c++ - Strlen returns unreasonable number

Question

If I write:

char  lili [3];
cout<<strlen(lili)<<endl;

then what is printed is : 11

but if I write:

char  lili [3];
lili [3]='';
cout<<strlen(lili)<<endl;

then I get 3.

I don't understand why it returns 11 on the first part?
Isn't strlen supposed to return 3, since I allocated 3 chars for lili?

Answer 1

It is because strlen works with "C-style" null terminated strings. If you give it a plain pointer or uninitialised buffer as you did in your first example, it will keep marching through memory until it a) finds a , at which point it will return the length of that "string", or b) until it reaches a protected memory location and generates an error.

Given that you've tagged this C++, perhaps you should consider using std::array or better yet, std::string. Both provide length-returning functions (size()) and both have some additional range checking logic that will help prevent your code from wandering into uninitialised memory regions as you're doing here.