Channels ▼

StringPrintf: A Typesafe printf Family for C++

August, 2005: StringPrintf: A Typesafe printf Family for C++

Unnamed Temporary C++ Objects

The main technique that makes StringPrintf possible is the use of unnamed temporary objects. Most C++ programmers use this technique very often, although most of the time, it is not explicit. For example, having a set of std::strings, the set function insert only accepts references to objects of type std::string. Nevertheless, you can correctly write:

<b>std::set<std::string> stringSet;</b>

This is possible because the compiler, when finding the C-string "ABC", looks for a way to convert the C-string to a const reference to a std::string object. It then finds that basic_string (the template base class of std::string) has a constructor basic_string(const char *s). The compiler uses this constructor to create an unnamed temporary object of std::string out of "ABC", and passes it to std::set.insert(). The line


is expanded to


A unnamed temporary std::string object is created and its reference is passed to the insert function. When the insert function returns, the temporary object is destroyed.

Related Reading

More Insights

Currently we allow the following HTML tags in comments:

Single tags


<br> Defines a single line break

<hr> Defines a horizontal line

Matching tags


<a> Defines an anchor

<b> Defines bold text

<big> Defines big text

<blockquote> Defines a long quotation

<caption> Defines a table caption

<cite> Defines a citation

<code> Defines computer code text

<em> Defines emphasized text

<fieldset> Defines a border around elements in a form

<h1> This is heading 1

<h2> This is heading 2

<h3> This is heading 3

<h4> This is heading 4

<h5> This is heading 5

<h6> This is heading 6

<i> Defines italic text

<p> Defines a paragraph

<pre> Defines preformatted text

<q> Defines a short quotation

<samp> Defines sample computer code text

<small> Defines small text

<span> Defines a section in a document

<s> Defines strikethrough text

<strike> Defines strikethrough text

<strong> Defines strong text

<sub> Defines subscripted text

<sup> Defines superscripted text

<u> Defines underlined text

