Re: Local Variable in Thread

SG <>
Mon, 13 Dec 2010 06:45:06 -0800 (PST)
On 13 Dez., 15:08, Manoj wrote:

  void ThreadCS(void* lp)
      const string str = string((char*) lp);

  int _tmain(int argc, _TCHAR* argv[])

        char szStr[99];

      for(int i=0; i<numThreads; i++)
          _beginthread(ThreadCS, 0, szStr);

Any clue ?

Give each thread a copy of the string instead of just a pointer. Using
a decent thread library (like Boost.Thread) it might look as simple as

   void my_thread_func(string const& s)
       lock lck (cout_mutex);
       cout << s << '\n';

   int main() {
       string foo = "hello";
       thread t1 ( boost::bind(my_thread_func,foo) );
       foo = "world";
       thread t2 ( boost::bind(my_thread_func,foo) );

boost::bind yields a function object that stores a copy of foo in this
case. The thread's constructor stores a copy of the function object
somewhere safe, starts the thread and disposes the function object
automatically. But passing a reference to foo is also possible.
Replace foo within bind with cref(foo) where cref is a function
template from Boost.Ref (reference wrappers).

If for some reason you cannot use a decent thread library, you have to
dynamically create copies of the string, pass a pointer to the copy to
the thread and let the thread delete the copy again.

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