Value and size of an uninitialized std::string variable in c++

c++ stdstring
Charzhard picture Charzhard · Jul 19, 2013 · Viewed 48.6k times · Source

If a string is defined like this

std::string name;

What will be the value of the uninitialized string "name" and what size it would be?

Answer

Pierre Fourgeaud picture Pierre Fourgeaud · Jul 19, 2013

Because it is not initialized, it is the default constructor that is called. Then :

empty string constructor (default constructor) :

Constructs an empty string, with a length of zero characters.

Take a look : http://www.cplusplus.com/reference/string/string/string/

EDIT : As stated in C++11, §21.4.2/1 :

Effects: Constructs an object of class basic_string. The postconditions of this function are indicated in Table 63.

-> Table 63
+-----------------------------------------------------------------------------+
| data()     | a non-null pointer that is copyable and can have 0 added to it |
+------------+----------------------------------------------------------------+
| size()     | 0                                                              |
+------------+----------------------------------------------------------------+
| capacity() | an unspecified value                                            |
+-----------------------------------------------------------------------------+

Related questions

std::string formatting like sprintf

I have to format std::string with sprintf and send it into file stream. How can I do this?

Read More
What's the best way to trim std::string?

I'm currently using the following code to right-trim all the std::strings in my programs: std::string s; s.erase(s.find_last_not_of(" \n\r\t")+1); It works fine, but I wonder if there are some end-cases where …

Read More
How to concatenate a std::string and an int?

I thought this would be really simple but it's presenting some difficulties. If I have std::string name = "John"; int age = 21; How do I combine them to get a single string "John21"?

Read More