c++ - Why sizeof() of a string variable always return the same number even when content changes?

Question

This is a rather simple problem but is pretty confusing.

string R = "hhhh" ;
cout<< sizeof( R )<<endl;

OUTPUT:

4

Variation:

string R = "hhuuuuuuhh" ; cout<< sizeof( R )<

OUTPUT2:

4

What is going wrong ? Should I use char array instead ?

Answer 1

Think of sizeof being compile-time evaluable. It evaluates to the size of the type, not the size of the contents. You can even write sizeof(std::string) which will be exactly the same as sizeof(foo) for any std::string instance foo.

To compute the number of characters in a std::string, use size().

If you have a character array, say char c[6] then the type of c is an array of 6 chars. So sizeof(c) (known at compile-time) will be 6 as the C++ standard defines the size of a single char to be 1.