C/C++ intrinsic __stosq

// test.cxx

#include <stdio.h>
#include <windows.h>

#include "test.h"

int __cdecl main( int argc, char* argv[ ] )
{
	unsigned long long* ptr = (unsigned long long*) new unsigned long long [ 16 ];
	unsigned long long refval = (unsigned long long) setval( ptr );
	unsigned long long val = (unsigned long long) getval( );

	printf( "refval: %I64u\n", refval );
	printf( "val: %I64u\n", val );
	printf( "*ptr: %I64u (before __stosq)\n", *ptr );

	__stosq( (unsigned __int64*) ptr, (unsigned __int64) 0ui64, 16 );

	printf( "*ptr: %I64u (after __stosq)\n", *ptr );

	delete [] ptr;

	return 0;
}

// test.h

#ifdef __cplusplus
extern "C" {
#endif

	unsigned __int64 __fastcall getval( void );
	unsigned __int64 __fastcall setval( unsigned __int64* refval );

#ifdef __cplusplus
}
#endif



;Assembler code for test.cxx program
;--------------------------------------------------------------------------
;unsigned __int64 __fastcall getval( void );
;unsigned __int64 __fastcall setval( unsigned __int64* refval );
;--------------------------------------------------------------------------

.CODE

;--------------------------------------------------------------------------

getval	PROC

	MOV	RAX,12345678ABCDEF00H
	RET

getval	ENDP

;--------------------------------------------------------------------------

refval$ = 8		; RCX

setval	PROC

	MOV	RAX,0FEDCBA987654321H
	XCHG	RAX,[RCX]
	RET

setval	ENDP

;--------------------------------------------------------------------------

END