Integer types in C

Question

Suppose I wish to write a C program (C99 or C2011) that I want to be completely portable and not tied to a particular architecture.

It seems that I would then want to make a clean break from the old integer types (int, long, short) and friends and use only int8_t, uint8_t, int32_t and so on (perhaps using the the least and fast versions as well).

What then is the return type of main? Or must we strick with int? Is it required by the standard to be int?

GCC-4.2 allows me to write

#include <stdint.h>
#include <stdio.h>
int32_t main() {
    printf("Hello\n");
    return 0;
}

but I cannot use uint32_t or even int8_t because then I get

hello.c:3: warning: return type of ‘main’ is not ‘int’

This is because of a typedef, no doubt. It seems this is one case where we are stuck with having to use the unspecified size types, since it's not truly portable unless we leave the return type up to the target architecture. Is this interpretation correct? It seems odd to have "just one" plain old int in the code base but I am happy to be pragmatic.

Answer 1

Suppose I wish to write a C program (C99 or C2011) that I want to be completely portable and not tied to a particular architecture.

It seems that I would then want to make a clean break from the old integer types (int, long, short) and friends and use only int8_t, uint8_t, int32_t and so on (perhaps using the the least and fast versions as well).

These two affirmations, in bold, are contradictory. That's because whether uint32_t, uint8_t and al are available or not is actually implementation-defined (C11, 7.20.1.1/3: Exact-width integer types).

If you want your program to be truly portable, you must use the built-in types (int, long, etc.) and stick to the minimum ranges defined in the C standard (i.e.: C11, 5.2.4.2.1: Sizes of integer types),

Per example, the standard says that both short and int should range from at least -32767 to at least 32767. So if you want to store a bigger or lesser value, say 42000, you'd use a long instead.

Answer 2

The return type of main is required by the Standard to be int in C89, C99 and in C11.

Now the exact-width integer types are alias to integer types. So if you use the right alias for int it will still be valid.

For example:

int32_t main(void)

if int32_t is a typedef to int.