Optimizing memory alignment not only in terms of performance, but also in memory size

Question

We know that there is a difference in size Awhen you define Aas follows:

class A 
{
  short a;
  double b;
  short c;
};

or how is it

class A 
{
  short a;
  short c;
  double b;
};

I assume we are compiling a 32-bit OS, and we told the compiler to align to 32 bits.

Does the compiler really reorder the definitions to get the minimum size, while also achieving the same performance?

Answer 1

It is very difficult. To arrange the fields in the same sequence as the structure definition, a certain structure is required.

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Answer 2

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class A
{
public:
  int a;
  int b;
private:
  int c;
 int d;
{'\;

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Answer 3

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