1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Backwards Compatibility</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content=" ISO C++ , backwards " /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="appendix_porting.html" title="Appendix��B.�� 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.�� 4 Porting and Maintenance 5 6</th><td width="20%" align="right">��<a accesskey="n" href="appendix_free.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Backwards Compatibility"><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" title="First"><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 7separate GNU project, although reliably paired with GCC. Rumors imply 8that it had a working relationship with at least two kinds of 9dinosaur. 10</p><p>Some background: libg++ was designed and created when there was no 11ISO standard to provide guidance. Classes like linked lists are now 12provided for by <code class="classname">list<T></code> and do not need to be 13created by <code class="function">genclass</code>. (For that matter, templates exist 14now and are well-supported, whereas genclass (mostly) predates them.) 15</p><p>There are other classes in libg++ that are not specified in the 16ISO Standard (e.g., statistical analysis). While there are a lot of 17really useful things that are used by a lot of people, the Standards 18Committee couldn't include everything, and so a lot of those 19<span class="quote">���<span class="quote">obvious</span>���</span> classes didn't get included. 20</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" title="No ios_base"><div class="titlepage"><div><div><h4 class="title"><a id="id646429"></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>. 21</p></div><div class="sect3" title="No cout in ostream.h, no cin in istream.h"><div class="titlepage"><div><div><h4 class="title"><a id="id646461"></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> 22 In earlier versions of the standard, 23 <code class="filename">fstream.h</code>, 24 <code class="filename">ostream.h</code> 25 and <code class="filename">istream.h</code> 26 used to define 27 <code class="code">cout</code>, <code class="code">cin</code> and so on. ISO C++ specifies that one needs to include 28 <code class="filename">iostream</code> 29 explicitly to get the required definitions. 30 </p><p> Some include adjustment may be required.</p><p>This project is no longer maintained or supported, and the sources 31archived. For the desperate, 32the <a class="ulink" href="http://gcc.gnu.org/extensions.html" target="_top">GCC extensions 33page</a> describes where to find the last libg++ source. The code is 34considered replaced and rewritten. 35</p></div></div><div class="sect2" title="Second"><div class="titlepage"><div><div><h3 class="title"><a id="backwards.second"></a>Second</h3></div></div></div><p> 36 The second generation GNU C++ library was called libstdc++, or 37 libstdc++-v2. It spans the time between libg++ and pre-ISO C++ 38 standardization and is usually associated with the following GCC 39 releases: egcs 1.x, gcc 2.95, and gcc 2.96. 40</p><p> 41 The STL portions of this library are based on SGI/HP STL release 3.11. 42</p><p> 43 This project is no longer maintained or supported, and the sources 44 archived. The code is considered replaced and rewritten. 45</p><p> 46 Portability notes and known implementation limitations are as follows. 47</p><div class="sect3" title="Namespace std:: not supported"><div class="titlepage"><div><div><h4 class="title"><a id="id646559"></a>Namespace <code class="code">std::</code> not supported</h4></div></div></div><p> 48 Some care is required to support C++ compiler and or library 49 implementation that do not have the standard library in 50 <code class="code">namespace std</code>. 51 </p><p> 52 The following sections list some possible solutions to support compilers 53 that cannot ignore <code class="code">std::</code>-qualified names. 54 </p><p> 55 First, see if the compiler has a flag for this. Namespace 56 back-portability-issues are generally not a problem for g++ 57 compilers that do not have libstdc++ in <code class="code">std::</code>, as the 58 compilers use <code class="code">-fno-honor-std</code> (ignore 59 <code class="code">std::</code>, <code class="code">:: = std::</code>) by default. That is, 60 the responsibility for enabling or disabling <code class="code">std::</code> is 61 on the user; the maintainer does not have to care about it. This 62 probably applies to some other compilers as well. 63 </p><p> 64 Second, experiment with a variety of pre-processor tricks. 65 </p><p> 66 By defining <code class="code">std</code> as a macro, fully-qualified namespace 67 calls become global. Volia. 68 </p><pre class="programlisting"> 69#ifdef WICKEDLY_OLD_COMPILER 70# define std 71#endif 72</pre><p> 73 Thanks to Juergen Heinzl who posted this solution on gnu.gcc.help. 74 </p><p> 75 Another pre-processor based approach is to define a macro 76 <code class="code">NAMESPACE_STD</code>, which is defined to either 77 <span class="quote">���<span class="quote"> </span>���</span> or <span class="quote">���<span class="quote">std</span>���</span> based on a compile-type 78 test. On GNU systems, this can be done with autotools by means of 79 an autoconf test (see below) for <code class="code">HAVE_NAMESPACE_STD</code>, 80 then using that to set a value for the <code class="code">NAMESPACE_STD</code> 81 macro. At that point, one is able to use 82 <code class="code">NAMESPACE_STD::string</code>, which will evaluate to 83 <code class="code">std::string</code> or <code class="code">::string</code> (i.e., in the 84 global namespace on systems that do not put <code class="code">string</code> in 85 <code class="code">std::</code>). 86 </p><pre class="programlisting"> 87dnl @synopsis AC_CXX_NAMESPACE_STD 88dnl 89dnl If the compiler supports namespace std, define 90dnl HAVE_NAMESPACE_STD. 91dnl 92dnl @category Cxx 93dnl @author Todd Veldhuizen 94dnl @author Luc Maisonobe <luc@spaceroots.org> 95dnl @version 2004-02-04 96dnl @license AllPermissive 97AC_DEFUN([AC_CXX_NAMESPACE_STD], [ 98 AC_CACHE_CHECK(if g++ supports namespace std, 99 ac_cv_cxx_have_std_namespace, 100 [AC_LANG_SAVE 101 AC_LANG_CPLUSPLUS 102 AC_TRY_COMPILE([#include <iostream> 103 std::istream& is = std::cin;],, 104 ac_cv_cxx_have_std_namespace=yes, ac_cv_cxx_have_std_namespace=no) 105 AC_LANG_RESTORE 106 ]) 107 if test "$ac_cv_cxx_have_std_namespace" = yes; then 108 AC_DEFINE(HAVE_NAMESPACE_STD,,[Define if g++ supports namespace std. ]) 109 fi 110]) 111</pre></div><div class="sect3" title="Illegal iterator usage"><div class="titlepage"><div><div><h4 class="title"><a id="id699742"></a>Illegal iterator usage</h4></div></div></div><p> 112 The following illustrate implementation-allowed illegal iterator 113 use, and then correct use. 114</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p> 115 you cannot do <code class="code">ostream::operator<<(iterator)</code> 116 to print the address of the iterator => use 117 <code class="code">operator<< &*iterator</code> instead 118 </p></li><li class="listitem"><p> 119 you cannot clear an iterator's reference (<code class="code">iterator = 120 0</code>) => use <code class="code">iterator = iterator_type();</code> 121 </p></li><li class="listitem"><p> 122 <code class="code">if (iterator)</code> won't work any more => use 123 <code class="code">if (iterator != iterator_type())</code> 124 </p></li></ul></div></div><div class="sect3" title="isspace from cctype is a macro"><div class="titlepage"><div><div><h4 class="title"><a id="id699804"></a><code class="code">isspace</code> from <code class="filename">cctype</code> is a macro 125 </h4></div></div></div><p> 126 Glibc 2.0.x and 2.1.x define <code class="filename">ctype.h</code> functionality as macros 127 (isspace, isalpha etc.). 128 </p><p> 129 This implementations of libstdc++, however, keep these functions 130 as macros, and so it is not back-portable to use fully qualified 131 names. For example: 132 </p><pre class="programlisting"> 133#include <cctype> 134int main() { std::isspace('X'); } 135</pre><p> 136 Results in something like this: 137</p><pre class="programlisting"> 138std:: (__ctype_b[(int) ( ( 'X' ) )] & (unsigned short int) _ISspace ) ; 139</pre><p> 140 A solution is to modify a header-file so that the compiler tells 141 <code class="filename">ctype.h</code> to define functions 142 instead of macros: 143</p><pre class="programlisting"> 144// This keeps isalnum, et al from being propagated as macros. 145#if __linux__ 146# define __NO_CTYPE 1 147#endif 148</pre><p> 149 Then, include <code class="filename">ctype.h</code> 150</p><p> 151 Another problem arises if you put a <code class="code">using namespace 152 std;</code> declaration at the top, and include <code class="filename">ctype.h</code>. This will result in 153 ambiguities between the definitions in the global namespace 154 (<code class="filename">ctype.h</code>) and the 155 definitions in namespace <code class="code">std::</code> 156 (<code class="code"><cctype></code>). 157</p></div><div class="sect3" title="No vector::at, deque::at, string::at"><div class="titlepage"><div><div><h4 class="title"><a id="id699897"></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> 158 One solution is to add an autoconf-test for this: 159</p><pre class="programlisting"> 160AC_MSG_CHECKING(for container::at) 161AC_TRY_COMPILE( 162[ 163#include <vector> 164#include <deque> 165#include <string> 166 167using namespace std; 168], 169[ 170deque<int> test_deque(3); 171test_deque.at(2); 172vector<int> test_vector(2); 173test_vector.at(1); 174string test_string(<span class="quote">���<span class="quote">test_string</span>���</span>); 175test_string.at(3); 176], 177[AC_MSG_RESULT(yes) 178AC_DEFINE(HAVE_CONTAINER_AT)], 179[AC_MSG_RESULT(no)]) 180</pre><p> 181 If you are using other (non-GNU) compilers it might be a good idea 182 to check for <code class="code">string::at</code> separately. 183</p></div><div class="sect3" title="No std::char_traits<char>::eof"><div class="titlepage"><div><div><h4 class="title"><a id="id716937"></a>No <code class="code">std::char_traits<char>::eof</code></h4></div></div></div><p> 184 Use some kind of autoconf test, plus this: 185</p><pre class="programlisting"> 186#ifdef HAVE_CHAR_TRAITS 187#define CPP_EOF std::char_traits<char>::eof() 188#else 189#define CPP_EOF EOF 190#endif 191</pre></div><div class="sect3" title="No string::clear"><div class="titlepage"><div><div><h4 class="title"><a id="id716955"></a>No <code class="code">string::clear</code></h4></div></div></div><p> 192 There are two functions for deleting the contents of a string: 193 <code class="code">clear</code> and <code class="code">erase</code> (the latter returns the 194 string). 195</p><pre class="programlisting"> 196void 197clear() { _M_mutate(0, this->size(), 0); } 198</pre><pre class="programlisting"> 199basic_string& 200erase(size_type __pos = 0, size_type __n = npos) 201{ 202 return this->replace(_M_check(__pos), _M_fold(__pos, __n), 203 _M_data(), _M_data()); 204} 205</pre><p> 206 Unfortunately, <code class="code">clear</code> is not implemented in this 207 version, so you should use <code class="code">erase</code> (which is probably 208 faster than <code class="code">operator=(charT*)</code>). 209</p></div><div class="sect3" title="Removal of ostream::form and istream::scan extensions"><div class="titlepage"><div><div><h4 class="title"><a id="id717001"></a> 210 Removal of <code class="code">ostream::form</code> and <code class="code">istream::scan</code> 211 extensions 212</h4></div></div></div><p> 213 These are no longer supported. Please use stringstreams instead. 214</p></div><div class="sect3" title="No basic_stringbuf, basic_stringstream"><div class="titlepage"><div><div><h4 class="title"><a id="id717020"></a>No <code class="code">basic_stringbuf</code>, <code class="code">basic_stringstream</code></h4></div></div></div><p> 215 Although the ISO standard <code class="code">i/ostringstream</code>-classes are 216 provided, (<code class="filename">sstream</code>), for 217 compatibility with older implementations the pre-ISO 218 <code class="code">i/ostrstream</code> (<code class="filename">strstream</code>) interface is also provided, 219 with these caveats: 220</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p> 221 <code class="code">strstream</code> is considered to be deprecated 222 </p></li><li class="listitem"><p> 223 <code class="code">strstream</code> is limited to <code class="code">char</code> 224 </p></li><li class="listitem"><p> 225 with <code class="code">ostringstream</code> you don't have to take care of 226 terminating the string or freeing its memory 227 </p></li><li class="listitem"><p> 228 <code class="code">istringstream</code> can be re-filled (clear(); 229 str(input);) 230 </p></li></ul></div><p> 231 You can then use output-stringstreams like this: 232</p><pre class="programlisting"> 233#ifdef HAVE_SSTREAM 234# include <sstream> 235#else 236# include <strstream> 237#endif 238 239#ifdef HAVE_SSTREAM 240 std::ostringstream oss; 241#else 242 std::ostrstream oss; 243#endif 244 245oss << <span class="quote">���<span class="quote">Name=</span>���</span> << m_name << <span class="quote">���<span class="quote">, number=</span>���</span> << m_number << std::endl; 246... 247#ifndef HAVE_SSTREAM 248 oss << std::ends; // terminate the char*-string 249#endif 250 251// str() returns char* for ostrstream and a string for ostringstream 252// this also causes ostrstream to think that the buffer's memory 253// is yours 254m_label.set_text(oss.str()); 255#ifndef HAVE_SSTREAM 256 // let the ostrstream take care of freeing the memory 257 oss.freeze(false); 258#endif 259</pre><p> 260 Input-stringstreams can be used similarly: 261</p><pre class="programlisting"> 262std::string input; 263... 264#ifdef HAVE_SSTREAM 265std::istringstream iss(input); 266#else 267std::istrstream iss(input.c_str()); 268#endif 269 270int i; 271iss >> i; 272</pre><p> One (the only?) restriction is that an istrstream cannot be re-filled: 273</p><pre class="programlisting"> 274std::istringstream iss(numerator); 275iss >> m_num; 276// this is not possible with istrstream 277iss.clear(); 278iss.str(denominator); 279iss >> m_den; 280</pre><p> 281If you don't care about speed, you can put these conversions in 282 a template-function: 283</p><pre class="programlisting"> 284template <class X> 285void fromString(const string& input, X& any) 286{ 287#ifdef HAVE_SSTREAM 288std::istringstream iss(input); 289#else 290std::istrstream iss(input.c_str()); 291#endif 292X temp; 293iss >> temp; 294if (iss.fail()) 295throw runtime_error(..) 296any = temp; 297} 298</pre><p> 299 Another example of using stringstreams is in <a class="link" href="bk01pt05ch13s05.html" title="Shrink to Fit">this howto</a>. 300</p><p> There is additional information in the libstdc++-v2 info files, in 301particular <span class="quote">���<span class="quote">info iostream</span>���</span>. 302</p></div><div class="sect3" title="Little or no wide character support"><div class="titlepage"><div><div><h4 class="title"><a id="id717171"></a>Little or no wide character support</h4></div></div></div><p> 303 Classes <code class="classname">wstring</code> and 304 <code class="classname">char_traits<wchar_t></code> are 305 not supported. 306 </p></div><div class="sect3" title="No templatized iostreams"><div class="titlepage"><div><div><h4 class="title"><a id="id717190"></a>No templatized iostreams</h4></div></div></div><p> 307 Classes <code class="classname">wfilebuf</code> and 308 <code class="classname">wstringstream</code> are not supported. 309 </p></div><div class="sect3" title="Thread safety issues"><div class="titlepage"><div><div><h4 class="title"><a id="id717209"></a>Thread safety issues</h4></div></div></div><p> 310 Earlier GCC releases had a somewhat different approach to 311 threading configuration and proper compilation. Before GCC 3.0, 312 configuration of the threading model was dictated by compiler 313 command-line options and macros (both of which were somewhat 314 thread-implementation and port-specific). There were no 315 guarantees related to being able to link code compiled with one 316 set of options and macro setting with another set. 317 </p><p> 318 For GCC 3.0, configuration of the threading model used with 319 libraries and user-code is performed when GCC is configured and 320 built using the --enable-threads and --disable-threads options. 321 The ABI is stable for symbol name-mangling and limited functional 322 compatibility exists between code compiled under different 323 threading models. 324 </p><p> 325 The libstdc++ library has been designed so that it can be used in 326 multithreaded applications (with libstdc++-v2 this was only true 327 of the STL parts.) The first problem is finding a 328 <span class="emphasis"><em>fast</em></span> method of implementation portable to 329 all platforms. Due to historical reasons, some of the library is 330 written against per-CPU-architecture spinlocks and other parts 331 against the gthr.h abstraction layer which is provided by gcc. A 332 minor problem that pops up every so often is different 333 interpretations of what "thread-safe" means for a 334 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 335 definition that SGI</a> uses for their STL subset. However, 336 the exception for read-only containers only applies to the STL 337 components. This definition is widely-used and something similar 338 will be used in the next version of the C++ standard library. 339 </p><p> 340 Here is a small link farm to threads (no pun) in the mail 341 archives that discuss the threading problem. Each link is to the 342 first relevant message in the thread; from there you can use 343 "Thread Next" to move down the thread. This farm is in 344 latest-to-oldest order. 345 </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p> 346 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 347 six situations involving threads</a> for the 3.0 348 release series. 349 </p></li><li class="listitem"><p> 350 <a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2001-05/msg00384.html" target="_top"> 351 This message</a> inspired a recent updating of issues with 352 threading and the SGI STL library. It also contains some 353 example POSIX-multithreaded STL code. 354 </p></li></ul></div><p> 355 (A large selection of links to older messages has been removed; 356 many of the messages from 1999 were lost in a disk crash, and the 357 few people with access to the backup tapes have been too swamped 358 with work to restore them. Many of the points have been 359 superseded anyhow.) 360 </p></div></div><div class="sect2" title="Third"><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 361libstdc++-v3. 362</p><p>The subset commonly known as the Standard Template Library 363 (chapters 23 through 25, mostly) is adapted from the final release 364 of the SGI STL (version 3.3), with extensive changes. 365 </p><p>A more formal description of the V3 goals can be found in the 366 official <a class="link" href="source_design_notes.html" title="Design Notes">design document</a>. 367 </p><p>Portability notes and known implementation limitations are as follows.</p><div class="sect3" title="Pre-ISO headers moved to backwards or removed"><div class="titlepage"><div><div><h4 class="title"><a id="id706015"></a>Pre-ISO headers moved to backwards or removed</h4></div></div></div><p> The pre-ISO C++ headers 368 (<code class="code">iostream.h</code>, <code class="code">defalloc.h</code> etc.) are 369 available, unlike previous libstdc++ versions, but inclusion 370 generates a warning that you are using deprecated headers. 371</p><p>This compatibility layer is constructed by including the 372 standard C++ headers, and injecting any items in 373 <code class="code">std::</code> into the global namespace. 374 </p><p>For those of you new to ISO C++ (welcome, time travelers!), no, 375 that isn't a typo. Yes, the headers really have new names. 376 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 377 [27.4]</a>. 378 </p><p> Some include adjustment may be required. What follows is an 379autoconf test that defines <code class="code">PRE_STDCXX_HEADERS</code> when they 380exist.</p><pre class="programlisting"> 381# AC_HEADER_PRE_STDCXX 382AC_DEFUN([AC_HEADER_PRE_STDCXX], [ 383 AC_CACHE_CHECK(for pre-ISO C++ include files, 384 ac_cv_cxx_pre_stdcxx, 385 [AC_LANG_SAVE 386 AC_LANG_CPLUSPLUS 387 ac_save_CXXFLAGS="$CXXFLAGS" 388 CXXFLAGS="$CXXFLAGS -Wno-deprecated" 389 390 # Omit defalloc.h, as compilation with newer compilers is problematic. 391 AC_TRY_COMPILE([ 392 #include <new.h> 393 #include <iterator.h> 394 #include <alloc.h> 395 #include <set.h> 396 #include <hashtable.h> 397 #include <hash_set.h> 398 #include <fstream.h> 399 #include <tempbuf.h> 400 #include <istream.h> 401 #include <bvector.h> 402 #include <stack.h> 403 #include <rope.h> 404 #include <complex.h> 405 #include <ostream.h> 406 #include <heap.h> 407 #include <iostream.h> 408 #include <function.h> 409 #include <multimap.h> 410 #include <pair.h> 411 #include <stream.h> 412 #include <iomanip.h> 413 #include <slist.h> 414 #include <tree.h> 415 #include <vector.h> 416 #include <deque.h> 417 #include <multiset.h> 418 #include <list.h> 419 #include <map.h> 420 #include <algobase.h> 421 #include <hash_map.h> 422 #include <algo.h> 423 #include <queue.h> 424 #include <streambuf.h> 425 ],, 426 ac_cv_cxx_pre_stdcxx=yes, ac_cv_cxx_pre_stdcxx=no) 427 CXXFLAGS="$ac_save_CXXFLAGS" 428 AC_LANG_RESTORE 429 ]) 430 if test "$ac_cv_cxx_pre_stdcxx" = yes; then 431 AC_DEFINE(PRE_STDCXX_HEADERS,,[Define if pre-ISO C++ header files are present. ]) 432 fi 433]) 434</pre><p>Porting between pre-ISO headers and ISO headers is simple: headers 435like <code class="filename">vector.h</code> can be replaced with <code class="filename">vector</code> and a using 436directive <code class="code">using namespace std;</code> can be put at the global 437scope. This should be enough to get this code compiling, assuming the 438other usage is correct. 439</p></div><div class="sect3" title="Extension headers hash_map, hash_set moved to ext or backwards"><div class="titlepage"><div><div><h4 class="title"><a id="id706097"></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 440 replaced by standardized libraries. 441 In particular, the unordered_map and unordered_set containers of TR1 442 are suitable replacement for the non-standard hash_map and hash_set 443 containers in the SGI STL. 444 </p><p> Header files <code class="filename">hash_map</code> and <code class="filename">hash_set</code> moved 445to <code class="filename">ext/hash_map</code> and <code class="filename">ext/hash_set</code>, 446respectively. At the same time, all types in these files are enclosed 447in <code class="code">namespace __gnu_cxx</code>. Later versions move deprecate 448these files, and suggest using TR1's <code class="filename">unordered_map</code> 449and <code class="filename">unordered_set</code> instead. 450</p><p>The extensions are no longer in the global or <code class="code">std</code> 451 namespaces, instead they are declared in the <code class="code">__gnu_cxx</code> 452 namespace. For maximum portability, consider defining a namespace 453 alias to use to talk about extensions, e.g.: 454 </p><pre class="programlisting"> 455 #ifdef __GNUC__ 456 #if __GNUC__ < 3 457 #include <hash_map.h> 458 namespace extension { using ::hash_map; }; // inherit globals 459 #else 460 #include <backward/hash_map> 461 #if __GNUC__ == 3 && __GNUC_MINOR__ == 0 462 namespace extension = std; // GCC 3.0 463 #else 464 namespace extension = ::__gnu_cxx; // GCC 3.1 and later 465 #endif 466 #endif 467 #else // ... there are other compilers, right? 468 namespace extension = std; 469 #endif 470 471 extension::hash_map<int,int> my_map; 472 </pre><p>This is a bit cleaner than defining typedefs for all the 473 instantiations you might need. 474 </p><p>The following autoconf tests check for working HP/SGI hash containers. 475</p><pre class="programlisting"> 476# AC_HEADER_EXT_HASH_MAP 477AC_DEFUN([AC_HEADER_EXT_HASH_MAP], [ 478 AC_CACHE_CHECK(for ext/hash_map, 479 ac_cv_cxx_ext_hash_map, 480 [AC_LANG_SAVE 481 AC_LANG_CPLUSPLUS 482 ac_save_CXXFLAGS="$CXXFLAGS" 483 CXXFLAGS="$CXXFLAGS -Werror" 484 AC_TRY_COMPILE([#include <ext/hash_map>], [using __gnu_cxx::hash_map;], 485 ac_cv_cxx_ext_hash_map=yes, ac_cv_cxx_ext_hash_map=no) 486 CXXFLAGS="$ac_save_CXXFLAGS" 487 AC_LANG_RESTORE 488 ]) 489 if test "$ac_cv_cxx_ext_hash_map" = yes; then 490 AC_DEFINE(HAVE_EXT_HASH_MAP,,[Define if ext/hash_map is present. ]) 491 fi 492]) 493</pre><pre class="programlisting"> 494# AC_HEADER_EXT_HASH_SET 495AC_DEFUN([AC_HEADER_EXT_HASH_SET], [ 496 AC_CACHE_CHECK(for ext/hash_set, 497 ac_cv_cxx_ext_hash_set, 498 [AC_LANG_SAVE 499 AC_LANG_CPLUSPLUS 500 ac_save_CXXFLAGS="$CXXFLAGS" 501 CXXFLAGS="$CXXFLAGS -Werror" 502 AC_TRY_COMPILE([#include <ext/hash_set>], [using __gnu_cxx::hash_set;], 503 ac_cv_cxx_ext_hash_set=yes, ac_cv_cxx_ext_hash_set=no) 504 CXXFLAGS="$ac_save_CXXFLAGS" 505 AC_LANG_RESTORE 506 ]) 507 if test "$ac_cv_cxx_ext_hash_set" = yes; then 508 AC_DEFINE(HAVE_EXT_HASH_SET,,[Define if ext/hash_set is present. ]) 509 fi 510]) 511</pre></div><div class="sect3" title="No ios::nocreate/ios::noreplace."><div class="titlepage"><div><div><h4 class="title"><a id="id706200"></a>No <code class="code">ios::nocreate/ios::noreplace</code>. 512</h4></div></div></div><p> The existence of <code class="code">ios::nocreate</code> being used for 513input-streams has been confirmed, most probably because the author 514thought it would be more correct to specify nocreate explicitly. So 515it can be left out for input-streams. 516</p><p>For output streams, <span class="quote">���<span class="quote">nocreate</span>���</span> is probably the default, 517unless you specify <code class="code">std::ios::trunc</code> ? To be safe, you can 518open the file for reading, check if it has been opened, and then 519decide whether you want to create/replace or not. To my knowledge, 520even older implementations support <code class="code">app</code>, <code class="code">ate</code> 521and <code class="code">trunc</code> (except for <code class="code">app</code> ?). 522</p></div><div class="sect3" title="No stream::attach(int fd)"><div class="titlepage"><div><div><h4 class="title"><a id="id703184"></a> 523No <code class="code">stream::attach(int fd)</code> 524</h4></div></div></div><p> 525 Phil Edwards writes: It was considered and rejected for the ISO 526 standard. Not all environments use file descriptors. Of those 527 that do, not all of them use integers to represent them. 528 </p><p> 529 For a portable solution (among systems which use 530 file descriptors), you need to implement a subclass of 531 <code class="code">std::streambuf</code> (or 532 <code class="code">std::basic_streambuf<..></code>) which opens a file 533 given a descriptor, and then pass an instance of this to the 534 stream-constructor. 535 </p><p> 536 An extension is available that implements this. 537 <code class="filename">ext/stdio_filebuf.h</code> contains a derived class called 538 <a class="ulink" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a00074.html" target="_top"><code class="code">__gnu_cxx::stdio_filebuf</code></a>. 539 This class can be constructed from a C <code class="code">FILE*</code> or a file 540 descriptor, and provides the <code class="code">fd()</code> function. 541 </p><p> 542 For another example of this, refer to 543 <a class="ulink" href="http://www.josuttis.com/cppcode/fdstream.html" target="_top">fdstream example</a> 544 by Nicolai Josuttis. 545</p></div><div class="sect3" title="Support for C++98 dialect."><div class="titlepage"><div><div><h4 class="title"><a id="id703247"></a> 546Support for C++98 dialect. 547</h4></div></div></div><p>Check for complete library coverage of the C++1998/2003 standard. 548</p><pre class="programlisting"> 549# AC_HEADER_STDCXX_98 550AC_DEFUN([AC_HEADER_STDCXX_98], [ 551 AC_CACHE_CHECK(for ISO C++ 98 include files, 552 ac_cv_cxx_stdcxx_98, 553 [AC_LANG_SAVE 554 AC_LANG_CPLUSPLUS 555 AC_TRY_COMPILE([ 556 #include <cassert> 557 #include <cctype> 558 #include <cerrno> 559 #include <cfloat> 560 #include <ciso646> 561 #include <climits> 562 #include <clocale> 563 #include <cmath> 564 #include <csetjmp> 565 #include <csignal> 566 #include <cstdarg> 567 #include <cstddef> 568 #include <cstdio> 569 #include <cstdlib> 570 #include <cstring> 571 #include <ctime> 572 573 #include <algorithm> 574 #include <bitset> 575 #include <complex> 576 #include <deque> 577 #include <exception> 578 #include <fstream> 579 #include <functional> 580 #include <iomanip> 581 #include <ios> 582 #include <iosfwd> 583 #include <iostream> 584 #include <istream> 585 #include <iterator> 586 #include <limits> 587 #include <list> 588 #include <locale> 589 #include <map> 590 #include <memory> 591 #include <new> 592 #include <numeric> 593 #include <ostream> 594 #include <queue> 595 #include <set> 596 #include <sstream> 597 #include <stack> 598 #include <stdexcept> 599 #include <streambuf> 600 #include <string> 601 #include <typeinfo> 602 #include <utility> 603 #include <valarray> 604 #include <vector> 605 ],, 606 ac_cv_cxx_stdcxx_98=yes, ac_cv_cxx_stdcxx_98=no) 607 AC_LANG_RESTORE 608 ]) 609 if test "$ac_cv_cxx_stdcxx_98" = yes; then 610 AC_DEFINE(STDCXX_98_HEADERS,,[Define if ISO C++ 1998 header files are present. ]) 611 fi 612]) 613</pre></div><div class="sect3" title="Support for C++TR1 dialect."><div class="titlepage"><div><div><h4 class="title"><a id="id703275"></a> 614Support for C++TR1 dialect. 615</h4></div></div></div><p>Check for library coverage of the TR1 standard. 616</p><pre class="programlisting"> 617# AC_HEADER_STDCXX_TR1 618AC_DEFUN([AC_HEADER_STDCXX_TR1], [ 619 AC_CACHE_CHECK(for ISO C++ TR1 include files, 620 ac_cv_cxx_stdcxx_tr1, 621 [AC_LANG_SAVE 622 AC_LANG_CPLUSPLUS 623 AC_TRY_COMPILE([ 624 #include <tr1/array> 625 #include <tr1/ccomplex> 626 #include <tr1/cctype> 627 #include <tr1/cfenv> 628 #include <tr1/cfloat> 629 #include <tr1/cinttypes> 630 #include <tr1/climits> 631 #include <tr1/cmath> 632 #include <tr1/complex> 633 #include <tr1/cstdarg> 634 #include <tr1/cstdbool> 635 #include <tr1/cstdint> 636 #include <tr1/cstdio> 637 #include <tr1/cstdlib> 638 #include <tr1/ctgmath> 639 #include <tr1/ctime> 640 #include <tr1/cwchar> 641 #include <tr1/cwctype> 642 #include <tr1/functional> 643 #include <tr1/memory> 644 #include <tr1/random> 645 #include <tr1/regex> 646 #include <tr1/tuple> 647 #include <tr1/type_traits> 648 #include <tr1/unordered_set> 649 #include <tr1/unordered_map> 650 #include <tr1/utility> 651 ],, 652 ac_cv_cxx_stdcxx_tr1=yes, ac_cv_cxx_stdcxx_tr1=no) 653 AC_LANG_RESTORE 654 ]) 655 if test "$ac_cv_cxx_stdcxx_tr1" = yes; then 656 AC_DEFINE(STDCXX_TR1_HEADERS,,[Define if ISO C++ TR1 header files are present. ]) 657 fi 658]) 659</pre><p>An alternative is to check just for specific TR1 includes, such as <unordered_map> and <unordered_set>. 660</p><pre class="programlisting"> 661# AC_HEADER_TR1_UNORDERED_MAP 662AC_DEFUN([AC_HEADER_TR1_UNORDERED_MAP], [ 663 AC_CACHE_CHECK(for tr1/unordered_map, 664 ac_cv_cxx_tr1_unordered_map, 665 [AC_LANG_SAVE 666 AC_LANG_CPLUSPLUS 667 AC_TRY_COMPILE([#include <tr1/unordered_map>], [using std::tr1::unordered_map;], 668 ac_cv_cxx_tr1_unordered_map=yes, ac_cv_cxx_tr1_unordered_map=no) 669 AC_LANG_RESTORE 670 ]) 671 if test "$ac_cv_cxx_tr1_unordered_map" = yes; then 672 AC_DEFINE(HAVE_TR1_UNORDERED_MAP,,[Define if tr1/unordered_map is present. ]) 673 fi 674]) 675</pre><pre class="programlisting"> 676# AC_HEADER_TR1_UNORDERED_SET 677AC_DEFUN([AC_HEADER_TR1_UNORDERED_SET], [ 678 AC_CACHE_CHECK(for tr1/unordered_set, 679 ac_cv_cxx_tr1_unordered_set, 680 [AC_LANG_SAVE 681 AC_LANG_CPLUSPLUS 682 AC_TRY_COMPILE([#include <tr1/unordered_set>], [using std::tr1::unordered_set;], 683 ac_cv_cxx_tr1_unordered_set=yes, ac_cv_cxx_tr1_unordered_set=no) 684 AC_LANG_RESTORE 685 ]) 686 if test "$ac_cv_cxx_tr1_unordered_set" = yes; then 687 AC_DEFINE(HAVE_TR1_UNORDERED_SET,,[Define if tr1/unordered_set is present. ]) 688 fi 689]) 690</pre></div><div class="sect3" title="Support for C++0x dialect."><div class="titlepage"><div><div><h4 class="title"><a id="id703319"></a> 691Support for C++0x dialect. 692</h4></div></div></div><p>Check for baseline language coverage in the compiler for the C++0xstandard. 693</p><pre class="programlisting"> 694# AC_COMPILE_STDCXX_OX 695AC_DEFUN([AC_COMPILE_STDCXX_0X], [ 696 AC_CACHE_CHECK(if g++ supports C++0x features without additional flags, 697 ac_cv_cxx_compile_cxx0x_native, 698 [AC_LANG_SAVE 699 AC_LANG_CPLUSPLUS 700 AC_TRY_COMPILE([ 701 template <typename T> 702 struct check 703 { 704 static_assert(sizeof(int) <= sizeof(T), "not big enough"); 705 }; 706 707 typedef check<check<bool>> right_angle_brackets; 708 709 int a; 710 decltype(a) b; 711 712 typedef check<int> check_type; 713 check_type c; 714 check_type&& cr = c;],, 715 ac_cv_cxx_compile_cxx0x_native=yes, ac_cv_cxx_compile_cxx0x_native=no) 716 AC_LANG_RESTORE 717 ]) 718 719 AC_CACHE_CHECK(if g++ supports C++0x features with -std=c++0x, 720 ac_cv_cxx_compile_cxx0x_cxx, 721 [AC_LANG_SAVE 722 AC_LANG_CPLUSPLUS 723 ac_save_CXXFLAGS="$CXXFLAGS" 724 CXXFLAGS="$CXXFLAGS -std=c++0x" 725 AC_TRY_COMPILE([ 726 template <typename T> 727 struct check 728 { 729 static_assert(sizeof(int) <= sizeof(T), "not big enough"); 730 }; 731 732 typedef check<check<bool>> right_angle_brackets; 733 734 int a; 735 decltype(a) b; 736 737 typedef check<int> check_type; 738 check_type c; 739 check_type&& cr = c;],, 740 ac_cv_cxx_compile_cxx0x_cxx=yes, ac_cv_cxx_compile_cxx0x_cxx=no) 741 CXXFLAGS="$ac_save_CXXFLAGS" 742 AC_LANG_RESTORE 743 ]) 744 745 AC_CACHE_CHECK(if g++ supports C++0x features with -std=gnu++0x, 746 ac_cv_cxx_compile_cxx0x_gxx, 747 [AC_LANG_SAVE 748 AC_LANG_CPLUSPLUS 749 ac_save_CXXFLAGS="$CXXFLAGS" 750 CXXFLAGS="$CXXFLAGS -std=gnu++0x" 751 AC_TRY_COMPILE([ 752 template <typename T> 753 struct check 754 { 755 static_assert(sizeof(int) <= sizeof(T), "not big enough"); 756 }; 757 758 typedef check<check<bool>> right_angle_brackets; 759 760 int a; 761 decltype(a) b; 762 763 typedef check<int> check_type; 764 check_type c; 765 check_type&& cr = c;],, 766 ac_cv_cxx_compile_cxx0x_gxx=yes, ac_cv_cxx_compile_cxx0x_gxx=no) 767 CXXFLAGS="$ac_save_CXXFLAGS" 768 AC_LANG_RESTORE 769 ]) 770 771 if test "$ac_cv_cxx_compile_cxx0x_native" = yes || 772 test "$ac_cv_cxx_compile_cxx0x_cxx" = yes || 773 test "$ac_cv_cxx_compile_cxx0x_gxx" = yes; then 774 AC_DEFINE(HAVE_STDCXX_0X,,[Define if g++ supports C++0x features. ]) 775 fi 776]) 777</pre><p>Check for library coverage of the C++0xstandard. 778</p><pre class="programlisting"> 779# AC_HEADER_STDCXX_0X 780AC_DEFUN([AC_HEADER_STDCXX_0X], [ 781 AC_CACHE_CHECK(for ISO C++ 0x include files, 782 ac_cv_cxx_stdcxx_0x, 783 [AC_REQUIRE([AC_COMPILE_STDCXX_0X]) 784 AC_LANG_SAVE 785 AC_LANG_CPLUSPLUS 786 ac_save_CXXFLAGS="$CXXFLAGS" 787 CXXFLAGS="$CXXFLAGS -std=gnu++0x" 788 789 AC_TRY_COMPILE([ 790 #include <cassert> 791 #include <ccomplex> 792 #include <cctype> 793 #include <cerrno> 794 #include <cfenv> 795 #include <cfloat> 796 #include <cinttypes> 797 #include <ciso646> 798 #include <climits> 799 #include <clocale> 800 #include <cmath> 801 #include <csetjmp> 802 #include <csignal> 803 #include <cstdarg> 804 #include <cstdbool> 805 #include <cstddef> 806 #include <cstdint> 807 #include <cstdio> 808 #include <cstdlib> 809 #include <cstring> 810 #include <ctgmath> 811 #include <ctime> 812 #include <cwchar> 813 #include <cwctype> 814 815 #include <algorithm> 816 #include <array> 817 #include <bitset> 818 #include <complex> 819 #include <deque> 820 #include <exception> 821 #include <fstream> 822 #include <functional> 823 #include <iomanip> 824 #include <ios> 825 #include <iosfwd> 826 #include <iostream> 827 #include <istream> 828 #include <iterator> 829 #include <limits> 830 #include <list> 831 #include <locale> 832 #include <map> 833 #include <memory> 834 #include <new> 835 #include <numeric> 836 #include <ostream> 837 #include <queue> 838 #include <random> 839 #include <regex> 840 #include <set> 841 #include <sstream> 842 #include <stack> 843 #include <stdexcept> 844 #include <streambuf> 845 #include <string> 846 #include <tuple> 847 #include <typeinfo> 848 #include <type_traits> 849 #include <unordered_map> 850 #include <unordered_set> 851 #include <utility> 852 #include <valarray> 853 #include <vector> 854 ],, 855 ac_cv_cxx_stdcxx_0x=yes, ac_cv_cxx_stdcxx_0x=no) 856 AC_LANG_RESTORE 857 CXXFLAGS="$ac_save_CXXFLAGS" 858 ]) 859 if test "$ac_cv_cxx_stdcxx_0x" = yes; then 860 AC_DEFINE(STDCXX_0X_HEADERS,,[Define if ISO C++ 0x header files are present. ]) 861 fi 862]) 863</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> 864</p><pre class="programlisting"> 865# AC_HEADER_UNORDERED_MAP 866AC_DEFUN([AC_HEADER_UNORDERED_MAP], [ 867 AC_CACHE_CHECK(for unordered_map, 868 ac_cv_cxx_unordered_map, 869 [AC_REQUIRE([AC_COMPILE_STDCXX_0X]) 870 AC_LANG_SAVE 871 AC_LANG_CPLUSPLUS 872 ac_save_CXXFLAGS="$CXXFLAGS" 873 CXXFLAGS="$CXXFLAGS -std=gnu++0x" 874 AC_TRY_COMPILE([#include <unordered_map>], [using std::unordered_map;], 875 ac_cv_cxx_unordered_map=yes, ac_cv_cxx_unordered_map=no) 876 CXXFLAGS="$ac_save_CXXFLAGS" 877 AC_LANG_RESTORE 878 ]) 879 if test "$ac_cv_cxx_unordered_map" = yes; then 880 AC_DEFINE(HAVE_UNORDERED_MAP,,[Define if unordered_map is present. ]) 881 fi 882]) 883</pre><pre class="programlisting"> 884# AC_HEADER_UNORDERED_SET 885AC_DEFUN([AC_HEADER_UNORDERED_SET], [ 886 AC_CACHE_CHECK(for unordered_set, 887 ac_cv_cxx_unordered_set, 888 [AC_REQUIRE([AC_COMPILE_STDCXX_0X]) 889 AC_LANG_SAVE 890 AC_LANG_CPLUSPLUS 891 ac_save_CXXFLAGS="$CXXFLAGS" 892 CXXFLAGS="$CXXFLAGS -std=gnu++0x" 893 AC_TRY_COMPILE([#include <unordered_set>], [using std::unordered_set;], 894 ac_cv_cxx_unordered_set=yes, ac_cv_cxx_unordered_set=no) 895 CXXFLAGS="$ac_save_CXXFLAGS" 896 AC_LANG_RESTORE 897 ]) 898 if test "$ac_cv_cxx_unordered_set" = yes; then 899 AC_DEFINE(HAVE_UNORDERED_SET,,[Define if unordered_set is present. ]) 900 fi 901]) 902</pre></div><div class="sect3" title="Container::iterator_type is not necessarily Container::value_type*"><div class="titlepage"><div><div><h4 class="title"><a id="id703396"></a> 903 Container::iterator_type is not necessarily Container::value_type* 904</h4></div></div></div><p> 905 This is a change in behavior from the previous version. Now, most 906 <span class="type">iterator_type</span> typedefs in container classes are POD 907 objects, not <span class="type">value_type</span> pointers. 908</p></div></div><div class="bibliography" title="Bibliography"><div class="titlepage"><div><div><h3 class="title"><a id="backwards.biblio"></a>Bibliography</h3></div></div></div><div class="biblioentry" title="Migrating to GCC 4.1"><a id="id703425"></a><p>[<abbr class="abbrev"> 909 kegel41 910 </abbr>] <span class="title"><i> 911 Migrating to GCC 4.1 912 </i>. </span><span class="author"><span class="firstname">Dan</span> <span class="surname">Kegel</span>. </span><span class="biblioid"> 913 <a class="ulink" href="http://www.kegel.com/gcc/gcc4.html" target="_top"> 914 </a> 915 . </span></p></div><div class="biblioentry" title="Building the Whole Debian Archive with GCC 4.1: A Summary"><a id="id703458"></a><p>[<abbr class="abbrev"> 916 kegel41 917 </abbr>] <span class="title"><i> 918 Building the Whole Debian Archive with GCC 4.1: A Summary 919 </i>. </span><span class="author"><span class="firstname">Martin</span> <span class="surname">Michlmayr</span>. </span><span class="biblioid"> 920 <a class="ulink" href="http://lists.debian.org/debian-gcc/2006/03/msg00405.html" target="_top"> 921 </a> 922 . </span></p></div><div class="biblioentry" title="Migration guide for GCC-3.2"><a id="id703491"></a><p>[<abbr class="abbrev"> 923 lbl32 924 </abbr>] <span class="title"><i> 925 Migration guide for GCC-3.2 926 </i>. </span><span class="biblioid"> 927 <a class="ulink" href="http://annwm.lbl.gov/~leggett/Atlas/gcc-3.2.html" target="_top"> 928 </a> 929 . </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.�� 930 Free Software Needs Free Documentation 931 932</td></tr></table></div></body></html> 933