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C++11 Threads

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I was just brushing up on some C++11 concepts the last few nights (looking for parts of the engine to improve) and noticed quite a few people struggling with threads inside classes, as in using a class object as a thread. Some of the responses were so confusing to say the least.

Also they were struggling with std::cout while threads were running. So here's some example code of these problems all in one. I hope it points someone in the right direction.

lsThread2.h / .cpp
lsThread.h / .cpp
core.h / .cpp
main.cpp// file : core.h#ifndef cppThreads_core_h#define cppThreads_core_h#include #include #include #include using namespace std;/*! Base class Used to start some lsThread objects. */class core{public: core(); virtual ~core(); void run(); void logText( const string& val, int tid ); private: int nr_threads; mutex m;};#endif// file : core.cpp?#include "core.h"#include "lsThread.h"core::core(){ nr_threads = 10;}core::~core(){}void core::run(){ cout << "########## Start test ##########" << endl; vector th; lsThread *mt = new lsThread[nr_threads]; //Launch a group of threads for( int i = 0; i < nr_threads; ++i ) { mt.setTid( i ); // Shows how to pass args to the start function in lsThread th.push_back( thread( &lsThread::start, mt, this, 5 ) ); } //Join the threads with the main thread which core is running for( auto &t : th ) { t.join(); } // delete our array of lsThread objects delete [] mt; cout << "########## End test ##########" << endl;}/*! Logging This function is here so its in a common thread for all other threads to call. Remember in a real world App you would make a better logger. */void core::logText( const string& val, int tid ){ // Lock for output m.lock(); cout << "Thread : " << tid << " - " << val << endl; m.unlock();}

Above: a base class that runs in the main thread.// file : lsThread.h?#ifndef cppThreads_lsThread_h#define cppThreads_lsThread_h#include #include #include class core;using namespace std;/*! Thread class Nothing special about this class, you could thread any class. */class lsThread{public: lsThread(); virtual ~lsThread(); virtual void start( core *c, int val ); void setTid( int val ) { tid = val; } private: int tid; };#endif// File : lsThread.cpp#include "core.h"#include "lsThread.h"#include "lsThread2.h"lsThread::lsThread(){ tid = 0;}lsThread::~lsThread(){}void lsThread::start( core *c, int val ){ c->logText( "lsThread start", tid ); // Here we create some more threads with a new class, based on the passed value. vector th; int nr_threads = val; lsThread2 *mt = new lsThread2[nr_threads]; //Launch a group of threads for( int i = 0; i < nr_threads; ++i ) { mt.setTid( i ); th.push_back( thread( &lsThread2::start, mt, c ) ); } // Join the threads with the current thread // This could be any of the threads created by the core class. for( auto &t : th ) { t.join(); } // delete our array of lsThread2 objects. delete [] mt;}

Above: This class show how to launch more threads inside the current thread.
// File : lsThread2.h#ifndef cppThreads_lsThread2_h#define cppThreads_lsThread2_h#include #include #include class core;using namespace std;class lsThread2{public: lsThread2(); virtual ~lsThread2(); virtual void start( core *c ); void setTid( int val ) { tid = val; } private: int tid;};#endif// File : lsThread2.cpp#include "core.h"#include "lsThread2.h"lsThread2::lsThread2(){ tid = 0;}lsThread2::~lsThread2(){}void lsThread2::start( core *c ){ // In this thread we just call the core class logging function c->logText( "lsThread2 start", tid );}

Above: Simple thread that will just output a message to stdout.// File : main.cpp#include "core.h"int main(int argc, const char * argv[]){ // Thread demo core *c = new core(); c->run(); delete c; return 0;}

Above: And last but not least the main()

I've kept this example as simple as possible but still trying to show as much as possible. Hope it helps someone.

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Is this straight c/c++? What does

for( auto &t : th )


What about


How can you use that as an argument?


[edit] Oh, C++11

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Yes its C++11, I might add some more comments to the code soon if anyone wants me too.

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