Array size error x64 process

Question

I was checking how big of an array can I create on a X64 application, my understanding was that I can create arrays bigger than 2^31 on X64 process but I'm getting a compilation error on VS2010 compiler, below code

const size_t ARRSIZE = size_t(1)<<32;
int main()
{
    char *cp = new char[ARRSIZE];
    return 0;
}

gives compiler error "error C2148: total size of array must not exceed 0x7fffffff bytes" on VS2010 on target x64 platform, I can create upto (size_t(1)<<32 - 1);

I have Linker->Advanced->Target Machine is Machinex64. Also Linker->System->Enable Large Addresses as Yes ( Not sure if this really matters ). Does the paging file\Physical Ram present in the pc matter here? (I'm sure that it is a 64-bit app because if I remove that line and just have char* cp; it is 8-byte.) Am I missing some settings?

Answer 1

This appears to be a defect in the 32-bit cross compiler for x64 targets. The Microsoft Connect link posted by icabod in the comments above addresses this particular issue. Unfortunately the bug's status has been set to Closed - Won't Fix.

The following code snippets will fail to compile using the 32-bit cross compiler for x64:

char* p = new char[(size_t)1 << 32];

and

const size_t sz = (size_t)1 << 32;
char* p = new char[sz];

Both of the above will fail with the error message error C2148: total size of array must not exceed 0x7fffffff bytes when compiled with the 32-bit cross compiler for x64. Unfortunately, Visual Studio does launch the 32-bit compiler even when run on a 64-bit version of Windows, targetting x64.

The following workarounds can be applied:

• Compiling the code using the native 64-bit compiler for x64 from the command line.

• Changing the code to either of the following:

  size_t sz = (size_t)1 << 32;  // sz is non-const
  char* p = new char[sz];
  

  or

  std::vector<char> v( (size_t)1 << 32 );
  

The bug is still present in Visual Studio 2012, and all workarounds still apply.