String Allocation In C++

Question

I was playing with the new and delete operators overloading when I noticed something strange. I have: ``` void* operator new(size_t size) { std::cout << "Allocating memory..." << std::endl; void* p = malloc(size); if (NULL == p) { throw std::bad_alloc(); } return p; } ``` When I do: ``` int main() { int* x = new int(1); std::cout << *x << std::endl; delete x; return EXIT_SUCCESS; } ``` Everything works as expected and I get: ``` Allocating memory... 1 ``` But when I do: ``` int main() { std::string* s = new std::string("Hello world"); std::cout << *s << std::endl; delete s; return EXIT_SUCCESS; } ``` I get: ``` Allocating memory... Allocating memory... Hello world ``` In fact, when I do: ``` int main() { std::string s = "Hello world"; return EXIT_SUCCESS; } ``` I still get `Allocating memory...`! Finally, I do: ``` int main() { std::string s = "Hello world"; std::cout << &s << std::endl; while (true); } ``` To get something like: ``` $ ./test & [1] 8979 Allocating memory... 0xbfc39a68…

Accepted Answer

When you write

```
std::string s = "Hello world";
```

you are calling the constructor `string (const char* s);`, the specification of this constructor is `Copies the null-terminated character sequence (C-string) pointed by s.` So the constructor allocates memory to store the copy.

String Allocation In C++

Solution

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