This doesn't make sense to me. You can't "allocate" more than SIZE_MAX bytes by definition. If you take "allocate" to mean "make it available in the process's address space", that is.
The calloc() [1] function mentioned above takes two values of type size_t, and allocates their product bytes.
I'm on mobile without (!) the C99 draft spec but at least the man page gives no such restriction.
calloc returns NULL when can't satisfy the request. The idea of taking two arguments is not to allow the user to specify a larger requested size, but to protect against overflows as it can happen with e.g. malloc() where the user has to compute the size of arrays by multiplying NUM_ELEMS * SIZE_PER_ELEM. And the user will normally do so less carefully than a library function.
However, the standard says (https://en.cppreference.com/w/c/types/size_t):
“size_t can store the maximum size of a theoretically possible object of any type (including array).”
and (https://en.cppreference.com/w/c/language/pointer):
“Pointer is a type of an object that refers to a function or an object of another type, possibly adding qualifiers. Pointer may also refer to nothing, which is indicated by the special null pointer value.”
⇒ pointers must either be null or point to an object, and objects aren’t larger than SIZE_MAX, so I think having a pointer pointing to a block larger than SIZE_MAX violates the standard.
it's simply not possible, by definition.