can we replace __int64 with something OS independent?

[bajajv]

Hi,
Is there any replacement for __int64 type with something which is OS independent? Do I need to include any file, or can do it with some typedef?

Thanks

[bajajv]

Can we do it using this - typedef long long int64_t?

Is there any good tutorial giving indepth explanation about the data types and their dependencies on compilers?

Thanks,

[RRick]

I have no idea why C/C++ compilers can't agree on sizes for the various int types. They keep playing the "less or equal to than" game, where char size is <= to short which is <= int etc., etc. I assume the C standard started all of this.

Many C/C++ compilers have informally standardized on char=8 bits, short=16, and int=32 in both the 32 and 64 bit systems.

With the 64 bit systems, long is now the unknown. Windows keeps long as 32 bits and linux upgraded long to 64 bits. I think long long is as close to an OS independent specification you'll find for a 64 bit int type.

[Banfa]

For C99 you can include stdint.h which defines lots of fixed size, minimum size and fastest size types similar to int32_t, int16_t, int64_t.

For C/C++ compilers that are C99 compilant (ish) this file exists so you can often included it even if you are actually using C89 or C++ however that does effectively make your code non-portable (although it gives it a single point of failure).

The reason that the types where never given fixed sizes is because of the original basic definitions of char and int.

char is a type that can address every byte of memory contiguously, the standard guarantees this.

int is the type that is most efficient for the processor to handle. So for 8 bit processor 8 bits, for 16 bit processors 16 bits and for 32 bit processors 32 bits.

The problems have arrisen because although the sizes of char, short, int and long are not fixed programmers programmed as though they were.

So in order to stop things breaking everywhere when PC processors jumped to 64 bit they didn't change the size of the various types even though from a standard point of view they probably should have done.

What windows has done with long on 64 bit machines is a little silly as there is now no standard built in integer type for C89 on Windows with 64 bits. I think the Linux approach makes more sense. But that is personal opinion.

What is important is that size of int is left to float to the most appropriate value for the platform.