VirtualAlloc2 funnies

main.c

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <stdio.h>

#define SIZE       (32ull * 1024 * 1024 * 1024)
#define BLOCKS     (32 * 32)
#define BLOCK_SIZE (SIZE / BLOCKS)
#define PAGE_SIZE  (4096)

void print_error(char* area, DWORD error);

int main()
{
    printf("foo!\n");

    // Based on https://learn.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-virtualalloc2#examples

    PCHAR range = (PCHAR) VirtualAlloc2(
        NULL,
        NULL,
        SIZE,
        MEM_RESERVE | MEM_RESERVE_PLACEHOLDER,
        PAGE_NOACCESS,
        NULL,
        0
    );

    printf("Range: %p, end: %p\n", range, (range + SIZE));

    DWORD error = GetLastError();

    for (int i = 0; i < BLOCKS - 1; i++)
    {
        PCHAR chunk = range + (BLOCK_SIZE * i);
        printf("VirtualFree %i: %p, %llu\n", i, chunk, BLOCK_SIZE);
        BOOL result = VirtualFree(
            chunk, 
            BLOCK_SIZE,
            MEM_RELEASE | MEM_PRESERVE_PLACEHOLDER);
        if (!result)
        {
            print_error("VirtualFree", GetLastError());
        }
    }

    HANDLE zero = CreateFileMappingW(
        INVALID_HANDLE_VALUE,
        NULL,
        PAGE_READWRITE,
        0,
        BLOCK_SIZE,
        NULL
    );

    if (zero == NULL)
    {
        print_error("CreateFileMappingW", GetLastError());
    }

    for (int i = 0; i < BLOCKS - 1; i++)
    {
        PCHAR chunk = range + (BLOCK_SIZE * i);

        PVOID result = MapViewOfFile3(
            zero,
            NULL,
            chunk,
            0,
            BLOCK_SIZE,
            MEM_REPLACE_PLACEHOLDER,
            PAGE_READONLY,
            NULL,
            0
        );

        if (result == NULL)
        {
            print_error("MapViewOfFile3", GetLastError());
        }
    }

    int* page = range + 5000 * 4096;

    printf("Read: %d\n", *page);

    // *page = 5;

    Sleep(1000000);


}

void print_error(char* area, DWORD error)
{
    char errBuf[512];
    DWORD errChars = FormatMessageA(
        FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        error,
        0,
        errBuf,
        sizeof(errBuf),
        NULL);

    if (errChars == 0) {
        fprintf(stderr, "Failed to print previous error!\n");
        exit(1);
    }

    fprintf(stderr, "%s: %s", area, errBuf);
    exit(1);
}