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Porting and Maintenance" /><link rel="prev" href="api.html" title="API Evolution and Deprecation History" /><link rel="next" href="appendix_free.html" title="Appendix C. Free Software Needs Free Documentation" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Backwards Compatibility</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="api.html">Prev</a> </td><th width="60%" align="center">Appendix B. - Porting and Maintenance - -</th><td width="20%" align="right"> <a accesskey="n" href="appendix_free.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.appendix.porting.backwards"></a>Backwards Compatibility</h2></div></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="backwards.first"></a>First</h3></div></div></div><p>The first generation GNU C++ library was called libg++. It was a -separate GNU project, although reliably paired with GCC. Rumors imply -that it had a working relationship with at least two kinds of -dinosaur. -</p><p>Some background: libg++ was designed and created when there was no -ISO standard to provide guidance. Classes like linked lists are now -provided for by <code class="classname">list<T></code> and do not need to be -created by <code class="function">genclass</code>. (For that matter, templates exist -now and are well-supported, whereas genclass (mostly) predates them.) -</p><p>There are other classes in libg++ that are not specified in the -ISO Standard (e.g., statistical analysis). While there are a lot of -really useful things that are used by a lot of people, the Standards -Committee couldn't include everything, and so a lot of those -“<span class="quote">obvious</span>” classes didn't get included. -</p><p>Known Issues include many of the limitations of its immediate ancestor.</p><p>Portability notes and known implementation limitations are as follows.</p><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id459608"></a>No <code class="code">ios_base</code></h4></div></div></div><p> At least some older implementations don't have <code class="code">std::ios_base</code>, so you should use <code class="code">std::ios::badbit</code>, <code class="code">std::ios::failbit</code> and <code class="code">std::ios::eofbit</code> and <code class="code">std::ios::goodbit</code>. -</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id444641"></a>No <code class="code">cout</code> in <code class="code">ostream.h</code>, no <code class="code">cin</code> in <code class="code">istream.h</code></h4></div></div></div><p> - In earlier versions of the standard, - <code class="filename">fstream.h</code>, - <code class="filename">ostream.h</code> - and <code class="filename">istream.h</code> - used to define - <code class="code">cout</code>, <code class="code">cin</code> and so on. ISO C++ specifies that one needs to include - <code class="filename">iostream</code> - 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. For the desperate, -the <a class="ulink" href="http://gcc.gnu.org/extensions.html" target="_top">GCC extensions -page</a> describes where to find the last libg++ source. The code is -considered replaced and rewritten. -</p></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="backwards.second"></a>Second</h3></div></div></div><p> - The second generation GNU C++ library was called libstdc++, or - libstdc++-v2. It spans the time between libg++ and pre-ISO C++ - standardization and is usually associated with the following GCC - releases: egcs 1.x, gcc 2.95, and gcc 2.96. -</p><p> - The STL portions of this library are based on SGI/HP STL release 3.11. -</p><p> - This project is no longer maintained or supported, and the sources - archived. The code is considered replaced and rewritten. -</p><p> - Portability notes and known implementation limitations are as follows. -</p><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id444741"></a>Namespace <code class="code">std::</code> not supported</h4></div></div></div><p> - Some care is required to support C++ compiler and or library - implementation that do not have the standard library in - <code class="code">namespace std</code>. - </p><p> - The following sections list some possible solutions to support compilers - that cannot ignore <code class="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 class="code">std::</code>, as the - compilers use <code class="code">-fno-honor-std</code> (ignore - <code class="code">std::</code>, <code class="code">:: = std::</code>) by default. That is, - the responsibility for enabling or disabling <code class="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 class="code">std</code> as a macro, fully-qualified namespace - calls become global. Volia. - </p><pre class="programlisting"> -#ifdef WICKEDLY_OLD_COMPILER -# define std -#endif -</pre><p> - Thanks to Juergen Heinzl who posted this solution on gnu.gcc.help. - </p><p> - Another pre-processor based approach is to define a macro - <code class="code">NAMESPACE_STD</code>, which is defined to either - “<span class="quote"> </span>” or “<span class="quote">std</span>” 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 class="code">HAVE_NAMESPACE_STD</code>, - then using that to set a value for the <code class="code">NAMESPACE_STD</code> - macro. At that point, one is able to use - <code class="code">NAMESPACE_STD::string</code>, which will evaluate to - <code class="code">std::string</code> or <code class="code">::string</code> (i.e., in the - global namespace on systems that do not put <code class="code">string</code> in - <code class="code">std::</code>). - </p><pre class="programlisting"> -dnl @synopsis AC_CXX_NAMESPACE_STD -dnl -dnl If the compiler supports namespace std, define -dnl HAVE_NAMESPACE_STD. -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_NAMESPACE_STD], [ - AC_CACHE_CHECK(if g++ supports namespace std, - ac_cv_cxx_have_std_namespace, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - AC_TRY_COMPILE([#include <iostream> - std::istream& is = std::cin;],, - 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_NAMESPACE_STD,,[Define if g++ supports namespace std. ]) - fi -]) -</pre></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id444864"></a>Illegal iterator usage</h4></div></div></div><p> - The following illustrate implementation-allowed illegal iterator - use, and then correct use. -</p><div class="itemizedlist"><ul type="disc"><li><p> - you cannot do <code class="code">ostream::operator<<(iterator)</code> - to print the address of the iterator => use - <code class="code">operator<< &*iterator</code> instead - </p></li><li><p> - you cannot clear an iterator's reference (<code class="code">iterator = - 0</code>) => use <code class="code">iterator = iterator_type();</code> - </p></li><li><p> - <code class="code">if (iterator)</code> won't work any more => use - <code class="code">if (iterator != iterator_type())</code> - </p></li></ul></div></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id444925"></a><code class="code">isspace</code> from <code class="filename">cctype</code> is a macro - </h4></div></div></div><p> - Glibc 2.0.x and 2.1.x define <code class="filename">ctype.h</code> 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 class="programlisting"> -#include <cctype> -int main() { std::isspace('X'); } -</pre><p> - Results in something like this: -</p><pre class="programlisting"> -std:: (__ctype_b[(int) ( ( 'X' ) )] & (unsigned short int) _ISspace ) ; -</pre><p> - A solution is to modify a header-file so that the compiler tells - <code class="filename">ctype.h</code> to define functions - instead of macros: -</p><pre class="programlisting"> -// This keeps isalnum, et al from being propagated as macros. -#if __linux__ -# define __NO_CTYPE 1 -#endif -</pre><p> - Then, include <code class="filename">ctype.h</code> -</p><p> - Another problem arises if you put a <code class="code">using namespace - std;</code> declaration at the top, and include <code class="filename">ctype.h</code>. This will result in - ambiguities between the definitions in the global namespace - (<code class="filename">ctype.h</code>) and the - definitions in namespace <code class="code">std::</code> - (<code class="code"><cctype></code>). -</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id445019"></a>No <code class="code">vector::at</code>, <code class="code">deque::at</code>, <code class="code">string::at</code></h4></div></div></div><p> - One solution is to add an autoconf-test for this: -</p><pre class="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(“<span class="quote">test_string</span>”); -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 class="code">string::at</code> separately. -</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id445057"></a>No <code class="code">std::char_traits<char>::eof</code></h4></div></div></div><p> - Use some kind of autoconf test, plus this: -</p><pre class="programlisting"> -#ifdef HAVE_CHAR_TRAITS -#define CPP_EOF std::char_traits<char>::eof() -#else -#define CPP_EOF EOF -#endif -</pre></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id445075"></a>No <code class="code">string::clear</code></h4></div></div></div><p> - There are two functions for deleting the contents of a string: - <code class="code">clear</code> and <code class="code">erase</code> (the latter returns the - string). -</p><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><p> - Unfortunately, <code class="code">clear</code> is not implemented in this - version, so you should use <code class="code">erase</code> (which is probably - faster than <code class="code">operator=(charT*)</code>). -</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id445120"></a> - Removal of <code class="code">ostream::form</code> and <code class="code">istream::scan</code> - extensions -</h4></div></div></div><p> - These are no longer supported. Please use stringstreams instead. -</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id445139"></a>No <code class="code">basic_stringbuf</code>, <code class="code">basic_stringstream</code></h4></div></div></div><p> - Although the ISO standard <code class="code">i/ostringstream</code>-classes are - provided, (<code class="filename">sstream</code>), for - compatibility with older implementations the pre-ISO - <code class="code">i/ostrstream</code> (<code class="filename">strstream</code>) interface is also provided, - with these caveats: -</p><div class="itemizedlist"><ul type="disc"><li><p> - <code class="code">strstream</code> is considered to be deprecated - </p></li><li><p> - <code class="code">strstream</code> is limited to <code class="code">char</code> - </p></li><li><p> - with <code class="code">ostringstream</code> you don't have to take care of - terminating the string or freeing its memory - </p></li><li><p> - <code class="code">istringstream</code> can be re-filled (clear(); - str(input);) - </p></li></ul></div><p> - You can then use output-stringstreams like this: -</p><pre class="programlisting"> -#ifdef HAVE_SSTREAM -# include <sstream> -#else -# include <strstream> -#endif - -#ifdef HAVE_SSTREAM - std::ostringstream oss; -#else - std::ostrstream oss; -#endif - -oss << “<span class="quote">Name=</span>” << m_name << “<span class="quote">, number=</span>” << 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 class="programlisting"> -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 class="programlisting"> -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 class="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; -} -</pre><p> - Another example of using stringstreams is in <a class="link" href="bk01pt05ch13s05.html" title="Shrink to Fit">this howto</a>. -</p><p> There is additional information in the libstdc++-v2 info files, in -particular “<span class="quote">info iostream</span>”. -</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id448793"></a>Little or no wide character support</h4></div></div></div><p> - Classes <code class="classname">wstring</code> and - <code class="classname">char_traits<wchar_t></code> are - not supported. - </p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id448812"></a>No templatized iostreams</h4></div></div></div><p> - Classes <code class="classname">wfilebuf</code> and - <code class="classname">wstringstream</code> are not supported. - </p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id448831"></a>Thread safety issues</h4></div></div></div><p> - Earlier GCC releases had a somewhat different approach to - threading configuration and proper compilation. Before GCC 3.0, - configuration of the threading model was dictated by compiler - command-line options and macros (both of which were somewhat - thread-implementation and port-specific). There were no - guarantees related to being able to link code compiled with one - set of options and macro setting with another set. - </p><p> - For GCC 3.0, configuration of the threading model used with - libraries and user-code is performed when GCC is configured and - built using the --enable-threads and --disable-threads options. - The ABI is stable for symbol name-mangling and limited functional - compatibility exists between code compiled under different - threading models. - </p><p> - The libstdc++ library has been designed so that it can be used in - multithreaded applications (with libstdc++-v2 this was only true - of the STL parts.) The first problem is finding a - <span class="emphasis"><em>fast</em></span> method of implementation portable to - all platforms. Due to historical reasons, some of the library is - written against per-CPU-architecture spinlocks and other parts - against the gthr.h abstraction layer which is provided by gcc. A - minor problem that pops up every so often is different - interpretations of what "thread-safe" means for a - library (not a general program). We currently use the <a class="ulink" href="http://www.sgi.com/tech/stl/thread_safety.html" target="_top">same - definition that SGI</a> uses for their STL subset. However, - the exception for read-only containers only applies to the STL - components. This definition is widely-used and something similar - will be used in the next version of the C++ standard library. - </p><p> - Here is a small link farm to threads (no pun) in the mail - archives that discuss the threading problem. Each link is to the - first relevant message in the thread; from there you can use - "Thread Next" to move down the thread. This farm is in - latest-to-oldest order. - </p><div class="itemizedlist"><ul type="disc"><li><p> - Our threading expert Loren gives a breakdown of <a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2001-10/msg00024.html" target="_top">the - six situations involving threads</a> for the 3.0 - release series. - </p></li><li><p> - <a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2001-05/msg00384.html" target="_top"> - This message</a> inspired a recent updating of issues with - threading and the SGI STL library. It also contains some - example POSIX-multithreaded STL code. - </p></li></ul></div><p> - (A large selection of links to older messages has been removed; - many of the messages from 1999 were lost in a disk crash, and the - few people with access to the backup tapes have been too swamped - with work to restore them. Many of the points have been - superseded anyhow.) - </p></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="backwards.third"></a>Third</h3></div></div></div><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 (version 3.3), with extensive changes. - </p><p>A more formal description of the V3 goals can be found in the - official <a class="ulink" href="../17_intro/DESIGN" target="_top">design document</a>. - </p><p>Portability notes and known implementation limitations are as follows.</p><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id448950"></a>Pre-ISO headers moved to backwards or removed</h4></div></div></div><p> The pre-ISO C++ headers - (<code class="code">iostream.h</code>, <code class="code">defalloc.h</code> etc.) are - available, unlike previous libstdc++ versions, 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 class="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 class="ulink" href="http://www.parashift.com/c++-faq-lite/coding-standards.html#faq-27.4" target="_top">item - [27.4]</a>. - </p><p> Some include adjustment may be required. What follows is an -autoconf test that defines <code class="code">PRE_STDCXX_HEADERS</code> when they -exist.</p><pre class="programlisting"> -# AC_HEADER_PRE_STDCXX -AC_DEFUN([AC_HEADER_PRE_STDCXX], [ - AC_CACHE_CHECK(for pre-ISO C++ include files, - ac_cv_cxx_pre_stdcxx, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - ac_save_CXXFLAGS="$CXXFLAGS" - CXXFLAGS="$CXXFLAGS -Wno-deprecated" - - # Omit defalloc.h, as compilation with newer compilers is problematic. - AC_TRY_COMPILE([ - #include <new.h> - #include <iterator.h> - #include <alloc.h> - #include <set.h> - #include <hashtable.h> - #include <hash_set.h> - #include <fstream.h> - #include <tempbuf.h> - #include <istream.h> - #include <bvector.h> - #include <stack.h> - #include <rope.h> - #include <complex.h> - #include <ostream.h> - #include <heap.h> - #include <iostream.h> - #include <function.h> - #include <multimap.h> - #include <pair.h> - #include <stream.h> - #include <iomanip.h> - #include <slist.h> - #include <tree.h> - #include <vector.h> - #include <deque.h> - #include <multiset.h> - #include <list.h> - #include <map.h> - #include <algobase.h> - #include <hash_map.h> - #include <algo.h> - #include <queue.h> - #include <streambuf.h> - ],, - ac_cv_cxx_pre_stdcxx=yes, ac_cv_cxx_pre_stdcxx=no) - CXXFLAGS="$ac_save_CXXFLAGS" - AC_LANG_RESTORE - ]) - if test "$ac_cv_cxx_pre_stdcxx" = yes; then - AC_DEFINE(PRE_STDCXX_HEADERS,,[Define if pre-ISO C++ header files are present. ]) - fi -]) -</pre><p>Porting between pre-ISO headers and ISO headers is simple: headers -like <code class="filename">vector.h</code> can be replaced with <code class="filename">vector</code> and a using -directive <code class="code">using namespace std;</code> can be put at the global -scope. This should be enough to get this code compiling, assuming the -other usage is correct. -</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id449032"></a>Extension headers hash_map, hash_set moved to ext or backwards</h4></div></div></div><p>At this time most of the features of the SGI STL extension have been - replaced by standardized libraries. - In particular, the unordered_map and unordered_set containers of TR1 - are suitable replacement for the non-standard hash_map and hash_set - containers in the SGI STL. - </p><p> Header files <code class="filename">hash_map</code> and <code class="filename">hash_set</code> moved -to <code class="filename">ext/hash_map</code> and <code class="filename">ext/hash_set</code>, -respectively. At the same time, all types in these files are enclosed -in <code class="code">namespace __gnu_cxx</code>. Later versions move deprecate -these files, and suggest using TR1's <code class="filename">unordered_map</code> -and <code class="filename">unordered_set</code> instead. -</p><p>The extensions are no longer in the global or <code class="code">std</code> - namespaces, instead they are declared in the <code class="code">__gnu_cxx</code> - namespace. For maximum portability, consider defining a namespace - alias to use to talk about extensions, e.g.: - </p><pre class="programlisting"> - #ifdef __GNUC__ - #if __GNUC__ < 3 - #include <hash_map.h> - namespace extension { using ::hash_map; }; // inherit globals - #else - #include <backward/hash_map> - #if __GNUC__ == 3 && __GNUC_MINOR__ == 0 - namespace extension = std; // GCC 3.0 - #else - namespace extension = ::__gnu_cxx; // GCC 3.1 and later - #endif - #endif - #else // ... there are other compilers, right? - namespace extension = std; - #endif - - extension::hash_map<int,int> my_map; - </pre><p>This is a bit cleaner than defining typedefs for all the - instantiations you might need. - </p><p>The following autoconf tests check for working HP/SGI hash containers. -</p><pre class="programlisting"> -# AC_HEADER_EXT_HASH_MAP -AC_DEFUN([AC_HEADER_EXT_HASH_MAP], [ - AC_CACHE_CHECK(for ext/hash_map, - ac_cv_cxx_ext_hash_map, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - ac_save_CXXFLAGS="$CXXFLAGS" - CXXFLAGS="$CXXFLAGS -Werror" - AC_TRY_COMPILE([#include <ext/hash_map>], [using __gnu_cxx::hash_map;], - ac_cv_cxx_ext_hash_map=yes, ac_cv_cxx_ext_hash_map=no) - CXXFLAGS="$ac_save_CXXFLAGS" - AC_LANG_RESTORE - ]) - if test "$ac_cv_cxx_ext_hash_map" = yes; then - AC_DEFINE(HAVE_EXT_HASH_MAP,,[Define if ext/hash_map is present. ]) - fi -]) -</pre><pre class="programlisting"> -# AC_HEADER_EXT_HASH_SET -AC_DEFUN([AC_HEADER_EXT_HASH_SET], [ - AC_CACHE_CHECK(for ext/hash_set, - ac_cv_cxx_ext_hash_set, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - ac_save_CXXFLAGS="$CXXFLAGS" - CXXFLAGS="$CXXFLAGS -Werror" - AC_TRY_COMPILE([#include <ext/hash_set>], [using __gnu_cxx::hash_set;], - ac_cv_cxx_ext_hash_set=yes, ac_cv_cxx_ext_hash_set=no) - CXXFLAGS="$ac_save_CXXFLAGS" - AC_LANG_RESTORE - ]) - if test "$ac_cv_cxx_ext_hash_set" = yes; then - AC_DEFINE(HAVE_EXT_HASH_SET,,[Define if ext/hash_set is present. ]) - fi -]) -</pre></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id449135"></a>No <code class="code">ios::nocreate/ios::noreplace</code>. -</h4></div></div></div><p> The existence of <code class="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, “<span class="quote">nocreate</span>” is probably the default, -unless you specify <code class="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 class="code">app</code>, <code class="code">ate</code> -and <code class="code">trunc</code> (except for <code class="code">app</code> ?). -</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id449183"></a> -No <code class="code">stream::attach(int fd)</code> -</h4></div></div></div><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 - file descriptors), you need to implement a subclass of - <code class="code">std::streambuf</code> (or - <code class="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 class="filename">ext/stdio_filebuf.h</code> contains a derived class called - <a class="ulink" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/class____gnu__cxx_1_1stdio__filebuf.html" target="_top"><code class="code">__gnu_cxx::stdio_filebuf</code></a>. - This class can be constructed from a C <code class="code">FILE*</code> or a file - descriptor, and provides the <code class="code">fd()</code> function. - </p><p> - For another example of this, refer to - <a class="ulink" href="http://www.josuttis.com/cppcode/fdstream.html" target="_top">fdstream example</a> - by Nicolai Josuttis. -</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id511531"></a> -Support for C++98 dialect. -</h4></div></div></div><p>Check for complete library coverage of the C++1998/2003 standard. -</p><pre class="programlisting"> -# AC_HEADER_STDCXX_98 -AC_DEFUN([AC_HEADER_STDCXX_98], [ - AC_CACHE_CHECK(for ISO C++ 98 include files, - ac_cv_cxx_stdcxx_98, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - AC_TRY_COMPILE([ - #include <cassert> - #include <cctype> - #include <cerrno> - #include <cfloat> - #include <ciso646> - #include <climits> - #include <clocale> - #include <cmath> - #include <csetjmp> - #include <csignal> - #include <cstdarg> - #include <cstddef> - #include <cstdio> - #include <cstdlib> - #include <cstring> - #include <ctime> - - #include <algorithm> - #include <bitset> - #include <complex> - #include <deque> - #include <exception> - #include <fstream> - #include <functional> - #include <iomanip> - #include <ios> - #include <iosfwd> - #include <iostream> - #include <istream> - #include <iterator> - #include <limits> - #include <list> - #include <locale> - #include <map> - #include <memory> - #include <new> - #include <numeric> - #include <ostream> - #include <queue> - #include <set> - #include <sstream> - #include <stack> - #include <stdexcept> - #include <streambuf> - #include <string> - #include <typeinfo> - #include <utility> - #include <valarray> - #include <vector> - ],, - ac_cv_cxx_stdcxx_98=yes, ac_cv_cxx_stdcxx_98=no) - AC_LANG_RESTORE - ]) - if test "$ac_cv_cxx_stdcxx_98" = yes; then - AC_DEFINE(STDCXX_98_HEADERS,,[Define if ISO C++ 1998 header files are present. ]) - fi -]) -</pre></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id511558"></a> -Support for C++TR1 dialect. -</h4></div></div></div><p>Check for library coverage of the TR1 standard. -</p><pre class="programlisting"> -# AC_HEADER_STDCXX_TR1 -AC_DEFUN([AC_HEADER_STDCXX_TR1], [ - AC_CACHE_CHECK(for ISO C++ TR1 include files, - ac_cv_cxx_stdcxx_tr1, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - AC_TRY_COMPILE([ - #include <tr1/array> - #include <tr1/ccomplex> - #include <tr1/cctype> - #include <tr1/cfenv> - #include <tr1/cfloat> - #include <tr1/cinttypes> - #include <tr1/climits> - #include <tr1/cmath> - #include <tr1/complex> - #include <tr1/cstdarg> - #include <tr1/cstdbool> - #include <tr1/cstdint> - #include <tr1/cstdio> - #include <tr1/cstdlib> - #include <tr1/ctgmath> - #include <tr1/ctime> - #include <tr1/cwchar> - #include <tr1/cwctype> - #include <tr1/functional> - #include <tr1/memory> - #include <tr1/random> - #include <tr1/regex> - #include <tr1/tuple> - #include <tr1/type_traits> - #include <tr1/unordered_set> - #include <tr1/unordered_map> - #include <tr1/utility> - ],, - ac_cv_cxx_stdcxx_tr1=yes, ac_cv_cxx_stdcxx_tr1=no) - AC_LANG_RESTORE - ]) - if test "$ac_cv_cxx_stdcxx_tr1" = yes; then - AC_DEFINE(STDCXX_TR1_HEADERS,,[Define if ISO C++ TR1 header files are present. ]) - fi -]) -</pre><p>An alternative is to check just for specific TR1 includes, such as <unordered_map> and <unordered_set>. -</p><pre class="programlisting"> -# AC_HEADER_TR1_UNORDERED_MAP -AC_DEFUN([AC_HEADER_TR1_UNORDERED_MAP], [ - AC_CACHE_CHECK(for tr1/unordered_map, - ac_cv_cxx_tr1_unordered_map, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - AC_TRY_COMPILE([#include <tr1/unordered_map>], [using std::tr1::unordered_map;], - ac_cv_cxx_tr1_unordered_map=yes, ac_cv_cxx_tr1_unordered_map=no) - AC_LANG_RESTORE - ]) - if test "$ac_cv_cxx_tr1_unordered_map" = yes; then - AC_DEFINE(HAVE_TR1_UNORDERED_MAP,,[Define if tr1/unordered_map is present. ]) - fi -]) -</pre><pre class="programlisting"> -# AC_HEADER_TR1_UNORDERED_SET -AC_DEFUN([AC_HEADER_TR1_UNORDERED_SET], [ - AC_CACHE_CHECK(for tr1/unordered_set, - ac_cv_cxx_tr1_unordered_set, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - AC_TRY_COMPILE([#include <tr1/unordered_set>], [using std::tr1::unordered_set;], - ac_cv_cxx_tr1_unordered_set=yes, ac_cv_cxx_tr1_unordered_set=no) - AC_LANG_RESTORE - ]) - if test "$ac_cv_cxx_tr1_unordered_set" = yes; then - AC_DEFINE(HAVE_TR1_UNORDERED_SET,,[Define if tr1/unordered_set is present. ]) - fi -]) -</pre></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id511602"></a> -Support for C++0x dialect. -</h4></div></div></div><p>Check for baseline language coverage in the compiler for the C++0xstandard. -</p><pre class="programlisting"> -# AC_COMPILE_STDCXX_OX -AC_DEFUN([AC_COMPILE_STDCXX_0X], [ - AC_CACHE_CHECK(if g++ supports C++0x features without additional flags, - ac_cv_cxx_compile_cxx0x_native, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - AC_TRY_COMPILE([ - template <typename T> - struct check - { - static_assert(sizeof(int) <= sizeof(T), "not big enough"); - }; - - typedef check<check<bool>> right_angle_brackets; - - int a; - decltype(a) b; - - typedef check<int> check_type; - check_type c; - check_type&& cr = c;],, - ac_cv_cxx_compile_cxx0x_native=yes, ac_cv_cxx_compile_cxx0x_native=no) - AC_LANG_RESTORE - ]) - - AC_CACHE_CHECK(if g++ supports C++0x features with -std=c++0x, - ac_cv_cxx_compile_cxx0x_cxx, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - ac_save_CXXFLAGS="$CXXFLAGS" - CXXFLAGS="$CXXFLAGS -std=c++0x" - AC_TRY_COMPILE([ - template <typename T> - struct check - { - static_assert(sizeof(int) <= sizeof(T), "not big enough"); - }; - - typedef check<check<bool>> right_angle_brackets; - - int a; - decltype(a) b; - - typedef check<int> check_type; - check_type c; - check_type&& cr = c;],, - ac_cv_cxx_compile_cxx0x_cxx=yes, ac_cv_cxx_compile_cxx0x_cxx=no) - CXXFLAGS="$ac_save_CXXFLAGS" - AC_LANG_RESTORE - ]) - - AC_CACHE_CHECK(if g++ supports C++0x features with -std=gnu++0x, - ac_cv_cxx_compile_cxx0x_gxx, - [AC_LANG_SAVE - AC_LANG_CPLUSPLUS - ac_save_CXXFLAGS="$CXXFLAGS" - CXXFLAGS="$CXXFLAGS -std=gnu++0x" - AC_TRY_COMPILE([ - template <typename T> - struct check - { - static_assert(sizeof(int) <= sizeof(T), "not big enough"); - }; - - typedef check<check<bool>> right_angle_brackets; - - int a; - decltype(a) b; - - typedef check<int> check_type; - check_type c; - check_type&& cr = c;],, - ac_cv_cxx_compile_cxx0x_gxx=yes, ac_cv_cxx_compile_cxx0x_gxx=no) - CXXFLAGS="$ac_save_CXXFLAGS" - AC_LANG_RESTORE - ]) - - if test "$ac_cv_cxx_compile_cxx0x_native" = yes || - test "$ac_cv_cxx_compile_cxx0x_cxx" = yes || - test "$ac_cv_cxx_compile_cxx0x_gxx" = yes; then - AC_DEFINE(HAVE_STDCXX_0X,,[Define if g++ supports C++0x features. ]) - fi -]) -</pre><p>Check for library coverage of the C++0xstandard. -</p><pre class="programlisting"> -# AC_HEADER_STDCXX_0X -AC_DEFUN([AC_HEADER_STDCXX_0X], [ - AC_CACHE_CHECK(for ISO C++ 0x include files, - ac_cv_cxx_stdcxx_0x, - [AC_REQUIRE([AC_COMPILE_STDCXX_0X]) - AC_LANG_SAVE - AC_LANG_CPLUSPLUS - ac_save_CXXFLAGS="$CXXFLAGS" - CXXFLAGS="$CXXFLAGS -std=gnu++0x" - - AC_TRY_COMPILE([ - #include <cassert> - #include <ccomplex> - #include <cctype> - #include <cerrno> - #include <cfenv> - #include <cfloat> - #include <cinttypes> - #include <ciso646> - #include <climits> - #include <clocale> - #include <cmath> - #include <csetjmp> - #include <csignal> - #include <cstdarg> - #include <cstdbool> - #include <cstddef> - #include <cstdint> - #include <cstdio> - #include <cstdlib> - #include <cstring> - #include <ctgmath> - #include <ctime> - #include <cwchar> - #include <cwctype> - - #include <algorithm> - #include <array> - #include <bitset> - #include <complex> - #include <deque> - #include <exception> - #include <fstream> - #include <functional> - #include <iomanip> - #include <ios> - #include <iosfwd> - #include <iostream> - #include <istream> - #include <iterator> - #include <limits> - #include <list> - #include <locale> - #include <map> - #include <memory> - #include <new> - #include <numeric> - #include <ostream> - #include <queue> - #include <random> - #include <regex> - #include <set> - #include <sstream> - #include <stack> - #include <stdexcept> - #include <streambuf> - #include <string> - #include <tuple> - #include <typeinfo> - #include <type_traits> - #include <unordered_map> - #include <unordered_set> - #include <utility> - #include <valarray> - #include <vector> - ],, - ac_cv_cxx_stdcxx_0x=yes, ac_cv_cxx_stdcxx_0x=no) - AC_LANG_RESTORE - CXXFLAGS="$ac_save_CXXFLAGS" - ]) - if test "$ac_cv_cxx_stdcxx_0x" = yes; then - AC_DEFINE(STDCXX_0X_HEADERS,,[Define if ISO C++ 0x header files are present. ]) - fi -]) -</pre><p>As is the case for TR1 support, these autoconf macros can be made for a finer-grained, per-header-file check. For <unordered_map> -</p><pre class="programlisting"> -# AC_HEADER_UNORDERED_MAP -AC_DEFUN([AC_HEADER_UNORDERED_MAP], [ - AC_CACHE_CHECK(for unordered_map, - ac_cv_cxx_unordered_map, - [AC_REQUIRE([AC_COMPILE_STDCXX_0X]) - AC_LANG_SAVE - AC_LANG_CPLUSPLUS - ac_save_CXXFLAGS="$CXXFLAGS" - CXXFLAGS="$CXXFLAGS -std=gnu++0x" - AC_TRY_COMPILE([#include <unordered_map>], [using std::unordered_map;], - ac_cv_cxx_unordered_map=yes, ac_cv_cxx_unordered_map=no) - CXXFLAGS="$ac_save_CXXFLAGS" - AC_LANG_RESTORE - ]) - if test "$ac_cv_cxx_unordered_map" = yes; then - AC_DEFINE(HAVE_UNORDERED_MAP,,[Define if unordered_map is present. ]) - fi -]) -</pre><pre class="programlisting"> -# AC_HEADER_UNORDERED_SET -AC_DEFUN([AC_HEADER_UNORDERED_SET], [ - AC_CACHE_CHECK(for unordered_set, - ac_cv_cxx_unordered_set, - [AC_REQUIRE([AC_COMPILE_STDCXX_0X]) - AC_LANG_SAVE - AC_LANG_CPLUSPLUS - ac_save_CXXFLAGS="$CXXFLAGS" - CXXFLAGS="$CXXFLAGS -std=gnu++0x" - AC_TRY_COMPILE([#include <unordered_set>], [using std::unordered_set;], - ac_cv_cxx_unordered_set=yes, ac_cv_cxx_unordered_set=no) - CXXFLAGS="$ac_save_CXXFLAGS" - AC_LANG_RESTORE - ]) - if test "$ac_cv_cxx_unordered_set" = yes; then - AC_DEFINE(HAVE_UNORDERED_SET,,[Define if unordered_set is present. ]) - fi -]) -</pre></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id511679"></a> - Container::iterator_type is not necessarily Container::value_type* -</h4></div></div></div><p> - This is a change in behavior from the previous version. Now, most - <span class="type">iterator_type</span> typedefs in container classes are POD - objects, not <span class="type">value_type</span> pointers. -</p></div></div><div class="bibliography"><div class="titlepage"><div><div><h3 class="title"><a id="backwards.biblio"></a>Bibliography</h3></div></div></div><div class="biblioentry"><a id="id511711"></a><p>[<abbr class="abbrev"> - kegel41 - </abbr>] <span class="title"><i> - Migrating to GCC 4.1 - </i>. </span><span class="author"><span class="firstname">Dan</span> <span class="surname">Kegel</span>. </span><span class="biblioid"> - <a class="ulink" href="http://www.kegel.com/gcc/gcc4.html" target="_top"> - </a> - . </span></p></div><div class="biblioentry"><a id="id511743"></a><p>[<abbr class="abbrev"> - kegel41 - </abbr>] <span class="title"><i> - Building the Whole Debian Archive with GCC 4.1: A Summary - </i>. </span><span class="author"><span class="firstname">Martin</span> <span class="surname">Michlmayr</span>. </span><span class="biblioid"> - <a class="ulink" href="http://lists.debian.org/debian-gcc/2006/03/msg00405.html" target="_top"> - </a> - . </span></p></div><div class="biblioentry"><a id="id511776"></a><p>[<abbr class="abbrev"> - lbl32 - </abbr>] <span class="title"><i> - Migration guide for GCC-3.2 - </i>. </span><span class="biblioid"> - <a class="ulink" href="http://annwm.lbl.gov/~leggett/Atlas/gcc-3.2.html" target="_top"> - </a> - . </span></p></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="api.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="appendix_porting.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="appendix_free.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">API Evolution and Deprecation History </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Appendix C. - Free Software Needs Free Documentation - -</td></tr></table></div></body></html> |