使用windowsthreads编程-杨全胜.ppt

* Thread handles left lying around take up memory space. Continuously creating threads without cleaning up the handles when done, could lead to a memory leak. Another possibility would be that the maximum number of threads that can be supported within a process will be reached and no more new threads will be able to be created. Clean up after your threads!! Examples within this talk don’t use this since they are so small and the exit of the process will do the resource reclamation automatically. * ExitThread always kill the thread it called. TerminateThread can kill all kind of Thread. * The independent task in this example is to print the phrase Hello Thread encapsulated into the helloFunc() function. The DWORD WINAPI declaration specifies that this function can be mapped to a thread when you call the CreateThread() function. When the program starts execution, the main (process) thread begins execution of the main() function. The main thread creates a child thread that will execute the helloFunc() function. After creation of the helloFunc thread, the main thread encounters the program termination, which will destroy all the child threads. If the created thread does not have enough time to print Hello Thread before the main thread exits, nothing will be printed from execution of this application. The main thread holds the process information. When the process terminates, all the threads terminate. Therefore, to ensure that the desired printing is accomplished, the main thread must wait for the created thread to finish before it exits. Therefore, to avoid writing applications that spawn threads and end before any useful work begins; you need a mechanism to wait for threads to finish their processing. Question for Discussion: What are the possible outcomes for the above code? Answer: Two possible outcomes: Message Hello Thread is printed on screen. Nothing printed on screen. This outcome is more likely that previous. Main thread is the process and when the