Warning C4312 (64-Bit portability)

In my code I am casting a DWORD to an int* and I get the following warning:

Code:

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warning C4312: 'type cast' : conversion from 'DWORD' to 'int *' of greater size

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Quote:

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Originally Posted by MSDN

This warning detects 64-bit portability issues. You attempted to assign a 32-bit value to a 64-bit type. For example, casting a 32-bit int or 32-bit long to a 64-bit pointer.

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I am compiling for Win32. Does my program still work on Windows XP 64 Bit Edition, despite the warning?

On a 64-bit platform, a 32-bit int (which is what a DWORD is) is not big enough to store a pointer.

Of course this will break a lot of Win32 SDK which relies on it. But then I guess you should be using Win64 SDK...

Quote:

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Originally Posted by phillkr

I am compiling for Win32. Does my program still work on Windows XP 64 Bit Edition, despite the warning?

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It works.
Win32 remains binary compatible.
Your program is executed in 32 bits mode of the 64 bits processor.
But, if you want to compile your program to Win64, with a 64 bits compiler, then it will not work.

You can use UINT_PTR instead of DWORD.
UINT_PTR basically is a type whose size is equal to the max of UINT and LPVOID
The MSDN documentation, now uses UINT_PTR in many places where DWORD were specified.
Under Win32, that is the same thing.
Under Win64, sizeof(UINT_PTR)==8, but sizeof(DWORD)==4.

Under Win64, pointers are 64 bits, while DWORD are 32 bits.

Thanks for the replies!

My recap: The warning is of no interest for me, because I am using Win32 SDK, which will also run on 64-bit system, because there is also a 32-bit mode for backward compatibility.

If you don't want to see that warning you can disable it with a pargma

Code:

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#pragma warning(disable: 4312)

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you have to put that before any includes.

Instead of disabling ALL 4312 warnings (some of them are not related to 64-bit compatibility), you should simply remove /Wp64 switch from your compiler's options