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3 <html xmlns="http://www.w3.org/1999/xhtml"><head><title>Backwards Compatibility</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><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"/><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 align="left"><a accesskey="p" href="api.html">Prev</a> </td><th width="60%" align="center">Appendix B.
4 Porting and Maintenance
6 </th><td align="right"> <a accesskey="n" href="appendix_free.html">Next</a></td></tr></table><hr/></div><div class="section" title="Backwards Compatibility"><div class="titlepage"><div><div><h2 class="title"><a id="manual.appendix.porting.backwards"/>Backwards Compatibility</h2></div></div></div><div class="section" title="First"><div class="titlepage"><div><div><h3 class="title"><a id="backwards.first"/>First</h3></div></div></div><p>The first generation GNU C++ library was called libg++. It was a
7 separate GNU project, although reliably paired with GCC. Rumors imply
8 that it had a working relationship with at least two kinds of
10 </p><p>Some background: libg++ was designed and created when there was no
11 ISO standard to provide guidance. Classes like linked lists are now
12 provided for by <code class="classname">list<T></code> and do not need to be
13 created by <code class="function">genclass</code>. (For that matter, templates exist
14 now and are well-supported, whereas genclass (mostly) predates them.)
15 </p><p>There are other classes in libg++ that are not specified in the
16 ISO Standard (e.g., statistical analysis). While there are a lot of
17 really useful things that are used by a lot of people, the Standards
18 Committee 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="section" title="No ios_base"><div class="titlepage"><div><div><h4 class="title"><a id="id494148"/>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="section" title="No cout in ostream.h, no cin in istream.h"><div class="titlepage"><div><div><h4 class="title"><a id="id494180"/>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>
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
31 archived. For the desperate,
32 the <a class="link" href="http://gcc.gnu.org/extensions.html">GCC extensions
33 page</a> describes where to find the last libg++ source. The code is
34 considered replaced and rewritten.
35 </p></div></div><div class="section" title="Second"><div class="titlepage"><div><div><h3 class="title"><a id="backwards.second"/>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.
41 The STL portions of this library are based on SGI/HP STL release 3.11.
43 This project is no longer maintained or supported, and the sources
44 archived. The code is considered replaced and rewritten.
46 Portability notes and known implementation limitations are as follows.
47 </p><div class="section" title="Namespace std:: not supported"><div class="titlepage"><div><div><h4 class="title"><a id="id494283"/>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>.
52 The following sections list some possible solutions to support compilers
53 that cannot ignore <code class="code">std::</code>-qualified names.
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.
64 Second, experiment with a variety of pre-processor tricks.
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
73 Thanks to Juergen Heinzl who posted this solution on gnu.gcc.help.
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">
87 dnl @synopsis AC_CXX_NAMESPACE_STD
89 dnl If the compiler supports namespace std, define
90 dnl HAVE_NAMESPACE_STD.
93 dnl @author Todd Veldhuizen
94 dnl @author Luc Maisonobe <luc@spaceroots.org>
95 dnl @version 2004-02-04
96 dnl @license AllPermissive
97 AC_DEFUN([AC_CXX_NAMESPACE_STD], [
98 AC_CACHE_CHECK(if g++ supports namespace std,
99 ac_cv_cxx_have_std_namespace,
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)
107 if test "$ac_cv_cxx_have_std_namespace" = yes; then
108 AC_DEFINE(HAVE_NAMESPACE_STD,,[Define if g++ supports namespace std. ])
111 </pre></div><div class="section" title="Illegal iterator usage"><div class="titlepage"><div><div><h4 class="title"><a id="id494409"/>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"><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="section" title="isspace from cctype is a macro"><div class="titlepage"><div><div><h4 class="title"><a id="id494471"/><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.).
129 This implementations of libstdc++, however, keep these functions
130 as macros, and so it is not back-portable to use fully qualified
132 </p><pre class="programlisting">
133 #include <cctype>
134 int main() { std::isspace('X'); }
136 Results in something like this:
137 </p><pre class="programlisting">
138 std:: (__ctype_b[(int) ( ( 'X' ) )] & (unsigned short int) _ISspace ) ;
140 A solution is to modify a header-file so that the compiler tells
141 <code class="filename">ctype.h</code> to define functions
143 </p><pre class="programlisting">
144 // This keeps isalnum, et al from being propagated as macros.
146 # define __NO_CTYPE 1
149 Then, include <code class="filename">ctype.h</code>
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="section" title="No vector::at, deque::at, string::at"><div class="titlepage"><div><div><h4 class="title"><a id="id494566"/>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">
160 AC_MSG_CHECKING(for container::at)
163 #include <vector>
164 #include <deque>
165 #include <string>
170 deque<int> test_deque(3);
172 vector<int> test_vector(2);
174 string test_string(<span class="quote">“<span class="quote">test_string</span>”</span>);
178 AC_DEFINE(HAVE_CONTAINER_AT)],
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="section" title="No std::char_traits<char>::eof"><div class="titlepage"><div><div><h4 class="title"><a id="id494605"/>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()
191 </pre></div><div class="section" title="No string::clear"><div class="titlepage"><div><div><h4 class="title"><a id="id494623"/>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
195 </p><pre class="programlisting">
197 clear() { _M_mutate(0, this->size(), 0); }
198 </pre><pre class="programlisting">
200 erase(size_type __pos = 0, size_type __n = npos)
202 return this->replace(_M_check(__pos), _M_fold(__pos, __n),
203 _M_data(), _M_data());
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="section" title="Removal of ostream::form and istream::scan extensions"><div class="titlepage"><div><div><h4 class="title"><a id="id494669"/>
210 Removal of <code class="code">ostream::form</code> and <code class="code">istream::scan</code>
212 </h4></div></div></div><p>
213 These are no longer supported. Please use stringstreams instead.
214 </p></div><div class="section" title="No basic_stringbuf, basic_stringstream"><div class="titlepage"><div><div><h4 class="title"><a id="id494688"/>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,
220 </p><div class="itemizedlist"><ul class="itemizedlist"><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();
230 </p></li></ul></div><p>
231 You can then use output-stringstreams like this:
232 </p><pre class="programlisting">
234 # include <sstream>
236 # include <strstream>
240 std::ostringstream oss;
245 oss << <span class="quote">“<span class="quote">Name=</span>”</span> << m_name << <span class="quote">“<span class="quote">, number=</span>”</span> << m_number << std::endl;
248 oss << std::ends; // terminate the char*-string
251 // str() returns char* for ostrstream and a string for ostringstream
252 // this also causes ostrstream to think that the buffer's memory
254 m_label.set_text(oss.str());
256 // let the ostrstream take care of freeing the memory
260 Input-stringstreams can be used similarly:
261 </p><pre class="programlisting">
265 std::istringstream iss(input);
267 std::istrstream iss(input.c_str());
272 </pre><p> One (the only?) restriction is that an istrstream cannot be re-filled:
273 </p><pre class="programlisting">
274 std::istringstream iss(numerator);
276 // this is not possible with istrstream
278 iss.str(denominator);
281 If you don't care about speed, you can put these conversions in
283 </p><pre class="programlisting">
284 template <class X>
285 void fromString(const string& input, X& any)
288 std::istringstream iss(input);
290 std::istrstream iss(input.c_str());
295 throw runtime_error(..)
299 Another example of using stringstreams is in <a class="link" href="strings.html#strings.string.shrink" title="Shrink to Fit">this howto</a>.
300 </p><p> There is additional information in the libstdc++-v2 info files, in
301 particular <span class="quote">“<span class="quote">info iostream</span>”</span>.
302 </p></div><div class="section" title="Little or no wide character support"><div class="titlepage"><div><div><h4 class="title"><a id="id494844"/>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
306 </p></div><div class="section" title="No templatized iostreams"><div class="titlepage"><div><div><h4 class="title"><a id="id494863"/>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="section" title="Thread safety issues"><div class="titlepage"><div><div><h4 class="title"><a id="id494881"/>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.
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
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="link" href="http://www.sgi.com/tech/stl/thread_safety.html">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.
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"><li class="listitem"><p>
346 Our threading expert Loren gives a breakdown of <a class="link" href="http://gcc.gnu.org/ml/libstdc++/2001-10/msg00024.html">the
347 six situations involving threads</a> for the 3.0
349 </p></li><li class="listitem"><p>
350 <a class="link" href="http://gcc.gnu.org/ml/libstdc++/2001-05/msg00384.html">
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
360 </p></div></div><div class="section" title="Third"><div class="titlepage"><div><div><h3 class="title"><a id="backwards.third"/>Third</h3></div></div></div><p> The third generation GNU C++ library is called libstdc++, or
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="section" title="Pre-ISO headers moved to backwards or removed"><div class="titlepage"><div><div><h4 class="title"><a id="id495006"/>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="link" href="http://www.parashift.com/c++-faq-lite/coding-standards.html#faq-27.4">item
378 </p><p> Some include adjustment may be required. What follows is an
379 autoconf test that defines <code class="code">PRE_STDCXX_HEADERS</code> when they
380 exist.</p><pre class="programlisting">
381 # AC_HEADER_PRE_STDCXX
382 AC_DEFUN([AC_HEADER_PRE_STDCXX], [
383 AC_CACHE_CHECK(for pre-ISO C++ include files,
384 ac_cv_cxx_pre_stdcxx,
387 ac_save_CXXFLAGS="$CXXFLAGS"
388 CXXFLAGS="$CXXFLAGS -Wno-deprecated"
390 # Omit defalloc.h, as compilation with newer compilers is problematic.
392 #include <new.h>
393 #include <iterator.h>
394 #include <alloc.h>
395 #include <set.h>
396 #include <hashtable.h>
397 #include <hash_set.h>
398 #include <fstream.h>
399 #include <tempbuf.h>
400 #include <istream.h>
401 #include <bvector.h>
402 #include <stack.h>
403 #include <rope.h>
404 #include <complex.h>
405 #include <ostream.h>
406 #include <heap.h>
407 #include <iostream.h>
408 #include <function.h>
409 #include <multimap.h>
410 #include <pair.h>
411 #include <stream.h>
412 #include <iomanip.h>
413 #include <slist.h>
414 #include <tree.h>
415 #include <vector.h>
416 #include <deque.h>
417 #include <multiset.h>
418 #include <list.h>
419 #include <map.h>
420 #include <algobase.h>
421 #include <hash_map.h>
422 #include <algo.h>
423 #include <queue.h>
424 #include <streambuf.h>
426 ac_cv_cxx_pre_stdcxx=yes, ac_cv_cxx_pre_stdcxx=no)
427 CXXFLAGS="$ac_save_CXXFLAGS"
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. ])
434 </pre><p>Porting between pre-ISO headers and ISO headers is simple: headers
435 like <code class="filename">vector.h</code> can be replaced with <code class="filename">vector</code> and a using
436 directive <code class="code">using namespace std;</code> can be put at the global
437 scope. This should be enough to get this code compiling, assuming the
438 other usage is correct.
439 </p></div><div class="section" title="Extension headers hash_map, hash_set moved to ext or backwards"><div class="titlepage"><div><div><h4 class="title"><a id="id495090"/>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
445 to <code class="filename">ext/hash_map</code> and <code class="filename">ext/hash_set</code>,
446 respectively. At the same time, all types in these files are enclosed
447 in <code class="code">namespace __gnu_cxx</code>. Later versions move deprecate
448 these files, and suggest using TR1's <code class="filename">unordered_map</code>
449 and <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">
457 #include <hash_map.h>
458 namespace extension { using ::hash_map; }; // inherit globals
460 #include <backward/hash_map>
461 #if __GNUC__ == 3 && __GNUC_MINOR__ == 0
462 namespace extension = std; // GCC 3.0
464 namespace extension = ::__gnu_cxx; // GCC 3.1 and later
467 #else // ... there are other compilers, right?
468 namespace extension = std;
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
477 AC_DEFUN([AC_HEADER_EXT_HASH_MAP], [
478 AC_CACHE_CHECK(for ext/hash_map,
479 ac_cv_cxx_ext_hash_map,
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"
489 if test "$ac_cv_cxx_ext_hash_map" = yes; then
490 AC_DEFINE(HAVE_EXT_HASH_MAP,,[Define if ext/hash_map is present. ])
493 </pre><pre class="programlisting">
494 # AC_HEADER_EXT_HASH_SET
495 AC_DEFUN([AC_HEADER_EXT_HASH_SET], [
496 AC_CACHE_CHECK(for ext/hash_set,
497 ac_cv_cxx_ext_hash_set,
500 ac_save_CXXFLAGS="$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"
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. ])
511 </pre></div><div class="section" title="No ios::nocreate/ios::noreplace."><div class="titlepage"><div><div><h4 class="title"><a id="id495193"/>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
513 input-streams has been confirmed, most probably because the author
514 thought it would be more correct to specify nocreate explicitly. So
515 it 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,
517 unless you specify <code class="code">std::ios::trunc</code> ? To be safe, you can
518 open the file for reading, check if it has been opened, and then
519 decide whether you want to create/replace or not. To my knowledge,
520 even older implementations support <code class="code">app</code>, <code class="code">ate</code>
521 and <code class="code">trunc</code> (except for <code class="code">app</code> ?).
522 </p></div><div class="section" title="No stream::attach(int fd)"><div class="titlepage"><div><div><h4 class="title"><a id="id495241"/>
523 No <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.
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
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="link" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a00074.html"><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.
542 For another example of this, refer to
543 <a class="link" href="http://www.josuttis.com/cppcode/fdstream.html">fdstream example</a>
545 </p></div><div class="section" title="Support for C++98 dialect."><div class="titlepage"><div><div><h4 class="title"><a id="id495309"/>
546 Support 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
550 AC_DEFUN([AC_HEADER_STDCXX_98], [
551 AC_CACHE_CHECK(for ISO C++ 98 include files,
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>
573 #include <algorithm>
574 #include <bitset>
575 #include <complex>
576 #include <deque>
577 #include <exception>
578 #include <fstream>
579 #include <functional>
580 #include <iomanip>
582 #include <iosfwd>
583 #include <iostream>
584 #include <istream>
585 #include <iterator>
586 #include <limits>
587 #include <list>
588 #include <locale>
590 #include <memory>
592 #include <numeric>
593 #include <ostream>
594 #include <queue>
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>
606 ac_cv_cxx_stdcxx_98=yes, ac_cv_cxx_stdcxx_98=no)
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. ])
613 </pre></div><div class="section" title="Support for C++TR1 dialect."><div class="titlepage"><div><div><h4 class="title"><a id="id495337"/>
614 Support 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
618 AC_DEFUN([AC_HEADER_STDCXX_TR1], [
619 AC_CACHE_CHECK(for ISO C++ TR1 include files,
620 ac_cv_cxx_stdcxx_tr1,
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>
652 ac_cv_cxx_stdcxx_tr1=yes, ac_cv_cxx_stdcxx_tr1=no)
655 if test "$ac_cv_cxx_stdcxx_tr1" = yes; then
656 AC_DEFINE(STDCXX_TR1_HEADERS,,[Define if ISO C++ TR1 header files are present. ])
659 </pre><p>An alternative is to check just for specific TR1 includes, such as <unordered_map> and <unordered_set>.
660 </p><pre class="programlisting">
661 # AC_HEADER_TR1_UNORDERED_MAP
662 AC_DEFUN([AC_HEADER_TR1_UNORDERED_MAP], [
663 AC_CACHE_CHECK(for tr1/unordered_map,
664 ac_cv_cxx_tr1_unordered_map,
667 AC_TRY_COMPILE([#include <tr1/unordered_map>], [using std::tr1::unordered_map;],
668 ac_cv_cxx_tr1_unordered_map=yes, ac_cv_cxx_tr1_unordered_map=no)
671 if test "$ac_cv_cxx_tr1_unordered_map" = yes; then
672 AC_DEFINE(HAVE_TR1_UNORDERED_MAP,,[Define if tr1/unordered_map is present. ])
675 </pre><pre class="programlisting">
676 # AC_HEADER_TR1_UNORDERED_SET
677 AC_DEFUN([AC_HEADER_TR1_UNORDERED_SET], [
678 AC_CACHE_CHECK(for tr1/unordered_set,
679 ac_cv_cxx_tr1_unordered_set,
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)
686 if test "$ac_cv_cxx_tr1_unordered_set" = yes; then
687 AC_DEFINE(HAVE_TR1_UNORDERED_SET,,[Define if tr1/unordered_set is present. ])
690 </pre></div><div class="section" title="Support for C++0x dialect."><div class="titlepage"><div><div><h4 class="title"><a id="id495381"/>
691 Support for C++0x dialect.
692 </h4></div></div></div><p>Check for baseline language coverage in the compiler for the C++0xstandard.
693 </p><pre class="programlisting">
694 # AC_COMPILE_STDCXX_OX
695 AC_DEFUN([AC_COMPILE_STDCXX_0X], [
696 AC_CACHE_CHECK(if g++ supports C++0x features without additional flags,
697 ac_cv_cxx_compile_cxx0x_native,
701 template <typename T>
704 static_assert(sizeof(int) <= sizeof(T), "not big enough");
707 typedef check<check<bool>> right_angle_brackets;
712 typedef check<int> check_type;
714 check_type&& cr = c;],,
715 ac_cv_cxx_compile_cxx0x_native=yes, ac_cv_cxx_compile_cxx0x_native=no)
719 AC_CACHE_CHECK(if g++ supports C++0x features with -std=c++0x,
720 ac_cv_cxx_compile_cxx0x_cxx,
723 ac_save_CXXFLAGS="$CXXFLAGS"
724 CXXFLAGS="$CXXFLAGS -std=c++0x"
726 template <typename T>
729 static_assert(sizeof(int) <= sizeof(T), "not big enough");
732 typedef check<check<bool>> right_angle_brackets;
737 typedef check<int> check_type;
739 check_type&& cr = c;],,
740 ac_cv_cxx_compile_cxx0x_cxx=yes, ac_cv_cxx_compile_cxx0x_cxx=no)
741 CXXFLAGS="$ac_save_CXXFLAGS"
745 AC_CACHE_CHECK(if g++ supports C++0x features with -std=gnu++0x,
746 ac_cv_cxx_compile_cxx0x_gxx,
749 ac_save_CXXFLAGS="$CXXFLAGS"
750 CXXFLAGS="$CXXFLAGS -std=gnu++0x"
752 template <typename T>
755 static_assert(sizeof(int) <= sizeof(T), "not big enough");
758 typedef check<check<bool>> right_angle_brackets;
763 typedef check<int> check_type;
765 check_type&& cr = c;],,
766 ac_cv_cxx_compile_cxx0x_gxx=yes, ac_cv_cxx_compile_cxx0x_gxx=no)
767 CXXFLAGS="$ac_save_CXXFLAGS"
771 if test "$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. ])
777 </pre><p>Check for library coverage of the C++0xstandard.
778 </p><pre class="programlisting">
779 # AC_HEADER_STDCXX_0X
780 AC_DEFUN([AC_HEADER_STDCXX_0X], [
781 AC_CACHE_CHECK(for ISO C++ 0x include files,
783 [AC_REQUIRE([AC_COMPILE_STDCXX_0X])
786 ac_save_CXXFLAGS="$CXXFLAGS"
787 CXXFLAGS="$CXXFLAGS -std=gnu++0x"
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>
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>
825 #include <iosfwd>
826 #include <iostream>
827 #include <istream>
828 #include <iterator>
829 #include <limits>
830 #include <list>
831 #include <locale>
833 #include <memory>
835 #include <numeric>
836 #include <ostream>
837 #include <queue>
838 #include <random>
839 #include <regex>
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>
855 ac_cv_cxx_stdcxx_0x=yes, ac_cv_cxx_stdcxx_0x=no)
857 CXXFLAGS="$ac_save_CXXFLAGS"
859 if test "$ac_cv_cxx_stdcxx_0x" = yes; then
860 AC_DEFINE(STDCXX_0X_HEADERS,,[Define if ISO C++ 0x header files are present. ])
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
866 AC_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])
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="$ac_save_CXXFLAGS"
879 if test "$ac_cv_cxx_unordered_map" = yes; then
880 AC_DEFINE(HAVE_UNORDERED_MAP,,[Define if unordered_map is present. ])
883 </pre><pre class="programlisting">
884 # AC_HEADER_UNORDERED_SET
885 AC_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])
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="$ac_save_CXXFLAGS"
898 if test "$ac_cv_cxx_unordered_set" = yes; then
899 AC_DEFINE(HAVE_UNORDERED_SET,,[Define if unordered_set is present. ])
902 </pre></div><div class="section" title="Container::iterator_type is not necessarily Container::value_type*"><div class="titlepage"><div><div><h4 class="title"><a id="id495459"/>
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"/>Bibliography</h3></div></div></div><div class="biblioentry"><a id="id495489"/><p><span class="biblioid">
909 . </span><span class="citetitle"><em class="citetitle">
911 </em>. </span><span class="author"><span class="firstname">Dan</span> <span class="surname">Kegel</span>. </span></p></div><div class="biblioentry"><a id="id495515"/><p><span class="biblioid">
912 . </span><span class="citetitle"><em class="citetitle">
913 Building the Whole Debian Archive with GCC 4.1: A Summary
914 </em>. </span><span class="author"><span class="firstname">Martin</span> <span class="surname">Michlmayr</span>. </span></p></div><div class="biblioentry"><a id="id495541"/><p><span class="biblioid">
915 . </span><span class="citetitle"><em class="citetitle">
916 Migration guide for GCC-3.2
917 </em>. </span></p></div></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="api.html">Prev</a> </td><td align="center"><a accesskey="u" href="appendix_porting.html">Up</a></td><td align="right"> <a accesskey="n" href="appendix_free.html">Next</a></td></tr><tr><td align="left" valign="top">API Evolution and Deprecation History </td><td align="center"><a accesskey="h" href="../spine.html">Home</a></td><td align="right" valign="top"> Appendix C.
918 Free Software Needs Free Documentation
920 </td></tr></table></div></body></html>