[PATCH] Fix crash with --help=^ (PR driver/71063)

[Marek Polacek]

We crashed when given --help=^ and Kyrill explained why in the PR
(<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71063#c2>).  The following
seems as good a fix as any, I think.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2016-05-11  Marek Polacek  <polacek@redhat.com>

	PR driver/71063
	* opts.c (common_handle_option): Detect missing argument for --help^.

	* gcc.dg/opts-7.c: New test.

diff --git gcc/opts.c gcc/opts.c
index 0f9431a..71e0779 100644
--- gcc/opts.c
+++ gcc/opts.c
@@ -1640,6 +1640,11 @@ common_handle_option (struct gcc_options *opts,
 	    if (* a == '^')
 	      {
 		++ a;
+		if (*a == '\0')
+		  {
+		    error_at (loc, "missing argument to %qs", "--help=^");
+		    break;
+		  }
 		pflags = & exclude_flags;
 	      }
 	    else
diff --git gcc/testsuite/gcc.dg/opts-7.c gcc/testsuite/gcc.dg/opts-7.c
index e69de29..c54d0b8 100644
--- gcc/testsuite/gcc.dg/opts-7.c
+++ gcc/testsuite/gcc.dg/opts-7.c
@@ -0,0 +1,6 @@
+/* PR driver/71063 */
+/* Test we don't ICE.  */
+/* { dg-do compile } */
+/* { dg-options "--help=^" } */
+
+/* { dg-error "missing argument to" "" { target *-*-* } 0 } */

	Marek