re PR c/2098 (compare with unsigned variable - no error reporting)

        PR c/2098
        * c-common.c (shorten_compare): Simplfy conditions leading to
        the generation of a warning.

	* gcc.dg/compare6.c: New.

From-SVN: r52778

gcc/ChangeLog

 2002-04-25  Richard Henderson  <rth@redhat.com>
 
+	PR c/2098
+	* c-common.c (shorten_compare): Simplfy conditions leading to
+	the generation of a warning.
+
+2002-04-25  Richard Henderson  <rth@redhat.com>
+
 	PR c/2035
 	* expmed.c (extract_bit_field): Fall through to generic code rather
 	than aborting on subreg special case.

gcc/c-common.c

@@ -1999,19 +1999,8 @@ shorten_compare (op0_ptr, op1_ptr, restype_ptr, rescode_ptr)
 	  type = c_common_unsigned_type (type);
 	}
 
-      if (!max_gt && !unsignedp0 && TREE_CODE (primop0) != INTEGER_CST)
+      if (TREE_CODE (primop0) != INTEGER_CST)
 	{
-	  /* This is the case of (char)x >?< 0x80, which people used to use
-	     expecting old C compilers to change the 0x80 into -0x80.  */
-	  if (val == boolean_false_node)
-	    warning ("comparison is always false due to limited range of data type");
-	  if (val == boolean_true_node)
-	    warning ("comparison is always true due to limited range of data type");
-	}
-
-      if (!min_lt && unsignedp0 && TREE_CODE (primop0) != INTEGER_CST)
-	{
-	  /* This is the case of (unsigned char)x >?< -1 or < 0.  */
 	  if (val == boolean_false_node)
 	    warning ("comparison is always false due to limited range of data type");
 	  if (val == boolean_true_node)

gcc/testsuite/gcc.dg/compare6.c

+/* PR c/2098 */
+/* Test for a warning on comparison on out-of-range data.  */
+/* { dg-do compile { xfail c4x-*-* } } */
+/* { dg-options "-Wall" } */
+
+signed char sc;
+unsigned char uc;
+
+void foo()
+{
+  if (sc == 10000) return; /* { dg-warning "always false" "signed" } */
+  if (uc == 10000) return; /* { dg-warning "always false" "unsigned" } */
+}