added a comment (see #109)

README.md

@@ -46,6 +46,8 @@ Though it's 2015 already, the support for C++11 is still a bit sparse. Currently
 - Clang 3.4 - 3.7
 - Microsoft Visual C++ 14.0 RC
 
+Note using GCC 4.8, the unit tests cannot be compiled due to a [bug in the preprocessor](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55971).
+
 I would be happy to learn about other compilers/versions.
 
 ## Examples