c-opts.c (c_common_finish): Write dependency information even if there are errors.

	* c-opts.c (c_common_finish): Write dependency information even if
	there are errors.

From-SVN: r251605

gcc/c-family/ChangeLog

+2017-09-01  Boris Kolpackov <boris@codesynthesis.com>
+
+	* c-opts.c (c_common_finish): Write dependency information even if
+	there are errors.
+
 2017-09-01  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/81887

gcc/c-family/c-opts.c

@@ -1145,8 +1145,11 @@ c_common_finish (void)
 {
   FILE *deps_stream = NULL;
 
-  /* Don't write the deps file if there are errors.  */
-  if (cpp_opts->deps.style != DEPS_NONE && !seen_error ())
+  /* Note that we write the dependencies even if there are errors. This is
+     useful for handling outdated generated headers that now trigger errors
+     (for example, with #error) which would be resolved by re-generating
+     them. In a sense, this complements -MG.  */
+  if (cpp_opts->deps.style != DEPS_NONE)
     {
       /* If -M or -MM was seen without -MF, default output to the
 	 output stream.  */