Yearly Archives: 2013

Using C++11 on Mac OS X 10.8

Recent Xcode versions for Mac OS X 10.7 and 10.8 ship with Clang, a modern compiler for C/C++/ObjC based on LLVM. It fully supports C++11: simply add -std=c++0x or -std=c++11 to your CXXFLAGS. This already gives you all the new language features such as the auto keyword.

However, when you get more in-depth with C++, you’ll also want to use the new features of the standard library, such as <array> or <random>.  This however results in strange error messages:

gamelogic/Board.cpp:11:10: fatal error: 'random' file not found
#include <random>

As it turns out, your binaries get linked to the system-default libstdc++ version (/usr/lib/libstdc++.6.dylib) which is too old to support C++11. However, Mac OS X also includes libc++ (/usr/lib/libc++.1.dylib), a complete reimplementation of the standard library by the LLVM team that is fully C++11 compatible. Simply tell the compiler to use it using -stdlib=libc++ and tell the linker to link against it using -lc++.

So for a qmake .pro project file, all this might look as follows. The conditional makes it compatible with other compilers such as g++ on Linux that already ship with a C++11-compatible standard library.

QMAKE_CXXFLAGS += -std=c++0x
macx {
 contains(QMAKE_CXX, /usr/bin/clang++) {
  message(Using LLVM libc++)
  QMAKE_CXXFLAGS += -stdlib=libc++
  QMAKE_LFLAGS += -lc++

UPDATE 2016: Mac OS X 10.9 and higher default to libc++ and don’t require the extra compiler flag. Since Mac OS X 10.8 is out of support anyway, there is no reason to use the flag anymore.

OpenVPN for iOS

Today, OpenVPN Technologies released OpenVPN Connect for iOS. Finally, we can use OpenVPN on all major platforms. I know many of my blog readers have been waiting for this: my article on the iOS VPN API is one of the most popular articles on my blog.

OpenVPN Connect is not based on the classic GPL OpenVPN software (supposedly GPL and App Store are not compatible), but supposed to be fully compatible with any OpenVPN server running version 2.1 or higher (including IPv6 support with servers running the recently-released version 2.3). Supposedly it can even be managed using the “Custom SSL” option in iPhone Configuration Utility.

Two points I’d like to mention which might temporarily disappoint some people:

  • It currently requires client certificates (but the help promises that that’ll change soon).
  • Layer 2 tap interfaces are not supported. As I noted in my VPN API blog post, iOS provides a utun interface, which only does layer 3.

Go check it out on the App Store or have a look at Gert Döring’s Google+ post.

Update December 2013: Version 1.0.2 (just released) finally works for me. 1.0.0 didn’t work without client certificates and 1.0.1 had some weird SSL library issue where it would reject my server certificate. In 1.0.2 I was  able to just drop my .ovpn file into iTunes and was up and running immediately, including IPv6 support.