threading from a static member in dll - multithreading

Question

I have a problem lunching a thread within a class A for example where the class A is a static member of class B with in a dll. I am using Visual Studio 9 and boost 1.40. Please consider the following code:
mylib.h:
#include <boost/thread.hpp>
#include <windows.h>
#ifdef FOO_STATIC
#define FOO_API
#else
#ifdef FOO_EXPORT
#define FOO_API __declspec(dllexport)
#else
#define FOO_API __declspec(dllimport)
#endif
#endif
class FOO_API foo{
boost::thread* thrd;
public:
foo();
~foo();
void do_work();
};
class FOO_API bar{
static foo f;
public:
static foo& instance();
};
mylib.cpp:
#include "mylib.h"
foo::foo()
{
thrd = new boost::thread(boost::bind(&foo::do_work,this));
}
foo::~foo(){
thrd->join();
delete thrd;
}
void foo::do_work(){
printf("doing some works\n");
}
foo& bar::instance(){return f;}
foo bar::f;
in the executable application, I have:
main.cpp:
#include "mylib.h"
void main(){
bar::instance();
}
If I link mylib statically to the executable app, It prints out "doing some works", while if I link it dynamically (dll), it does nothing.
I really appreciate any help.

Answer 1

Your program could be exiting before the thread completes. You might try waiting after the bar::instance() call, or joining the thread in main. Something else to try would be to flush stdout after the printf call.

Answer 2

From the MSDN documentation:
If your DLL is linked with the C
run-time library (CRT), the entry
point provided by the CRT calls the
constructors and destructors for
global and static C++ objects.
Therefore, these restrictions (*) for
DllMain also apply to constructors and
destructors and any code that is
called from them.
(*) The restrictions include communicating with threads.
It's best to make the global variable a pointer, and construct and release the object in dedicated callback routines.
See also this helpful SO answer.