lib_cpp.html

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You can subsequently ignore namespace
considerations in the remainder of the translation unit.
You also avoid most dialect differences across different
translation environments.</P>

<P>Unless specifically indicated otherwise, you may not define names in
the <CODE>std</CODE> namespace, or in a namespace nested within the
<CODE>std</CODE> namespace.</P>

<H2><A NAME="C++ Library Conventions">C++ Library Conventions</A></H2>

<P>The C++ library obeys much the same
<A HREF="lib_over.html#C Library Conventions">conventions</A>
as the Standard C library, plus a few more outlined here.

<P>An implementation has certain latitude in how it declares types
and functions in the C++ library:</P>

<UL>
<LI>Names of functions in the Standard C library may have either
<B><A NAME="extern &quot;C++&quot;"><CODE>extern "C++"</CODE></A></B> or
<B><A NAME="extern &quot;C&quot;"><CODE>extern "C"</CODE></A></B> linkage.
Include the appropriate
<A HREF="lib_over.html#standard headers">Standard C header</A>
rather than declare a library entity inline.</LI>

<LI>A member function name in a library class may have additional
function signatures over those listed in this document. You can
be sure that a function call described here behaves as expected,
but you cannot reliably take the address of a library member function.
(The type may not be what you expect.)</LI>

<LI>A library class may have undocumented (non-virtual) base classes.
A class documented as derived from another class may, in fact,
be derived from that class through other undocumented classes.</LI>

<LI>A type defined as a synonym for some integer type may be the
same as one of several different integer types.</LI>

<LI>A <B><A NAME="bitmask type">bitmask type</A></B> can
be implemented as either an integer type or an enumeration.
In either case, you can perform bitwise operations (such as AND
and OR) on values of the same bitmask type. The <I>elements</I>
<CODE>A</CODE> and <CODE>B</CODE> of a bitmask type are nonzero
values such that <CODE>A & B</CODE> is zero.</LI>

<LI>A library function that has no exception specification can
throw an arbitrary exception, unless its definition clearly
restricts such a possibility.</LI>
</UL>

<P>On the other hand, there are some restrictions you can count on:</P>

<UL>
<LI>The Standard C library uses no
<A NAME="masking macro">masking macros</A>. Only specific function
signatures are reserved, not the names of the functions themselves.</LI>

<LI>A library function name outside a class will <I>not</I> have
additional, undocumented, function signatures. You can reliably
take its address.</LI>

<LI>Base classes and member functions described as virtual are
assuredly virtual, while those described as non-virtual are
assuredly non-virtual.</LI>

<LI>Two types defined by the C++ library
are always different unless this document explicitly suggests
otherwise.</LI>

<LI>Functions supplied by the library, including the default versions of
<A HREF="new.html#replaceable functions">replaceable functions</A>,
can throw <I>at most</I> those exceptions listed in any exception
specification.
No destructors supplied by the library throw exceptions.
Functions in the
<A HREF="index.html#Standard C Library">Standard C library</A>
may propagate an exception, as when
<CODE><A HREF="stdlib.html#qsort">qsort</A></CODE> calls a comparison
function that throws an exception, but they do not otherwise throw
exceptions.</LI>
</UL>

<H2><A NAME="iostreams">Iostreams Conventions</A></H2>

<P>The <B>iostreams</B> headers support conversions
between text and encoded forms, and input and output to external
<A HREF="lib_file.html#files">files</A>:
<CODE><A HREF="fstream.html">&lt;fstream&gt;</A></CODE>,
<CODE><A HREF="iomanip.html">&lt;iomanip&gt;</A></CODE>,
<CODE><A HREF="ios.html">&lt;ios&gt;</A></CODE>,
<CODE><A HREF="iosfwd.html">&lt;iosfwd&gt;</A></CODE>,
<CODE><A HREF="iostream.html">&lt;iostream&gt;</A></CODE>,
<CODE><A HREF="istream.html">&lt;istream&gt;</A></CODE>,
<CODE><A HREF="ostream.html">&lt;ostream&gt;</A></CODE>,
<CODE><A HREF="sstream.html">&lt;sstream&gt;</A></CODE>,
<CODE><A HREF="streambu.html">&lt;streambuf&gt;</A></CODE>, and
<CODE><A HREF="strstrea.html">&lt;strstream&gt;</A></CODE>.</P>

<P>The simplest use of iostreams requires only that you include
the header <CODE>&lt;iostream&gt;</CODE>. You can then extract values from
<A HREF="iostream.html#cin"><CODE>cin</CODE></A>, to read the
<A HREF="lib_over.html#standard input">standard input</A>.
The rules for doing so are outlined in the description of the class
<CODE><A HREF="istream.html#basic_istream">basic_istream</A></CODE>.
You can also insert values to
<A HREF="iostream.html#cout"><CODE>cout</CODE></A>, to write the
<A HREF="lib_over.html#standard output">standard output</A>.
The rules for doing so are outlined in the description of the class
<CODE><A HREF="ostream.html#basic_ostream">basic_ostream</A></CODE>.
Format control common to both extractors and insertors is managed
by the class <CODE><A HREF="ios.html#basic_ios">basic_ios</A></CODE>.
Manipulating this format information in the guise of extracting and
inserting objects is the province of several
<A HREF="iomanip.html">manipulators</A>.</P>

<P>You can perform the same iostreams operations on files that you
open by name, using the classes declared in
<CODE>&lt;fstream&gt;</CODE>.
To convert between iostreams and objects of class
<CODE><A HREF="string2.html#basic_string">basic_string</A></CODE>,
use the classes declared in <CODE>&lt;sstream&gt;</CODE>.
And to do the same with <A HREF="lib_over.html#C string">C strings</A>,
use the classes declared in <CODE>&lt;strstream&gt;</CODE>.</P>

<P>The remaining headers provide support services, typically of direct
interest to only the most advanced users of the iostreams classes.</P>

<H2><A NAME="C++ Program Startup and Termination">
C++ Program Startup and Termination</A></H2>

<P>A C++ program performs the same operations as does a C program
<A HREF="lib_over.html#program startup">program startup</A> and at
<A HREF="lib_over.html#program termination">program termination</A>,
plus a few more outlined here.</P>

<P>Before the target environment calls the function
<A HREF="lib_over.html#main"><CODE>main</CODE></A>, and after it stores
any constant initial values you specify in all objects that have
static duration, the program executes any remaining constructors
for such static objects. The order of execution is not specified
between translation units, but you can nevertheless assume that some
<A HREF="#iostreams">iostreams</A> objects are properly initialized
for use by these static constructors. These control
text streams:</P>

<UL>
<LI><B><A HREF="iostream.html#cin"><CODE>cin</CODE></A></B> --
for <A HREF="lib_over.html#standard input">standard input</A></LI>

<LI><B><A HREF="iostream.html#cout"><CODE>cout</CODE></A></B> --
for <A HREF="lib_over.html#standard output">standard output</A></LI>

<LI><B><A HREF="iostream.html#cerr"><CODE>cerr</CODE></A></B> --
for unbuffered
<A HREF="lib_over.html#standard error">standard error</A> output</LI>

<LI><B><A HREF="iostream.html#clog"><CODE>clog</CODE></A></B> --
for buffered
<A HREF="lib_over.html#standard error">standard error</A> output</LI>
</UL>

<P>You can also use these objects within the destructors called for
static objects, during
<A HREF="lib_over.html#program termination">program termination</A>.

<P>As with C, returning
from <A HREF="lib_over.html#main"><CODE>main</CODE></A> or calling
<A HREF="stdlib.html#exit"><CODE>exit</CODE></A>
calls all functions registered with
<A HREF="stdlib.html#atexit"><CODE>atexit</CODE></A>
in reverse order of registry.
An exception thrown from such a registered function calls
<CODE><A HREF="exceptio.html#terminate">terminate</A>()</CODE>.</P>


<HR>
<P>See also the
<B><A HREF="index.html#Table of Contents">Table of Contents</A></B> and the
<B><A HREF="_index.html">Index</A></B>.</P>

<P><I>
<A HREF="crit_pjp.html">Copyright</A> &#169; 1992-2002
by P.J. Plauger. All rights reserved.</I></P>

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