Fix README.md for linking with GCC >4 on Linux with Clang

Change-Id: Id0d1e4e5bc10adef96dd1d3afa65e3e4247f5815
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

1 files changed, 17 insertions, 0 deletions

diff --git a/README.md b/README.md
index 3fc07539e3..275a3e1f00 100644
--- a/README.md
+++ b/README.md
@@ -216,6 +216,23 @@ shipped together with Qt Creator. In addition, the packages for Windows are
 faster due to profile-guided optimization. If the prebuilt packages do not
 match your configuration, you need to build LLVM/Clang manually.
 
+If you use GCC 5 or higher on Linux, please do not use our LLVM package, but get
+the package for your distribution. Our LLVM package is compiled with GCC 4, so
+you get linking errors, because GCC 5 is using a C++ 11 conforming string
+implementation, which is not used by GCC 4. To sum it up, do not mix GCC 5 and
+GCC 4 binaries. On Ubuntu, you can download the package from
+http://apt.llvm.org/ with:
+
+   wget -O - http://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
+   sudo apt-add-repository "deb http://apt.llvm.org/`lsb_release -cs`/ llvm-toolchain-`lsb_release -cs`-3.9 main"
+   sudo apt-get update
+   sudo apt-get install libclang-3.9-dev
+
+There is a workaround to set _GLIBCXX_USE_CXX11_ABI to 1 or 0, but we recommend
+to download the package from http://apt.llvm.org/.
+
+   https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html
+
 ### Building LLVM/Clang manually
 
 You need to install CMake in order to build LLVM/Clang.