fix warnings in unwind-dw2.c

[Zack Weinberg <zackw at panix dot com>]

This patch silences a warning about a variable used uninitialized in
unwind-dw2.c.  The issue is that we have nested switch statements of
the form

	switch (op) { 
	case a: case b: case c:
		common_code();
		switch (op) {
		case a:	result = code_a();
		case b: result = code_b();
		case c: result = code_c();
		}
	default:  abort();
	}

	use(result);

GCC doesn't know that control cannot reach the inner switch unless op
is one of a, b, c, so it thinks there is a code path reaching the use
on which result is not initialized.

The patch just adds default: abort(); to the inner switches to nullify
the bogus code paths.

zw

	* unwind-dw2.c (execute_stack_op): Add default aborts to
	the inner switches to prevent warnings.

===================================================================
Index: unwind-dw2.c
--- unwind-dw2.c	2001/08/17 21:23:12	1.6
+++ unwind-dw2.c	2001/08/18 21:31:08
@@ -563,6 +563,9 @@ execute_stack_op (const unsigned char *o
 	      op_ptr = read_uleb128 (op_ptr, &ptrtmp); reg = ptrtmp;
 	      result += reg;
 	      break;
+
+	    default:
+	      abort ();
 	    }
 	  break;
 
@@ -640,6 +643,9 @@ execute_stack_op (const unsigned char *o
 	    case DW_OP_ne:
 	      result = (_Unwind_Sword)first != (_Unwind_Sword)second;
 	      break;
+
+	    default:
+	      abort ();
 	    }
 	  }
 	  break;