Andrey Karpov

Apr 05 2013

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#Cpp #64bit

Can I use 32-bit pointers in a 64-bit application?

At present, the Microsoft Visual C++ and GCC compilers do not allow you to use 32-bit pointers in 64-bit software created for processors based on x86-64 architecture. You can use 64-bit registers and instruction sets together with 32-bit pointers in 32-bit programs on some other platforms (for instance, PowerPC).

The simplest way to circumvent the impossibility of using 32-bit pointers is to store data in global arrays using 32-bit types to index them. The drawback of this method is the impossibility of dynamic memory allocation for such structures durring runtime.

Another way is to encode 64-bit pointers into 32 bits. This article thoroughly describes the operation principles of the 'sptr' function intended for data alignment and specifics and restrictions of its use. The article contains samples illustrating mechanisms of encoding 64-bit pointers into 32-bit ones.

References

• Discussion at www.stackoverflow.com. Can a C compiler generate an executable 64-bits where pointers are 32-bits?
• The Code Project. 32-bit pointers in a 64-bit world
• Knowledge Base. How to correctly cast a pointer to int in a 64-bit application?
• Knowledge Base. What is the POINTER_32 macro?

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