cpuid: add null fallback

CMakeLists.txt

@@ -194,7 +194,11 @@ if (host_cpu STREQUAL "x86_64")
         cpuid/x86.hpp
     )
 else ()
-    message (FATAL_ERROR "Unknown architecture ${host_cpu}")
+    message (WARNING "Unknown architecture ${host_cpu}. Defaulting to null implementation")
+    list (APPEND UTIL_FILES
+        cpuid/none.cpp
+        cpuid/none.hpp
+    )
 endif ()
 
 

cpuid/none.cpp

@@ -0,0 +1,19 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2019 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "none.hpp"
+
+#include <ostream>
+
+
+///////////////////////////////////////////////////////////////////////////////
+std::ostream&
+cruft::cpu::operator<< (std::ostream &os, none const &)
+{
+    return os << "{ }";
+}

cpuid/none.hpp

@@ -0,0 +1,17 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2019 Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include <iosfwd>
+
+namespace cruft::cpu {
+    struct none { };
+
+    std::ostream& operator<< (std::ostream &os, none const &);
+};