MinGW std::thread fix

I talked earlier about a basic fix for MinGW enabling the use of std::thread and friends in MinGW. Since I will probably use them a lot, I wrote a small header file which does the work for you. It is available on github as a gist : https://gist.github.com/1154023

Since I believe people are too lazy to click links, and also because I want my blog to appear to have a lot of code in it, you will also find it just below:

/* Only use the code below if we have GCC with no support for GNU
 * threads 
 */
#if !defined(_GLIBCXX_HAS_GTHREADS) && defined(__GNUG__)

/* The boost thread library is used as a replacement for the
 * standard thread library. We'll consider it to be fully 
 * compatible with the missing library. See http://www.open-std.org/
 * ...jtc1/sc22/wg21/docs/papers/2008/n2497.html
 */

#include <boost/thread/thread.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/recursive_mutex.hpp>
#include <boost/thread/locks.hpp>
#include <boost/thread/condition_variable.hpp>

/* Only classes are copied. Use boost directly or a real standard
 * library if you want free functions.
 */

namespace std {
  using boost::thread;
  
  using boost::mutex;
  using boost::timed_mutex;
  using boost::recursive_mutex;
  using boost::recursive_timed_mutex;
  
  using boost::lock_guard;
  using boost::unique_lock;
  
  using boost::condition_variable;
  using boost::condition_variable_any;
}

#endif /* Crippled GCC */

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C++11 standard library threads with MinGW

When trying to compile a C++11-enable application under MinGW, I ran into a strange error.

bougabouga.cpp:42:1: error: 'mutex' in namespace 'std' does not name a type

What ? Did my fellow programmer, who gave me this code, made a typo ? Or forgot to #include some files ? Not at all. Let's consider this simple piece of code :

#include <mutex>
std::mutex mutex;

Well, isn't that something simple. But still, it won't compile, complaining about this missing std::mutex we just added to the namespace chain. So let's see what happens in this header file :

On line 50, we may have found our culprit :

#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)

This macro wraps the entire source file. So, do we have them ? The answer is yes, we have this stdint macro, but no, we don't have GNU threads. Simply because MinGW has no support for these. So instead of issuing an error, this header file happily discards all its content. This is unexpected behaviour, but it will be helpful when the time comes to make a workaround for that.

And this workaround is, as always, to rely on good ol' boost. Many classes of the standard thread library (If not all, but I did not have read the specs) can be easily replaced with the boost ones. So, a fix header file would look like that :

#include <boost/thread.hpp>

namespace std {
  using boost::mutex;
  using boost::recursive_mutex;
  using boost::lock_guard;
  using boost::condition_variable;
  using boost::unique_lock;
  using boost::thread;
}


Isn't that pretty ? You don't even have to change your code. Now you have several options : either you add it to a central header file (If you're the StdAfx.h type, you're lucky), or you add it either manually or with a script to your source files, or you modify your gcc header files (they are useless anyway). Keep in mind that you will still need to add the boost thread library at link time.

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