Fix Windows threading for MinGW builds

- Fix pthread_create macro: cast thread_func to LPTHREAD_START_ROUTINE
  and properly check for CreateThread failure (returns NULL)
- Fix pthread_mutex_trylock macro: use 0 instead of NULL for timeout
- Extend N2N_THREAD_RETURN_DATATYPE and N2N_THREAD_PARAMETER_DATATYPE
  definitions to also apply to __MINGW32__, not just _MSC_VER

Made-with: Cursor

Author: mchsk

include/n2n_define.h

@@ -196,7 +196,7 @@ enum skip_add {SN_ADD = 0, SN_ADD_SKIP = 1, SN_ADD_ADDED = 2};
 #define N2N_IFNAMSIZ               16 /* 15 chars * NULL */
 #endif
 
-#ifdef _MSC_VER
+#if defined(_MSC_VER) || defined(__MINGW32__)
 #define N2N_THREAD_RETURN_DATATYPE       DWORD WINAPI
 #define N2N_THREAD_PARAMETER_DATATYPE    LPVOID
 #else

win32/n2n_win32.h

@@ -105,9 +105,9 @@ typedef struct tuntap_dev {
 #define pthread_mutex_t HANDLE
 
 #define pthread_create(p_thread_handle, attr, thread_func, p_param)                         \
-    (*p_thread_handle = CreateThread(0 /* default security flags */, 0 /*default stack*/,   \
-                 thread_func, p_param, 0 /* default creation flags */,                      \
-                 NULL) == 0)
+    ((*p_thread_handle = CreateThread(0 /* default security flags */, 0 /*default stack*/,  \
+                 (LPTHREAD_START_ROUTINE)thread_func, p_param, 0 /* default creation flags */, \
+                 NULL)) == NULL)
 
 #define pthread_cancel(p_thread_handle) \
     TerminateThread(p_thread_handle, 0)
@@ -120,7 +120,7 @@ typedef struct tuntap_dev {
     WaitForSingleObject(*mutex, INFINITE)
 
 #define pthread_mutex_trylock(mutex)  \
-    WaitForSingleObject(*mutex, NULL)
+    WaitForSingleObject(*mutex, 0)
 
 #define pthread_mutex_unlock(mutex) \
     ReleaseMutex(*mutex)