What is the “real” memory size occupied by a dynamic array?

问题

Example:

procedure Test;
var
  AText: array of AnsiChar;
begin
  SetLength(AText, 7);
end;

Question

What is the real size of AText occupied in memory? Is it 7 + Cardinal size of its length, that is, 7 + 4 = 11 bytes?

回答1:

That plus 4 bytes reference count. And of course heapmanager overhead (which depends on delphi version and uses memory manager, which can easily be 12-16 bytes).

So that means:

• sizeof(element)*elementcount
• sizeof(refcount)
  
  • current implementations :sizeof(integer)=4
• sizeof(elementnumber)
  
  • FPC actually stores highest element, not elementcount. Don't know about Delphi)
  • current implementations :sizeof(integer)=4
• heap overhead.
  • At least the allocated size for the entire block.
  • Probably one or two pointers also (next block). But this depends on memory manager
  • many memory managers have a minimal blocksize of 16 or 32.

来源：https://stackoverflow.com/questions/4448897/what-is-the-real-memory-size-occupied-by-a-dynamic-array