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Hello,

> I have been recently surprised to see that the following C program
> has a different output on Solaris 10 and NetBSD 3, for the same
> hardware (and both while using gcc):
>=20
> #include <stdio.h>
> #define type(a) printf("sizeof(%s) =3D %d\n", "" # a, sizeof(a));
> int main(void)
> {
>         type(char);
>         type(short);
>         type(int);
>         type(float);
>         type(double);
>         type(long);
>         type(long long);
>         return 0;
> }
>=20
> So on Solaris 10 I obtain:
> $ ./sizes
> sizeof(char) =3D 1
> sizeof(short) =3D 2
> sizeof(int) =3D 4
> sizeof(float) =3D 4
> sizeof(double) =3D 8
> sizeof(long) =3D 4
> sizeof(long long) =3D 8
>=20
> while NetBSD 3 gives:
>=20
> $ ./sizes
> sizeof(char) =3D 1
> sizeof(short) =3D 2
> sizeof(int) =3D 4
> sizeof(float) =3D 4
> sizeof(double) =3D 8
> sizeof(long) =3D 8
> sizeof(long long) =3D 8
>=20
> ok, the only difference is actually the size of long integers,
> respectively 32 and 64 bits. From my reading of the ANSI C standard I
> understood this is possible.

Check the resulting binary - on NetBSD it will be ELF64, on Solaris it's
apparently 32bit.

> I have a few questions about this though, if appropriate:
> - who sets this?

The compiler.

> - why not keep long as 32 bits and let int default to 64 bits instead?
>   This would help the short/long/long long hierarchy coherence, and
>   let int default to the native processor size (and 486 would be 16
>   bits!)

Only if you run the 486 in real or 16bit protected mode.

> - has this ever been observed to cause portability or stability issues
>   on this platform?

People blindly assuming sizeof(long) =3D=3D 4 or - even worse sizeof(int)
=3D=3D sizeof(void *) - cause endless headaches.

> My concern is, I have seen programmers assume sizeof(int) or
> sizeof(long) are 32 bits, even while writing portable 32/64 bits code
> (and I was myself wrong at first, since it is apparently very platform
> dependant even on 64 bits hardware).

Yes, and they're dead wrong. Code that assumes sizeof(long) =3D=3D
sizeof(int) is /not/ portable, it will break when compiled on a 64bit
target. This is also not really platform or OS dependent - in a 64bit
binary running on solaris you'll get sizeof(long) =3D=3D sizeof(void*) =3D=
=3D 8

> Morale =3D> #include <stdint.h> ?

If you depend on size use size-safe types like uint32_t and friends.

have fun
Michael

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