Is there a safe way to cast DWORD_PTR into DWORD? - c++

Question

I implemented this function to convert from dword_ptr to dword but if there is other way with less code that will be appreciated.
this code should be compatible with 32bit and 64bit windows
I have seen this Question but the answer contains new and delete operations
inline unsigned long Convert_to_DWORD(unsigned long long data)
{
//typedef unsigned __int64 ULONG_PTR
//typedef ULONG_PTR DWORD_PTR
//typedef unsigned long DWORD;
assert(UINT_MAX > data);
unsigned long* value = reinterpret_cast<unsigned long*>(&data);
return *value;
}

Answer 1

Is there a safe way to cast DWORD_PTR into DWORD?
Integer types are implicitly convertible to each other. Such conversion is safe in the sense that there is no UB involved
DWORD_PTR original;
DWORD converted = original;
On a 64 bit system DWORD may be smaller than DWORD_PTR, in which case it cannot represent all the values representable by DWORD_PTR. Therefore if you do the inverse conversion, you do not get the same original value back unless the high order bytes happened to be zero. Furthermore, if DWORD_PTR represented a pointer value, then converting the value to DWORD then back to DWORD_PTR then back into a pointer then using the resulting pointer would not be safe.
Since the conversion is narrowing, a compiler might generate a warning. An explicit conversion makes your intention unambiguous and should silence such warning:
DWORD converted = DWORD(original);