common.opt (undef): New.

	* common.opt (undef): New.

testsuite:
	* gcc.dg/cpp/undef-opt-1.c: New test.

From-SVN: r164599

gcc/ChangeLog

+2010-09-24  Joseph Myers  <joseph@codesourcery.com>
+
+	* common.opt (undef): New.
+
 2010-09-24  Jakub Jelinek  <jakub@redhat.com>
 
 	PR middle-end/45234

gcc/common.opt

@@ -1924,6 +1924,10 @@ Driver JoinedOrMissing
 u
 Driver Joined Separate
 
+undef
+Driver
+; C option, but driver must not handle as "-u ndef".
+
 v
 Driver
 

gcc/testsuite/ChangeLog

+2010-09-24  Joseph Myers  <joseph@codesourcery.com>
+
+	* gcc.dg/cpp/undef-opt-1.c: New test.
+
 2010-09-24  Jason Merrill  <jason@redhat.com>
 
 	* g++.dg/other/error10.C: Adjust expected output.

gcc/testsuite/gcc.dg/cpp/undef-opt-1.c

+/* Test -undef.  A bug in its handling broke glibc builds because
+   "linux" was wrongly defined.  */
+/* { dg-do preprocess } */
+/* { dg-options "-undef" } */
+
+#ifdef linux
+#error -undef broken
+#endif