Thread: Strange type incompatibility using function pointers

  1. #1
    Registered User
    Join Date
    May 2006

    Strange type incompatibility using function pointers

    Hey guys/girls ! I'm programming an application for which I have built classes ThreadedWorker and ThreadedWorkerManager. The ThreadedWorkerManager class needs to have a pointer to the callback function that will be used by the CreateThread() function. To lighten up a little bit the code, I have typedef'ed the function pointer and named it THREAD_PROC. The constructor of my ThreadedWorkerManager class takes a THREAD_PROC as only argument and later uses it. However, when I instantiate it, I get the following error:

    'ThreadedWorkerManager<T>::ThreadedWorkerManager(THREAD_FUNC)' : cannot convert parameter 1 from 'DWORD (void *)' to 'THREAD_FUNC'
                T=WorkData *
    I don't quite get why it complains, here's part of the code for ThreadedWorkerManager:
    typedef DWORD (*THREAD_FUNC)(void*);
    template <typename T> class ThreadedWorkerManager;
    template <typename T> class ThreadedWorker;
    template <typename T>
    class ThreadedWorkerManager {
    	ThreadedWorkerManager(THREAD_FUNC ptr = 0) : WorkerProc(ptr) {
    		// ...
    	// ...
    	THREAD_FUNC WorkerProc;
    And this, is where the error occurs:
    DWORD WINAPI ThreadProc(void* data) {
    	// ...
    SettingsManager::SettingsManager() {
    	// Bang ! I'm dead !
    	TWMgr = new ThreadedWorkerManager<WorkData*>(ThreadProc);
    	// ...
    Do you guys have any idea of what could cause this error ? My friend and I are stumped and can't get how this is wrong.


    PS: I'm using MSVC++ 7.1

  2. #2
    Registered User Tonto's Avatar
    Join Date
    Jun 2005
    New York
    That WINAPI changes it (__stdcall, default is __cdecl).

  3. #3
    Yes, my avatar is stolen anonytmouse's Avatar
    Join Date
    Dec 2002
    Your calling conventions don't match. The typedef needs to be:
    typedef DWORD (WINAPI *THREAD_FUNC)(void*);

  4. #4
    Registered User
    Join Date
    May 2006
    Thanks. I fixed the other dozen of errors and now I'm ready to test. Lots of fun predicted -.-

    Ahah, thanks again mates.

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