sizeof() with vectors

[Jicamas]

hi!

  vector<bool> b(9,true);
  cout<<sizeof(b); //show 40 and not 2 

why it show 40?, i hope it show 2 because vector<bool> use a bit.
//sorry for my bad english :v

[TheIdeasMan]

Hi,

vector<bool> may not necessarily use a bit, maybe you need std::bitset ?


Why are you worried about the sizeof it? You have already specified you want 9 of them. There are a bunch of member functions to get info you might want.

http://en.cppreference.com/w/cpp/container/vector_bool
http://en.cppreference.com/w/cpp/utility/bitset
http://www.cplusplus.com/reference/bitset/bitset/

good Luck!!

[ne555]

sizeof is computed at compile time.
all objects of the same class have the same sizeof, its state is irrelevant.

A vector does not store the data, but pointers that tell where the data is. So when computing sizeof() you don't get the size of the data, but of the pointers.