fdiagnostics-color=never does not disable color for some diagnostics

Actually, I was trying to reject non-warning options as argument to
-Werror=. However, the new test fails because -fdiagnostics-color=never is
always placed by the driver after the warning options when calling the compiler
proper. This patch prunes all -fdiagnostics-color from the command-line but the
last one, which is moved to the first position.

gcc/ChangeLog:

2015-09-24  Manuel López-Ibáñez  <manu@gcc.gnu.org>

	PR driver/67640
	* opts-common.c (prune_options): Discard all -fdiagnostics-color
	but the last one, which is moved to the front to be processed
	first.
	* opts.c (enable_warning_as_error): Reject options that do not
	control warnings.

gcc/testsuite/ChangeLog:

2015-09-24  Manuel López-Ibáñez  <manu@gcc.gnu.org>

	PR driver/67640
	* gcc.dg/Werror-13.c: New test.

From-SVN: r228094

1 files changed, 4 insertions, 3 deletions

diff --git a/gcc/opts.c b/gcc/opts.c
index f1a9acd..b437114 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -2359,9 +2359,10 @@ enable_warning_as_error (const char *arg, int value, unsigned int lang_mask,
   strcpy (new_option + 1, arg);
   option_index = find_opt (new_option, lang_mask);
   if (option_index == OPT_SPECIAL_unknown)
-    {
-      error_at (loc, "-Werror=%s: no option -%s", arg, new_option);
-    }
+    error_at (loc, "-Werror=%s: no option -%s", arg, new_option);
+  else if (!(cl_options[option_index].flags & CL_WARNING))
+    error_at (loc, "-Werror=%s: -%s is not an option that controls warnings",
+	      arg, new_option);
   else
     {
       const diagnostic_t kind = value ? DK_ERROR : DK_WARNING;