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porting-howto.html: New version.

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2000-09-08  Felix Natter  <fnatter@gmx.net>

	* docs/17_intro/porting-howto.html:  New version.

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Felix Natter 2000-09-08 20:30:24 +00:00 committed by Phil Edwards
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libstdc++-v3/ChangeLog
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@ -1,3 +1,7 @@
2000-09-08 Felix Natter <fnatter@gmx.net>
* docs/17_intro/porting-howto.html: New version.
2000-09-07 Benjamin Kosnik <bkoz@purist.soma.redhat.com>
* config/cpu/i386/bits/atomicity.h (__exchange_and_add): Change unused

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libstdc++-v3/docs/17_intro/porting-howto.html
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@ -34,11 +34,17 @@
+ second upload to libstdc++-page.
</td>
</tr>
<tr>
<td align="left">Revision 0.9</td><td align="left">Wed Sep 6 02:59:32 2000</td><td align="left">fnatter</td>
</tr>
<tr>
<td colspan="3" align="left">5 new sections.</td>
</tr>
</table>
</div>
<div class="abstract">
<p>
<a name="N2672"></a><b>Abstract</b>
<a name="N2688"></a><b>Abstract</b>
</p>
<p>
Some notes on porting applications from libstdc++-2.90 (or earlier
@ -97,7 +103,19 @@
Libc-macros (i.e. <b>isspace</b> from
<tt>&lt;cctype&gt;</tt>)</a>
</dt>
<dt>7. <a href="#sec-about">About...</a>
<dt>7. <a href="#sec-stream-state">
State of streams
</a>
</dt>
<dt>8. <a href="#sec-vector-at">vector::at is missing (i.e. gcc 2.95.2)</a>
</dt>
<dt>9. <a href="#sec-eof">Using std::char_traits&lt;char&gt;::eof()</a>
</dt>
<dt>10. <a href="#sec-string-clear">Using string::clear()/string::erase()</a>
</dt>
<dt>11. <a href="#sec-stringstream">Using stringstream's</a>
</dt>
<dt>12. <a href="#sec-about">About...</a>
</dt>
</dl>
</div>
@ -119,14 +137,14 @@
<div class="itemizedlist">
<ul>
<li>
<a name="N2696"></a>
<a name="N2712"></a>
<p>wrap your code in <b>namespace std {
... }</b> =&gt; This is not an option because only symbols
from the standard c++-library are defined in namespace std::.
</p>
</li>
<li>
<a name="N2705"></a>
<a name="N2721"></a>
<p>put a kind of
<i>using-declaration</i> in your source (either
<b>using namespace std;</b> or i.e. <b>using
@ -135,7 +153,7 @@
</p>
</li>
<li>
<a name="N2720"></a>
<a name="N2736"></a>
<p>use a <i>fully qualified name</i> for
each libstdc++-symbol (i.e. <b>std::string</b>,
<b>std::cout</b>) =&gt; can always be used
@ -240,7 +258,7 @@
</p>
<div class="table">
<p>
<a name="N2885"></a><b>Table 1. Namespace std:: in Open-Source programs</b>
<a name="N2901"></a><b>Table 1. Namespace std:: in Open-Source programs</b>
</p>
<table border="1">
<colgroup>
@ -269,7 +287,7 @@
</div>
<div class="table">
<p>
<a name="N2962"></a><b>Table 2. Notations for categories</b>
<a name="N2978"></a><b>Table 2. Notations for categories</b>
</p>
<table border="1">
<colgroup>
@ -295,8 +313,7 @@
<p>
As you can see, this currently lacks an example of a project which
uses libstdc++-symbols in headers in a back-portable way (except
for Gtk--: see the <a href="#sec-gtkmm-hack">section on the Gtk-- hack
</a>).
for Gtk--: see the <a href="#"></a>).
</p>
</div>
</div>
@ -328,10 +345,10 @@
</h2>
<p>
When using libstdc++-v3, you can use
<div id="N3066" class="funcsynopsis">
<div id="N3082" class="funcsynopsis">
<p>
</p>
<a name="N3066"></a>
<a name="N3082"></a>
<pre class="funcsynopsisinfo">
#include &lt;fstream&gt;
</pre>
@ -412,7 +429,7 @@
<div class="itemizedlist">
<ul>
<li>
<a name="N3266"></a>
<a name="N3282"></a>
<p>you cannot do
<b>ostream::operator&lt;&lt;(iterator)</b> to
print the address of the iterator =&gt; use
@ -420,14 +437,14 @@
</p>
</li>
<li>
<a name="N3287"></a>
<a name="N3303"></a>
<p>you cannot clear an iterator's reference
(<b>iterator = 0</b>) =&gt; use
<b>iterator = iterator_type();</b> ?
</p>
</li>
<li>
<a name="N3300"></a>
<a name="N3316"></a>
<p>
<b>if (iterator)</b> won't work any
more =&gt; use <b>if (iterator != iterator_type())</b>
@ -446,7 +463,7 @@
<p>
Glibc 2.0.x and 2.1.x define the <tt>&lt;ctype.h&gt;</tt> -functionality as
macros (isspace, isalpha etc.). Libstdc++-v3 "shadows" these macros
as described in the <a href="#sec-cheaders">section on C-headers</a>.
as described in the <a href="#"></a>.
</p>
<p>
Older implementations of libstdc++ (g++-2 for egcs 1.x and g++-3
@ -499,9 +516,204 @@
"
</p>
</div>
<div class="section" id="sec-stream-state">
<h2 class="title" style="clear: all">
<a name="sec-stream-state"><b>7.
State of streams
</b></a>
</h2>
<p>
At least some older implementations don't have
<b>std::ios_base</b>, so you should use
<b>std::ios::badbit</b>, <b>std::ios::failbit</b>
and <b>std::ios::eofbit</b> and
<b>std::ios::goodbit</b>.
</p>
</div>
<div class="section" id="sec-vector-at">
<h2 class="title" style="clear: all">
<a name="sec-vector-at"><b>8. vector::at is missing (i.e. gcc 2.95.2)</b></a>
</h2>
<p>
For my use, I added it to
<tt>prefix/include/g++-3/stl_vector.h</tt>:
<pre class="programlisting">
reference operator[](size_type __n) { return *(begin() + __n); }
reference at(size_type __n) {
if (begin() + __n &gt;= end())
throw out_of_range("vector::at");
return *(begin() + __n);
}
const_reference operator[](size_type __n) const { return *(begin() + __n); }
const_reference at(size_type __n) const {
if (begin() + __n &gt;= end())
throw out_of_range("vector::at");
return *(begin() + __n);
}
</pre>
</p>
</div>
<div class="section" id="sec-eof">
<h2 class="title" style="clear: all">
<a name="sec-eof"><b>9. Using std::char_traits&lt;char&gt;::eof()</b></a>
</h2>
<p>
<pre class="programlisting">
#ifdef HAVE_CHAR_TRAITS
#define CPP_EOF std::char_traits&lt;char&gt;::eof()
#else
#define CPP_EOF EOF
#endif
</pre>
</p>
</div>
<div class="section" id="sec-string-clear">
<h2 class="title" style="clear: all">
<a name="sec-string-clear"><b>10. Using string::clear()/string::erase()</b></a>
</h2>
<p>
There are two functions for deleting the contents of a string:
<b>clear</b> and <b>erase</b> (the latter
returns the string).
<pre class="programlisting">
void
clear() { _M_mutate(0, this-&gt;size(), 0); }
</pre>
<pre class="programlisting">
basic_string&amp;
erase(size_type __pos = 0, size_type __n = npos)
{
return this-&gt;replace(_M_check(__pos), _M_fold(__pos, __n),
_M_data(), _M_data());
}
</pre>
The implementation of <b>erase</b> seems to be more
complicated (from libstdc++-v3), but <b>clear</b> is not
implemented in gcc 2.95.2's libstdc++, so you should use
<b>erase</b> (which is probably faster than
<b>operator=(charT*)</b>).
</p>
</div>
<div class="section" id="sec-stringstream">
<h2 class="title" style="clear: all">
<a name="sec-stringstream"><b>11. Using stringstream's</b></a>
</h2>
<p>
Libstdc++-v3 includes the new
<b>i/ostringstream</b>-classes, (<tt>&lt;sstream&gt;</tt>), but with older
implementations you still have to use <b>i/ostrstream</b>
(<tt>&lt;strstream&gt;</tt>):
<pre class="programlisting">
#ifdef HAVE_SSTREAM
#include &lt;sstream&gt;
#else
#include &lt;strstream&gt;
#endif
</pre>
<div class="itemizedlist">
<ul>
<li>
<a name="N3595"></a>
<p> <b>strstream</b> is considered to be
deprecated
</p>
</li>
<li>
<a name="N3603"></a>
<p> <b>strstream</b> is limited to
<b>char</b>
</p>
</li>
<li>
<a name="N3614"></a>
<p> with <b>ostringstream</b> you don't
have to take care of terminating the string or freeing its
memory
</p>
</li>
<li>
<a name="N3622"></a>
<p> <b>istringstream</b> can be re-filled
(clear(); str(input);)
</p>
</li>
</ul>
</div>
</p>
<p>
You can then use output-stringstreams like this:
<pre class="programlisting">
#ifdef HAVE_SSTREAM
std::ostringstream oss;
#else
std::ostrstream oss;
#endif
oss &lt;&lt; "Name=" &lt;&lt; m_name &lt;&lt; ", number=" &lt;&lt; m_number &lt;&lt; std::endl;
...
#ifndef HAVE_SSTREAM
oss &lt;&lt; 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>
<p>
Input-stringstreams can be used similarly:
<pre class="programlisting">
std::string input;
...
#ifdef HAVE_SSTREAM
std::istringstream iss(input);
#else
std::istrstream iss(input.c_str());
#endif
int i;
iss &gt;&gt; i;
</pre>
One (the only?) restriction is that an istrstream cannot be re-filled:
<pre class="programlisting">
std::istringstream iss(numerator);
iss &gt;&gt; m_num;
// this is not possible with istrstream
iss.clear();
iss.str(denominator);
iss &gt;&gt; m_den;
</pre>
If you don't care about speed, you can put these conversions in
a template-function:
<pre class="programlisting">
template &lt;class X&gt;
void fromString(const string&amp; input, X&amp; any)
{
#ifdef HAVE_SSTREAM
std::istringstream iss(input);
#else
std::istrstream iss(input.c_str());
#endif
X temp;
iss &gt;&gt; temp;
if (iss.fail())
throw runtime_error(..)
any = temp;
}
</pre>
</p>
<p>
I have read the Josuttis book on Standard C++, so some information
comes from there. Additionally, there is information in
"info iostream", which covers the old implementation that gcc 2.95.2
uses.
</p>
</div>
<div class="section" id="sec-about">
<h2 class="title" style="clear: all">
<a name="sec-about"><b>7. About...</b></a>
<a name="sec-about"><b>12. About...</b></a>
</h2>
<p>
Please send any experience, additions, corrections or questions to