       error ("Cannot make an internal variable an alias");
     case SYMBOL_LOCALIZED:
       error ("Don't know how to make a localized variable an alias");
+    case SYMBOL_PLAINVAL:
+    case SYMBOL_VARALIAS:
+      break;
+    default:
+      emacs_abort ();
     }
 
   /* http://lists.gnu.org/archive/html/emacs-devel/2008-04/msg00834.html
@@ -640,6 +645,17 @@ default_toplevel_binding (Lisp_Object symbol)
 	  if (EQ (specpdl_symbol (pdl), symbol))
 	    binding = pdl;
 	  break;
+
+	case SPECPDL_UNWIND:
+	case SPECPDL_UNWIND_PTR:
+	case SPECPDL_UNWIND_INT:
+	case SPECPDL_UNWIND_VOID:
+	case SPECPDL_BACKTRACE:
+	case SPECPDL_LET_LOCAL:
+	  break;
+
+	default:
+	  emacs_abort ();
 	}
     }
   return binding;
@@ -3462,6 +3478,17 @@ NFRAMES and BASE specify the activation frame to use, as in `backtrace-frame'.
 	      else
 		result = Fcons (Fcons (sym, val), result);
 	    }
+	    break;
+
+	  case SPECPDL_UNWIND:
+	  case SPECPDL_UNWIND_PTR:
+	  case SPECPDL_UNWIND_INT:
+	  case SPECPDL_UNWIND_VOID:
+	  case SPECPDL_BACKTRACE:
+	    break;
+
+	  default:
+	    emacs_abort ();
 	  }
       }
   }
@@ -3504,6 +3531,14 @@ mark_specpdl (void)
 	  mark_object (specpdl_symbol (pdl));
 	  mark_object (specpdl_old_value (pdl));
 	  break;
+
+	case SPECPDL_UNWIND_PTR:
+	case SPECPDL_UNWIND_INT:
+	case SPECPDL_UNWIND_VOID:
+	  break;
+
+	default:
+	  emacs_abort ();
 	}
     }
 }
diff --git a/src/lisp.h b/src/lisp.h
index acbd679b44b..15fe40db780 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4353,12 +4353,13 @@ INLINE ptrdiff_t
 lisp_word_count (ptrdiff_t nbytes)
 {
   if (-1 >> 1 == -1)
-    switch (word_size)
+    switch (word_size + 0)
       {
       case 2: return nbytes >> 1;
       case 4: return nbytes >> 2;
       case 8: return nbytes >> 3;
       case 16: return nbytes >> 4;
+      default: break;
       }
   return nbytes / word_size - (nbytes % word_size < 0);
 }
diff --git a/src/syntax.c b/src/syntax.c
index de45c50ca3f..55a4ba0abd4 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -2799,12 +2799,8 @@ scan_lists (EMACS_INT from, EMACS_INT count, EMACS_INT depth, bool sexpflag)
 		      : c_code == Sstring_fence)
 		    break;
 
-		  switch (c_code)
-		    {
-		    case Scharquote:
-		    case Sescape:
-		      INC_BOTH (from, from_byte);
-		    }
+		  if (c_code == Scharquote || c_code == Sescape)
+		    INC_BOTH (from, from_byte);
 		  INC_BOTH (from, from_byte);
 		}
 	      INC_BOTH (from, from_byte);
@@ -3419,11 +3415,16 @@ do { prev_from = from;				\
 		  case Sstring_fence:
 		    if (!nofence) goto string_end;
 		    break;
+
 		  case Scharquote:
 		  case Sescape:
 		    INC_FROM;
 		  startquotedinstring:
 		    if (from >= end) goto endquoted;
+		    break;
+
+		  default:
+		    break;
 		  }
 		INC_FROM;
 	      }
diff --git a/src/vm-limit.c b/src/vm-limit.c
index ab102e32623..503aaaebf8a 100644
--- a/src/vm-limit.c
+++ b/src/vm-limit.c
@@ -170,19 +170,13 @@ check_memory_limits (void)
   if (new_warnlevel > warnlevel || new_warnlevel == warned_95)
     {
       warnlevel = new_warnlevel;
-      switch (warnlevel)
+      static char const *const warn_diagnostic[] =
 	{
-	case warned_75:
-	  (*warn_function) ("Warning: past 75% of memory limit");
-	  break;
-
-	case warned_85:
-	  (*warn_function) ("Warning: past 85% of memory limit");
-	  break;
-
-	case warned_95:
-	  (*warn_function) ("Warning: past 95% of memory limit");
-	}
+	  "Warning: past 75% of memory limit",
+	  "Warning: past 85% of memory limit",
+	  "Warning: past 95% of memory limit"
+	};
+      warn_function (warn_diagnostic[warnlevel - 1]);
     }
   /* Handle going down in usage levels, with some hysteresis.  */
   else
diff --git a/src/window.c b/src/window.c
index f6fe0cdb059..f1af68eff18 100644
--- a/src/window.c
+++ b/src/window.c
@@ -1291,10 +1291,18 @@ window_relative_x_coord (struct window *w, enum window_part part, int x)
 	      + window_box_width (w, RIGHT_MARGIN_AREA)
 	      + ((WINDOW_HAS_FRINGES_OUTSIDE_MARGINS (w))
 		 ? WINDOW_RIGHT_FRINGE_WIDTH (w) : 0));
-    }
 
-  /* ON_SCROLL_BAR, ON_NOTHING, and ON_VERTICAL_BORDER:  */
-  return 0;
+    case ON_NOTHING:
+    case ON_VERTICAL_BORDER:
+    case ON_VERTICAL_SCROLL_BAR:
+    case ON_HORIZONTAL_SCROLL_BAR:
+    case ON_RIGHT_DIVIDER:
+    case ON_BOTTOM_DIVIDER:
+      return 0;
+
+    default:
+      emacs_abort ();
+    }
 }
 
 
diff --git a/src/xdisp.c b/src/xdisp.c
index b86307776e2..a3224e2510f 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -5895,6 +5895,13 @@ push_it (struct it *it, struct text_pos *position)
     case GET_FROM_STRETCH:
       p->u.stretch.object = it->object;
       break;
+    case GET_FROM_BUFFER:
+    case GET_FROM_DISPLAY_VECTOR:
+    case GET_FROM_STRING:
+    case GET_FROM_C_STRING:
+      break;
+    default:
+      emacs_abort ();
     }
   p->position = position ? *position : it->position;
   p->current = it->current;
@@ -6017,6 +6024,11 @@ pop_it (struct it *it)
 	  it->method = GET_FROM_BUFFER;
 	  it->object = it->w->contents;
 	}
+      break;
+    case GET_FROM_C_STRING:
+      break;
+    default:
+      emacs_abort ();
     }
   it->end_charpos = p->end_charpos;
   it->string_nchars = p->string_nchars;
diff --git a/src/xterm.c b/src/xterm.c
index 9ee76e967e1..13e1902a0bb 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -5407,6 +5407,8 @@ xg_scroll_callback (GtkRange     *range,
 	      ? scroll_bar_after_handle : scroll_bar_below_handle);
       bar->dragging = -1;
       break;
+    default:
+      break;
     }
 
   if (part != scroll_bar_nowhere)
@@ -10193,6 +10195,9 @@ x_check_fullscreen (struct frame *f)
         case FULLSCREEN_HEIGHT:
           lval = Qfullheight;
           height = x_display_pixel_height (dpyinfo);
+	  break;
+	default:
+	  emacs_abort ();
         }
 
       frame_size_history_add