Thread local storage in C++ language

Introduction

"thread-local storage" is very similar to "global" (or "static storage"), only that instead of "duration of the entire program" you have "duration of the entire thread". So a block-local thread-local variable is initialized the first time control passes through its declaration, but separately within each thread, and it's destroyed when the thread ends.

C++0x introduces the thread_local keyword.

Example

#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; // modifying outside a lock is okay; this is a thread-local variable 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"); { std::lock_guard<std::mutex> lock(cout_mutex); std::cout << "Rage counter for main: " << rage << '\n'; } a.join(); b.join();}

Reference

http://stackoverflow.com/questions/7047226/using-thread-in-c0x

http://en.cppreference.com/w/cpp/language/storage_duration

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