C++ Error in array of pointers

You can't have a varible sized array in C++. Adding const to CPUs doesn't help, it only makes the variable read-only, but it's still not a compile time constant because it's initialized by a function at run-time.

The usual solution is to use a vector:

std::vector<FILE*> newFile(CPUs);

The value of GetNumCPUs() may or may not change every time you run the program - so it is not constant. If you want an array that has a variable amount of elements, try std::vector:

std::vector<FILE*> newFile(GetNumCPUs());

In your code, const doesn't mean "constant". In this context, it means the object is read-only — i.e you can't modify the object. You're trying to create a variable length array, which isn't allowed in C++. Use std::vector, use new to allocate memory, or write a C99 program where VLAs like the one you're trying to make are allowed.

Using a const doesn't fix all of your problems in this scenario. The problem is that arrays must be initialized at compile time, so if you have a function return a variable (GetNumCPUs()) and assign it to a constant (const int CPUs), the variable isn't known at compile time but runtime, and the compiler can't allocate data space for the array.

Using an std::vector, however, allows for variable storage space.

std::vector<FILE*> newFile(CPUs);

This should work fine. Here's a couple tutorials:

http://www.codeguru.com/cpp/cpp/cpp_mfc/stl/article.php/c4027/C-Tutorial-A-Beginners-Guide-to-stdvector-Part-1.htm

http://www.dreamincode.net/forums/topic/33631-c-vector-tutorial/

CPUs is no known at compile time.

You should dynamically create the array with new[]

int CPUs = GetNumCPUs();
FILE** newFile = new (FILE*)[CPUs];

After you're done with it, you're now responsible for deleting it as well:

delete[] newFile;