Question

I’m trying to port some code to 64-bit, but it seems that the thread address identifier in _beginthreadex is unsigned int which is 32-bits and I can’t pass/receive a 64-bit address identifier from the function:

uintptr_t _beginthreadex( // NATIVE CODE
   void *security,
   unsigned stack_size,
   unsigned ( __stdcall *start_address )( void * ),
   void *arglist,
   unsigned initflag,
   unsigned *thrdaddr // <-- 32-bit address
);

I checked the MSDN documentation, but I didn’t see a 64-bit version of the function. Am I including the wrong header, per-processor flag or is there some other way to create a thread with a 64-bit address identifier?

Update

The documentation states that the thrdaddr parameter is 32-bit:

Thrdaddr

Points to a 32-bit variable that receives the thread identifier. Might be NULL, in which case it is not used.

Answer 1

The thrdaddr parameter receives the thread ID. It is not the address of the thread function. It appears to be an exceedingly badly named parameter.

The start_address parameter is the thread function pointer and you can pass your 64 bit function pointer in that parameter.

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Your update to the question suggests that you believe that the thread ID is a 64 bit value on 64 bit Windows. That is a mis-think. Thread IDs are 32 bit values on all flavours of Windows.