From c8df88d8c61197d8f019efa0ba373ed14a28d914 Mon Sep 17 00:00:00 2001
From: Bardur Arantsson <bardur@scientician.net>
Date: Tue, 29 Mar 2016 20:32:55 +0200
Subject: Introduce new way of handling flags

---
 src/include/tome/pp/global_constexpr.hpp | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 src/include/tome/pp/global_constexpr.hpp

(limited to 'src/include/tome/pp/global_constexpr.hpp')

diff --git a/src/include/tome/pp/global_constexpr.hpp b/src/include/tome/pp/global_constexpr.hpp
new file mode 100644
index 00000000..83168c59
--- /dev/null
+++ b/src/include/tome/pp/global_constexpr.hpp
@@ -0,0 +1,21 @@
+#pragma once
+
+/**
+ * Macro for declaring a global constexpr variable without
+ * violating the ODR and without running into the SIOF.
+ *
+ * Shamelessly cribbed from http://stackoverflow.com/a/20374473
+ */
+#define PP_GLOBAL_CONSTEXPR_CONST(type, var, value)                      \
+namespace global_constexpr { namespace var {                             \
+template<class = void>                                                   \
+struct wrapper                                                           \
+{                                                                        \
+     static constexpr type var = value;                                  \
+};                                                                       \
+template<class T>                                                        \
+constexpr type wrapper<T>::var;                                          \
+} }                                                                      \
+namespace {                                                              \
+auto const& var = global_constexpr::var::wrapper<>::var;                 \
+}
-- 
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