Merge branch 'master' into dgit/siddebian/2.4.0-ah-1archive/debian/2.4.0-ah-1

1 files changed, 21 insertions, 0 deletions

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;                 \
+}