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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-NS Stylesheets V1.76.1" /><meta name="keywords" content=" ISO C++ , backwards " /><meta name="keywords" content=" ISO C++ , library " /><meta name="keywords" content=" ISO C++ , runtime , library " /><link rel="home" href="../index.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 width="20%" 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 width="20%" 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" style="clear: both"><a id="manual.appendix.porting.backwards"></a>Backwards Compatibility</h2></div></div></div><div class="section" 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
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="backwards.first.ios_base"></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="section" title="No cout in <ostream.h>, no cin in <istream.h>"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.first.cout_cin"></a>No <code class="code">cout</code> in <code class="filename"><ostream.h></code>, no <code class="code">cin</code> in <code class="filename"><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" target="_top">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"></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.
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="backwards.second.std"></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>.
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="option">-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="backwards.second.iterators"></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="section" title="isspace from <cctype> is a macro"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.second.isspace"></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.).
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
153 <code class="filename"><ctype.h></code>. This will
154 result in ambiguities between the definitions in the global namespace
155 (<code class="filename"><ctype.h></code>) and the
156 definitions in namespace <code class="code">std::</code>
157 (<code class="code"><cctype></code>).
158 </p></div><div class="section" title="No vector::at, deque::at, string::at"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.second.at"></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>
159 One solution is to add an autoconf-test for this:
160 </p><pre class="programlisting">
161 AC_MSG_CHECKING(for container::at)
164 #include <vector>
165 #include <deque>
166 #include <string>
171 deque<int> test_deque(3);
173 vector<int> test_vector(2);
175 string test_string(<span class="quote">“<span class="quote">test_string</span>”</span>);
179 AC_DEFINE(HAVE_CONTAINER_AT)],
182 If you are using other (non-GNU) compilers it might be a good idea
183 to check for <code class="code">string::at</code> separately.
184 </p></div><div class="section" title="No std::char_traits<char>::eof"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.second.eof"></a>No <code class="code">std::char_traits<char>::eof</code></h4></div></div></div><p>
185 Use some kind of autoconf test, plus this:
186 </p><pre class="programlisting">
187 #ifdef HAVE_CHAR_TRAITS
188 #define CPP_EOF std::char_traits<char>::eof()
192 </pre></div><div class="section" title="No string::clear"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.second.stringclear"></a>No <code class="code">string::clear</code></h4></div></div></div><p>
193 There are two functions for deleting the contents of a string:
194 <code class="code">clear</code> and <code class="code">erase</code> (the latter returns the
196 </p><pre class="programlisting">
198 clear() { _M_mutate(0, this->size(), 0); }
199 </pre><pre class="programlisting">
201 erase(size_type __pos = 0, size_type __n = npos)
203 return this->replace(_M_check(__pos), _M_fold(__pos, __n),
204 _M_data(), _M_data());
207 Unfortunately, <code class="code">clear</code> is not implemented in this
208 version, so you should use <code class="code">erase</code> (which is probably
209 faster than <code class="code">operator=(charT*)</code>).
210 </p></div><div class="section" title="Removal of ostream::form and istream::scan extensions"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.second.ostreamform_istreamscan"></a>
211 Removal of <code class="code">ostream::form</code> and <code class="code">istream::scan</code>
213 </h4></div></div></div><p>
214 These are no longer supported. Please use stringstreams instead.
215 </p></div><div class="section" title="No basic_stringbuf, basic_stringstream"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.second.stringstreams"></a>No <code class="code">basic_stringbuf</code>, <code class="code">basic_stringstream</code></h4></div></div></div><p>
216 Although the ISO standard <code class="code">i/ostringstream</code>-classes are
217 provided, (<code class="filename"><sstream></code>), for
218 compatibility with older implementations the pre-ISO
219 <code class="code">i/ostrstream</code> (<code class="filename"><strstream></code>) interface is also provided,
221 </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
222 <code class="code">strstream</code> is considered to be deprecated
223 </p></li><li class="listitem"><p>
224 <code class="code">strstream</code> is limited to <code class="code">char</code>
225 </p></li><li class="listitem"><p>
226 with <code class="code">ostringstream</code> you don't have to take care of
227 terminating the string or freeing its memory
228 </p></li><li class="listitem"><p>
229 <code class="code">istringstream</code> can be re-filled (clear();
231 </p></li></ul></div><p>
232 You can then use output-stringstreams like this:
233 </p><pre class="programlisting">
235 # include <sstream>
237 # include <strstream>
241 std::ostringstream oss;
246 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;
249 oss << std::ends; // terminate the char*-string
252 // str() returns char* for ostrstream and a string for ostringstream
253 // this also causes ostrstream to think that the buffer's memory
255 m_label.set_text(oss.str());
257 // let the ostrstream take care of freeing the memory
261 Input-stringstreams can be used similarly:
262 </p><pre class="programlisting">
266 std::istringstream iss(input);
268 std::istrstream iss(input.c_str());
273 </pre><p> One (the only?) restriction is that an istrstream cannot be re-filled:
274 </p><pre class="programlisting">
275 std::istringstream iss(numerator);
277 // this is not possible with istrstream
279 iss.str(denominator);
282 If you don't care about speed, you can put these conversions in
284 </p><pre class="programlisting">
285 template <class X>
286 void fromString(const string& input, X& any)
289 std::istringstream iss(input);
291 std::istrstream iss(input.c_str());
296 throw runtime_error(..)
300 Another example of using stringstreams is in <a class="link" href="strings.html#strings.string.shrink" title="Shrink to Fit">this howto</a>.
301 </p><p> There is additional information in the libstdc++-v2 info files, in
302 particular <span class="quote">“<span class="quote">info iostream</span>”</span>.
303 </p></div><div class="section" title="Little or no wide character support"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.second.wchar"></a>Little or no wide character support</h4></div></div></div><p>
304 Classes <code class="classname">wstring</code> and
305 <code class="classname">char_traits<wchar_t></code> are
307 </p></div><div class="section" title="No templatized iostreams"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.second.iostream_templates"></a>No templatized iostreams</h4></div></div></div><p>
308 Classes <code class="classname">wfilebuf</code> and
309 <code class="classname">wstringstream</code> are not supported.
310 </p></div><div class="section" title="Thread safety issues"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.second.thread_safety"></a>Thread safety issues</h4></div></div></div><p>
311 Earlier GCC releases had a somewhat different approach to
312 threading configuration and proper compilation. Before GCC 3.0,
313 configuration of the threading model was dictated by compiler
314 command-line options and macros (both of which were somewhat
315 thread-implementation and port-specific). There were no
316 guarantees related to being able to link code compiled with one
317 set of options and macro setting with another set.
319 For GCC 3.0, configuration of the threading model used with
320 libraries and user-code is performed when GCC is configured and
321 built using the --enable-threads and --disable-threads options.
322 The ABI is stable for symbol name-mangling and limited functional
323 compatibility exists between code compiled under different
326 The libstdc++ library has been designed so that it can be used in
327 multithreaded applications (with libstdc++-v2 this was only true
328 of the STL parts.) The first problem is finding a
329 <span class="emphasis"><em>fast</em></span> method of implementation portable to
330 all platforms. Due to historical reasons, some of the library is
331 written against per-CPU-architecture spinlocks and other parts
332 against the gthr.h abstraction layer which is provided by gcc. A
333 minor problem that pops up every so often is different
334 interpretations of what "thread-safe" means for a
335 library (not a general program). We currently use the <a class="link" href="http://www.sgi.com/tech/stl/thread_safety.html" target="_top">same
336 definition that SGI</a> uses for their STL subset. However,
337 the exception for read-only containers only applies to the STL
338 components. This definition is widely-used and something similar
339 will be used in the next version of the C++ standard library.
341 Here is a small link farm to threads (no pun) in the mail
342 archives that discuss the threading problem. Each link is to the
343 first relevant message in the thread; from there you can use
344 "Thread Next" to move down the thread. This farm is in
345 latest-to-oldest order.
346 </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
347 Our threading expert Loren gives a breakdown of <a class="link" href="http://gcc.gnu.org/ml/libstdc++/2001-10/msg00024.html" target="_top">the
348 six situations involving threads</a> for the 3.0
350 </p></li><li class="listitem"><p>
351 <a class="link" href="http://gcc.gnu.org/ml/libstdc++/2001-05/msg00384.html" target="_top">
352 This message</a> inspired a recent updating of issues with
353 threading and the SGI STL library. It also contains some
354 example POSIX-multithreaded STL code.
355 </p></li></ul></div><p>
356 (A large selection of links to older messages has been removed;
357 many of the messages from 1999 were lost in a disk crash, and the
358 few people with access to the backup tapes have been too swamped
359 with work to restore them. Many of the points have been
361 </p></div></div><div class="section" 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
363 </p><p>The subset commonly known as the Standard Template Library
364 (chapters 23 through 25, mostly) is adapted from the final release
365 of the SGI STL (version 3.3), with extensive changes.
366 </p><p>A more formal description of the V3 goals can be found in the
367 official <a class="link" href="source_design_notes.html" title="Design Notes">design document</a>.
368 </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="backwards.third.headers"></a>Pre-ISO headers moved to backwards or removed</h4></div></div></div><p> The pre-ISO C++ headers
369 (<code class="filename"><iostream.h></code>,
370 <code class="filename"><defalloc.h></code> etc.) are
371 available, unlike previous libstdc++ versions, but inclusion
372 generates a warning that you are using deprecated headers.
373 </p><p>This compatibility layer is constructed by including the
374 standard C++ headers, and injecting any items in
375 <code class="code">std::</code> into the global namespace.
376 </p><p>For those of you new to ISO C++ (welcome, time travelers!), no,
377 that isn't a typo. Yes, the headers really have new names.
378 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" target="_top">item
380 </p><p> Some include adjustment may be required. What follows is an
381 autoconf test that defines <code class="code">PRE_STDCXX_HEADERS</code> when they
382 exist.</p><pre class="programlisting">
383 # AC_HEADER_PRE_STDCXX
384 AC_DEFUN([AC_HEADER_PRE_STDCXX], [
385 AC_CACHE_CHECK(for pre-ISO C++ include files,
386 ac_cv_cxx_pre_stdcxx,
389 ac_save_CXXFLAGS="$CXXFLAGS"
390 CXXFLAGS="$CXXFLAGS -Wno-deprecated"
392 # Omit defalloc.h, as compilation with newer compilers is problematic.
394 #include <new.h>
395 #include <iterator.h>
396 #include <alloc.h>
397 #include <set.h>
398 #include <hashtable.h>
399 #include <hash_set.h>
400 #include <fstream.h>
401 #include <tempbuf.h>
402 #include <istream.h>
403 #include <bvector.h>
404 #include <stack.h>
405 #include <rope.h>
406 #include <complex.h>
407 #include <ostream.h>
408 #include <heap.h>
409 #include <iostream.h>
410 #include <function.h>
411 #include <multimap.h>
412 #include <pair.h>
413 #include <stream.h>
414 #include <iomanip.h>
415 #include <slist.h>
416 #include <tree.h>
417 #include <vector.h>
418 #include <deque.h>
419 #include <multiset.h>
420 #include <list.h>
421 #include <map.h>
422 #include <algobase.h>
423 #include <hash_map.h>
424 #include <algo.h>
425 #include <queue.h>
426 #include <streambuf.h>
428 ac_cv_cxx_pre_stdcxx=yes, ac_cv_cxx_pre_stdcxx=no)
429 CXXFLAGS="$ac_save_CXXFLAGS"
432 if test "$ac_cv_cxx_pre_stdcxx" = yes; then
433 AC_DEFINE(PRE_STDCXX_HEADERS,,[Define if pre-ISO C++ header files are present. ])
436 </pre><p>Porting between pre-ISO headers and ISO headers is simple: headers
437 like <code class="filename"><vector.h></code> can be replaced with <code class="filename"><vector></code> and a using
438 directive <code class="code">using namespace std;</code> can be put at the global
439 scope. This should be enough to get this code compiling, assuming the
440 other usage is correct.
441 </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="backwards.third.hash"></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
442 replaced by standardized libraries.
443 In particular, the <code class="classname">unordered_map</code> and
444 <code class="classname">unordered_set</code> containers of TR1 and C++ 2011
445 are suitable replacements for the non-standard
446 <code class="classname">hash_map</code> and <code class="classname">hash_set</code>
447 containers in the SGI STL.
448 </p><p> Header files <code class="filename"><hash_map></code> and <code class="filename"><hash_set></code> moved
449 to <code class="filename"><ext/hash_map></code> and <code class="filename"><ext/hash_set></code>,
450 respectively. At the same time, all types in these files are enclosed
451 in <code class="code">namespace __gnu_cxx</code>. Later versions deprecate
452 these files, and suggest using TR1's <code class="filename"><unordered_map></code>
453 and <code class="filename"><unordered_set></code> instead.
454 </p><p>The extensions are no longer in the global or <code class="code">std</code>
455 namespaces, instead they are declared in the <code class="code">__gnu_cxx</code>
456 namespace. For maximum portability, consider defining a namespace
457 alias to use to talk about extensions, e.g.:
458 </p><pre class="programlisting">
461 #include <hash_map.h>
462 namespace extension { using ::hash_map; }; // inherit globals
464 #include <backward/hash_map>
465 #if __GNUC__ == 3 && __GNUC_MINOR__ == 0
466 namespace extension = std; // GCC 3.0
468 namespace extension = ::__gnu_cxx; // GCC 3.1 and later
471 #else // ... there are other compilers, right?
472 namespace extension = std;
475 extension::hash_map<int,int> my_map;
476 </pre><p>This is a bit cleaner than defining typedefs for all the
477 instantiations you might need.
478 </p><p>The following autoconf tests check for working HP/SGI hash containers.
479 </p><pre class="programlisting">
480 # AC_HEADER_EXT_HASH_MAP
481 AC_DEFUN([AC_HEADER_EXT_HASH_MAP], [
482 AC_CACHE_CHECK(for ext/hash_map,
483 ac_cv_cxx_ext_hash_map,
486 ac_save_CXXFLAGS="$CXXFLAGS"
487 CXXFLAGS="$CXXFLAGS -Werror"
488 AC_TRY_COMPILE([#include <ext/hash_map>], [using __gnu_cxx::hash_map;],
489 ac_cv_cxx_ext_hash_map=yes, ac_cv_cxx_ext_hash_map=no)
490 CXXFLAGS="$ac_save_CXXFLAGS"
493 if test "$ac_cv_cxx_ext_hash_map" = yes; then
494 AC_DEFINE(HAVE_EXT_HASH_MAP,,[Define if ext/hash_map is present. ])
497 </pre><pre class="programlisting">
498 # AC_HEADER_EXT_HASH_SET
499 AC_DEFUN([AC_HEADER_EXT_HASH_SET], [
500 AC_CACHE_CHECK(for ext/hash_set,
501 ac_cv_cxx_ext_hash_set,
504 ac_save_CXXFLAGS="$CXXFLAGS"
505 CXXFLAGS="$CXXFLAGS -Werror"
506 AC_TRY_COMPILE([#include <ext/hash_set>], [using __gnu_cxx::hash_set;],
507 ac_cv_cxx_ext_hash_set=yes, ac_cv_cxx_ext_hash_set=no)
508 CXXFLAGS="$ac_save_CXXFLAGS"
511 if test "$ac_cv_cxx_ext_hash_set" = yes; then
512 AC_DEFINE(HAVE_EXT_HASH_SET,,[Define if ext/hash_set is present. ])
515 </pre></div><div class="section" title="No ios::nocreate/ios::noreplace."><div class="titlepage"><div><div><h4 class="title"><a id="backwards.third.nocreate_noreplace"></a>No <code class="code">ios::nocreate/ios::noreplace</code>.
516 </h4></div></div></div><p> The existence of <code class="code">ios::nocreate</code> being used for
517 input-streams has been confirmed, most probably because the author
518 thought it would be more correct to specify nocreate explicitly. So
519 it can be left out for input-streams.
520 </p><p>For output streams, <span class="quote">“<span class="quote">nocreate</span>”</span> is probably the default,
521 unless you specify <code class="code">std::ios::trunc</code> ? To be safe, you can
522 open the file for reading, check if it has been opened, and then
523 decide whether you want to create/replace or not. To my knowledge,
524 even older implementations support <code class="code">app</code>, <code class="code">ate</code>
525 and <code class="code">trunc</code> (except for <code class="code">app</code> ?).
526 </p></div><div class="section" title="No stream::attach(int fd)"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.third.streamattach"></a>
527 No <code class="code">stream::attach(int fd)</code>
528 </h4></div></div></div><p>
529 Phil Edwards writes: It was considered and rejected for the ISO
530 standard. Not all environments use file descriptors. Of those
531 that do, not all of them use integers to represent them.
533 For a portable solution (among systems which use
534 file descriptors), you need to implement a subclass of
535 <code class="code">std::streambuf</code> (or
536 <code class="code">std::basic_streambuf<..></code>) which opens a file
537 given a descriptor, and then pass an instance of this to the
540 An extension is available that implements this.
541 <code class="filename"><ext/stdio_filebuf.h></code> contains a derived class called
542 <a class="link" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a00074.html" target="_top"><code class="code">__gnu_cxx::stdio_filebuf</code></a>.
543 This class can be constructed from a C <code class="code">FILE*</code> or a file
544 descriptor, and provides the <code class="code">fd()</code> function.
546 For another example of this, refer to
547 <a class="link" href="http://www.josuttis.com/cppcode/fdstream.html" target="_top">fdstream example</a>
549 </p></div><div class="section" title="Support for C++98 dialect."><div class="titlepage"><div><div><h4 class="title"><a id="backwards.third.support_cxx98"></a>
550 Support for C++98 dialect.
551 </h4></div></div></div><p>Check for complete library coverage of the C++1998/2003 standard.
552 </p><pre class="programlisting">
553 # AC_HEADER_STDCXX_98
554 AC_DEFUN([AC_HEADER_STDCXX_98], [
555 AC_CACHE_CHECK(for ISO C++ 98 include files,
560 #include <cassert>
561 #include <cctype>
562 #include <cerrno>
563 #include <cfloat>
564 #include <ciso646>
565 #include <climits>
566 #include <clocale>
567 #include <cmath>
568 #include <csetjmp>
569 #include <csignal>
570 #include <cstdarg>
571 #include <cstddef>
572 #include <cstdio>
573 #include <cstdlib>
574 #include <cstring>
575 #include <ctime>
577 #include <algorithm>
578 #include <bitset>
579 #include <complex>
580 #include <deque>
581 #include <exception>
582 #include <fstream>
583 #include <functional>
584 #include <iomanip>
586 #include <iosfwd>
587 #include <iostream>
588 #include <istream>
589 #include <iterator>
590 #include <limits>
591 #include <list>
592 #include <locale>
594 #include <memory>
596 #include <numeric>
597 #include <ostream>
598 #include <queue>
600 #include <sstream>
601 #include <stack>
602 #include <stdexcept>
603 #include <streambuf>
604 #include <string>
605 #include <typeinfo>
606 #include <utility>
607 #include <valarray>
608 #include <vector>
610 ac_cv_cxx_stdcxx_98=yes, ac_cv_cxx_stdcxx_98=no)
613 if test "$ac_cv_cxx_stdcxx_98" = yes; then
614 AC_DEFINE(STDCXX_98_HEADERS,,[Define if ISO C++ 1998 header files are present. ])
617 </pre></div><div class="section" title="Support for C++TR1 dialect."><div class="titlepage"><div><div><h4 class="title"><a id="backwards.third.support_tr1"></a>
618 Support for C++TR1 dialect.
619 </h4></div></div></div><p>Check for library coverage of the TR1 standard.
620 </p><pre class="programlisting">
621 # AC_HEADER_STDCXX_TR1
622 AC_DEFUN([AC_HEADER_STDCXX_TR1], [
623 AC_CACHE_CHECK(for ISO C++ TR1 include files,
624 ac_cv_cxx_stdcxx_tr1,
628 #include <tr1/array>
629 #include <tr1/ccomplex>
630 #include <tr1/cctype>
631 #include <tr1/cfenv>
632 #include <tr1/cfloat>
633 #include <tr1/cinttypes>
634 #include <tr1/climits>
635 #include <tr1/cmath>
636 #include <tr1/complex>
637 #include <tr1/cstdarg>
638 #include <tr1/cstdbool>
639 #include <tr1/cstdint>
640 #include <tr1/cstdio>
641 #include <tr1/cstdlib>
642 #include <tr1/ctgmath>
643 #include <tr1/ctime>
644 #include <tr1/cwchar>
645 #include <tr1/cwctype>
646 #include <tr1/functional>
647 #include <tr1/memory>
648 #include <tr1/random>
649 #include <tr1/regex>
650 #include <tr1/tuple>
651 #include <tr1/type_traits>
652 #include <tr1/unordered_set>
653 #include <tr1/unordered_map>
654 #include <tr1/utility>
656 ac_cv_cxx_stdcxx_tr1=yes, ac_cv_cxx_stdcxx_tr1=no)
659 if test "$ac_cv_cxx_stdcxx_tr1" = yes; then
660 AC_DEFINE(STDCXX_TR1_HEADERS,,[Define if ISO C++ TR1 header files are present. ])
663 </pre><p>An alternative is to check just for specific TR1 includes, such as <unordered_map> and <unordered_set>.
664 </p><pre class="programlisting">
665 # AC_HEADER_TR1_UNORDERED_MAP
666 AC_DEFUN([AC_HEADER_TR1_UNORDERED_MAP], [
667 AC_CACHE_CHECK(for tr1/unordered_map,
668 ac_cv_cxx_tr1_unordered_map,
671 AC_TRY_COMPILE([#include <tr1/unordered_map>], [using std::tr1::unordered_map;],
672 ac_cv_cxx_tr1_unordered_map=yes, ac_cv_cxx_tr1_unordered_map=no)
675 if test "$ac_cv_cxx_tr1_unordered_map" = yes; then
676 AC_DEFINE(HAVE_TR1_UNORDERED_MAP,,[Define if tr1/unordered_map is present. ])
679 </pre><pre class="programlisting">
680 # AC_HEADER_TR1_UNORDERED_SET
681 AC_DEFUN([AC_HEADER_TR1_UNORDERED_SET], [
682 AC_CACHE_CHECK(for tr1/unordered_set,
683 ac_cv_cxx_tr1_unordered_set,
686 AC_TRY_COMPILE([#include <tr1/unordered_set>], [using std::tr1::unordered_set;],
687 ac_cv_cxx_tr1_unordered_set=yes, ac_cv_cxx_tr1_unordered_set=no)
690 if test "$ac_cv_cxx_tr1_unordered_set" = yes; then
691 AC_DEFINE(HAVE_TR1_UNORDERED_SET,,[Define if tr1/unordered_set is present. ])
694 </pre></div><div class="section" title="Support for C++11 dialect."><div class="titlepage"><div><div><h4 class="title"><a id="backwards.third.support_cxx11"></a>
695 Support for C++11 dialect.
696 </h4></div></div></div><p>Check for baseline language coverage in the compiler for the C++11 standard.
697 </p><pre class="programlisting">
698 # AC_COMPILE_STDCXX_11
699 AC_DEFUN([AC_COMPILE_STDCXX_11], [
700 AC_CACHE_CHECK(if g++ supports C++11 features without additional flags,
701 ac_cv_cxx_compile_cxx11_native,
705 template <typename T>
708 static constexpr T value{ __cplusplus };
711 typedef check<check<bool>> right_angle_brackets;
716 typedef check<int> check_type;
718 check_type&& cr = static_cast<check_type&&>(c);
720 static_assert(check_type::value == 201103L, "C++11 compiler");],,
721 ac_cv_cxx_compile_cxx11_native=yes, ac_cv_cxx_compile_cxx11_native=no)
725 AC_CACHE_CHECK(if g++ supports C++11 features with -std=c++11,
726 ac_cv_cxx_compile_cxx11_cxx,
729 ac_save_CXXFLAGS="$CXXFLAGS"
730 CXXFLAGS="$CXXFLAGS -std=c++11"
732 template <typename T>
735 static constexpr T value{ __cplusplus };
738 typedef check<check<bool>> right_angle_brackets;
743 typedef check<int> check_type;
745 check_type&& cr = static_cast<check_type&&>(c);
747 static_assert(check_type::value == 201103L, "C++11 compiler");],,
748 ac_cv_cxx_compile_cxx11_cxx=yes, ac_cv_cxx_compile_cxx11_cxx=no)
749 CXXFLAGS="$ac_save_CXXFLAGS"
753 AC_CACHE_CHECK(if g++ supports C++11 features with -std=gnu++11,
754 ac_cv_cxx_compile_cxx11_gxx,
757 ac_save_CXXFLAGS="$CXXFLAGS"
758 CXXFLAGS="$CXXFLAGS -std=gnu++11"
760 template <typename T>
763 static constexpr T value{ __cplusplus };
766 typedef check<check<bool>> right_angle_brackets;
771 typedef check<int> check_type;
773 check_type&& cr = static_cast<check_type&&>(c);
775 static_assert(check_type::value == 201103L, "C++11 compiler");],,
776 ac_cv_cxx_compile_cxx11_gxx=yes, ac_cv_cxx_compile_cxx11_gxx=no)
777 CXXFLAGS="$ac_save_CXXFLAGS"
781 if test "$ac_cv_cxx_compile_cxx11_native" = yes ||
782 test "$ac_cv_cxx_compile_cxx11_cxx" = yes ||
783 test "$ac_cv_cxx_compile_cxx11_gxx" = yes; then
784 AC_DEFINE(HAVE_STDCXX_11,,[Define if g++ supports C++11 features. ])
787 </pre><p>Check for library coverage of the C++2011 standard.
788 (Some library headers are commented out in this check, they are
789 not currently provided by libstdc++).
790 </p><pre class="programlisting">
791 # AC_HEADER_STDCXX_11
792 AC_DEFUN([AC_HEADER_STDCXX_11], [
793 AC_CACHE_CHECK(for ISO C++11 include files,
795 [AC_REQUIRE([AC_COMPILE_STDCXX_11])
798 ac_save_CXXFLAGS="$CXXFLAGS"
799 CXXFLAGS="$CXXFLAGS -std=gnu++11"
802 #include <cassert>
803 #include <ccomplex>
804 #include <cctype>
805 #include <cerrno>
806 #include <cfenv>
807 #include <cfloat>
808 #include <cinttypes>
809 #include <ciso646>
810 #include <climits>
811 #include <clocale>
812 #include <cmath>
813 #include <csetjmp>
814 #include <csignal>
815 #include <cstdalign>
816 #include <cstdarg>
817 #include <cstdbool>
818 #include <cstddef>
819 #include <cstdint>
820 #include <cstdio>
821 #include <cstdlib>
822 #include <cstring>
823 #include <ctgmath>
824 #include <ctime>
825 // #include <cuchar>
826 #include <cwchar>
827 #include <cwctype>
829 #include <algorithm>
830 #include <array>
831 #include <atomic>
832 #include <bitset>
833 #include <chrono>
834 // #include <codecvt>
835 #include <complex>
836 #include <condition_variable>
837 #include <deque>
838 #include <exception>
839 #include <forward_list>
840 #include <fstream>
841 #include <functional>
842 #include <future>
843 #include <initializer_list>
844 #include <iomanip>
846 #include <iosfwd>
847 #include <iostream>
848 #include <istream>
849 #include <iterator>
850 #include <limits>
851 #include <list>
852 #include <locale>
854 #include <memory>
855 #include <mutex>
857 #include <numeric>
858 #include <ostream>
859 #include <queue>
860 #include <random>
861 #include <ratio>
862 #include <regex>
863 #include <scoped_allocator>
865 #include <sstream>
866 #include <stack>
867 #include <stdexcept>
868 #include <streambuf>
869 #include <string>
870 #include <system_error>
871 #include <thread>
872 #include <tuple>
873 #include <typeindex>
874 #include <typeinfo>
875 #include <type_traits>
876 #include <unordered_map>
877 #include <unordered_set>
878 #include <utility>
879 #include <valarray>
880 #include <vector>
882 ac_cv_cxx_stdcxx_11=yes, ac_cv_cxx_stdcxx_11=no)
884 CXXFLAGS="$ac_save_CXXFLAGS"
886 if test "$ac_cv_cxx_stdcxx_11" = yes; then
887 AC_DEFINE(STDCXX_11_HEADERS,,[Define if ISO C++11 header files are present. ])
890 </pre><p>As is the case for TR1 support, these autoconf macros can be made for a finer-grained, per-header-file check. For
891 <code class="filename"><unordered_map></code>
892 </p><pre class="programlisting">
893 # AC_HEADER_UNORDERED_MAP
894 AC_DEFUN([AC_HEADER_UNORDERED_MAP], [
895 AC_CACHE_CHECK(for unordered_map,
896 ac_cv_cxx_unordered_map,
897 [AC_REQUIRE([AC_COMPILE_STDCXX_11])
900 ac_save_CXXFLAGS="$CXXFLAGS"
901 CXXFLAGS="$CXXFLAGS -std=gnu++11"
902 AC_TRY_COMPILE([#include <unordered_map>], [using std::unordered_map;],
903 ac_cv_cxx_unordered_map=yes, ac_cv_cxx_unordered_map=no)
904 CXXFLAGS="$ac_save_CXXFLAGS"
907 if test "$ac_cv_cxx_unordered_map" = yes; then
908 AC_DEFINE(HAVE_UNORDERED_MAP,,[Define if unordered_map is present. ])
911 </pre><pre class="programlisting">
912 # AC_HEADER_UNORDERED_SET
913 AC_DEFUN([AC_HEADER_UNORDERED_SET], [
914 AC_CACHE_CHECK(for unordered_set,
915 ac_cv_cxx_unordered_set,
916 [AC_REQUIRE([AC_COMPILE_STDCXX_11])
919 ac_save_CXXFLAGS="$CXXFLAGS"
920 CXXFLAGS="$CXXFLAGS -std=gnu++11"
921 AC_TRY_COMPILE([#include <unordered_set>], [using std::unordered_set;],
922 ac_cv_cxx_unordered_set=yes, ac_cv_cxx_unordered_set=no)
923 CXXFLAGS="$ac_save_CXXFLAGS"
926 if test "$ac_cv_cxx_unordered_set" = yes; then
927 AC_DEFINE(HAVE_UNORDERED_SET,,[Define if unordered_set is present. ])
931 Some C++11 features first appeared in GCC 4.3 and could be enabled by
932 <code class="option">-std=c++0x</code> and <code class="option">-std=gnu++0x</code> for GCC
933 releases which pre-date the 2011 standard. Those C++11 features and GCC's
934 support for them were still changing until the 2011 standard was finished,
935 but the autoconf checks above could be extended to test for incomplete
936 C++11 support with <code class="option">-std=c++0x</code> and
937 <code class="option">-std=gnu++0x</code>.
938 </p></div><div class="section" title="Container::iterator_type is not necessarily Container::value_type*"><div class="titlepage"><div><div><h4 class="title"><a id="backwards.third.iterator_type"></a>
939 <code class="code">Container::iterator_type</code> is not necessarily <code class="code">Container::value_type*</code>
940 </h4></div></div></div><p>
941 This is a change in behavior from older versions. Now, most
942 <span class="type">iterator_type</span> typedefs in container classes are POD
943 objects, not <span class="type">value_type</span> pointers.
944 </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="idp23375200"></a><p><span class="title"><em>
945 <a class="link" href="http://www.kegel.com/gcc/gcc4.html" target="_top">
948 </em>. </span><span class="author"><span class="firstname">Dan</span> <span class="surname">Kegel</span>. </span></p></div><div class="biblioentry" title="Building the Whole Debian Archive with GCC 4.1: A Summary"><a id="idp23377984"></a><p><span class="title"><em>
949 <a class="link" href="http://lists.debian.org/debian-gcc/2006/03/msg00405.html" target="_top">
950 Building the Whole Debian Archive with GCC 4.1: A Summary
952 </em>. </span><span class="author"><span class="firstname">Martin</span> <span class="surname">Michlmayr</span>. </span></p></div><div class="biblioentry" title="Migration guide for GCC-3.2"><a id="idp23380832"></a><p><span class="title"><em>
953 <a class="link" href="http://annwm.lbl.gov/~leggett/Atlas/gcc-3.2.html" target="_top">
954 Migration guide for GCC-3.2
956 </em>. </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="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Appendix C.
957 Free Software Needs Free Documentation
959 </td></tr></table></div></body></html>