CreateFileMapping error code 8

Question

CreateFileMapping error code 8.Not enough storage is available to process this command. Im trying to create file mapping with 4 Gb (0xFFFFFFFF) on 64bit Win10 visual c++.

#define UBS_MEM_SIZE 0xffffffff

HANDLE hMapObject = CreateFileMapping(INVALID_HANDLE_VALUE, nullptr,           
PAGE_READWRITE, HIWORD(UBS_MEM_SIZE), LOWORD(UBS_MEM_SIZE),     
TEXT("dllmemfilemap"));

How can i solve this "ERROR 8" problem?

Yes, i tried to build 64 and 86, same error. But does it matter? — Smit Ycyken, Sep 21 '15 at 10:45
Yes, because it is not possible to use 4Gb with 32-bit programs. — alain, Sep 21 '15 at 10:46
How did you determine the 16GB (or GiB?) of virtual memory? Virtual memory space doesn't correspond to installed RAM. That said, what is the meaning of error 8? The VC IDE comes with an error lookup tool, use that to find out! Also, what is the maximum size that you can map successfully using this approach? — Ulrich Eckhardt, Sep 21 '15 at 10:48

Hans Passant · Accepted Answer · 2015-09-21T17:28:12.750

   CreateFileMapping(..., HIWORD(UBS_MEM_SIZE), LOWORD(UBS_MEM_SIZE), ...)

The LO/HIWORD macros generate a WORD, a 16-bit value. You are asking for a 0xffff0000ffff memory-mapped file. That's 282 terabytes. Current x64 processors are limited to a 48-bit VM-address, most top out at 8 terabytes. So yes, error 8 (ERROR_NOT_ENOUGH_MEMORY) is entirely expected.

Don't use those macros. You can use LARGE_INTEGER as an alternative:

LARGE_INTEGER size;
size.QuadPart = UBS_MEM_SIZE;
HANDLE hMapObject = CreateFileMapping(..., size.HighPart, size.LowPart, ...);

bogdan · Answer 2 · 2015-09-21T14:45:27.700

The HIWORD and LOWORD macros are intended to extract the high and low 16-bit words from a 32-bit DWORD. CreateFileMapping, on the other hand, expects two DWORDs that together make up a 64-bit unsigned integer, which is the size of the mapping object.

Both HIWORD(UBS_MEM_SIZE) and LOWORD(UBS_MEM_SIZE) yield 0xffff (the two 16-bit halves), which are then converted to 32-bit unsigned integers (which is what the function expects).

So, what you're actually doing is asking for a file mapping of size 0x0000ffff0000ffff. This is more than 255 TB. Since you're using INVALID_HANDLE_VALUE, this has to be backed by RAM or the system page file; I doubt you have that much available in there.

If UBS_MEM_SIZE is always 32-bit, you can simply use

HANDLE hMapObject = CreateFileMapping(INVALID_HANDLE_VALUE, nullptr,
   PAGE_READWRITE, 0, UBS_MEM_SIZE,
   TEXT("dllmemfilemap"));

If you actually need to handle sizes over 4 GB, you can do something like this:

HANDLE hMapObject = CreateFileMapping(INVALID_HANDLE_VALUE, nullptr, PAGE_READWRITE, 
   static_cast<DWORD>(UBS_MEM_SIZE >> 32), static_cast<DWORD>(UBS_MEM_SIZE), 
   TEXT("dllmemfilemap"));

Make sure UBS_MEM_SIZE actually has a type larger than 32-bit (even if its value may be less than that), since otherwise shifting by 32 bits is undefined behaviour in C++. So, if you want to use the second variant above with your initial value, it will have to be something like

#define UBS_MEM_SIZE 0xFFFFFFFFull

(By the way, use const...)

To make it safer, I'd wrap the call into something like this:

inline HANDLE MyCreateMapping(unsigned long long size, LPCTSTR name)
{
   return CreateFileMapping(INVALID_HANDLE_VALUE, nullptr, PAGE_READWRITE,
      static_cast<DWORD>(size >> 32), static_cast<DWORD>(size), name);
}

This way, you don't need to remember any tricky details about bits, shifts and integer type sizes.

CreateFileMapping error code 8

2 Answers2