sij/mapnik
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

implement DCLP using c++11 (http://preshing.com/20130930/double-checked-locking-is-fixed-in-cpp11/)

Browse source 
ref #2838
This commit is contained in:
artemp 2015-06-02 10:24:38 +01:00
parent c399469d95
commit b3af8bd5f9
1 changed files with 32 additions and 29 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

19
include/mapnik/utils.hpp
View file

@ -29,7 +29,7 @@
#include <stdexcept> // std::runtime_error
#include <cstdlib> // std::atexit
#include <new> // operator new
#include <atomic>
#ifdef MAPNIK_THREADSAFE
#include <mutex>
#endif
@ -93,7 +93,7 @@ template <typename T,
{
#endif
friend class CreatePolicy<T>;
static T* pInstance_;
static std::atomic<T*> pInstance_;
static bool destroyed_;
singleton(const singleton &rhs);
singleton& operator=(const singleton&);
@ -116,15 +116,18 @@ protected:
static std::mutex mutex_;
#endif
singleton() {}
public:
static T& instance()
{
if (! pInstance_)
T * tmp = pInstance_.load(std::memory_order_acquire);
if (tmp == nullptr)
{
#ifdef MAPNIK_THREADSAFE
std::lock_guard<std::mutex> lock(mutex_);
#endif
if (! pInstance_)
tmp = pInstance_.load(std::memory_order_relaxed);
if (tmp == nullptr)
{
if (destroyed_)
{
@ -133,14 +136,14 @@ protected:
}
else
{
pInstance_ = CreatePolicy<T>::create();
tmp = CreatePolicy<T>::create();
pInstance_.store(tmp, std::memory_order_release);
// register destruction
std::atexit(&DestroySingleton);
}
}
}
return *pInstance_;
return *tmp;
}
};
@ -150,7 +153,7 @@ protected:
#endif
template <typename T,
template <typename U> class CreatePolicy> T* singleton<T,CreatePolicy>::pInstance_=0;
template <typename U> class CreatePolicy> std::atomic<T*> singleton<T,CreatePolicy>::pInstance_;
template <typename T,
template <typename U> class CreatePolicy> bool singleton<T,CreatePolicy>::destroyed_=false;