Fix c++/27975.

        * c.opt (Wenum-compare): New warning option.
        * doc/invoke.texi (Warning Options): Document -Wenum-compare.

cp/
        * call.c (build_new_op): Make warning conditional on OPT_Wenum_compare.

testsuite/
        * g++.dg/warn/Wenum-compare.C: New testcase.
        * g++.dg/warn/Wenum-compare-no.C: Ditto.

From-SVN: r136035

gcc/ChangeLog

 2008-05-27  Michael Matz  <matz@suse.de>
 
+	PR c++/27975
+	* c.opt (Wenum-compare): New warning option.
+	* doc/invoke.texi  (Warning Options): Document -Wenum-compare.
+
+2008-05-27  Michael Matz  <matz@suse.de>
+
 	PR middle-end/36326
 	* tree-gimple.c (is_gimple_mem_rhs): Remove work-around for
 	non-BLKmode types.

gcc/c.opt

@@ -195,6 +195,10 @@ Wendif-labels
 C ObjC C++ ObjC++ Warning
 Warn about stray tokens after #elif and #endif
 
+Wenum-compare
+C++ ObjC++ Var(warn_enum_compare) Init(1) Warning
+Warn about comparison of different enum types
+
 Werror
 C ObjC C++ ObjC++
 ; Documented in common.opt

gcc/cp/ChangeLog

+2008-05-27  Michael Matz  <matz@suse.de>
+
+	PR c++/27975
+	* call.c (build_new_op): Make warning conditional on
+	OPT_Wenum_compare.
+
 2008-05-27  Alexandre Oliva  <aoliva@redhat.com>
 
 	PR c++/35909

gcc/cp/call.c

@@ -4004,7 +4004,8 @@ build_new_op (enum tree_code code, int flags, tree arg1, tree arg2, tree arg3,
 		      != TYPE_MAIN_VARIANT (TREE_TYPE (arg2)))
 		  && (complain & tf_warning))
 		{
-		  warning (0, "comparison between %q#T and %q#T",
+		  warning (OPT_Wenum_compare,
+			   "comparison between %q#T and %q#T",
 			   TREE_TYPE (arg1), TREE_TYPE (arg2));
 		}
 	      break;

gcc/doc/invoke.texi

@@ -232,7 +232,7 @@ Objective-C and Objective-C++ Dialects}.
 -Wchar-subscripts -Wclobbered  -Wcomment @gol
 -Wconversion  -Wcoverage-mismatch  -Wno-deprecated  @gol
 -Wno-deprecated-declarations -Wdisabled-optimization  -Wno-div-by-zero  @gol
--Wempty-body  -Wno-endif-labels @gol
+-Wempty-body  -Wenum-compare -Wno-endif-labels @gol
 -Werror  -Werror=* @gol
 -Wfatal-errors  -Wfloat-equal  -Wformat  -Wformat=2 @gol
 -Wno-format-contains-nul -Wno-format-extra-args -Wformat-nonliteral @gol
@@ -3658,6 +3658,11 @@ while} statement.  Additionally, in C++, warn when an empty body occurs
 in a @samp{while} or @samp{for} statement with no whitespacing before
 the semicolon.  This warning is also enabled by @option{-Wextra}.
 
+@item -Wenum-compare @r{(C++ and Objective-C++ only)}
+@opindex Wenum-compare
+@opindex Wno-enum-compare
+Warn about a comparison between values of different enum types.
+
 @item -Wsign-compare
 @opindex Wsign-compare
 @opindex Wno-sign-compare

gcc/testsuite/ChangeLog

+2008-05-27  Michael Matz  <matz@suse.de>
+
+	PR c++/27975
+	* g++.dg/warn/Wenum-compare.C: New testcase.
+	* g++.dg/warn/Wenum-compare-no.C: Ditto.
+
 2008-05-27  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/36339

gcc/testsuite/g++.dg/warn/Wenum-compare-no.C

+/* Test disabling -Wenum-compare (on by default).  See PR27975.  */
+/* { dg-do compile } */
+/* { dg-options "-Wno-enum-compare" } */
+enum E1 { a };
+enum E2 { b };
+
+int foo (E1 e1, E2 e2)
+{
+  return e1 == e2;  /* { dg-bogus "comparison between" } */
+}

gcc/testsuite/g++.dg/warn/Wenum-compare.C

+/* Test that we get the -Wenum-compare by default.  See PR27975.  */
+/* { dg-do compile } */
+/* { dg-options "" } */
+enum E1 { a };
+enum E2 { b };
+
+int foo (E1 e1, E2 e2)
+{
+  return e1 == e2;  /* { dg-warning "comparison between" } */
+}