RE: error C2678 and C2440

["Burkhardt, Glenn" <Glenn dot Burkhardt at goodrich dot com>]

Look at the declaration for 'pthread_t' in pthread.h.  It's a structure,
not a pointer or an integer:

/*
 * Generic handle type - intended to extend uniqueness beyond
 * that available with a simple pointer. It should scale for either
 * IA-32 or IA-64.
 */
typedef struct {
    void * p;                   /* Pointer to actual object */
    unsigned int x;             /* Extra information - reuse count etc
*/
} ptw32_handle_t;

typedef ptw32_handle_t pthread_t;

I can't say I like this either.  All other implementations I've seen use
a pointer for pthread_t.  It must be a Windows thing. 

> -----Original Message-----
> From: pthreads-win32-owner@sourceware.org 
> [mailto:pthreads-win32-owner@sourceware.org] On Behalf Of satish
> Sent: Friday, December 14, 2007 4:11 AM
> To: pthreads-win32@sourceware.org
> Subject: error C2678 and C2440
> 
> Hi,
> I am porting my multi threading(using pthread) Linux project 
> to windows. The compiler is MS VC++ 2005.
> I am using pthread-win32, downloaded from 
> "http://sourceware.org/pthreads-win32/";.
> For version, here is a line from pthread.h "#define 
> PTW32_VERSION 2,7,0,0"
> 
> The project compilation is almost done but I am  getting few 
> errors related to pthread.
> 
> A.:- Have a look on following code,
> ----------------------------------------------------------------
> #define MAXTHREADS 1000
> typedef struct {
> 	pthread_t id;
> 	pthread_mutex_t lock;
> 	pthread_cond_t cond;
> } THREADLIST;
> 
> THREADLIST threads[MAXTHREADS];
> 
> 1281 int thread_find() {
> 1282	int thread = -1;
> 1283	pthread_t self = pthread_self();
> 1284	pthread_mutex_lock(&threadlistlock);
> 1285	for (int i = 0; i < MAXTHREADS; i++) {
> 1286		if (threads[i].flags != THREAD_UNUSED && 
> threads[i].id ==
> self)				1287				
> thread = i;
> 1288			break;
> 1289		}
> 1290	}
> 1291	pthread_mutex_unlock(&threadlistlock);
> 1292	return thread;
> 1293 }
> ----------------------------------------------------------------
> 
> The error, I am getting is,
> 
> 1>main.cpp(1286) : error C2678: binary '==' : no operator found which
> takes a left-hand operand of type 'pthread_t' (or there is no 
> acceptable conversion)
> 1> c:\program files\microsoft visual studio
> 8\vc\platformsdk\include\guiddef.h(192): could be 'int 
> operator ==(const GUID &,const GUID &)'
> 1> while trying to match the argument list '(pthread_t, pthread_t)'
> 
> 
> B.:- Another piece of code on which I am getting error is,
> ----------------------------------------------------------------
> 50 unsigned long MY_pthreads_thread_id(void)
> 51 {
> 52    int ret;
> 53	ret = pthread_self();
> 54	return (ret);
> 55 }
> ----------------------------------------------------------------
> Here, it gives error like,
> 
> 1>main.cpp(53) : error C2440: '=' : cannot convert from 
> 'pthread_t' to 'int'
> 
> Can you please tell me the reason behind these errors?
> I will be very thankful to you.
> 
> Regards
> Satish
>