skyking - 1 year ago 42

C Question

When looking for evidence of

`unsigned long`

`size_t`

`printf`

First there's this answer stating that

`long`

`size_t`

`printf("%lu", (unsigned long)x)`

`x`

`size_t`

So the question is could you assume or were you guaranteed that

`long`

`size_t`

`size_t`

`ssize_t`

`ptrdiff_t`

Answer Source

There is no such guarantee.

While it is common for implementation to have same size for `long`

and `size_t`

, it is not always the case. As put in the comments Windows 64-bit have different size for `long`

and `size_t`

.

Also notice that the minimum value of `SIZE_MAX`

for an implementation is `65535`

while the minimum value of `ULONG_MAX`

is `4294967295`

(`2147483647`

for `LONG_MAX`

). (Note that `SIZE_MAX`

appeared with C99.) It means that `size_t`

is guaranteed to be at least 16-bit but `unsigned long`

/ `long`

are guaranteed to be at least 32-bit.

**EDIT:** Question has changed a little bit after this answer... So:

*So the question is could you assume or were you guaranteed that long were enough to hold size_t in pre C99.*

There is no such guarantee even in C89. `long`

can be 32-bit and `size_t`

64-bit. (See C89 example with MSVC in Windows 64-bit above.)

*The other question is whether there exists any guarantee that size_t would fit in any of the other standardized integer types (except the obvious exceptions like ssize_t, ptrdiff_t and such).*

Again there is no such guarantee by the Standard. `size_t`

is an alias for another standard unsigned integer type (and it cannot be an extended integer type as C89 does not have extended integer types).