The boost::signals2::keywords namespace contains classes that make it possible to pass template parameters by name. Fortunately, Boost.Signals2 offers a simpler way to disable synchronization than passing the complete list of parameters. Out of the many template parameters supported by boost::signals2::signal, the last one defines the type of mutex used for synchronization. Typedef keywords::mutex_type dummy_mutex To avoid having the two threads interrupt each other while writing to standard output, a mutex is used to synchronize access to std::cout.įor single-threaded applications, support for multithreading can be disabled in Boost.Signals2. Because two threads access s, the associated lambda function runs in parallel in two threads. However, Example 67.17 still requires synchronization. However, because boost::signals2::signal can be accessed from different threads, the program will not crash. Because i is incremented in two threads and written to the standard output stream in the lambda function, the numbers will not only be displayed twice, they will also overlap. Boost.Signals2 explicitly supports simultaneous access from different threads to objects of type boost::signals2::signal.Įxample 67.17 displays numbers from 0 to 99. Example 67.17 creates two threads that execute the loop() function, which accesses s one hundred times to call the associated lambda function.
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