diff options
| author | Paolo Carlini <pcarlini@suse.de> | 2007-01-13 12:24:02 +0000 |
|---|---|---|
| committer | Paolo Carlini <paolo@gcc.gnu.org> | 2007-01-13 12:24:02 +0000 |
| commit | d8867564fe73d2f013c8ec5a4e03f1aba1acd549 (patch) | |
| tree | eae7ce21a6b3b367008ba8891ccc2fa03a6876eb /libstdc++-v3/docs/html | |
| parent | 8bcd6380d1a8cdd5de8095599ea452885b6d3959 (diff) | |
| download | gcc-d8867564fe73d2f013c8ec5a4e03f1aba1acd549.zip gcc-d8867564fe73d2f013c8ec5a4e03f1aba1acd549.tar.gz gcc-d8867564fe73d2f013c8ec5a4e03f1aba1acd549.tar.bz2 | |
re PR libstdc++/14991 (stream::attach(int fd) porting entry out-of-date)
2007-01-13 Paolo Carlini <pcarlini@suse.de>
PR libstdc++/14991
* docs/html/17_intro/porting-howto.html ([3]): Mention stdio_filebuf.
* docs/html/17_intro/porting-howto.xml: Remove.
* docs/html/17_intro/porting-howto.html: Remove spurious end tags
pointed out by validator.w3.org.
From-SVN: r120749
Diffstat (limited to 'libstdc++-v3/docs/html')
| -rw-r--r-- | libstdc++-v3/docs/html/17_intro/porting-howto.html | 46 | ||||
| -rw-r--r-- | libstdc++-v3/docs/html/17_intro/porting-howto.xml | 785 |
2 files changed, 13 insertions, 818 deletions
diff --git a/libstdc++-v3/docs/html/17_intro/porting-howto.html b/libstdc++-v3/docs/html/17_intro/porting-howto.html index 4a2d91a..d6bedb2 100644 --- a/libstdc++-v3/docs/html/17_intro/porting-howto.html +++ b/libstdc++-v3/docs/html/17_intro/porting-howto.html @@ -113,7 +113,7 @@ with this</a> </dt> </dl></dd> -<dt>2. <a href="#sec-nocreate">there is no ios::nocreate/ios::noreplace +<dt>2. <a href="#sec-nocreate">There is no ios::nocreate/ios::noreplace in ISO 14882</a> </dt> <dt>3. <a href="#sec-stream::attach">stream::attach(int @@ -182,7 +182,6 @@ <b>std::cout</b>) => can always be used </p></li> </ul></div> - </p> <p> Because there are many compilers which still use an implementation that does not have the standard C++-library in namespace @@ -235,7 +234,6 @@ libstdc++ in <b>std::</b> or not). (ideas from <tt><<a href="mailto:llewelly@dbritsch.dsl.xmission.com">llewelly@dbritsch.dsl.xmission.com</a>></tt>, Karl Nelson <tt><<a href="mailto:kenelson@ece.ucdavis.edu">kenelson@ece.ucdavis.edu</a>></tt>) - </p> </div> <div class="section"> <div class="titlepage"><div><h3 class="title"> @@ -248,7 +246,6 @@ namespace std { } using namespace std; </pre> - </p> </div> <div class="section"> <div class="titlepage"><div><h3 class="title"> @@ -270,7 +267,7 @@ </pre> (thanks to Juergen Heinzl who posted this solution on gnu.gcc.help) - </p></li> + </li> <li><p> Define a macro NS_STD, which is defined to either "" or "std" @@ -280,8 +277,6 @@ systems that do not put string in std::. (This is untested) </p></li> </ul></div> - - </p> </div> <div class="section"> <div class="titlepage"><div><h3 class="title"> @@ -356,7 +351,7 @@ </div> <div class="section"> <div class="titlepage"><div><h2 class="title" style="clear: both"> -<a name="sec-nocreate"></a>there is no ios::nocreate/ios::noreplace +<a name="sec-nocreate"></a>There is no ios::nocreate/ios::noreplace in ISO 14882</h2></div></div> <p> I have seen <b>ios::nocreate</b> being used for @@ -383,22 +378,8 @@ It was considered and rejected. Not all environments use file descriptors. Of those that do, not all of them use integers to represent them. - </p> -<p> - When using libstdc++-v3, you can use - <div class="funcsynopsis"> -<pre class="funcsynopsisinfo"> - #include <fstream> - </pre> -<p><code><code class="funcdef"> - <b class="fsfunc">basic_filebuf<...>::basic_filebuf<...> - </b> - </code>(<var class="pdparam">file</var>, <var class="pdparam">mode</var>, <var class="pdparam">size</var>);<br>__c_file_type* <var class="pdparam">file</var>;<br>ios_base::open_mode <var class="pdparam">mode</var>;<br>int <var class="pdparam">size</var>;</code></p> -</div> - but the the signature of this constructor has changed often, and - it might change again. For the current state of this, check - <a href="../ext/howto.html" target="_top">the howto for extensions</a>. - </p> + </p> + <p> For a portable solution (among systems which use filedescriptors), you need to implement a subclass of @@ -409,6 +390,14 @@ <a href="http://www.josuttis.com/cppcode/fdstream.html" target="_top">fdstream example</a> by Nicolai Josuttis. </p> + +<p> + An extension is also available: + <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> </div> <div class="section"> <div class="titlepage"><div><h2 class="title" style="clear: both"> @@ -491,7 +480,6 @@ more => use <b>if (iterator != iterator_type())</b> ?</p></li> </ul></div> - </p> </div> <div class="section"> <div class="titlepage"><div><h2 class="title" style="clear: both"> @@ -518,7 +506,6 @@ std:: (__ctype_b[(int) ( ( 'X' ) )] & (unsigned short int) _ISspace ) ; </pre> - </p> <p> One solution I can think of is to test for -v3 using autoconf-macros, and define macros for each of the C-functions @@ -537,7 +524,6 @@ [ now include <ctype.h> ] </pre> - </p> <p> Another problem arises if you put a <b>using namespace std;</b> declaration at the top, and include <tt><ctype.h></tt>. This will result in @@ -598,7 +584,6 @@ </pre> If you are using other (non-GNU) compilers it might be a good idea to check for <b>string::at</b> separately. - </p> </div> <div class="section"> <div class="titlepage"><div><h2 class="title" style="clear: both"> @@ -611,7 +596,6 @@ #define CPP_EOF EOF #endif </pre> - </p> </div> <div class="section"> <div class="titlepage"><div><h2 class="title" style="clear: both"> @@ -637,7 +621,6 @@ implemented in gcc 2.95.x's libstdc++, so you should use <b>erase</b> (which is probably faster than <b>operator=(charT*)</b>). - </p> </div> <div class="section"> <div class="titlepage"><div><h2 class="title" style="clear: both"> @@ -678,7 +661,6 @@ (clear(); str(input);) </p></li> </ul></div> - </p> <p> You can then use output-stringstreams like this: <pre class="programlisting"> @@ -701,7 +683,6 @@ oss.freeze(false); #endif </pre> - </p> <p> Input-stringstreams can be used similarly: <pre class="programlisting"> @@ -743,7 +724,6 @@ } </pre> Another example of using stringstreams is in <a href="../21_strings/howto.html" target="_top">this howto</a>. - </p> <p> I have read the Josuttis book on Standard C++, so some information comes from there. Additionally, there is information in diff --git a/libstdc++-v3/docs/html/17_intro/porting-howto.xml b/libstdc++-v3/docs/html/17_intro/porting-howto.xml deleted file mode 100644 index cea9111..0000000 --- a/libstdc++-v3/docs/html/17_intro/porting-howto.xml +++ /dev/null @@ -1,785 +0,0 @@ -<?xml version="1.0" encoding="ISO-8859-1"?> - -<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1//EN" - "http://www.oasis-open.org/docbook/xml/4.0/docbookx.dtd"> - -<?xml-stylesheet type="text/xsl" href="docbook-xslt/docbook/html/docbook.xsl"?> - -<!-- - This is written using docbook 4.1 xml. HTML is generated using - the xslt-stylesheets from http://www.nwalsh.com. - - xsltproc is an xslt-processor included in libxslt: - (http://xmlsoft.org/XSLT/ or here: - ftp://ftp.gnome.org/pub/GNOME/unstable/sources/libxslt/) - (it requires libxml2: http://xmlsoft.org - or here: ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/) - - You can find the latest version of this document here: - http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/porting-howto(.html|.xml) ---> - -<!-- TODO: -o remove //@label: use automatic numbering -o make this work: <link linkend="sec-gtkmm-hack" endterm="sec-gtkmm-hack.title"/>. -o clean up the section-numbering ---> - -<article class = "whitepaper" id = "libstdc++-porting-howto" lang = "en"> - <articleinfo> - <title>Libstdc++-porting-howto</title> - <author> - <firstname>Felix</firstname> - <surname>Natter</surname> - </author> - <address> - <email>fnatter@gmx.net</email> - </address> - <revhistory> - <revision> - <revnumber>0.5</revnumber> - <date>Thu Jun 1 13:06:50 2000</date> - <authorinitials>fnatter</authorinitials> - <revremark>First docbook-version.</revremark> - </revision> - <revision> - <revnumber>0.8</revnumber> - <date>Sun Jul 30 20:28:40 2000</date> - <authorinitials>fnatter</authorinitials> - <revremark>First released version using docbook-xml - + second upload to libstdc++-page. - </revremark> - </revision> - <revision> - <revnumber>0.9</revnumber> - <date>Wed Sep 6 02:59:32 2000</date> - <authorinitials>fnatter</authorinitials> - <revremark>5 new sections.</revremark> - </revision> - <revision> - <revnumber>0.9.1</revnumber> - <date>Sat Sep 23 14:20:15 2000</date> - <authorinitials>fnatter</authorinitials> - <revremark>added information about why file-descriptors are not in the - standard</revremark> - </revision> - <revision> - <revnumber>0.9.2</revnumber> - <date>Tue Jun 5 20:07:49 2001</date> - <authorinitials>fnatter</authorinitials> - <revremark> - a fix, added hint on increased portability of C-shadow-headers, - added autoconf-test HAVE_CONTAINER_AT - </revremark> - </revision> - <revision> - <revnumber>0.9.3</revnumber> - <date>Fri Jun 29 16:15:56 2001</date> - <authorinitials>fnatter</authorinitials> - <revremark> - changed signature of nonstandard filebuf-constructor and - update the section on filebuf::attach to point to ../ext/howto.html, - added link to ../21/strings/howto.html - in sec-stringstream, changed <link>-tags to have content - (so that these links work), - replace "user-space" by "global namespace" - add note about gcc 3.0 and shadow-headers - add section about ostream::form and istream::scan - sec-vector-at: remove hint to modify headers - fix spelling error in sec-stringstream - </revremark> - </revision> - <revision> - <revnumber>0.9.4</revnumber> - <date>Mon Nov 5 17:01:04 2001</date> - <authorinitials>fnatter</authorinitials> - <revremark> - rewrite section 1.1.3 because of gnu.gcc.help-post by - Juergen Heinzl - </revremark> - </revision> - </revhistory> - <legalnotice><title>Legal Notice</title> - <para> - This document can be distributed under the FDL - (<ulink url = "http://www.gnu.org">www.gnu.org</ulink>) - </para> - </legalnotice> - - <pubdate>Tue Jun 5 20:07:49 2001</pubdate> - <abstract> - <para> - Some notes on porting applications from libstdc++-2.90 (or earlier - versions) to libstdc++-v3. Not speaking in terms of the GNU libstdc++ - implementations, this means porting from earlier versions of the - C++-Standard to ISO 14882. - </para> - </abstract> - </articleinfo> - - <para> - In the following, when I say portable, I will refer to "portable among ISO - 14882-implementations". On the other hand, if I say "backportable" or - "conservative", I am talking about "compiles with older - libstdc++-implementations". - </para> - - <section id="sec-nsstd" label="1"><title>Namespace std::</title> - <para> - The latest C++-standard (ISO-14882) requires that the standard - C++-library is defined in namespace std::. Thus, in order to use - classes from the standard C++-library, you can do one of three - things: - <itemizedlist> - - <listitem><para>wrap your code in <command>namespace std { - ... }</command> => This is not an option because only symbols - from the standard c++-library are defined in namespace std::. - </para></listitem> - - <listitem><para>put a kind of - <emphasis>using-declaration</emphasis> in your source (either - <command>using namespace std;</command> or i.e. <command>using - std::string;</command>) => works well for source-files, but - cannot be used in header-files. - </para></listitem> - - <listitem><para>use a <emphasis>fully qualified name</emphasis> for - each libstdc++-symbol (i.e. <command>std::string</command>, - <command>std::cout</command>) => can always be used - </para></listitem> - </itemizedlist> - </para> - - <para> - Because there are many compilers which still use an implementation - that does not have the standard C++-library in namespace - <command>std::</command>, some care is required to support these as - well. - </para> - - <para> - Namespace back-portability-issues are generally not a problem with - g++, because versions of g++ that do not have libstdc++ in - <command>std::</command> use <command>-fno-honor-std</command> - (ignore <command>std::</command>, <command>:: = std::</command>) by - default. That is, the responsibility for enabling or disabling - <command>std::</command> is on the user; the maintainer does not have - to care about it. This probably applies to some other compilers as - well. - </para> - <para> - The following sections list some possible solutions to support compilers - that cannot ignore std::. - </para> - - <section id = "sec-gtkmm-hack" label = "1.1"> - <title id="sec-gtkmm-hack.title">Using <emphasis>namespace - composition</emphasis> if the project uses a separate - namespace</title> - <para> - <ulink url = "http://gtkmm.sourceforge.net">Gtk--</ulink> defines - most of its classes in namespace Gtk::. Thus, it was possible to - adapt Gtk-- to namespace std:: by using a C++-feature called - <emphasis>namespace composition</emphasis>. This is what happens if - you put a <emphasis>using</emphasis>-declaration into a - namespace-definition: the imported symbol(s) gets imported into the - currently active namespace(s). For example: - <programlisting> - namespace Gtk { - using std::string; - class Window { ... } - } - </programlisting> - In this example, <command>std::string</command> gets imported into - namespace Gtk::. The result is that you don't have to use - <command>std::string</command> in this header, but still - <command>std::string</command> does not get imported into - the global namespace (::) unless the user does - <command>using namespace Gtk;</command> (which is not recommended - practice for Gtk--, so it is not a problem). Additionally, the - <command>using</command>-declarations are wrapped in macros that - are set based on autoconf-tests to either "" or i.e. <command>using - std::string;</command> (depending on whether the system has - libstdc++ in <command>std::</command> or not). (ideas from - <email>llewelly@dbritsch.dsl.xmission.com</email>, Karl Nelson - <email>kenelson@ece.ucdavis.edu</email>) - </para> - </section> - - <section id = "sec-emptyns" label = "1.2"> - <title id="sec-emptyns.title">Defining an empty namespace std</title> - <para> - By defining an (empty) namespace <command>std::</command> before - using it, you avoid getting errors on systems where no part of the - library is in namespace std: - <programlisting> - namespace std { } - using namespace std; - </programlisting> - </para> - </section> - - <section id = "sec-avoidfqn" label = "1.3"> - <title id="sec-avoidfqn.title">Avoid to use fully qualified names - (i.e. std::string)</title> - <para> - If some compilers complain about <command>using - std::string;</command>, and if the "hack" for gtk-- mentioned above - does not work, then I see two solutions: - - <itemizedlist> - <listitem><para> - Define <command>std::</command> as a macro if the compiler - doesn't know about <command>std::</command>. - <programlisting> - #ifdef OLD_COMPILER - #define std - #endif - </programlisting> - (thanks to Juergen Heinzl who posted this solution on - gnu.gcc.help) - </para></listitem> - - <listitem><para> - Define a macro <symbol>NS_STD</symbol>, which is defined to - either "" or "std" - based on an autoconf-test. Then you should be able to use - <command>NS_STD::string</command>, which will evaluate to - <command>::string</command> ("string in the global namespace") on - systems that do not put string in std::. (This is untested) - </para></listitem> - </itemizedlist> - - </para> - </section> - - <section id = "sec-osprojects" label = "1.4"> - <title id="sec-osprojects.title">How some open-source-projects deal - with this</title> - <para> - This information was gathered around May 2000. It may not be correct - by the time you read this. - </para> - <table><title>Namespace std:: in Open-Source programs</title> - <tgroup cols = "2"> - <tbody> - <row> - <entry><ulink url = "http://www.clanlib.org">clanlib</ulink> - </entry> - <entry>usual</entry> - </row> - <row> - <entry><ulink url = "http://pingus.seul.org">pingus</ulink> - </entry> - <entry>usual</entry> - </row> - <row> - <entry><ulink url = "http://www.mozilla.org">mozilla</ulink> - </entry> - <entry>usual</entry> - </row> - <row> - <entry><ulink url = "http://libsigc.sourceforge.net"> - libsigc++</ulink></entry> - <entry>conservative-impl</entry> - </row> - </tbody> - </tgroup> - </table> - - <table><title>Notations for categories</title> - <tgroup cols = "2"> - <tbody> - <row> - <entry>usual</entry> - <entry>mostly fully qualified names and some - using-declarations (but not in headers)</entry> - </row> - <row> - <entry>none</entry> <entry>no namespace std at all</entry> - </row> - <row> - <entry>conservative-impl</entry> - <entry>wrap all - namespace-handling in macros to support compilers without - namespace-support (no libstdc++ used in headers)</entry> - </row> - </tbody> - </tgroup> - </table> - - <para> - 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 <link linkend="sec-gtkmm-hack" - endterm="sec-gtkmm-hack.title">section on the gtkmm-hack</link>). - </para> - </section> - </section> <!-- end of namespace-section --> - - <section id = "sec-nocreate" label = "2"> - <title id="sec-nocreate.title">there is no ios::nocreate/ios::noreplace - in ISO 14882</title> - <para> - I have seen <command>ios::nocreate</command> being used for - input-streams, most probably because the author thought it would be - more correct to specify nocreate "explicitly". So you can simply - leave it out for input-streams. - </para> - <para> - For output streams, "nocreate" is probably the default, unless you - specify <command>std::ios::trunc</command> ? 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 <command>app</command>, - <command>ate</command> and <command>trunc</command> (except for - <command>app</command> ?). - </para> - </section> - - <section id = "sec-stream::attach" label = "3"> - <title id="sec-stream::attach.title"><command>stream::attach(int - fd)</command> is not in the standard any more</title> - <para> - Phil Edwards <email>pedwards@disaster.jaj.com</email> writes: - It was considered and rejected. Not all environments use file - descriptors. Of those that do, not all of them use integers to represent - them. - </para> - <para> - When using libstdc++-v3, you can use - <funcsynopsis> - <funcsynopsisinfo format="linespecific"> - #include <fstream> - </funcsynopsisinfo> - <funcprototype> - <funcdef> - <function>basic_filebuf<...>::basic_filebuf<...> - </function> - </funcdef> - <paramdef>__c_file_type* <parameter>file</parameter></paramdef> - <paramdef>ios_base::open_mode <parameter>mode</parameter></paramdef> - <paramdef>int <parameter>size</parameter></paramdef> - </funcprototype> - </funcsynopsis> - but the signature of this constructor has changed often, and - it might change again. For the current state of this, check - <ulink url="../ext/howto.html">the howto for extensions</ulink>. - </para> - <para> - For a portable solution (among systems which use - filedescriptors), you need to implement a subclass of - <command>std::streambuf</command> (or - <command>std::basic_streambuf<..></command>) which opens a file - given a descriptor, and then pass an instance of this to the - stream-constructor. For an example of this, refer to - <ulink url="http://www.josuttis.com/cppcode/fdstream.html">fdstream example</ulink> - by Nicolai Josuttis. - </para> - </section> - - <section id = "sec-headers" label = "4"> - <title id="sec-headers.title">The new headers</title> - <para> - All new headers can be seen in this <ulink url="headers_cc.txt"> - source-code</ulink>. - </para> - <para> - The old C++-headers (iostream.h etc.) are available, but gcc generates - a warning that you are using deprecated headers. - </para> - - <section id = "sec-cheaders" label = "4.1"> - <title id="sec-cheaders.title">New headers replacing C-headers</title> - <para> - You should not use the C-headers (except for system-level - headers) from C++ programs. Instead, you should use a set of - headers that are named by prepending 'c' and, as usual, - omitting the extension (.h). For example, instead of using - <filename class="headerfile"><math.h></filename>, you - should use <filename class = - "headerfile"><cmath></filename>. In some cases this has - the advantage that the C++-header is more standardized than - the C-header (i.e. <filename - class="headerfile"><ctime></filename> (almost) - corresponds to either <filename class = - "headerfile"><time.h></filename> or <filename class = - "headerfile"><sys/time.h></filename>). - - The standard specifies that if you include the C-style header - (<filename class = "headerfile"><math.h></filename> in - this case), the symbols will be available both in the global - namespace and in namespace <command>std::</command> (but - libstdc++ does not yet have fully compliant headers) On the - other hand, if you include only the new header (i.e. <filename - class = "headerfile"><cmath></filename>), the symbols - will only be defined in namespace <command>std::</command> - (and macros will be converted to inline-functions). - </para> - <para> - For more information on this, and for information on how the - GNU C++ implementation might reuse ("shadow") the C - library-functions, have a look at <ulink - url="http://www.cantrip.org/cheaders.html"> - www.cantrip.org</ulink>. - </para> - </section> - - <section id = "sec-fstream-header" label = "4.2"> - <title id="sec-fstream-header.title"> - <filename class="headerfile"><fstream></filename> does - not define <command>std::cout</command>, - <command>std::cin</command> etc.</title> - <para> - In earlier versions of the standard, - <filename class="headerfile"><fstream.h></filename>, - <filename class="headerfile"><ostream.h></filename> - and <filename class="headerfile"><istream.h></filename> - used to define - <command>cout</command>, <command>cin</command> and so on. Because - of the templatized iostreams in libstdc++-v3, you need to include - <filename class = "headerfile"><iostream></filename> - explicitly to define these. - </para> - </section> - </section> - - <section id = "sec-iterators" label = "5"> - <title id="sec-iterators.title">Iterators</title> - <para> - The following are not proper uses of iterators, but may be working - fixes for existing uses of iterators. - <itemizedlist> - <listitem><para>you cannot do - <command>ostream::operator<<(iterator)</command> to - print the address of the iterator => use - <command>operator<< &*iterator</command> instead ? - </para> - </listitem> - <listitem><para>you cannot clear an iterator's reference - (<command>iterator = 0</command>) => use - <command>iterator = iterator_type();</command> ? - </para> - </listitem> - <listitem><para><command>if (iterator)</command> won't work any - more => use <command>if (iterator != iterator_type())</command> - ?</para> - </listitem> - </itemizedlist> - </para> - </section> - - <section id = "sec-macros" label = "6"> - <title id="sec-macros.title"> - Libc-macros (i.e. <command>isspace</command> from - <filename class = "headerfile"><cctype></filename>)</title> - <para> - Glibc 2.0.x and 2.1.x define the - <filename class="headerfile"><ctype.h></filename> - -functionality as macros (isspace, isalpha etc.). Libstdc++-v3 - "shadows" these macros as described in the <link - linkend="sec-cheaders" endterm="sec-cheaders.title">section about - c-headers</link>. - </para> - <para> - Older implementations of libstdc++ (g++-2 for egcs 1.x and g++-3 - for gcc 2.95.x), however, keep these functions as macros, and so it - is not back-portable to use fully qualified names. For example: - <programlisting> - #include <cctype> - int main() { std::isspace('X'); } - </programlisting> - will result in something like this (unless using g++-v3): - <programlisting> - std:: (__ctype_b[(int) ( ( 'X' ) )] & (unsigned short int) - _ISspace ) ; - </programlisting> - </para> - <para> - One solution I can think of is to test for -v3 using - autoconf-macros, and define macros for each of the C-functions - (maybe that is possible with one "wrapper" macro as well ?). - </para> - <para> - Another solution which would fix g++ is to tell the user to modify a - header-file so that g++-2 (egcs 1.x) and g++-3 (gcc 2.95.x) define a - macro which tells <filename - class="headerfile"><ctype.h></filename> to define functions - instead of macros: - <programlisting> - // This keeps isalnum, et al from being propagated as macros. - #if __linux__ - #define __NO_CTYPE 1 - #endif - - [ now include <ctype.h> ] - </programlisting> - </para> - <para> - Another problem arises if you put a <command>using namespace - std;</command> declaration at the top, and include <filename class - = "headerfile"><ctype.h></filename>. This will result in - ambiguities between the definitions in the global namespace - (<filename class = "headerfile"><ctype.h></filename>) and the - definitions in namespace <command>std::</command> - (<command><cctype></command>). - </para> - <para> - The solution to this problem was posted to the libstdc++-v3 - mailing-list: - Benjamin Kosnik <email>bkoz@redhat.com</email> writes: - <quote> - --enable-cshadow-headers is currently broken. As a result, shadow - headers are not being searched.... - </quote> - This is now outdated, but gcc 3.0 still does not have fully - compliant "shadow headers". - </para> - </section> - - <section id="sec-stream-state" label="7"> - <title id="sec-stream-state.title">State of streams</title> - <para> - At least some older implementations don't have - <command>std::ios_base</command>, so you should use - <command>std::ios::badbit</command>, <command>std::ios::failbit</command> - and <command>std::ios::eofbit</command> and - <command>std::ios::goodbit</command>. - </para> - </section> - - <section id="sec-vector-at" label="8"> - <title>vector::at is missing (i.e. gcc 2.95.x)</title> - <para> - One solution is to add an autoconf-test for this: - <programlisting> - 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)]) - </programlisting> - If you are using other (non-GNU) compilers it might be a good idea - to check for <command>string::at</command> separately. - </para> - </section> - - <section id="sec-eof" label="9"> - <title>Using std::char_traits<char>::eof()</title> - <para> - <programlisting> - #ifdef HAVE_CHAR_TRAITS - #define CPP_EOF std::char_traits<char>::eof() - #else - #define CPP_EOF EOF - #endif - </programlisting> - </para> - </section> - - <section id="sec-string-clear" label="10"> - <title>Using string::clear()/string::erase()</title> - <para> - There are two functions for deleting the contents of a string: - <command>clear</command> and <command>erase</command> (the latter - returns the string). - <programlisting> - void - clear() { _M_mutate(0, this->size(), 0); } - </programlisting> - <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()); - } - </programlisting> - The implementation of <command>erase</command> seems to be more - complicated (from libstdc++-v3), but <command>clear</command> is not - implemented in gcc 2.95.x's libstdc++, so you should use - <command>erase</command> (which is probably faster than - <command>operator=(charT*)</command>). - </para> - </section> - - <section id="sec-scan-form" label="11"> - <title>GNU Extensions ostream::form and istream::scan</title> - <para> - These are not supported any more - use - <link linkend="sec-stringstream" endterm="sec-stringstream.title"> - stringstreams</link> instead. - </para> - </section> - - <section id="sec-stringstream" label="12"> - <title>Using stringstreams</title> - <para> - Libstdc++-v3 provides the new - <command>i/ostringstream</command>-classes, (<filename - class="headerfile"><sstream></filename>), but for compatibility - with older implementations you still have to use - <command>i/ostrstream</command> (<filename - class="headerfile"><strstream></filename>): - <programlisting> - #ifdef HAVE_SSTREAM - #include <sstream> - #else - #include <strstream> - #endif - </programlisting> - <itemizedlist> - <listitem><para> <command>strstream</command> is considered to be - deprecated - </para> - </listitem> - <listitem><para> <command>strstream</command> is limited to - <command>char</command> - </para> - </listitem> - <listitem><para> with <command>ostringstream</command> you don't - have to take care of terminating the string or freeing its - memory - </para> - </listitem> - <listitem><para> <command>istringstream</command> can be re-filled - (clear(); str(input);) - </para> - </listitem> - </itemizedlist> - </para> - <para> - You can then use output-stringstreams like this: - <programlisting> - #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 - </programlisting> - </para> - <para> - Input-stringstreams can be used similarly: - <programlisting> - std::string input; - ... - #ifdef HAVE_SSTREAM - std::istringstream iss(input); - #else - std::istrstream iss(input.c_str()); - #endif - int i; - iss >> i; - </programlisting> - One (the only?) restriction is that an istrstream cannot be re-filled: - <programlisting> - std::istringstream iss(numerator); - iss >> m_num; - // this is not possible with istrstream - iss.clear(); - iss.str(denominator); - iss >> m_den; - </programlisting> - If you don't care about speed, you can put these conversions in - a template-function: - <programlisting> - 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; - } - </programlisting> - Another example of using stringstreams is in <ulink - url="../21_strings/howto.html">this howto</ulink>. - </para> - <para> - 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.x - uses. - </para> - </section> - - <section id = "sec-about" label="13"> - <title id="sec-about.title">About...</title> - <para> - Please send any experience, additions, corrections or questions to - <ulink url = "mailto:fnatter@gmx.net">fnatter@gmx.net</ulink> or for - discussion to the libstdc++-v3-mailing-list. - </para> - </section> - -</article> - - <!-- this is now obsolete, since the nwalsh-stylesheet generates an index -<para> -<itemizedlist> -<listitem><para> -<link linkend = "sec-nsstd" endterm = "sec-nsstd.title"/> -</para></listitem> -<listitem><para> -<link linkend = "sec-nocreate" endterm = "sec-nocreate.title"/> -</para></listitem> -<listitem><para> -<link linkend = "sec-stream::attach" - endterm = "sec-stream::attach.title"/> -</para></listitem> -<listitem><para> -<link linkend = "sec-headers" endterm = "sec-headers.title"/> -</para></listitem> -<listitem><para> -<link linkend = "sec-iterators" endterm = "sec-iterators.title"/> -</para></listitem> -<listitem><para> -<link linkend = "sec-macros" endterm = "sec-macros.title"/> -</para></listitem> -<listitem><para> -<link linkend = "sec-about" endterm = "sec-about.title"/> -</para></listitem> -</itemizedlist> -</para> - --> - -<!-- -Local Variables: -compile-command: "xsltproc -o porting-howto.html docbook-xslt/docbook/html/docbook.xsl porting-howto.xml" -End: ---> |