Re: STL string and assignment operator. Plz Help.

From:

=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?= <Erik-wikstrom@telia.com>

Newsgroups:

comp.lang.c++

Date:

Mon, 01 Oct 2007 12:38:21 GMT

Message-ID:

<1T5Mi.10145$ZA.6783@newsb.telia.net>

On 2007-10-01 13:40, developer28 wrote:

Hi,

I would like to know the following.

suppose i write.

string str1 = "TestString";

string str2;

str2 = str1

Now can someone tell me how this assignment operator works internally.

No, since I do not know how std::string (on your implementation) works.
But I can make an educated guess.

actually i do something like

const char * temp = str1.c_str();

that converts it to a c type string.

and then when i modify the contents of temp, it also affects str2.

Now this makes me doubtful about the fact that internally both the
objects are using the same pointer.

They are not using the same pointer, each string uses separate data. A
simplified string class might look something like this:

class String
{
  int size;
  char* data;
public:
  String& operator=(const String& s)
  {
    delete data;
    data = new char[s.size];
    strcpy(data, s.data);
    size = s.size;
  }
};

In other words the assignment operator creates a copy of the string.

--
Erik Wikstr??m