dynamically determine the type of integer based on the system (c++)

Question

I am writing a program to store data to a file on the unit of every 32 bits (i.e. 4 bytes at a time). I wrote the code in 64-bit windows system but the compiler I used is 32 bits (mingw32). In the current system, the size of int an long are the same, 32 bits (4bytes). I am current porting the code to other systems by recompiling with g++ (without changing the code). However, I found that the size of int or long are different and depending on the system. Is that any way (like using a macro in the header file) to determine the size of an integer so to decide if int or long should be used as the data type in the code? I have to recompile the code in 4 different type of system, it is really a headache if I modify the code to have 4 different copies for each system.

Answer 1

What you want to do is use the standard types like int32_t. This type is always 32 bits. I currently use these types in a portable database (berkeley db) for cross-system compatibility.

See here for all of them.

Include stdint.h to get these definitions.

Answer 2

This is a common problem with a canonical solution provided by C99.

The <stdint.h> header defines a set of types that provide integers of specific sizes, fastest sizes, and minimum sizes. It's quite useful when solving exactly your problem.

It's a good thing you are using mingw32, because unfortunately, the last time I checked Microsoft didn't provide stdint.h with their API. If anyone does need this for Windows, there is an open-source version, see: http://code.google.com/p/msinttypes/