Assuming many consecutive calls of foo in the below correctly-functioning class. Also, my code need not be thread-safe but small memory-footprint is critical.

class A{
public:
  void foo(){
    double x[10000];
    // ...
  }
};

Question: (How) Should I change the implementation of x to improve performance?

Ideas:

• I could leave it as is because freeing the space of x might be beneficial to keep the whole stack in cache at every time, e.g., when other functions (bar) also use an internal buffer of considerable size.
• I could make it a private class attribute but then its reserved memory could not be used by B::bar.
• If I assume that cache is no issue and if I assume I do not want to litter my class attribute list with internal function buffers, I might want to use static double x[10000];?