我对boost :: threads很新,我阅读了文档,但是我在实践中应用它有些麻烦,也许你可以帮忙吗?首先,我花时间编写了一个自包含的代码清单,演示了两种我无法理解的行为……
该程序允许用户发出3个不同的命令,
目的是任务将在新线程上启动一些工作,但在执行工作时返回到命令提示符.用户可以使用info命令找出哪些任务已完成,哪些未完成.
我使用双核Win7机器和Visual Studio 2008 Express.
问题1>
发出命令,任务p1 p2 p3,启动3个任务正在运行.这可以通过发布信息来检查.几秒钟后,工作完成,但由于某种原因,完成的标志并不总是在1或2个任务上设置为true.
问题2>
Windows has triggered a breakpoint in example.exe. This may be due to a corruption of the heap,which indicates a bug in example.exe or any of the DLLs it has loaded.
This may also be due to the user pressing F12 while example.exe has focus.
The output window may have more diagnostic information.
希望您可以重现此行为并提供帮助.
提前致谢.
亚历克斯.
//WARNING: THIS CODE DOES NOT BEHAVE EXACTLY AS INTENDED #include <iostream> #include <string> #include <sstream> #include <boost/thread.hpp> using namespace std; class task { public: string mname; bool completed; void start() { int a = 0; for (int i=0 ; i<10000; i++) { for (int j=0 ; j<100000; j++) { a= i*2; } } this->completed = true; } task(string name) { mname = name; completed = false; } }; class taskManager{ public: boost::thread_group threads; void startTask( string name ) { //add new task to vector list mtasks.push_back( task(name) ); // execute start() on a new thread threads.create_thread( boost::bind( &task::start,&mtasks.back()) ); } int tasksTotal() { return mtasks.size(); } string taskInfo(int i) { string compstr("Not Completed"); if ( mtasks[i].completed == true ) { compstr = "Completed"; } return mtasks[i].mname + " " + compstr; } private: vector<task> mtasks; }; int main(int argc,char* argv[]) { string cmd,temp; stringstream os; bool quit = false; taskManager mm; cout << "PROMPT>"; while (quit == false) { //Wait for a valid command from user getline(cin,cmd); // Reset stringstream and assign new cmd string os.clear(); os << ""; os << cmd; //parse input string while (os >> temp) { if ( temp.compare("task") == 0 ) { while (os >> temp) { mm.startTask( temp ); } } if ( temp.compare("info") == 0 ) { // Returns a list of all completed and not completed tasks for (int i = 0; i<mm.tasksTotal(); i++) { cout << mm.taskInfo(i).c_str() << endl; } } if ( temp.compare("quit") == 0 ){ quit = true; } } cout << "PROMPT>"; } mm.threads.join_all(); return 0; };@H_301_32@
解决方法
您在taskManager :: startTask方法中的代码存在问题:
mtasks.push_back( task(name) ); // execute start() on a new thread threads.create_thread( boost::bind( &task::start,&mtasks.back())@H_301_32@这里的问题是,在推回新任务时,您的向量可能必须重新分配一些空间,这样会使对旧向量元素的引用无效,例如以下对taskinfo的调用将引用错误的元素.当你删除旧元素时,你的堆会以某种方式被破坏.
一个简单的解决方法是在taskManager类的构造函数中为向量保留一些空间,但是您应该更改任务/任务管理器模型的设计.另一种方法是使用std :: deque,因为它不会重新分配内存.