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<meta name="AUTHOR" content="bkoz@gcc.gnu.org (Benjamin Kosnik), Felix Natter" />
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<meta name="DESCRIPTION" content="API evolution and deprecation history" />
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<title>API Evolution and Deprecation History</title>
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<h1 class="centered"><a name="top">API Evolution and Deprecation History</a></h1>
<p class="fineprint"><em>
The latest version of this document is always available at
<a href="http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/api.html">
http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/abi.html</a>.
</em></p>
<p><em>
To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++ homepage</a>.
</em></p>
<!-- ####################################################### -->
<hr />
<h3 class="left">
<a name="C++ API v1">First.</a>
</h3>
<p>2.72</p>
<p> The first generation GNU C++ library was called libg++. It had a
working relationship with at least two kinds of dinosaur. Sadly, the
details were not pried away from the estate.
</p>
<p>
</p>
<p>Known Issues include many of the limitations of its immediate ancestor.</p>
<h5>No <code>ios_base</code></h5>
<p> At least some older implementations don't have <code>std::ios_base</code>, so you should use <code>std::ios::badbit</code>, <code>std::ios::failbit</code> and <code>std::ios::eofbit</code> and <code>std::ios::goodbit</code>.
</p>
<h5>No <code>cout</code> in <code>ostream.h</code>, no <code>cin</code> in <code>istream.h</code</h5>
<p>
In earlier versions of the standard,
<tt><fstream.h></tt>,
<tt><ostream.h></tt>
and <tt><istream.h></tt>
used to define
<code>cout</code>, <code>cin</code> and so on. ISO C++ specifies that one needs to include
<tt><iostream></tt>
explicitly to get the required definitions.
</p>
<p> Some include adjustment may be required.</p>
<p>This project is no longer maintained or supported, and the sources
archived. The code is considered replaced and rewritten.
</p>
<hr />
<h3 class="left">
<a name="C++ API v1">Second.</a>
</h3>
<p> The second generation GNU C++ library was called libstdc++, or
libstdc++-v2. It was a separate GNU project, although reliably paired
with GCC. It spans the time between libg++ and pre-ISO C++.
</p>
<p>egcs 1.x</p>
<p>2.95</p>
<p>2.96</p>
<p>Portability Notes</p>
<p>Implementation Limitations</p>
<h5>Namespace <code>std::</code> not supported.</h5>
<p>
Some care is required to support C++ compiler and or library
implementation that do not have the standard library in
<code>namespace std</code>.
</p>
<p>
The following sections list some possible solutions to support compilers
that cannot ignore <code>std::</code>-qualified names.
</p>
<p> First, see if the compiler has a flag for this. Namespace
back-portability-issues are generally not a problem for g++
compilers that do not have libstdc++ in <code>std::</code>, as
the compilers use <code>-fno-honor-std</code> (ignore
<code>std::</code>, <code>:: = std::</code>) by default. That
is, the responsibility for enabling or disabling
<code>std::</code> is on the user; the maintainer does not have
to care about it. This probably applies to some other compilers
as well.
</p>
<p>Second, experiment with a variety of pre-processor tricks.</p>
<p> By defining <code>std</code> as a macro, fully-qualified namespace calls become global. Volia.
<pre class="programlisting">
#ifdef WICKEDLY_OLD_COMPILER
# define std
#endif
</pre>
(thanks to Juergen Heinzl who posted this solution on gnu.gcc.help)
<p>Define a macro <code>NAMESPACE_STD</code>, which is defined to
either "" or "std" based on a compile-type
test. On GNU systems, this can be done with autotools by means of an
autoconf test (see below) for <code>HAVE_NAMESPACE_STD</code>, then
using that to set a value for the <code>NAMESPACE_STD</code> macro.
At that point, one is able to use <code>NAMESPACE_STD::string</code>,
which will evaluate to <code>std::string</code> or
<code>::string</code> (ie, in the global namespace on systems that do
not put <code>string</code> in <code>std::</code>). </p>
<p>
<pre>
dnl @synopsis AC_CXX_HAVE_STD_NAMESPACE
dnl
dnl If the compiler supports the std namespace, define
dnl HAVE_STD_NAMESPACE.
dnl
dnl @category Cxx
dnl @author Todd Veldhuizen
dnl @author Luc Maisonobe <luc@spaceroots.org>
dnl @version 2004-02-04
dnl @license AllPermissive
AC_DEFUN([AC_CXX_HAVE_STD_NAMESPACE],
[AC_CACHE_CHECK(whether the compiler supports the std namespace,
ac_cv_cxx_have_std_namespace,
[AC_LANG_SAVE
AC_LANG_CPLUSPLUS
AC_TRY_COMPILE([#include <iostream>
std::istream& is = std::cin;
],[return 0;],
ac_cv_cxx_have_std_namespace=yes, ac_cv_cxx_have_std_namespace=no)
AC_LANG_RESTORE
])
if test "$ac_cv_cxx_have_std_namespace" = yes; then
AC_DEFINE(HAVE_STD_NAMESPACE,,[define if the compiler supports the std namespace])
fi
])
</pre>
<h5>Illegal iterator usage.</h5>
<p>
The following illustrate implementation-allowed illegal iterator
use, and then correct use. <div class="itemizedlist"><ul
type="disc"> <li><p>you cannot do
<code>ostream::operator<<(iterator)</code> to print the
address of the iterator => use <code>operator<<
&*iterator</code> instead ?
</p></li>
<li><p>you cannot clear an iterator's reference
(<code>iterator = 0</code>) => use
<code>iterator = iterator_type();</code> ?
</p></li>
<li><p>
<code>if (iterator)</code> won't work any
more => use <code>if (iterator != iterator_type())</code>
?</p></li>
</ul>
<h5><code>isspace</code> from <tt><cctype></tt> is a macro
</h5>
<p> Glibc 2.0.x and 2.1.x define <tt><ctype.h></tt>
functionality as macros (isspace, isalpha etc.).
</p>
<p>
This implementations of libstdc++, however, keep these functions as
macros, and so it is not back-portable to use fully qualified
names. For example:
</p>
<pre>
#include <cctype>
int main() { std::isspace('X'); }
</pre>
<p>Results in something like this:
</p>
<pre>
std:: (__ctype_b[(int) ( ( 'X' ) )] & (unsigned short int) _ISspace ) ;
</pre>
<p> A solution is to modify a header-file so that the compiler tells
<tt><ctype.h></tt> to define functions instead of macros:
</p>
<pre>
// This keeps isalnum, et al from being propagated as macros.
#if __linux__
# define __NO_CTYPE 1
#endif
</pre>
<p>Then, include <ctype.h>
</p>
<p>
Another problem arises if you put a <code>using namespace std;</code>
declaration at the top, and include <tt><ctype.h></tt>. This
will result in ambiguities between the definitions in the global
namespace (<tt><ctype.h></tt>) and the definitions in namespace
<code>std::</code> (<code><cctype></code>).
</p>
<h5>No <code>vector::at</code>, <code>deque::at</code>, <code>string::at</code></h5>
<p>
One solution is to add an autoconf-test for this:
</p>
<pre>
AC_MSG_CHECKING(for container::at)
AC_TRY_COMPILE(
[
#include <vector>
#include <deque>
#include <string>
using namespace std;
],
[
deque<int> test_deque(3);
test_deque.at(2);
vector<int> test_vector(2);
test_vector.at(1);
string test_string("test_string");
test_string.at(3);
],
[AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_CONTAINER_AT)],
[AC_MSG_RESULT(no)])
</pre>
<p>
If you are using other (non-GNU) compilers it might be a good idea
to check for <code>string::at</code> separately.
</p>
<h5>No <code>std::char_traits<char>::eof</code></h5>
<p>
Use some kind of autoconf test, plus this:
</p>
<pre>
#ifdef HAVE_CHAR_TRAITS
#define CPP_EOF std::char_traits<char>::eof()
#else
#define CPP_EOF EOF
#endif
</pre>
<h5>No <code>string::clear</code></h5>
<p>
There are two functions for deleting the contents of a string:
<code>clear</code> and <code>erase</code> (the latter
returns the string).
<pre class="programlisting">
void
clear() { _M_mutate(0, this->size(), 0); }
</pre>
<pre class="programlisting">
basic_string&
erase(size_type __pos = 0, size_type __n = npos)
{
return this->replace(_M_check(__pos), _M_fold(__pos, __n),
_M_data(), _M_data());
}
</pre>
Unfortunately, ut <code>clear</code> is not
implemented in this version, so you should use
<code>erase</code> (which is probably faster than
<code>operator=(charT*)</code>).
</p>
<h5>Removal of <code>ostream::form</code> and
<code>istream::scan</code> extensions.</h5>
<p> These are no longer supported. Please use
<a href="#sec-stringstream" title="Using stringstreams">
stringstreams</a> instead.
</p>
<h5>No <code>basic_stringbuf</code>, <code>basic_stringstream<code></h5>
<p>
Libstdc++ provides the new
<code>i/ostringstream</code>-classes, (<tt><sstream></tt>), but for compatibility
with older implementations you still have to use
<code>i/ostrstream</code> (<tt><strstream></tt>):
<pre >
#ifdef HAVE_SSTREAM
#include <sstream>
#else
#include <strstream>
#endif
</pre>
<div class="itemizedlist"><ul type="disc">
<li><p> <code>strstream</code> is considered to be
deprecated
</p></li>
<li><p> <code>strstream</code> is limited to
<code>char</code>
</p></li>
<li><p> with <code>ostringstream</code> you don't
have to take care of terminating the string or freeing its
memory
</p></li>
<li><p> <code>istringstream</code> can be re-filled
(clear(); str(input);)
</p></li>
</ul></div>
<p>
You can then use output-stringstreams like this:
<pre >
#ifdef HAVE_SSTREAM
std::ostringstream oss;
#else
std::ostrstream oss;
#endif
oss << "Name=" << m_name << ", number=" << m_number << std::endl;
...
#ifndef HAVE_SSTREAM
oss << std::ends; // terminate the char*-string
#endif
// str() returns char* for ostrstream and a string for ostringstream
// this also causes ostrstream to think that the buffer's memory
// is yours
m_label.set_text(oss.str());
#ifndef HAVE_SSTREAM
// let the ostrstream take care of freeing the memory
oss.freeze(false);
#endif
</pre>
<p>
Input-stringstreams can be used similarly:
</p>
<pre>
std::string input;
...
#ifdef HAVE_SSTREAM
std::istringstream iss(input);
#else
std::istrstream iss(input.c_str());
#endif
int i;
iss >> i;
</pre>
<p> One (the only?) restriction is that an istrstream cannot be re-filled:
</p>
<pre >
std::istringstream iss(numerator);
iss >> m_num;
// this is not possible with istrstream
iss.clear();
iss.str(denominator);
iss >> m_den;
</pre>
<p>
If you don't care about speed, you can put these conversions in
a template-function:
</p>
<pre >
template <class X>
void fromString(const string& input, X& any)
{
#ifdef HAVE_SSTREAM
std::istringstream iss(input);
#else
std::istrstream iss(input.c_str());
#endif
X temp;
iss >> temp;
if (iss.fail())
throw runtime_error(..)
any = temp;
}
</pre>
<p> Another example of using stringstreams is in <a href="../21_strings/howto.html" target="_top">this howto</a>.
</p>
<p> There is additional information in the libstdc++-v2 info files, in
particular "info iostream".
</p>
<h5>Little or no wide character support</h5>
<h5>No templatized iostreams</h5>
<h5>Thread safety issues.</h5>
<p>This project is no longer maintained or supported, and the sources
archived. The code is considered replaced and rewritten.
</p>
<hr />
<h3 class="left">
<a name="C++ API v1">Third.</a>
</h3>
<p> The third generation GNU C++ library is called libstdc++, or
libstdc++-v3.
</p>
<p>The subset commonly known as the Standard Template Library
(chapters 23 through 25, mostly) is adapted from the final release
of the SGI STL, with extensive changes.
</p>
<p>A more formal description of the V3 goals can be found in the
official <a href="../17_intro/DESIGN">design document</a>.
</p>
<p>Portability Notes</p>
<h5>Pre-ISO headers moved to backwards</h5>
<p> The pre-ISO C++ headers (iostream.h etc.) are available, but inclusion
generates a warning that you are using deprecated headers.
</p>
<p>This compatibility layer is constructed by including the
standard C++ headers, and injecting any items in
<code>std::</code> into the global namespace.
</p>
<p>For those of you new to ISO C++ (welcome, time travelers!), no,
that isn't a typo. Yes, the headers really have new names.
Marshall Cline's C++ FAQ Lite has a good explanation in <a
href="http://www.parashift.com/c++-faq-lite/coding-standards.html#faq-27.4">item
[27.4]</a>.
</p>
<p> Some include adjustment may be required.</p>
<h5>Extension headers hash_map, hash_set moved to ext</h5>
<p> Header files <code>hash_map</code> and <code>hash_set</code>
moved to <code>ext/hash_map</code> and <code>ext/hash_set</code>,
respectively. At the same time, all types in these files are enclosed
in <code>namespace __gnu_cxx</code>.
</p>
<h5>
No <code>ios::nocreate/ios::noreplace</code>.
</h5>
<p> The existence of <code>ios::nocreate</code> being used for
input-streams has been confirmed, most probably because the author
thought it would be more correct to specify nocreate explicitly. So
it can be left out for input-streams.
</p>
<p>For output streams, "nocreate" is probably the default,
unless you specify <code>std::ios::trunc</code> ? To be safe, you can
open the file for reading, check if it has been opened, and then
decide whether you want to create/replace or not. To my knowledge,
even older implementations support <code>app</code>, <code>ate</code>
and <code>trunc</code> (except for <code>app</code> ?).
</p>
<h5>
No <code>stream::attach(int fd)</code>.
</h5>
<p>
Phil Edwards writes: It was considered and rejected for the ISO
standard. Not all environments use file descriptors. Of those
that do, not all of them use integers to represent them.
</p>
<p>
For a portable solution (among systems which use
filedescriptors), you need to implement a subclass of
<code>std::streambuf</code> (or
<code>std::basic_streambuf<..></code>) which opens a file
given a descriptor, and then pass an instance of this to the
stream-constructor.
</p>
<p>
An extension is available that implements this.
<code><ext/stdio_filebuf.h></code> contains a derived class called
<a href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/class____gnu__cxx_1_1stdio__filebuf.html"><code>__gnu_cxx::stdio_filebuf</code></a>.
This class can be constructed from a C <code>FILE*</code> or a file
descriptor, and provides the <code>fd()</code> function.
</p>
<p>
For another example of this, refer to
<a href="http://www.josuttis.com/cppcode/fdstream.html" target="_top">fdstream example</a>
by Nicolai Josuttis.
</p>
<p><a href="http://gcc.gnu.org/bugzilla/buglist.cgi?cmdtype=runnamed&namedcmd=libstdc%2B%2B">Known Issues</a></p>
<h5>
container iterator types are not necessarily container value_type*
</h5>
<p>API History, User Visible Changes</p>
<p>3.0.0</p>
<p>3.1.0</p>
<p>3.2.0</p>
<p>3.3.0</p>
<p>3.4.0</p>
Macro guard for libstdc++ changed, from _GLIBCPP_ to _GLIBCXX_, to
accomodate a request from the C Pre Processor maintainer.
<p>4.0.0</p>
<p>4.1.0</p>
<cassert> how has to be explicitly included for <code>std::assert</code> calls.
<p>4.2.0</p>
<p>4.3.0</p>
Header streamlining.
Backward include edit.
PCH files built but not installed.
Namespace pb_ds moved to __gnu_pb_ds.
C++OX features appear.
<hr />
<h3 class="left">
<a name="C++ API v1">Fourth, and future</a>
</h3>
<hr />
<h3 class="left">
<a name="Deprecation">Deprecation and Backwards Compatibility</a>
</h3>
<hr />
<h3 class="left">
<a name="Links">Links</a>
</h3>
<p>
<a href="http://www.kegel.com/gcc/gcc4.html">Migrating to gcc-4.1</a>, by Dan Kegel.
</p>
<p>
<a href="http://lists.debian.org/debian-gcc/2006/03/msg00405.html">Building the whole Debian archive with GCC 4.1: a summary</a>, by Martin Michlmayr
</p>
<p>
<a href="http://annwm.lbl.gov/~leggett/Atlas/gcc-3.2.html">Migration guide for GCC-3.2</a>
</p>
</body>
</html>
|
