How to you get the address of an element in an std::string in C++?

Question

For example, i have the following string :

std::string s = "Hello, World!"

I want the address of the last element of s which is '!'.

I tried the following code, but it does not seem to output what I want it to.

std::cout << &s[s.length() - 1];

That outputs '!' not it's address, the same happens with s.back()

Is it because of the formatting caused by std::cout or is the problem elsewhere?

Basically I want a function that outputs the address of the last (and if possible, the first) element in a string.

score 9 · Accepted Answer · edited Jul 04 '17 at 16:33

9

Currently, you're using the overload of operator<< that takes a const char* as input. It treats the input as a null-terminated C string.

If you cast to (const void*) the problem will go away:

std::cout << (const void*)(&s[s.length() - 1]);

edited Jul 04 '17 at 16:33

Remy Lebeau

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answered Jul 04 '17 at 16:14

Bathsheba

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My only complaint is that you use a C-style cast.. A `static_cast` should be preferred IMO. :) – Some programmer dude Jul 04 '17 at 16:15
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@Someprogrammerdude: I see your point, but I feel that's at the expense of readability at the call site. Perhaps I spent too much time in my youth programming in C ;-) – Bathsheba Jul 04 '17 at 16:16
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You're still in your youth! – Hatted Rooster Jul 04 '17 at 16:37

score 1 · Answer 2 · answered Jul 04 '17 at 16:14

1

auto address_back = &s.back();
auto address_front = &s.front();

cout << static_cast<void*>(address_back) << endl;
cout << static_cast<void*>(address_front) << endl;

answered Jul 04 '17 at 16:14

Curious

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How to you get the address of an element in an std::string in C++?

2 Answers2