Re: Is there a maximum contiguous memory allocation?

From:

"Giovanni Dicanio" <giovanniDOTdicanio@REMOVEMEgmail.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Sat, 19 Dec 2009 20:07:29 +0100

Message-ID:

<OweWJ6NgKHA.2104@TK2MSFTNGP05.phx.gbl>

"Peter Olcott" <NoSpam@SeeScreen.com> ha scritto nel messaggio
news:GsSdnVt8x8CAc7HWnZ2dnUVZ_oCdnZ2d@giganews.com...

I have read the Microsoft has placed and artificial 2GB limit on the size
of an array. I also read that this same limit applies to 64 bit .NET
applications, maximum object size of 2GB.

Considering your request of allocating a huge std::vector, I wrote this
simple console-mode program in VS2008 SP1, that you can build in x64:

<code>

#include <Windows.h>
#include <stdlib.h>

#include <vector>
#include <iostream>
#include <exception>

using namespace std;

int main(int argc, char * argv[])
{
    try
    {
        if ( argc != 2 )
        {
            cout << "Syntax: " << argv[0] << " <gigabytes>" << endl;
            return EXIT_FAILURE;
        }

        int gigabyteCount = atoi(argv[1]);

        cout << "Try allocating " << gigabyteCount << "GB in a vector..." <<
endl;
        static const size_t gigabyte = 1024 * 1024 * 1024;
        vector< BYTE > big( gigabyteCount * gigabyte );

        cout << "Vector allocated." << endl;
    }
    catch (exception & e)
    {
        cout << "*** ERROR: " << e.what() << endl;
    }

    return 0;
}

</code>

I tested it on Windows 7 x64, and the allocation of a 4 GB std::vector
seemed to succeed; so I would think that the limit of 2GB does not apply to
native code.

Giovanni