How to allocate thread local storage?

Question

I have a variable in my function that is static, but I would like it to be static on a per thread basis.

How can I allocate the memory for my C++ class such that each thread has its own copy of the class instance?

AnotherClass::threadSpecificAction() {   // How to allocate this with thread local storage?   static MyClass *instance = new MyClass();    instance->doSomething(); } 

This is on Linux. I'm not using C++0x and this is gcc v3.4.6.

Answer 1

#include <boost/thread/tss.hpp> static boost::thread_specific_ptr< MyClass> instance; if( ! instance.get() ) {     // first time called by this thread     // construct test element to be used in all subsequent calls from this thread     instance.reset( new MyClass); }     instance->doSomething(); 

Answer 2

It is worth noting that C++11 introduces the thread_local keyword.

Here is an example from Storage duration specifiers:

#include <iostream> #include <string> #include <thread> #include <mutex>  thread_local unsigned int rage = 1;  std::mutex cout_mutex;  void increase_rage(const std::string& thread_name) {     ++rage;     std::lock_guard<std::mutex> lock(cout_mutex);     std::cout << "Rage counter for " << thread_name << ": " << rage << '\n'; }  int main() {     std::thread a(increase_rage, "a"), b(increase_rage, "b");     increase_rage("main");      a.join();     b.join();      return 0; } 

Possible output:

Rage counter for a: 2 Rage counter for main: 2 Rage counter for b: 2