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   4   Porting and Maintenance
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   7 </p><div class="sect2" title="The C++ Interface"><div class="titlepage"><div><div><h3 class="title"><a id="abi.cxx_interface"></a>The C++ Interface</h3></div></div></div><p>
   8   C++ applications often dependent on specific language support
   9   routines, say for throwing exceptions, or catching exceptions, and
  10   perhaps also dependent on features in the C++ Standard Library.
  11 </p><p>
  12   The C++ Standard Library has many include files, types defined in
  13   those include files, specific named functions, and other
  14   behavior. The text of these behaviors, as written in source include
  15   files, is called the Application Programing Interface, or API.
  16 </p><p>
  17   Furthermore, C++ source that is compiled into object files is
  18   transformed by the compiler: it arranges objects with specific
  19   alignment and in a particular layout, mangling names according to a
  20   well-defined algorithm, has specific arrangements for the support of
  21   virtual functions, etc. These details are defined as the compiler
  22   Application Binary Interface, or ABI. The GNU C++ compiler uses an
  23   industry-standard C++ ABI starting with version 3. Details can be
  24   found in the <a class="ulink" href="http://www.codesourcery.com/cxx-abi/abi.html" target="_top"> ABI
  25   specification</a>.
  26 </p><p>
  27  The GNU C++ compiler, g++, has a compiler command line option to
  28   switch between various different C++ ABIs. This explicit version
  29   switch is the flag <code class="code">-fabi-version</code>. In addition, some
  30   g++ command line options may change the ABI as a side-effect of
  31   use. Such flags include <code class="code">-fpack-struct</code> and
  32   <code class="code">-fno-exceptions</code>, but include others: see the complete
  33   list in the GCC manual under the heading <a class="ulink" href="http://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#Code%20Gen%20Options" target="_top">Options
  34   for Code Generation Conventions</a>.
  35 </p><p>
  36   The configure options used when building a specific libstdc++
  37   version may also impact the resulting library ABI. The available
  38   configure options, and their impact on the library ABI, are
  39   documented
  40 <a class="link" href="configure.html" title="Configure">here</a>.
  41 </p><p> Putting all of these ideas together results in the C++ Standard
  42 library ABI, which is the compilation of a given library API by a
  43 given compiler ABI. In a nutshell:
  44 </p><p>
  45   <span class="quote">“<span class="quote">
  46     library API + compiler ABI = library ABI
  47   </span>”</span>
  48 </p><p>
  49  The library ABI is mostly of interest for end-users who have
  50  unresolved symbols and are linking dynamically to the C++ Standard
  51  library, and who thus must be careful to compile their application
  52  with a compiler that is compatible with the available C++ Standard
  53  library binary. In this case, compatible is defined with the equation
  54  above: given an application compiled with a given compiler ABI and
  55  library API, it will work correctly with a Standard C++ Library
  56  created with the same constraints.
  57 </p><p>
  58   To use a specific version of the C++ ABI, one must use a
  59   corresponding GNU C++ toolchain (i.e., g++ and libstdc++) that
  60   implements the C++ ABI in question.
  61 </p></div><div class="sect2" title="Versioning"><div class="titlepage"><div><div><h3 class="title"><a id="abi.versioning"></a>Versioning</h3></div></div></div><p> The C++ interface has evolved throughout the history of the GNU
  62 C++ toolchain. With each release, various details have been changed so
  63 as to give distinct versions to the C++ interface.
  64 </p><div class="sect3" title="Goals"><div class="titlepage"><div><div><h4 class="title"><a id="abi.versioning.goals"></a>Goals</h4></div></div></div><p>Extending existing, stable ABIs. Versioning gives subsequent
  65 releases of library binaries the ability to add new symbols and add
  66 functionality, all the while retaining compatibility with the previous
  67 releases in the series. Thus, program binaries linked with the initial
  68 release of a library binary will still link correctly if the library
  69 binary is replaced by carefully-managed subsequent library
  70 binaries. This is called forward compatibility.
  71 </p><p>
  72 The reverse (backwards compatibility) is not true. It is not possible
  73 to take program binaries linked with the latest version of a library
  74 binary in a release series (with additional symbols added), substitute
  75 in the initial release of the library binary, and remain link
  76 compatible.
  77 </p><p>Allows multiple, incompatible ABIs to coexist at the same time.
  78 </p></div><div class="sect3" title="History"><div class="titlepage"><div><div><h4 class="title"><a id="abi.versioning.history"></a>History</h4></div></div></div><p>
  79  How can this complexity be managed? What does C++ versioning mean?
  80   Because library and compiler changes often make binaries compiled
  81   with one version of the GNU tools incompatible with binaries
  82   compiled with other (either newer or older) versions of the same GNU
  83   tools, specific techniques are used to make managing this complexity
  84   easier.
  85 </p><p>
  86   The following techniques are used:
  87 </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Release versioning on the libgcc_s.so binary. </p><p>This is implemented via file names and the ELF
  88     <code class="constant">DT_SONAME</code> mechanism (at least on ELF
  89     systems). It is versioned as follows:
  90     </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>gcc-3.0.0: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.0.1: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.0.2: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.0.3: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.0.4: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.1.0: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.1.1: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.2.0: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.2.1: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.2.2: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.2.3: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.3.0: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.3.1: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.3.2: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.3.3: libgcc_s.so.1</p></li><li class="listitem"><p>gcc-3.4.x, gcc-4.[0-5].x: on m68k-linux and
  91     hppa-linux this is either libgcc_s.so.1 (when configuring
  92     <code class="code">--with-sjlj-exceptions</code>) or libgcc_s.so.2. For all
  93     others, this is libgcc_s.so.1.  </p></li></ul></div></li><li class="listitem"><p>Symbol versioning on the libgcc_s.so binary.</p><p>It is versioned with the following labels and version
  94    definitions, where the version definition is the maximum for a
  95    particular release. Labels are cumulative. If a particular release
  96    is not listed, it has the same version labels as the preceding
  97    release.</p><p>This corresponds to the mapfile: gcc/libgcc-std.ver</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>gcc-3.0.0: GCC_3.0</p></li><li class="listitem"><p>gcc-3.3.0: GCC_3.3</p></li><li class="listitem"><p>gcc-3.3.1: GCC_3.3.1</p></li><li class="listitem"><p>gcc-3.3.2: GCC_3.3.2</p></li><li class="listitem"><p>gcc-3.3.4: GCC_3.3.4</p></li><li class="listitem"><p>gcc-3.4.0: GCC_3.4</p></li><li class="listitem"><p>gcc-3.4.2: GCC_3.4.2</p></li><li class="listitem"><p>gcc-3.4.4: GCC_3.4.4</p></li><li class="listitem"><p>gcc-4.0.0: GCC_4.0.0</p></li><li class="listitem"><p>gcc-4.1.0: GCC_4.1.0</p></li><li class="listitem"><p>gcc-4.2.0: GCC_4.2.0</p></li><li class="listitem"><p>gcc-4.3.0: GCC_4.3.0</p></li><li class="listitem"><p>gcc-4.4.0: GCC_4.4.0</p></li></ul></div></li><li class="listitem"><p>
  98         Release versioning on the libstdc++.so binary, implemented in
  99         the same was as the libgcc_s.so binary above. Listed is the
 100         filename: <code class="constant">DT_SONAME</code> can be deduced from
 101         the filename by removing the last two period-delimited numbers. For
 102         example, filename <code class="filename">libstdc++.so.5.0.4</code>
 103         corresponds to a <code class="constant">DT_SONAME</code> of
 104         <code class="constant">libstdc++.so.5</code>. Binaries with equivalent
 105         <code class="constant">DT_SONAME</code>s are forward-compatibile: in
 106         the table below, releases incompatible with the previous
 107         one are explicitly noted.
 108       </p><p>It is versioned as follows:
 109     </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>gcc-3.0.0: libstdc++.so.3.0.0</p></li><li class="listitem"><p>gcc-3.0.1: libstdc++.so.3.0.1</p></li><li class="listitem"><p>gcc-3.0.2: libstdc++.so.3.0.2</p></li><li class="listitem"><p>gcc-3.0.3: libstdc++.so.3.0.2 (See Note 1)</p></li><li class="listitem"><p>gcc-3.0.4: libstdc++.so.3.0.4</p></li><li class="listitem"><p>gcc-3.1.0: libstdc++.so.4.0.0 <span class="emphasis"><em>(Incompatible with previous)</em></span></p></li><li class="listitem"><p>gcc-3.1.1: libstdc++.so.4.0.1</p></li><li class="listitem"><p>gcc-3.2.0: libstdc++.so.5.0.0 <span class="emphasis"><em>(Incompatible with previous)</em></span></p></li><li class="listitem"><p>gcc-3.2.1: libstdc++.so.5.0.1</p></li><li class="listitem"><p>gcc-3.2.2: libstdc++.so.5.0.2</p></li><li class="listitem"><p>gcc-3.2.3: libstdc++.so.5.0.3 (See Note 2)</p></li><li class="listitem"><p>gcc-3.3.0: libstdc++.so.5.0.4</p></li><li class="listitem"><p>gcc-3.3.1: libstdc++.so.5.0.5</p></li><li class="listitem"><p>gcc-3.3.2: libstdc++.so.5.0.5</p></li><li class="listitem"><p>gcc-3.3.3: libstdc++.so.5.0.5</p></li><li class="listitem"><p>gcc-3.4.0: libstdc++.so.6.0.0 <span class="emphasis"><em>(Incompatible with previous)</em></span></p></li><li class="listitem"><p>gcc-3.4.1: libstdc++.so.6.0.1</p></li><li class="listitem"><p>gcc-3.4.2: libstdc++.so.6.0.2</p></li><li class="listitem"><p>gcc-3.4.3: libstdc++.so.6.0.3</p></li><li class="listitem"><p>gcc-3.4.4: libstdc++.so.6.0.3</p></li><li class="listitem"><p>gcc-3.4.5: libstdc++.so.6.0.3</p></li><li class="listitem"><p>gcc-3.4.6: libstdc++.so.6.0.3</p></li><li class="listitem"><p>gcc-4.0.0: libstdc++.so.6.0.4</p></li><li class="listitem"><p>gcc-4.0.1: libstdc++.so.6.0.5</p></li><li class="listitem"><p>gcc-4.0.2: libstdc++.so.6.0.6</p></li><li class="listitem"><p>gcc-4.0.3: libstdc++.so.6.0.7</p></li><li class="listitem"><p>gcc-4.1.0: libstdc++.so.6.0.7</p></li><li class="listitem"><p>gcc-4.1.1: libstdc++.so.6.0.8</p></li><li class="listitem"><p>gcc-4.1.2: libstdc++.so.6.0.8</p></li><li class="listitem"><p>gcc-4.2.0: libstdc++.so.6.0.9</p></li><li class="listitem"><p>gcc-4.2.1: libstdc++.so.6.0.9 (See Note 3)</p></li><li class="listitem"><p>gcc-4.2.2: libstdc++.so.6.0.9</p></li><li class="listitem"><p>gcc-4.2.3: libstdc++.so.6.0.9</p></li><li class="listitem"><p>gcc-4.2.4: libstdc++.so.6.0.9</p></li><li class="listitem"><p>gcc-4.3.0: libstdc++.so.6.0.10</p></li><li class="listitem"><p>gcc-4.3.1: libstdc++.so.6.0.10</p></li><li class="listitem"><p>gcc-4.3.2: libstdc++.so.6.0.10</p></li><li class="listitem"><p>gcc-4.3.3: libstdc++.so.6.0.10</p></li><li class="listitem"><p>gcc-4.3.4: libstdc++.so.6.0.10</p></li><li class="listitem"><p>gcc-4.4.0: libstdc++.so.6.0.11</p></li><li class="listitem"><p>gcc-4.4.1: libstdc++.so.6.0.12</p></li><li class="listitem"><p>gcc-4.4.2: libstdc++.so.6.0.13</p></li><li class="listitem"><p>gcc-4.5.0: libstdc++.so.6.0.14</p></li></ul></div><p>
 110       Note 1: Error should be libstdc++.so.3.0.3.
 111     </p><p>
 112       Note 2: Not strictly required.
 113     </p><p>
 114       Note 3: This release (but not previous or subsequent) has one
 115       known incompatibility, see <a class="ulink" href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33678" target="_top">33678</a>
 116       in the GCC bug database.
 117     </p></li><li class="listitem"><p>Symbol versioning on the libstdc++.so binary.</p><p>mapfile: libstdc++/config/linker-map.gnu</p><p>It is versioned with the following labels and version
 118    definitions, where the version definition is the maximum for a
 119    particular release. Note, only symbol which are newly introduced
 120    will use the maximum version definition. Thus, for release series
 121    with the same label, but incremented version definitions, the later
 122    release has both versions. (An example of this would be the
 123    gcc-3.2.1 release, which has GLIBCPP_3.2.1 for new symbols and
 124    GLIBCPP_3.2 for symbols that were introduced in the gcc-3.2.0
 125    release.) If a particular release is not listed, it has the same
 126    version labels as the preceding release.
 127    </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>gcc-3.0.0: (Error, not versioned)</p></li><li class="listitem"><p>gcc-3.0.1: (Error, not versioned)</p></li><li class="listitem"><p>gcc-3.0.2: (Error, not versioned)</p></li><li class="listitem"><p>gcc-3.0.3: (Error, not versioned)</p></li><li class="listitem"><p>gcc-3.0.4: (Error, not versioned)</p></li><li class="listitem"><p>gcc-3.1.0: GLIBCPP_3.1, CXXABI_1</p></li><li class="listitem"><p>gcc-3.1.1: GLIBCPP_3.1, CXXABI_1</p></li><li class="listitem"><p>gcc-3.2.0: GLIBCPP_3.2, CXXABI_1.2</p></li><li class="listitem"><p>gcc-3.2.1: GLIBCPP_3.2.1, CXXABI_1.2</p></li><li class="listitem"><p>gcc-3.2.2: GLIBCPP_3.2.2, CXXABI_1.2</p></li><li class="listitem"><p>gcc-3.2.3: GLIBCPP_3.2.2, CXXABI_1.2</p></li><li class="listitem"><p>gcc-3.3.0: GLIBCPP_3.2.2, CXXABI_1.2.1</p></li><li class="listitem"><p>gcc-3.3.1: GLIBCPP_3.2.3, CXXABI_1.2.1</p></li><li class="listitem"><p>gcc-3.3.2: GLIBCPP_3.2.3, CXXABI_1.2.1</p></li><li class="listitem"><p>gcc-3.3.3: GLIBCPP_3.2.3, CXXABI_1.2.1</p></li><li class="listitem"><p>gcc-3.4.0: GLIBCXX_3.4, CXXABI_1.3</p></li><li class="listitem"><p>gcc-3.4.1: GLIBCXX_3.4.1, CXXABI_1.3</p></li><li class="listitem"><p>gcc-3.4.2: GLIBCXX_3.4.2</p></li><li class="listitem"><p>gcc-3.4.3: GLIBCXX_3.4.3</p></li><li class="listitem"><p>gcc-4.0.0: GLIBCXX_3.4.4, CXXABI_1.3.1</p></li><li class="listitem"><p>gcc-4.0.1: GLIBCXX_3.4.5</p></li><li class="listitem"><p>gcc-4.0.2: GLIBCXX_3.4.6</p></li><li class="listitem"><p>gcc-4.0.3: GLIBCXX_3.4.7</p></li><li class="listitem"><p>gcc-4.1.1: GLIBCXX_3.4.8</p></li><li class="listitem"><p>gcc-4.2.0: GLIBCXX_3.4.9</p></li><li class="listitem"><p>gcc-4.3.0: GLIBCXX_3.4.10, CXXABI_1.3.2</p></li><li class="listitem"><p>gcc-4.4.0: GLIBCXX_3.4.11, CXXABI_1.3.3</p></li><li class="listitem"><p>gcc-4.4.1: GLIBCXX_3.4.12, CXXABI_1.3.3</p></li><li class="listitem"><p>gcc-4.4.2: GLIBCXX_3.4.13, CXXABI_1.3.3</p></li><li class="listitem"><p>gcc-4.5.0: GLIBCXX_3.4.14, CXXABI_1.3.4</p></li></ul></div></li><li class="listitem"><p>Incremental bumping of a compiler pre-defined macro,
 128     __GXX_ABI_VERSION. This macro is defined as the version of the
 129     compiler v3 ABI, with g++ 3.0.x being version 100. This macro will
 130     be automatically defined whenever g++ is used (the curious can
 131     test this by invoking g++ with the '-v' flag.)
 132     </p><p>
 133     This macro was defined in the file "lang-specs.h" in the gcc/cp directory.
 134     Later versions defined it in "c-common.c" in the gcc directory, and from
 135     G++ 3.4 it is defined in c-cppbuiltin.c and its value determined by the
 136     '-fabi-version' command line option.
 137     </p><p>
 138     It is versioned as follows, where 'n' is given by '-fabi-version=n':
 139     </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>gcc-3.0.x: 100</p></li><li class="listitem"><p>gcc-3.1.x: 100 (Error, should be 101)</p></li><li class="listitem"><p>gcc-3.2.x: 102</p></li><li class="listitem"><p>gcc-3.3.x: 102</p></li><li class="listitem"><p>gcc-3.4.x, gcc-4.[0-5].x: 102 (when n=1)</p></li><li class="listitem"><p>gcc-3.4.x, gcc-4.[0-5].x: 1000 + n (when n&gt;1) </p></li><li class="listitem"><p>gcc-3.4.x, gcc-4.[0-5].x: 999999 (when n=0)</p></li></ul></div><p></p></li><li class="listitem"><p>Changes to the default compiler option for
 140     <code class="code">-fabi-version</code>.
 141     </p><p>
 142     It is versioned as follows:
 143     </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>gcc-3.0.x: (Error, not versioned) </p></li><li class="listitem"><p>gcc-3.1.x: (Error, not versioned) </p></li><li class="listitem"><p>gcc-3.2.x: <code class="code">-fabi-version=1</code></p></li><li class="listitem"><p>gcc-3.3.x: <code class="code">-fabi-version=1</code></p></li><li class="listitem"><p>gcc-3.4.x, gcc-4.[0-5].x: <code class="code">-fabi-version=2</code> <span class="emphasis"><em>(Incompatible with previous)</em></span></p></li></ul></div><p></p></li><li class="listitem"><p>Incremental bumping of a library pre-defined macro. For releases
 144     before 3.4.0, the macro is __GLIBCPP__. For later releases, it's
 145     __GLIBCXX__. (The libstdc++ project generously changed from CPP to
 146     CXX throughout its source to allow the "C" pre-processor the CPP
 147     macro namespace.) These macros are defined as the date the library
 148     was released, in compressed ISO date format, as an unsigned long.
 149     </p><p>
 150     This macro is defined in the file "c++config" in the
 151     "libstdc++/include/bits" directory. (Up to gcc-4.1.0, it was
 152     changed every night by an automated script. Since gcc-4.1.0, it is
 153     the same value as gcc/DATESTAMP.)
 154     </p><p>
 155     It is versioned as follows:
 156     </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>gcc-3.0.0: 20010615</p></li><li class="listitem"><p>gcc-3.0.1: 20010819</p></li><li class="listitem"><p>gcc-3.0.2: 20011023</p></li><li class="listitem"><p>gcc-3.0.3: 20011220</p></li><li class="listitem"><p>gcc-3.0.4: 20020220</p></li><li class="listitem"><p>gcc-3.1.0: 20020514</p></li><li class="listitem"><p>gcc-3.1.1: 20020725</p></li><li class="listitem"><p>gcc-3.2.0: 20020814</p></li><li class="listitem"><p>gcc-3.2.1: 20021119</p></li><li class="listitem"><p>gcc-3.2.2: 20030205</p></li><li class="listitem"><p>gcc-3.2.3: 20030422</p></li><li class="listitem"><p>gcc-3.3.0: 20030513</p></li><li class="listitem"><p>gcc-3.3.1: 20030804</p></li><li class="listitem"><p>gcc-3.3.2: 20031016</p></li><li class="listitem"><p>gcc-3.3.3: 20040214</p></li><li class="listitem"><p>gcc-3.4.0: 20040419</p></li><li class="listitem"><p>gcc-3.4.1: 20040701</p></li><li class="listitem"><p>gcc-3.4.2: 20040906</p></li><li class="listitem"><p>gcc-3.4.3: 20041105</p></li><li class="listitem"><p>gcc-3.4.4: 20050519</p></li><li class="listitem"><p>gcc-3.4.5: 20051201</p></li><li class="listitem"><p>gcc-3.4.6: 20060306</p></li><li class="listitem"><p>gcc-4.0.0: 20050421</p></li><li class="listitem"><p>gcc-4.0.1: 20050707</p></li><li class="listitem"><p>gcc-4.0.2: 20050921</p></li><li class="listitem"><p>gcc-4.0.3: 20060309</p></li><li class="listitem"><p>gcc-4.1.0: 20060228</p></li><li class="listitem"><p>gcc-4.1.1: 20060524</p></li><li class="listitem"><p>gcc-4.1.2: 20070214</p></li><li class="listitem"><p>gcc-4.2.0: 20070514</p></li><li class="listitem"><p>gcc-4.2.1: 20070719</p></li><li class="listitem"><p>gcc-4.2.2: 20071007</p></li><li class="listitem"><p>gcc-4.2.3: 20080201</p></li><li class="listitem"><p>gcc-4.2.4: 20080519</p></li><li class="listitem"><p>gcc-4.3.0: 20080306</p></li><li class="listitem"><p>gcc-4.3.1: 20080606</p></li><li class="listitem"><p>gcc-4.3.2: 20080827</p></li><li class="listitem"><p>gcc-4.3.3: 20090124</p></li><li class="listitem"><p>gcc-4.4.0: 20090421</p></li><li class="listitem"><p>gcc-4.4.1: 20090722</p></li><li class="listitem"><p>gcc-4.4.2: 20091015</p></li></ul></div><p></p></li><li class="listitem"><p>
 157     Incremental bumping of a library pre-defined macro,
 158     _GLIBCPP_VERSION. This macro is defined as the released version of
 159     the library, as a string literal. This is only implemented in
 160     gcc-3.1.0 releases and higher, and is deprecated in 3.4 (where it
 161     is called _GLIBCXX_VERSION).
 162     </p><p>
 163     This macro is defined in the file "c++config" in the
 164     "libstdc++/include/bits" directory and is generated
 165     automatically by autoconf as part of the configure-time generation
 166     of config.h.
 167     </p><p>
 168     It is versioned as follows:
 169     </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>gcc-3.0.0: "3.0.0"</p></li><li class="listitem"><p>gcc-3.0.1: "3.0.0" (Error, should be "3.0.1")</p></li><li class="listitem"><p>gcc-3.0.2: "3.0.0" (Error, should be "3.0.2")</p></li><li class="listitem"><p>gcc-3.0.3: "3.0.0" (Error, should be "3.0.3")</p></li><li class="listitem"><p>gcc-3.0.4: "3.0.0" (Error, should be "3.0.4")</p></li><li class="listitem"><p>gcc-3.1.0: "3.1.0"</p></li><li class="listitem"><p>gcc-3.1.1: "3.1.1"</p></li><li class="listitem"><p>gcc-3.2.0: "3.2"</p></li><li class="listitem"><p>gcc-3.2.1: "3.2.1"</p></li><li class="listitem"><p>gcc-3.2.2: "3.2.2"</p></li><li class="listitem"><p>gcc-3.2.3: "3.2.3"</p></li><li class="listitem"><p>gcc-3.3.0: "3.3"</p></li><li class="listitem"><p>gcc-3.3.1: "3.3.1"</p></li><li class="listitem"><p>gcc-3.3.2: "3.3.2"</p></li><li class="listitem"><p>gcc-3.3.3: "3.3.3"</p></li><li class="listitem"><p>gcc-3.4.x: "version-unused"</p></li><li class="listitem"><p>gcc-4.[0-5].x: "version-unused"</p></li></ul></div><p></p></li><li class="listitem"><p>
 170     Matching each specific C++ compiler release to a specific set of
 171     C++ include files. This is only implemented in gcc-3.1.1 releases
 172     and higher.
 173     </p><p>
 174     All C++ includes are installed in include/c++, then nest in a
 175     directory hierarchy corresponding to the C++ compiler's released
 176     version. This version corresponds to the variable "gcc_version" in
 177     "libstdc++/acinclude.m4," and more details can be found in that
 178     file's macro GLIBCXX_CONFIGURE (GLIBCPP_CONFIGURE before gcc-3.4.0).
 179     </p><p>
 180     C++ includes are versioned as follows:
 181     </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>gcc-3.0.0: include/g++-v3</p></li><li class="listitem"><p>gcc-3.0.1: include/g++-v3</p></li><li class="listitem"><p>gcc-3.0.2: include/g++-v3</p></li><li class="listitem"><p>gcc-3.0.3: include/g++-v3</p></li><li class="listitem"><p>gcc-3.0.4: include/g++-v3</p></li><li class="listitem"><p>gcc-3.1.0: include/g++-v3</p></li><li class="listitem"><p>gcc-3.1.1: include/c++/3.1.1</p></li><li class="listitem"><p>gcc-3.2.0: include/c++/3.2</p></li><li class="listitem"><p>gcc-3.2.1: include/c++/3.2.1</p></li><li class="listitem"><p>gcc-3.2.2: include/c++/3.2.2</p></li><li class="listitem"><p>gcc-3.2.3: include/c++/3.2.3</p></li><li class="listitem"><p>gcc-3.3.0: include/c++/3.3</p></li><li class="listitem"><p>gcc-3.3.1: include/c++/3.3.1</p></li><li class="listitem"><p>gcc-3.3.2: include/c++/3.3.2</p></li><li class="listitem"><p>gcc-3.3.3: include/c++/3.3.3</p></li><li class="listitem"><p>gcc-3.4.0: include/c++/3.4.0</p></li><li class="listitem"><p>gcc-3.4.1: include/c++/3.4.1</p></li><li class="listitem"><p>gcc-3.4.2: include/c++/3.4.2</p></li><li class="listitem"><p>gcc-3.4.3: include/c++/3.4.3</p></li><li class="listitem"><p>gcc-3.4.4: include/c++/3.4.4</p></li><li class="listitem"><p>gcc-3.4.5: include/c++/3.4.5</p></li><li class="listitem"><p>gcc-3.4.6: include/c++/3.4.6</p></li><li class="listitem"><p>gcc-4.0.0: include/c++/4.0.0</p></li><li class="listitem"><p>gcc-4.0.1: include/c++/4.0.1</p></li><li class="listitem"><p>gcc-4.0.2: include/c++/4.0.2</p></li><li class="listitem"><p>gcc-4.0.3: include/c++/4.0.3</p></li><li class="listitem"><p>gcc-4.1.0: include/c++/4.1.0</p></li><li class="listitem"><p>gcc-4.1.1: include/c++/4.1.1</p></li><li class="listitem"><p>gcc-4.1.2: include/c++/4.1.2</p></li><li class="listitem"><p>gcc-4.2.0: include/c++/4.2.0</p></li><li class="listitem"><p>gcc-4.2.1: include/c++/4.2.1</p></li><li class="listitem"><p>gcc-4.2.2: include/c++/4.2.2</p></li><li class="listitem"><p>gcc-4.2.3: include/c++/4.2.3</p></li><li class="listitem"><p>gcc-4.2.4: include/c++/4.2.4</p></li><li class="listitem"><p>gcc-4.3.0: include/c++/4.3.0</p></li><li class="listitem"><p>gcc-4.3.1: include/c++/4.3.1</p></li><li class="listitem"><p>gcc-4.3.3: include/c++/4.3.3</p></li><li class="listitem"><p>gcc-4.3.4: include/c++/4.3.4</p></li><li class="listitem"><p>gcc-4.4.0: include/c++/4.4.0</p></li><li class="listitem"><p>gcc-4.4.1: include/c++/4.4.1</p></li><li class="listitem"><p>gcc-4.4.2: include/c++/4.4.2</p></li><li class="listitem"><p>gcc-4.5.0: include/c++/4.5.0</p></li></ul></div><p></p></li></ol></div><p>
 182   Taken together, these techniques can accurately specify interface
 183   and implementation changes in the GNU C++ tools themselves. Used
 184   properly, they allow both the GNU C++ tools implementation, and
 185   programs using them, an evolving yet controlled development that
 186   maintains backward compatibility.
 187 </p></div><div class="sect3" title="Prerequisites"><div class="titlepage"><div><div><h4 class="title"><a id="abi.versioning.prereq"></a>Prerequisites</h4></div></div></div><p>
 188       Minimum environment that supports a versioned ABI: A supported
 189       dynamic linker, a GNU linker of sufficient vintage to understand
 190       demangled C++ name globbing (ld), a shared executable compiled
 191       with g++, and shared libraries (libgcc_s, libstdc++) compiled by
 192       a compiler (g++) with a compatible ABI. Phew.
 193     </p><p>
 194       On top of all that, an additional constraint: libstdc++ did not
 195       attempt to version symbols (or age gracefully, really) until
 196       version 3.1.0.
 197     </p><p>
 198       Most modern Linux and BSD versions, particularly ones using
 199       gcc-3.1.x tools and more recent vintages, will meet the
 200       requirements above.
 201     </p></div><div class="sect3" title="Configuring"><div class="titlepage"><div><div><h4 class="title"><a id="abi.versioning.config"></a>Configuring</h4></div></div></div><p>
 202       It turns out that most of the configure options that change
 203       default behavior will impact the mangled names of exported
 204       symbols, and thus impact versioning and compatibility.
 205     </p><p>
 206       For more information on configure options, including ABI
 207       impacts, see:
 208       http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html
 209     </p><p>
 210       There is one flag that explicitly deals with symbol versioning:
 211       --enable-symvers.
 212     </p><p>
 213       In particular, libstdc++/acinclude.m4 has a macro called
 214       GLIBCXX_ENABLE_SYMVERS that defaults to yes (or the argument
 215       passed in via --enable-symvers=foo). At that point, the macro
 216       attempts to make sure that all the requirement for symbol
 217       versioning are in place. For more information, please consult
 218       acinclude.m4.
 219     </p></div><div class="sect3" title="Checking Active"><div class="titlepage"><div><div><h4 class="title"><a id="abi.versioning.active"></a>Checking Active</h4></div></div></div><p>
 220       When the GNU C++ library is being built with symbol versioning
 221       on, you should see the following at configure time for
 222       libstdc++:
 223     </p><pre class="screen">
 224 <code class="computeroutput">
 225   checking versioning on shared library symbols... gnu
 226 </code>
 227 </pre><p>
 228   If you don't see this line in the configure output, or if this line
 229   appears but the last word is 'no', then you are out of luck.
 230 </p><p>
 231   If the compiler is pre-installed, a quick way to test is to compile
 232   the following (or any) simple C++ file and link it to the shared
 233   libstdc++ library:
 234 </p><pre class="programlisting">
 235 #include &lt;iostream&gt;
 236
 237 int main()
 238 { std::cout &lt;&lt; "hello" &lt;&lt; std::endl; return 0; }
 239
 240 %g++ hello.cc -o hello.out
 241
 242 %ldd hello.out
 243         libstdc++.so.5 =&gt; /usr/lib/libstdc++.so.5 (0x00764000)
 244         libm.so.6 =&gt; /lib/tls/libm.so.6 (0x004a8000)
 245         libgcc_s.so.1 =&gt; /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x40016000)
 246         libc.so.6 =&gt; /lib/tls/libc.so.6 (0x0036d000)
 247         /lib/ld-linux.so.2 =&gt; /lib/ld-linux.so.2 (0x00355000)
 248
 249 %nm hello.out
 250 </pre><p>
 251 If you see symbols in the resulting output with "GLIBCXX_3" as part
 252 of the name, then the executable is versioned. Here's an example:
 253 </p><p>
 254    <code class="code">U _ZNSt8ios_base4InitC1Ev@@GLIBCXX_3.4</code>
 255 </p></div></div><div class="sect2" title="Allowed Changes"><div class="titlepage"><div><div><h3 class="title"><a id="abi.changes_allowed"></a>Allowed Changes</h3></div></div></div><p>
 256 The following will cause the library minor version number to
 257 increase, say from "libstdc++.so.3.0.4" to "libstdc++.so.3.0.5".
 258 </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Adding an exported global or static data member</p></li><li class="listitem"><p>Adding an exported function, static or non-virtual member function</p></li><li class="listitem"><p>Adding an exported symbol or symbols by additional instantiations</p></li></ol></div><p>
 259 Other allowed changes are possible.
 260 </p></div><div class="sect2" title="Prohibited Changes"><div class="titlepage"><div><div><h3 class="title"><a id="abi.changes_no"></a>Prohibited Changes</h3></div></div></div><p>
 261 The following non-exhaustive list will cause the library major version
 262 number to increase, say from "libstdc++.so.3.0.4" to
 263 "libstdc++.so.4.0.0".
 264 </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Changes in the gcc/g++ compiler ABI</p></li><li class="listitem"><p>Changing size of an exported symbol</p></li><li class="listitem"><p>Changing alignment of an exported symbol</p></li><li class="listitem"><p>Changing the layout of an exported symbol</p></li><li class="listitem"><p>Changing mangling on an exported symbol</p></li><li class="listitem"><p>Deleting an exported symbol</p></li><li class="listitem"><p>Changing the inheritance properties of a type by adding or removing
 265     base classes</p></li><li class="listitem"><p>
 266   Changing the size, alignment, or layout of types
 267   specified in the C++ standard. These may not necessarily be
 268   instantiated or otherwise exported in the library binary, and
 269   include all the required locale facets, as well as things like
 270   std::basic_streambuf, et al.
 271 </p></li><li class="listitem"><p> Adding an explicit copy constructor or destructor to a
 272 class that would otherwise have implicit versions. This will change
 273 the way the compiler deals with this class in by-value return
 274 statements or parameters: instead of being passing instances of this
 275 class in registers, the compiler will be forced to use memory. See <a class="ulink" href="http://www.codesourcery.com/cxx-abi/abi.html#calls" target="_top"> this part</a>
 276  of the C++ ABI documentation for further details.
 277  </p></li></ol></div></div><div class="sect2" title="Implementation"><div class="titlepage"><div><div><h3 class="title"><a id="abi.impl"></a>Implementation</h3></div></div></div><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
 278      Separation of interface and implementation
 279    </p><p>
 280      This is accomplished by two techniques that separate the API from
 281      the ABI: forcing undefined references to link against a library
 282      binary for definitions.
 283    </p><div class="variablelist"><dl><dt><span class="term">Include files have declarations, source files have defines</span></dt><dd><p>
 284         For non-templatized types, such as much of <code class="code">class
 285         locale</code>, the appropriate standard C++ include, say
 286         <code class="code">locale</code>, can contain full declarations, while
 287         various source files (say <code class="code"> locale.cc, locale_init.cc,
 288         localename.cc</code>) contain definitions.
 289       </p></dd><dt><span class="term">Extern template on required types</span></dt><dd><p>
 290        For parts of the standard that have an explicit list of
 291        required instantiations, the GNU extension syntax <code class="code"> extern
 292        template </code> can be used to control where template
 293        definitions reside. By marking required instantiations as
 294        <code class="code"> extern template </code> in include files, and providing
 295        explicit instantiations in the appropriate instantiation files,
 296        non-inlined template functions can be versioned. This technique
 297        is mostly used on parts of the standard that require <code class="code">
 298        char</code> and <code class="code"> wchar_t</code> instantiations, and
 299        includes <code class="code"> basic_string</code>, the locale facets, and the
 300        types in <code class="code"> iostreams</code>.
 301      </p></dd></dl></div><p>
 302    In addition, these techniques have the additional benefit that they
 303    reduce binary size, which can increase runtime performance.
 304  </p></li><li class="listitem"><p>
 305      Namespaces linking symbol definitions to export mapfiles
 306    </p><p>
 307      All symbols in the shared library binary are processed by a
 308      linker script at build time that either allows or disallows
 309      external linkage. Because of this, some symbols, regardless of
 310      normal C/C++ linkage, are not visible. Symbols that are internal
 311      have several appealing characteristics: by not exporting the
 312      symbols, there are no relocations when the shared library is
 313      started and thus this makes for faster runtime loading
 314      performance by the underlying dynamic loading mechanism. In
 315      addition, they have the possibility of changing without impacting
 316      ABI compatibility.
 317    </p><p>The following namespaces are transformed by the mapfile:</p><div class="variablelist"><dl><dt><span class="term"><code class="code">namespace std</code></span></dt><dd><p> Defaults to exporting all symbols in label
 318 <code class="code">GLIBCXX</code> that do not begin with an underscore, i.e.,
 319 <code class="code">__test_func</code> would not be exported by default. Select
 320 exceptional symbols are allowed to be visible.</p></dd><dt><span class="term"><code class="code">namespace __gnu_cxx</code></span></dt><dd><p> Defaults to not exporting any symbols in label
 321 <code class="code">GLIBCXX</code>, select items are allowed to be visible.</p></dd><dt><span class="term"><code class="code">namespace __gnu_internal</code></span></dt><dd><p> Defaults to not exported, no items are allowed to be visible.</p></dd><dt><span class="term"><code class="code">namespace __cxxabiv1</code>, aliased to <code class="code"> namespace abi</code></span></dt><dd><p> Defaults to not exporting any symbols in label
 322 <code class="code">CXXABI</code>, select items are allowed to be visible.</p></dd></dl></div><p>
 323 </p></li><li class="listitem"><p>Freezing the API</p><p>Disallowed changes, as above, are not made on a stable release
 324 branch. Enforcement tends to be less strict with GNU extensions that
 325 standard includes.</p></li></ol></div></div><div class="sect2" title="Testing"><div class="titlepage"><div><div><h3 class="title"><a id="abi.testing"></a>Testing</h3></div></div></div><div class="sect3" title="Single ABI Testing"><div class="titlepage"><div><div><h4 class="title"><a id="abi.testing.single"></a>Single ABI Testing</h4></div></div></div><p>
 326       Testing for GNU C++ ABI changes is composed of two distinct
 327       areas: testing the C++ compiler (g++) for compiler changes, and
 328       testing the C++ library (libstdc++) for library changes.
 329     </p><p>
 330       Testing the C++ compiler ABI can be done various ways.
 331     </p><p>
 332       One.  Intel ABI checker.
 333     </p><p>
 334 Two.
 335 The second is yet unreleased, but has been announced on the gcc
 336 mailing list. It is yet unspecified if these tools will be freely
 337 available, and able to be included in a GNU project. Please contact
 338 Mark Mitchell (mark@codesourcery.com) for more details, and current
 339 status.
 340 </p><p>
 341 Three.
 342 Involves using the vlad.consistency test framework. This has also been
 343 discussed on the gcc mailing lists.
 344 </p><p>
 345 Testing the C++ library ABI can also be done various ways.
 346 </p><p>
 347 One.
 348 (Brendan Kehoe, Jeff Law suggestion to run 'make check-c++' two ways,
 349 one with a new compiler and an old library, and the other with an old
 350 compiler and a new library, and look for testsuite regressions)
 351 </p><p>
 352 Details on how to set this kind of test up can be found here:
 353 http://gcc.gnu.org/ml/gcc/2002-08/msg00142.html
 354 </p><p>
 355 Two.
 356 Use the 'make check-abi' rule in the libstdc++ Makefile.
 357 </p><p>
 358 This is a proactive check the library ABI. Currently, exported symbol
 359 names that are either weak or defined are checked against a last known
 360 good baseline. Currently, this baseline is keyed off of 3.4.0
 361 binaries, as this was the last time the .so number was incremented. In
 362 addition, all exported names are demangled, and the exported objects
 363 are checked to make sure they are the same size as the same object in
 364 the baseline.
 365
 366 Notice that each baseline is relative to a <span class="emphasis"><em>default</em></span>
 367 configured library and compiler: in particular, if options such as
 368 --enable-clocale, or --with-cpu, in case of multilibs, are used at
 369 configure time, the check may fail, either because of substantive
 370 differences or because of limitations of the current checking
 371 machinery.
 372 </p><p>
 373 This dataset is insufficient, yet a start. Also needed is a
 374 comprehensive check for all user-visible types part of the standard
 375 library for sizeof() and alignof() changes.
 376 </p><p>
 377 Verifying compatible layouts of objects is not even attempted.  It
 378 should be possible to use sizeof, alignof, and offsetof to compute
 379 offsets for each structure and type in the standard library, saving to
 380 another datafile. Then, compute this in a similar way for new
 381 binaries, and look for differences.
 382 </p><p>
 383 Another approach might be to use the -fdump-class-hierarchy flag to
 384 get information. However, currently this approach gives insufficient
 385 data for use in library testing, as class data members, their offsets,
 386 and other detailed data is not displayed with this flag.
 387 (See g++/7470 on how this was used to find bugs.)
 388 </p><p>
 389 Perhaps there are other C++ ABI checkers. If so, please notify
 390 us. We'd like to know about them!
 391 </p></div><div class="sect3" title="Multiple ABI Testing"><div class="titlepage"><div><div><h4 class="title"><a id="abi.testing.multi"></a>Multiple ABI Testing</h4></div></div></div><p>
 392 A "C" application, dynamically linked to two shared libraries, liba,
 393 libb. The dependent library liba is C++ shared library compiled with
 394 gcc-3.3.x, and uses io, exceptions, locale, etc. The dependent library
 395 libb is a C++ shared library compiled with gcc-3.4.x, and also uses io,
 396 exceptions, locale, etc.
 397 </p><p> As above, libone is constructed as follows: </p><pre class="programlisting">
 398 %$bld/H-x86-gcc-3.4.0/bin/g++ -fPIC -DPIC -c a.cc
 399
 400 %$bld/H-x86-gcc-3.4.0/bin/g++ -shared -Wl,-soname -Wl,libone.so.1 -Wl,-O1 -Wl,-z,defs a.o -o libone.so.1.0.0
 401
 402 %ln -s libone.so.1.0.0 libone.so
 403
 404 %$bld/H-x86-gcc-3.4.0/bin/g++ -c a.cc
 405
 406 %ar cru libone.a a.o
 407 </pre><p> And, libtwo is constructed as follows: </p><pre class="programlisting">
 408 %$bld/H-x86-gcc-3.3.3/bin/g++ -fPIC -DPIC -c b.cc
 409
 410 %$bld/H-x86-gcc-3.3.3/bin/g++ -shared -Wl,-soname -Wl,libtwo.so.1 -Wl,-O1 -Wl,-z,defs b.o -o libtwo.so.1.0.0
 411
 412 %ln -s libtwo.so.1.0.0 libtwo.so
 413
 414 %$bld/H-x86-gcc-3.3.3/bin/g++ -c b.cc
 415
 416 %ar cru libtwo.a b.o
 417 </pre><p> ...with the resulting libraries looking like </p><pre class="screen">
 418 <code class="computeroutput">
 419 %ldd libone.so.1.0.0
 420         libstdc++.so.6 =&gt; /usr/lib/libstdc++.so.6 (0x40016000)
 421         libm.so.6 =&gt; /lib/tls/libm.so.6 (0x400fa000)
 422         libgcc_s.so.1 =&gt; /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x4011c000)
 423         libc.so.6 =&gt; /lib/tls/libc.so.6 (0x40125000)
 424         /lib/ld-linux.so.2 =&gt; /lib/ld-linux.so.2 (0x00355000)
 425
 426 %ldd libtwo.so.1.0.0
 427         libstdc++.so.5 =&gt; /usr/lib/libstdc++.so.5 (0x40027000)
 428         libm.so.6 =&gt; /lib/tls/libm.so.6 (0x400e1000)
 429         libgcc_s.so.1 =&gt; /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x40103000)
 430         libc.so.6 =&gt; /lib/tls/libc.so.6 (0x4010c000)
 431         /lib/ld-linux.so.2 =&gt; /lib/ld-linux.so.2 (0x00355000)
 432 </code>
 433 </pre><p>
 434   Then, the "C" compiler is used to compile a source file that uses
 435   functions from each library.
 436 </p><pre class="programlisting">
 437 gcc test.c -g -O2 -L. -lone -ltwo /usr/lib/libstdc++.so.5 /usr/lib/libstdc++.so.6
 438 </pre><p>
 439   Which gives the expected:
 440 </p><pre class="screen">
 441 <code class="computeroutput">
 442 %ldd a.out
 443         libstdc++.so.5 =&gt; /usr/lib/libstdc++.so.5 (0x00764000)
 444         libstdc++.so.6 =&gt; /usr/lib/libstdc++.so.6 (0x40015000)
 445         libc.so.6 =&gt; /lib/tls/libc.so.6 (0x0036d000)
 446         libm.so.6 =&gt; /lib/tls/libm.so.6 (0x004a8000)
 447         libgcc_s.so.1 =&gt; /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x400e5000)
 448         /lib/ld-linux.so.2 =&gt; /lib/ld-linux.so.2 (0x00355000)
 449 </code>
 450 </pre><p>
 451   This resulting binary, when executed, will be able to safely use
 452   code from both liba, and the dependent libstdc++.so.6, and libb,
 453   with the dependent libstdc++.so.5.
 454 </p></div></div><div class="sect2" title="Outstanding Issues"><div class="titlepage"><div><div><h3 class="title"><a id="abi.issues"></a>Outstanding Issues</h3></div></div></div><p>
 455   Some features in the C++ language make versioning especially
 456   difficult. In particular, compiler generated constructs such as
 457   implicit instantiations for templates, typeinfo information, and
 458   virtual tables all may cause ABI leakage across shared library
 459   boundaries. Because of this, mixing C++ ABIs is not recommended at
 460   this time.
 461 </p><p>
 462   For more background on this issue, see these bugzilla entries:
 463 </p><p>
 464 <a class="ulink" href="http://gcc.gnu.org/PR24660" target="_top">24660: versioning weak symbols in libstdc++</a>
 465 </p><p>
 466 <a class="ulink" href="http://gcc.gnu.org/PR19664" target="_top">19664: libstdc++ headers should have pop/push of the visibility around the declarations</a>
 467 </p></div><div class="bibliography" title="Bibliography"><div class="titlepage"><div><div><h3 class="title"><a id="abi.biblio"></a>Bibliography</h3></div></div></div><div class="biblioentry" title="ABIcheck, a vague idea of checking ABI compatibility"><a id="id725008"></a><p><span class="title"><i>
 468       ABIcheck, a vague idea of checking ABI compatibility
 469     </i>. </span><span class="biblioid">
 470       <a class="ulink" href="http://abicheck.sourceforge.net/" target="_top">
 471       </a>
 472     . </span></p></div><div class="biblioentry" title="C++ ABI Reference"><a id="id725026"></a><p><span class="title"><i>
 473       C++ ABI Reference
 474     </i>. </span><span class="biblioid">
 475       <a class="ulink" href="http://www.codesourcery.com/public/cxx-abi/" target="_top">
 476       </a>
 477     . </span></p></div><div class="biblioentry" title="Intel® Compilers for Linux* -Compatibility with the GNU Compilers"><a id="id725043"></a><p><span class="title"><i>
 478       Intel® Compilers for Linux* -Compatibility with the GNU Compilers
 479     </i>. </span><span class="biblioid">
 480       <a class="ulink" href="http://www.intel.com/cd/software/products/asmo-na/eng/284736.htm" target="_top">
 481       </a>
 482     . </span></p></div><div class="biblioentry" title="Sun Solaris 2.9 : Linker and Libraries Guide (document 816-1386)"><a id="id725060"></a><p><span class="title"><i>
 483       Sun Solaris 2.9 : Linker and Libraries Guide (document 816-1386)
 484     </i>. </span><span class="biblioid">
 485       <a class="ulink" href="http://docs.sun.com/app/docs/doc/817-1984" target="_top">
 486       </a>
 487     . </span></p></div><div class="biblioentry" title="Sun Solaris 2.9 : C++ Migration Guide (document 816-2459)"><a id="id725077"></a><p><span class="title"><i>
 488       Sun Solaris 2.9 : C++ Migration Guide (document 816-2459)
 489     </i>. </span><span class="biblioid">
 490       <a class="ulink" href="http://docs.sun.com/app/docs/doc/819-5266" target="_top">
 491       </a>
 492     . </span></p></div><div class="biblioentry" title="How to Write Shared Libraries"><a id="id725094"></a><p><span class="title"><i>
 493       How to Write Shared Libraries
 494     </i>. </span><span class="author"><span class="firstname">Ulrich</span> <span class="surname">Drepper</span>. </span><span class="biblioid">
 495       <a class="ulink" href="http://people.redhat.com/drepper/dsohowto.pdf" target="_top">
 496       </a>
 497     . </span></p></div><div class="biblioentry" title="C++ ABI for the ARM Architecture"><a id="id725122"></a><p><span class="title"><i>
 498       C++ ABI for the ARM Architecture
 499     </i>. </span><span class="biblioid">
 500       <a class="ulink" href="http://www.arm.com/miscPDFs/8033.pdf" target="_top">
 501       </a>
 502     . </span></p></div><div class="biblioentry" title="Dynamic Shared Objects: Survey and Issues"><a id="id651420"></a><p><span class="title"><i>
 503       Dynamic Shared Objects: Survey and Issues
 504     </i>. </span><span class="subtitle">
 505       ISO C++ J16/06-0046
 506     . </span><span class="author"><span class="firstname">Benjamin</span> <span class="surname">Kosnik</span>. </span><span class="biblioid">
 507       <a class="ulink" href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1976.html" target="_top">
 508       </a>
 509     . </span></p></div><div class="biblioentry" title="Versioning With Namespaces"><a id="id651453"></a><p><span class="title"><i>
 510       Versioning With Namespaces
 511     </i>. </span><span class="subtitle">
 512       ISO C++ J16/06-0083
 513     . </span><span class="author"><span class="firstname">Benjamin</span> <span class="surname">Kosnik</span>. </span><span class="biblioid">
 514       <a class="ulink" href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2013.html" target="_top">
 515       </a>
 516     . </span></p></div><div class="biblioentry" title="Binary Compatibility of Shared Libraries Implemented in C++ on GNU/Linux Systems"><a id="id651486"></a><p><span class="title"><i>
 517       Binary Compatibility of Shared Libraries Implemented in C++ on GNU/Linux Systems
 518     </i>. </span><span class="subtitle">
 519 SYRCoSE 2009
 520     . </span><span class="author"><span class="firstname">Pavel</span> <span class="surname">Shved</span>. </span><span class="author"><span class="firstname">Denis</span> <span class="surname">Silakov</span>. </span><span class="biblioid">
 521       <a class="ulink" href="http://syrcose.ispras.ru/2009/files/SYRCoSE2009-CfP.pdf" target="_top">
 522       </a>
 523     . </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="test.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="api.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Test </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> API Evolution and Deprecation History</td></tr></table></div></body></html>