Converting 32-bit Application Into 64-bit Application in C

Question

I am presently working on converting a 32bits application into a 64bits application in C. This application is currently working on x86 architecture (Windows, osx, Unix, Linu

Answer 1

The two major differences between 32-bit and 64-bit programming in C are sizeof(void*) and sizeof(long). The major problem that you will have is that the most Unix systems use the I32LP64 standard which defines a long as 64 bits and Win64 uses the IL32LLP64 standard which defines a long as 32 bits. If you need to support cross-platform compilation, you may want to use a set of architecture based typedefs for 32-bit and 64-bit integers to ensure that all code will behave consistently. This is provided as part of stdint.h as part of the C99 standard. If you are not using a C99 compiler, you may need to roll your own equivalent

As noted elsewhere the primary concerns for conversion will be code that assume sizeof(int) == sizeof(long) == sizeof(void*), code to support data that has been written to disk and code for cross platform IPC.

For a good review of the history behind this, take a look at this article from ACM Queue.