Memory limits in Ada where Fortran has none

["braver" <deliverable@gmail.com>]

I'm interoperating with a Fortran algorithm using a very large array of
integers:

      PARAMETER (NMAX=100000000) ! a hundred million
      DIMENSION ND(NMAX)
C ...

In Ada, I declared it as

   type Intarray is array (Positive range <>) of Integer;

   ND: Intarray(1..NMAX); -- (1)

-- then I get a STORAGE_ERROR right about NMAX is 2_000_000.

If I do, instead,

   type Intarray_Ptr is access Intarray;
   ND: Intarray_Ptr;
-- ...
   ND := new Intarray(1..NMAX);

-- I get the STORAGE_ERROR right about NMAX=256*1024*256, which, given
the size of Integer as 32 bits, shows the limit of the _total heap size
in bits_ as the max 32 value.  So it leaves me with a 256 MB heap size,
or about 67_108_864 elements -- ~2/3 of what I need.
How do I increase the heap size, if at all possible, or the main memory
size?

In GNU f77, the array allocates and works fine, so I thought to import
it with pragma Import, just as I do with subroutines -- but the linkage
name for a variable in MAIN__ is not showing in mn main.o!  Any idea
how to link/import a GNU f77 _variable_ from GNAT?

Overall, Ada being the language for large systems, I found it
surprising that Fortran can allocate enough arrays to fill in my
memory, or even take up virtual memory, while Ada raises
STORAGE_ERRORs!  I'd like to simply use (1), as in Fortran, and be done
with it...

Cheers,
Alexy