abi.xml revision 1.1.1.9
1<section xmlns="http://docbook.org/ns/docbook" version="5.0" 2 xml:id="appendix.porting.abi" xreflabel="abi"> 3<?dbhtml filename="abi.html"?> 4 5<info><title>ABI Policy and Guidelines</title> 6 <keywordset> 7 <keyword>C++</keyword> 8 <keyword>ABI</keyword> 9 <keyword>version</keyword> 10 <keyword>dynamic</keyword> 11 <keyword>shared</keyword> 12 <keyword>compatibility</keyword> 13 </keywordset> 14</info> 15 16 17 18<para> 19</para> 20 21<section xml:id="abi.cxx_interface"><info><title>The C++ Interface</title></info> 22 23 24<para> 25 C++ applications often depend on specific language support 26 routines, say for throwing exceptions, or catching exceptions, and 27 perhaps also depend on features in the C++ Standard Library. 28</para> 29 30<para> 31 The C++ Standard Library has many include files, types defined in 32 those include files, specific named functions, and other 33 behavior. The text of these behaviors, as written in source include 34 files, is called the Application Programing Interface, or API. 35</para> 36 37<para> 38 Furthermore, C++ source that is compiled into object files is 39 transformed by the compiler: it arranges objects with specific 40 alignment and in a particular layout, mangling names according to a 41 well-defined algorithm, has specific arrangements for the support of 42 virtual functions, etc. These details are defined as the compiler 43 Application Binary Interface, or ABI. From GCC version 3 onwards the 44 GNU C++ compiler uses an industry-standard C++ ABI, the 45 <link linkend="biblio.cxxabi">Itanium C++ ABI</link>. 46</para> 47 48<para> 49 The GNU C++ compiler, g++, has a compiler command line option to 50 switch between various different C++ ABIs. This explicit version 51 switch is the flag <code>-fabi-version</code>. In addition, some 52 g++ command line options may change the ABI as a side-effect of 53 use. Such flags include <code>-fpack-struct</code> and 54 <code>-fno-exceptions</code>, but include others: see the complete 55 list in the GCC manual under the heading <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#Code%20Gen%20Options">Options 56 for Code Generation Conventions</link>. 57</para> 58 59<para> 60 The configure options used when building a specific libstdc++ 61 version may also impact the resulting library ABI. The available 62 configure options, and their impact on the library ABI, are 63 documented 64<link linkend="manual.intro.setup.configure">here</link>. 65</para> 66 67<para> Putting all of these ideas together results in the C++ Standard 68Library ABI, which is the compilation of a given library API by a 69given compiler ABI. In a nutshell: 70</para> 71 72<para> 73 <quote> 74 library API + compiler ABI = library ABI 75 </quote> 76</para> 77 78<para> 79 The library ABI is mostly of interest for end-users who have 80 unresolved symbols and are linking dynamically to the C++ Standard 81 library, and who thus must be careful to compile their application 82 with a compiler that is compatible with the available C++ Standard 83 library binary. In this case, compatible is defined with the equation 84 above: given an application compiled with a given compiler ABI and 85 library API, it will work correctly with a Standard C++ Library 86 created with the same constraints. 87</para> 88 89<para> 90 To use a specific version of the C++ ABI, one must use a 91 corresponding GNU C++ toolchain (i.e., g++ and libstdc++) that 92 implements the C++ ABI in question. 93</para> 94 95</section> 96 97<section xml:id="abi.versioning"><info><title>Versioning</title></info> 98 99 100<para> The C++ interface has evolved throughout the history of the GNU 101C++ toolchain. With each release, various details have been changed so 102as to give distinct versions to the C++ interface. 103</para> 104 105 <section xml:id="abi.versioning.goals"><info><title>Goals</title></info> 106 107 108<para>Extending existing, stable ABIs. Versioning gives subsequent 109releases of library binaries the ability to add new symbols and add 110functionality, all the while retaining compatibility with the previous 111releases in the series. Thus, program binaries linked with the initial 112release of a library binary will still run correctly if the library 113binary is replaced by carefully-managed subsequent library 114binaries. This is called forward compatibility. 115</para> 116<para> 117The reverse (backwards compatibility) is not true. It is not possible 118to take program binaries linked with the latest version of a library 119binary in a release series (with additional symbols added), substitute 120in the initial release of the library binary, and remain link 121compatible. 122</para> 123 124<para>Allows multiple, incompatible ABIs to coexist at the same time. 125</para> 126 </section> 127 128 <section xml:id="abi.versioning.history"><info><title>History</title></info> 129 130 131<para> 132 How can this complexity be managed? What does C++ versioning mean? 133 Because library and compiler changes often make binaries compiled 134 with one version of the GNU tools incompatible with binaries 135 compiled with other (either newer or older) versions of the same GNU 136 tools, specific techniques are used to make managing this complexity 137 easier. 138</para> 139 140<para> 141 The following techniques are used: 142</para> 143 144 <orderedlist> 145 146 <listitem><para>Release versioning on the libgcc_s.so binary. </para> 147 148 <para>This is implemented via file names and the ELF 149 <constant>DT_SONAME</constant> mechanism (at least on ELF 150 systems). It is versioned as follows: 151 </para> 152 153 <itemizedlist> 154 <listitem><para>GCC 3.x: libgcc_s.so.1</para></listitem> 155 <listitem><para>GCC 4.x: libgcc_s.so.1</para></listitem> 156 </itemizedlist> 157 158 <para>For m68k-linux the versions differ as follows: </para> 159 160 <itemizedlist> 161 <listitem><para>GCC 3.4, GCC 4.x: libgcc_s.so.1 162 when configuring <code>--with-sjlj-exceptions</code>, or 163 libgcc_s.so.2 </para> </listitem> 164 </itemizedlist> 165 166 <para>For hppa-linux the versions differ as follows: </para> 167 168 <itemizedlist> 169 <listitem><para>GCC 3.4, GCC 4.[0-1]: either libgcc_s.so.1 170 when configuring <code>--with-sjlj-exceptions</code>, or 171 libgcc_s.so.2 </para> </listitem> 172 <listitem><para>GCC 4.[2-7]: either libgcc_s.so.3 when configuring 173 <code>--with-sjlj-exceptions</code>) or libgcc_s.so.4 174 </para> </listitem> 175 </itemizedlist> 176 177 </listitem> 178 179 <listitem><para>Symbol versioning on the libgcc_s.so binary.</para> 180 181 <para>It is versioned with the following labels and version 182 definitions, where the version definition is the maximum for a 183 particular release. Labels are cumulative. If a particular release 184 is not listed, it has the same version labels as the preceding 185 release.</para> 186 187 <para>This corresponds to the mapfile: gcc/libgcc-std.ver</para> 188 <itemizedlist> 189 <listitem><para>GCC 3.0.0: GCC_3.0</para></listitem> 190 <listitem><para>GCC 3.3.0: GCC_3.3</para></listitem> 191 <listitem><para>GCC 3.3.1: GCC_3.3.1</para></listitem> 192 <listitem><para>GCC 3.3.2: GCC_3.3.2</para></listitem> 193 <listitem><para>GCC 3.3.4: GCC_3.3.4</para></listitem> 194 <listitem><para>GCC 3.4.0: GCC_3.4</para></listitem> 195 <listitem><para>GCC 3.4.2: GCC_3.4.2</para></listitem> 196 <listitem><para>GCC 3.4.4: GCC_3.4.4</para></listitem> 197 <listitem><para>GCC 4.0.0: GCC_4.0.0</para></listitem> 198 <listitem><para>GCC 4.1.0: GCC_4.1.0</para></listitem> 199 <listitem><para>GCC 4.2.0: GCC_4.2.0</para></listitem> 200 <listitem><para>GCC 4.3.0: GCC_4.3.0</para></listitem> 201 <listitem><para>GCC 4.4.0: GCC_4.4.0</para></listitem> 202 <listitem><para>GCC 4.5.0: GCC_4.5.0</para></listitem> 203 <listitem><para>GCC 4.6.0: GCC_4.6.0</para></listitem> 204 <listitem><para>GCC 4.7.0: GCC_4.7.0</para></listitem> 205 <listitem><para>GCC 4.8.0: GCC_4.8.0</para></listitem> 206 </itemizedlist> 207 </listitem> 208 209 <listitem> 210 <para> 211 Release versioning on the libstdc++.so binary, implemented in 212 the same way as the libgcc_s.so binary above. Listed is the 213 filename: <constant>DT_SONAME</constant> can be deduced from 214 the filename by removing the last two period-delimited numbers. For 215 example, filename <filename>libstdc++.so.5.0.4</filename> 216 corresponds to a <constant>DT_SONAME</constant> of 217 <constant>libstdc++.so.5</constant>. Binaries with equivalent 218 <constant>DT_SONAME</constant>s are forward-compatibile: in 219 the table below, releases incompatible with the previous 220 one are explicitly noted. 221 If a particular release is not listed, its libstdc++.so binary 222 has the same filename and <constant>DT_SONAME</constant> as the 223 preceding release. 224 </para> 225 226 <para>It is versioned as follows: 227 </para> 228 <itemizedlist> 229 <listitem><para>GCC 3.0.0: libstdc++.so.3.0.0</para></listitem> 230 <listitem><para>GCC 3.0.1: libstdc++.so.3.0.1</para></listitem> 231 <listitem><para>GCC 3.0.2: libstdc++.so.3.0.2</para></listitem> 232 <listitem><para>GCC 3.0.3: libstdc++.so.3.0.2 (See Note 1)</para></listitem> 233 <listitem><para>GCC 3.0.4: libstdc++.so.3.0.4</para></listitem> 234 <listitem><para>GCC 3.1.0: libstdc++.so.4.0.0 <emphasis>(Incompatible with previous)</emphasis></para></listitem> 235 <listitem><para>GCC 3.1.1: libstdc++.so.4.0.1</para></listitem> 236 <listitem><para>GCC 3.2.0: libstdc++.so.5.0.0 <emphasis>(Incompatible with previous)</emphasis></para></listitem> 237 <listitem><para>GCC 3.2.1: libstdc++.so.5.0.1</para></listitem> 238 <listitem><para>GCC 3.2.2: libstdc++.so.5.0.2</para></listitem> 239 <listitem><para>GCC 3.2.3: libstdc++.so.5.0.3 (See Note 2)</para></listitem> 240 <listitem><para>GCC 3.3.0: libstdc++.so.5.0.4</para></listitem> 241 <listitem><para>GCC 3.3.1: libstdc++.so.5.0.5</para></listitem> 242 <listitem><para>GCC 3.4.0: libstdc++.so.6.0.0 <emphasis>(Incompatible with previous)</emphasis></para></listitem> 243 <listitem><para>GCC 3.4.1: libstdc++.so.6.0.1</para></listitem> 244 <listitem><para>GCC 3.4.2: libstdc++.so.6.0.2</para></listitem> 245 <listitem><para>GCC 3.4.3: libstdc++.so.6.0.3</para></listitem> 246 <listitem><para>GCC 4.0.0: libstdc++.so.6.0.4</para></listitem> 247 <listitem><para>GCC 4.0.1: libstdc++.so.6.0.5</para></listitem> 248 <listitem><para>GCC 4.0.2: libstdc++.so.6.0.6</para></listitem> 249 <listitem><para>GCC 4.0.3: libstdc++.so.6.0.7</para></listitem> 250 <listitem><para>GCC 4.1.0: libstdc++.so.6.0.7</para></listitem> 251 <listitem><para>GCC 4.1.1: libstdc++.so.6.0.8</para></listitem> 252 <listitem><para>GCC 4.2.0: libstdc++.so.6.0.9</para></listitem> 253 <listitem><para>GCC 4.2.1: libstdc++.so.6.0.9 (See Note 3)</para></listitem> 254 <listitem><para>GCC 4.2.2: libstdc++.so.6.0.9</para></listitem> 255 <listitem><para>GCC 4.3.0: libstdc++.so.6.0.10</para></listitem> 256 <listitem><para>GCC 4.4.0: libstdc++.so.6.0.11</para></listitem> 257 <listitem><para>GCC 4.4.1: libstdc++.so.6.0.12</para></listitem> 258 <listitem><para>GCC 4.4.2: libstdc++.so.6.0.13</para></listitem> 259 <listitem><para>GCC 4.5.0: libstdc++.so.6.0.14</para></listitem> 260 <listitem><para>GCC 4.6.0: libstdc++.so.6.0.15</para></listitem> 261 <listitem><para>GCC 4.6.1: libstdc++.so.6.0.16</para></listitem> 262 <listitem><para>GCC 4.7.0: libstdc++.so.6.0.17</para></listitem> 263 <listitem><para>GCC 4.8.0: libstdc++.so.6.0.18</para></listitem> 264 <listitem><para>GCC 4.8.3: libstdc++.so.6.0.19</para></listitem> 265 <listitem><para>GCC 4.9.0: libstdc++.so.6.0.20</para></listitem> 266 <listitem><para>GCC 5.1.0: libstdc++.so.6.0.21</para></listitem> 267 <listitem><para>GCC 6.1.0: libstdc++.so.6.0.22</para></listitem> 268 <listitem><para>GCC 7.1.0: libstdc++.so.6.0.23</para></listitem> 269 <listitem><para>GCC 7.2.0: libstdc++.so.6.0.24</para></listitem> 270 </itemizedlist> 271 <para> 272 Note 1: Error should be libstdc++.so.3.0.3. 273 </para> 274 <para> 275 Note 2: Not strictly required. 276 </para> 277 <para> 278 Note 3: This release (but not previous or subsequent) has one 279 known incompatibility, see <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33678">33678</link> 280 in the GCC bug database. 281 </para> 282 </listitem> 283 284 <listitem><para>Symbol versioning on the libstdc++.so binary.</para> 285 286 <para>mapfile: libstdc++-v3/config/abi/pre/gnu.ver</para> 287 <para>It is versioned with the following labels and version 288 definitions, where the version definition is the maximum for a 289 particular release. Note, only symbols which are newly introduced 290 will use the maximum version definition. Thus, for release series 291 with the same label, but incremented version definitions, the later 292 release has both versions. (An example of this would be the 293 GCC 3.2.1 release, which has GLIBCPP_3.2.1 for new symbols and 294 GLIBCPP_3.2 for symbols that were introduced in the GCC 3.2.0 295 release.) If a particular release is not listed, it has the same 296 version labels as the preceding release. 297 </para> 298 <itemizedlist> 299 <listitem><para>GCC 3.0.0: (Error, not versioned)</para></listitem> 300 <listitem><para>GCC 3.0.1: (Error, not versioned)</para></listitem> 301 <listitem><para>GCC 3.0.2: (Error, not versioned)</para></listitem> 302 <listitem><para>GCC 3.0.3: (Error, not versioned)</para></listitem> 303 <listitem><para>GCC 3.0.4: (Error, not versioned)</para></listitem> 304 <listitem><para>GCC 3.1.0: GLIBCPP_3.1, CXXABI_1</para></listitem> 305 <listitem><para>GCC 3.1.1: GLIBCPP_3.1, CXXABI_1</para></listitem> 306 <listitem><para>GCC 3.2.0: GLIBCPP_3.2, CXXABI_1.2</para></listitem> 307 <listitem><para>GCC 3.2.1: GLIBCPP_3.2.1, CXXABI_1.2</para></listitem> 308 <listitem><para>GCC 3.2.2: GLIBCPP_3.2.2, CXXABI_1.2</para></listitem> 309 <listitem><para>GCC 3.2.3: GLIBCPP_3.2.2, CXXABI_1.2</para></listitem> 310 <listitem><para>GCC 3.3.0: GLIBCPP_3.2.2, CXXABI_1.2.1</para></listitem> 311 <listitem><para>GCC 3.3.1: GLIBCPP_3.2.3, CXXABI_1.2.1</para></listitem> 312 <listitem><para>GCC 3.3.2: GLIBCPP_3.2.3, CXXABI_1.2.1</para></listitem> 313 <listitem><para>GCC 3.3.3: GLIBCPP_3.2.3, CXXABI_1.2.1</para></listitem> 314 <listitem><para>GCC 3.4.0: GLIBCXX_3.4, CXXABI_1.3</para></listitem> 315 <listitem><para>GCC 3.4.1: GLIBCXX_3.4.1, CXXABI_1.3</para></listitem> 316 <listitem><para>GCC 3.4.2: GLIBCXX_3.4.2</para></listitem> 317 <listitem><para>GCC 3.4.3: GLIBCXX_3.4.3</para></listitem> 318 <listitem><para>GCC 4.0.0: GLIBCXX_3.4.4, CXXABI_1.3.1</para></listitem> 319 <listitem><para>GCC 4.0.1: GLIBCXX_3.4.5</para></listitem> 320 <listitem><para>GCC 4.0.2: GLIBCXX_3.4.6</para></listitem> 321 <listitem><para>GCC 4.0.3: GLIBCXX_3.4.7</para></listitem> 322 <listitem><para>GCC 4.1.1: GLIBCXX_3.4.8</para></listitem> 323 <listitem><para>GCC 4.2.0: GLIBCXX_3.4.9</para></listitem> 324 <listitem><para>GCC 4.3.0: GLIBCXX_3.4.10, CXXABI_1.3.2</para></listitem> 325 <listitem><para>GCC 4.4.0: GLIBCXX_3.4.11, CXXABI_1.3.3</para></listitem> 326 <listitem><para>GCC 4.4.1: GLIBCXX_3.4.12, CXXABI_1.3.3</para></listitem> 327 <listitem><para>GCC 4.4.2: GLIBCXX_3.4.13, CXXABI_1.3.3</para></listitem> 328 <listitem><para>GCC 4.5.0: GLIBCXX_3.4.14, CXXABI_1.3.4</para></listitem> 329 <listitem><para>GCC 4.6.0: GLIBCXX_3.4.15, CXXABI_1.3.5</para></listitem> 330 <listitem><para>GCC 4.6.1: GLIBCXX_3.4.16, CXXABI_1.3.5</para></listitem> 331 <listitem><para>GCC 4.7.0: GLIBCXX_3.4.17, CXXABI_1.3.6</para></listitem> 332 <listitem><para>GCC 4.8.0: GLIBCXX_3.4.18, CXXABI_1.3.7</para></listitem> 333 <listitem><para>GCC 4.8.3: GLIBCXX_3.4.19, CXXABI_1.3.7</para></listitem> 334 <listitem><para>GCC 4.9.0: GLIBCXX_3.4.20, CXXABI_1.3.8</para></listitem> 335 <listitem><para>GCC 5.1.0: GLIBCXX_3.4.21, CXXABI_1.3.9</para></listitem> 336 <listitem><para>GCC 6.1.0: GLIBCXX_3.4.22, CXXABI_1.3.10</para></listitem> 337 <listitem><para>GCC 7.1.0: GLIBCXX_3.4.23, CXXABI_1.3.11</para></listitem> 338 <listitem><para>GCC 7.2.0: GLIBCXX_3.4.24, CXXABI_1.3.11</para></listitem> 339 </itemizedlist> 340 </listitem> 341 342 <listitem> 343 <para>Incremental bumping of a compiler pre-defined macro, 344 __GXX_ABI_VERSION. This macro is defined as the version of the 345 compiler v3 ABI, with g++ 3.0 being version 100. This macro will 346 be automatically defined whenever g++ is used (the curious can 347 test this by invoking g++ with the '-v' flag.) 348 </para> 349 350 <para> 351 This macro was defined in the file "lang-specs.h" in the gcc/cp directory. 352 Later versions defined it in "c-common.c" in the gcc directory, and from 353 G++ 3.4 it is defined in c-cppbuiltin.c and its value determined by the 354 '-fabi-version' command line option. 355 </para> 356 357 <para> 358 It is versioned as follows, where 'n' is given by '-fabi-version=n': 359 </para> 360 <itemizedlist> 361 <listitem><para>GCC 3.0: 100</para></listitem> 362 <listitem><para>GCC 3.1: 100 (Error, should be 101)</para></listitem> 363 <listitem><para>GCC 3.2: 102</para></listitem> 364 <listitem><para>GCC 3.3: 102</para></listitem> 365 <listitem><para>GCC 3.4, GCC 4.x: 102 (when n=1)</para></listitem> 366 <listitem><para>GCC 3.4, GCC 4.x: 1000 + n (when n>1) </para></listitem> 367 <listitem><para>GCC 3.4, GCC 4.x: 999999 (when n=0)</para></listitem> 368 </itemizedlist> 369 <para/> 370 </listitem> 371 372 <listitem> 373 <para>Changes to the default compiler option for 374 <code>-fabi-version</code>. 375 </para> 376 <para> 377 It is versioned as follows: 378 </para> 379 <itemizedlist> 380 <listitem><para>GCC 3.0: (Error, not versioned) </para></listitem> 381 <listitem><para>GCC 3.1: (Error, not versioned) </para></listitem> 382 <listitem><para>GCC 3.2: <code>-fabi-version=1</code></para></listitem> 383 <listitem><para>GCC 3.3: <code>-fabi-version=1</code></para></listitem> 384 <listitem><para>GCC 3.4, GCC 4.x: <code>-fabi-version=2</code> <emphasis>(Incompatible with previous)</emphasis></para></listitem> 385 <listitem><para>GCC 5 and higher: <code>-fabi-version=0</code> <emphasis>(See GCC manual for meaning)</emphasis></para></listitem> 386 </itemizedlist> 387 <para/> 388 </listitem> 389 390 <listitem xml:id="abi.versioning.__GLIBCXX__"> 391 <para>Incremental bumping of a library pre-defined macro. For releases 392 before 3.4.0, the macro is <symbol>__GLIBCPP__</symbol>. For later 393 releases, it's <symbol>__GLIBCXX__</symbol>. (The libstdc++ project 394 generously changed from CPP to CXX throughout its source to allow the 395 "C" pre-processor the CPP macro namespace.) These macros are defined 396 as the date the library was released, in compressed ISO date format, 397 as an integer constant. 398 </para> 399 400 <para> 401 This macro is defined in the file 402 <filename class="headerfile">c++config</filename> in the 403 <filename class="directory">libstdc++-v3/include/bits</filename> 404 directory. Up to GCC 4.1.0, it was 405 changed every night by an automated script. Since GCC 4.1.0 it is set 406 during configuration to the same value as 407 <filename>gcc/DATESTAMP</filename>, so for an official release its value 408 is the same as the date of the release, which is given in the <link 409 xmlns:xlink="http://www.w3.org/1999/xlink" 410 xlink:href="https://gcc.gnu.org/develop.html#timeline">GCC Release 411 Timeline</link>. 412 </para> 413 414 <para> 415 This macro can be used in code to detect whether the C++ Standard Library 416 implementation in use is libstdc++, but is not useful for detecting the 417 libstdc++ version, nor whether particular features are supported. 418 The macro value might be a date after a feature was added to the 419 development trunk, but the release could be from an older branch without 420 the feature. For example, in the 5.4.0 release the macro has the value 421 <literal>20160603</literal> which is greater than the 422 <literal>20160427</literal> value of the macro in the 6.1.0 release, 423 but there are features supported in the 6.1.0 release that are not 424 supported in 5.4.0 release. 425 You also can't test for the exact values listed below to try and 426 identify a release, because a snapshot taken from the gcc-5-branch on 427 2016-04-27 would have the same value for the macro as the 6.1.0 release 428 despite being a different version. 429 Many GNU/Linux distributions build their GCC packages from snapshots, so 430 the macro can have dates that don't correspond to official releases. 431 </para> 432 433 <para> 434 It is versioned as follows: 435 </para> 436 <itemizedlist> 437 <listitem><para>GCC 3.0.0: <literal>20010615</literal></para></listitem> 438 <listitem><para>GCC 3.0.1: <literal>20010819</literal></para></listitem> 439 <listitem><para>GCC 3.0.2: <literal>20011023</literal></para></listitem> 440 <listitem><para>GCC 3.0.3: <literal>20011220</literal></para></listitem> 441 <listitem><para>GCC 3.0.4: <literal>20020220</literal></para></listitem> 442 <listitem><para>GCC 3.1.0: <literal>20020514</literal></para></listitem> 443 <listitem><para>GCC 3.1.1: <literal>20020725</literal></para></listitem> 444 <listitem><para>GCC 3.2.0: <literal>20020814</literal></para></listitem> 445 <listitem><para>GCC 3.2.1: <literal>20021119</literal></para></listitem> 446 <listitem><para>GCC 3.2.2: <literal>20030205</literal></para></listitem> 447 <listitem><para>GCC 3.2.3: <literal>20030422</literal></para></listitem> 448 <listitem><para>GCC 3.3.0: <literal>20030513</literal></para></listitem> 449 <listitem><para>GCC 3.3.1: <literal>20030804</literal></para></listitem> 450 <listitem><para>GCC 3.3.2: <literal>20031016</literal></para></listitem> 451 <listitem><para>GCC 3.3.3: <literal>20040214</literal></para></listitem> 452 <listitem><para>GCC 3.4.0: <literal>20040419</literal></para></listitem> 453 <listitem><para>GCC 3.4.1: <literal>20040701</literal></para></listitem> 454 <listitem><para>GCC 3.4.2: <literal>20040906</literal></para></listitem> 455 <listitem><para>GCC 3.4.3: <literal>20041105</literal></para></listitem> 456 <listitem><para>GCC 3.4.4: <literal>20050519</literal></para></listitem> 457 <listitem><para>GCC 3.4.5: <literal>20051201</literal></para></listitem> 458 <listitem><para>GCC 3.4.6: <literal>20060306</literal></para></listitem> 459 <listitem><para>GCC 4.0.0: <literal>20050421</literal></para></listitem> 460 <listitem><para>GCC 4.0.1: <literal>20050707</literal></para></listitem> 461 <listitem><para>GCC 4.0.2: <literal>20050921</literal></para></listitem> 462 <listitem><para>GCC 4.0.3: <literal>20060309</literal></para></listitem> 463 <listitem><para> 464 GCC 4.1.0 and later: the GCC release date, as shown in the 465 <link xmlns:xlink="http://www.w3.org/1999/xlink" 466 xlink:href="https://gcc.gnu.org/develop.html#timeline">GCC 467 Release Timeline</link> 468 </para></listitem> 469 </itemizedlist> 470 <para/> 471 </listitem> 472 473 <listitem> 474 <para> 475 Since GCC 7, incremental bumping of a library pre-defined macro, 476 <symbol>_GLIBCXX_RELEASE</symbol>. This macro is defined to the GCC 477 major version that the libstdc++ headers belong to, as an integer constant. 478 When compiling with GCC it has the same value as GCC's pre-defined 479 macro <symbol>__GNUC__</symbol>. 480 This macro can be used when libstdc++ is used with a non-GNU 481 compiler where <symbol>__GNUC__</symbol> is not defined, or has a 482 different value that doesn't correspond to the libstdc++ version. 483 </para> 484 485 <para> 486 This macro is defined in the file 487 <filename class="headerfile">c++config</filename> in the 488 <filename class="directory">libstdc++-v3/include/bits</filename> 489 directory and is generated automatically by autoconf as part of the 490 configure-time generation of 491 <filename class="headerfile">config.h</filename> and subsequently 492 <filename class="headerfile"><bits/c++config.h></filename>. 493 </para> 494 </listitem> 495 496 <listitem> 497 <para> 498 Historically, incremental bumping of a library pre-defined macro, 499 <symbol>_GLIBCPP_VERSION</symbol>. This macro was defined as the 500 released version of the library, as a string literal. This was only 501 implemented in GCC 3.1.0 releases and higher, and was deprecated in 502 3.4.x (where it was called <symbol>_GLIBCXX_VERSION</symbol>), 503 and is not defined in 4.0.0 and higher. 504 </para> 505 506 <para> 507 This macro is defined in the same file as 508 <symbol>_GLIBCXX_RELEASE</symbol>, described above. 509 </para> 510 511 <para> 512 It is versioned as follows: 513 </para> 514 <itemizedlist> 515 <listitem><para>GCC 3.0.0: <literal>"3.0.0"</literal></para></listitem> 516 <listitem><para>GCC 3.0.1: <literal>"3.0.0"</literal> (Error, should be <literal>"3.0.1"</literal>)</para></listitem> 517 <listitem><para>GCC 3.0.2: <literal>"3.0.0"</literal> (Error, should be <literal>"3.0.2"</literal>)</para></listitem> 518 <listitem><para>GCC 3.0.3: <literal>"3.0.0"</literal> (Error, should be <literal>"3.0.3"</literal>)</para></listitem> 519 <listitem><para>GCC 3.0.4: <literal>"3.0.0"</literal> (Error, should be <literal>"3.0.4"</literal>)</para></listitem> 520 <listitem><para>GCC 3.1.0: <literal>"3.1.0"</literal></para></listitem> 521 <listitem><para>GCC 3.1.1: <literal>"3.1.1"</literal></para></listitem> 522 <listitem><para>GCC 3.2.0: <literal>"3.2"</literal></para></listitem> 523 <listitem><para>GCC 3.2.1: <literal>"3.2.1"</literal></para></listitem> 524 <listitem><para>GCC 3.2.2: <literal>"3.2.2"</literal></para></listitem> 525 <listitem><para>GCC 3.2.3: <literal>"3.2.3"</literal></para></listitem> 526 <listitem><para>GCC 3.3.0: <literal>"3.3"</literal></para></listitem> 527 <listitem><para>GCC 3.3.1: <literal>"3.3.1"</literal></para></listitem> 528 <listitem><para>GCC 3.3.2: <literal>"3.3.2"</literal></para></listitem> 529 <listitem><para>GCC 3.3.3: <literal>"3.3.3"</literal></para></listitem> 530 <listitem><para>GCC 3.4: <literal>"version-unused"</literal></para></listitem> 531 <listitem><para>GCC 4 and later: not defined</para></listitem> 532 </itemizedlist> 533 <para/> 534 </listitem> 535 536 <listitem> 537 <para> 538 Matching each specific C++ compiler release to a specific set of 539 C++ include files. This is only implemented in GCC 3.1.1 releases 540 and higher. 541 </para> 542 <para> 543 All C++ includes are installed in 544 <filename class="directory">include/c++</filename>, then nested in a 545 directory hierarchy corresponding to the C++ compiler's released 546 version. This version corresponds to the variable "gcc_version" in 547 "libstdc++-v3/acinclude.m4," and more details can be found in that 548 file's macro GLIBCXX_CONFIGURE (GLIBCPP_CONFIGURE before GCC 3.4.0). 549 </para> 550 <para> 551 C++ includes are versioned as follows: 552 </para> 553 <itemizedlist> 554 <listitem><para>GCC 3.0.0: include/g++-v3</para></listitem> 555 <listitem><para>GCC 3.0.1: include/g++-v3</para></listitem> 556 <listitem><para>GCC 3.0.2: include/g++-v3</para></listitem> 557 <listitem><para>GCC 3.0.3: include/g++-v3</para></listitem> 558 <listitem><para>GCC 3.0.4: include/g++-v3</para></listitem> 559 <listitem><para>GCC 3.1.0: include/g++-v3</para></listitem> 560 <listitem><para>GCC 3.1.1: include/c++/3.1.1</para></listitem> 561 <listitem><para>GCC 3.2.0: include/c++/3.2</para></listitem> 562 <listitem><para>GCC 3.2.1: include/c++/3.2.1</para></listitem> 563 <listitem><para>GCC 3.2.2: include/c++/3.2.2</para></listitem> 564 <listitem><para>GCC 3.2.3: include/c++/3.2.3</para></listitem> 565 <listitem><para>GCC 3.3.0: include/c++/3.3</para></listitem> 566 <listitem><para>GCC 3.3.1: include/c++/3.3.1</para></listitem> 567 <listitem><para>GCC 3.3.2: include/c++/3.3.2</para></listitem> 568 <listitem><para>GCC 3.3.3: include/c++/3.3.3</para></listitem> 569 <listitem><para>GCC 3.4.x: include/c++/3.4.x</para></listitem> 570 <listitem><para>GCC 4.x.y: include/c++/4.x.y</para></listitem> 571 <listitem><para>GCC 5.x.0: include/c++/5.x.0</para></listitem> 572 </itemizedlist> 573 <para/> 574 </listitem> 575 </orderedlist> 576 577<para> 578 Taken together, these techniques can accurately specify interface 579 and implementation changes in the GNU C++ tools themselves. Used 580 properly, they allow both the GNU C++ tools implementation, and 581 programs using them, an evolving yet controlled development that 582 maintains backward compatibility. 583</para> 584 585 586 </section> 587 588 <section xml:id="abi.versioning.prereq"><info><title>Prerequisites</title></info> 589 590 <para> 591 Minimum environment that supports a versioned ABI: A supported 592 dynamic linker, a GNU linker of sufficient vintage to understand 593 demangled C++ name globbing (ld) or the Sun linker, a shared 594 executable compiled 595 with g++, and shared libraries (libgcc_s, libstdc++) compiled by 596 a compiler (g++) with a compatible ABI. Phew. 597 </para> 598 599 <para> 600 On top of all that, an additional constraint: libstdc++ did not 601 attempt to version symbols (or age gracefully, really) until 602 version 3.1.0. 603 </para> 604 605 <para> 606 Most modern GNU/Linux and BSD versions, particularly ones using 607 GCC 3.1 and later, will meet the 608 requirements above, as does Solaris 2.5 and up. 609 </para> 610 </section> 611 612 <section xml:id="abi.versioning.config"><info><title>Configuring</title></info> 613 614 615 <para> 616 It turns out that most of the configure options that change 617 default behavior will impact the mangled names of exported 618 symbols, and thus impact versioning and compatibility. 619 </para> 620 621 <para> 622 For more information on configure options, including ABI 623 impacts, see: 624 <link linkend="manual.intro.setup.configure">here</link> 625 </para> 626 627 <para> 628 There is one flag that explicitly deals with symbol versioning: 629 --enable-symvers. 630 </para> 631 632 <para> 633 In particular, libstdc++-v3/acinclude.m4 has a macro called 634 GLIBCXX_ENABLE_SYMVERS that defaults to yes (or the argument 635 passed in via --enable-symvers=foo). At that point, the macro 636 attempts to make sure that all the requirement for symbol 637 versioning are in place. For more information, please consult 638 acinclude.m4. 639 </para> 640 </section> 641 642 <section xml:id="abi.versioning.active"><info><title>Checking Active</title></info> 643 644 645 <para> 646 When the GNU C++ library is being built with symbol versioning 647 on, you should see the following at configure time for 648 libstdc++ (showing either 'gnu' or another of the supported styles): 649 </para> 650 651<screen> 652<computeroutput> 653 checking versioning on shared library symbols... gnu 654</computeroutput> 655</screen> 656 657<para> 658 If you don't see this line in the configure output, or if this line 659 appears but the last word is 'no', then you are out of luck. 660</para> 661 662<para> 663 If the compiler is pre-installed, a quick way to test is to compile 664 the following (or any) simple C++ file and link it to the shared 665 libstdc++ library: 666</para> 667 668<programlisting> 669#include <iostream> 670 671int main() 672{ std::cout << "hello" << std::endl; return 0; } 673 674%g++ hello.cc -o hello.out 675 676%ldd hello.out 677 libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0x00764000) 678 libm.so.6 => /lib/tls/libm.so.6 (0x004a8000) 679 libgcc_s.so.1 => /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x40016000) 680 libc.so.6 => /lib/tls/libc.so.6 (0x0036d000) 681 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x00355000) 682 683%nm hello.out 684</programlisting> 685 686<para> 687If you see symbols in the resulting output with "GLIBCXX_3" as part 688of the name, then the executable is versioned. Here's an example: 689</para> 690 691<para> 692 <code>U _ZNSt8ios_base4InitC1Ev@@GLIBCXX_3.4</code> 693</para> 694 695<para> 696On Solaris 2, you can use <code>pvs -r</code> instead: 697</para> 698 699<programlisting> 700%g++ hello.cc -o hello.out 701 702%pvs -r hello.out 703 libstdc++.so.6 (GLIBCXX_3.4, GLIBCXX_3.4.12); 704 libgcc_s.so.1 (GCC_3.0); 705 libc.so.1 (SUNWprivate_1.1, SYSVABI_1.3); 706</programlisting> 707 708<para> 709<code>ldd -v</code> works too, but is very verbose. 710</para> 711 712 </section> 713</section> 714 715<section xml:id="abi.changes_allowed"><info><title>Allowed Changes</title></info> 716 717 718<para> 719The following will cause the library minor version number to 720increase, say from "libstdc++.so.3.0.4" to "libstdc++.so.3.0.5". 721</para> 722<orderedlist> 723 <listitem><para>Adding an exported global or static data member</para></listitem> 724 <listitem><para>Adding an exported function, static or non-virtual member function</para></listitem> 725 <listitem><para>Adding an exported symbol or symbols by additional instantiations</para></listitem> 726</orderedlist> 727<para> 728Other allowed changes are possible. 729</para> 730 731</section> 732 733<section xml:id="abi.changes_no"><info><title>Prohibited Changes</title></info> 734 735 736<para> 737The following non-exhaustive list will cause the library major version 738number to increase, say from "libstdc++.so.3.0.4" to 739"libstdc++.so.4.0.0". 740</para> 741 742<orderedlist> 743 <listitem><para>Changes in the gcc/g++ compiler ABI</para></listitem> 744<listitem><para>Changing size of an exported symbol</para></listitem> 745<listitem><para>Changing alignment of an exported symbol</para></listitem> 746<listitem><para>Changing the layout of an exported symbol</para></listitem> 747<listitem><para>Changing mangling on an exported symbol</para></listitem> 748<listitem><para>Deleting an exported symbol</para></listitem> 749<listitem><para>Changing the inheritance properties of a type by adding or removing 750 base classes</para></listitem> 751<listitem><para> 752 Changing the size, alignment, or layout of types 753 specified in the C++ standard. These may not necessarily be 754 instantiated or otherwise exported in the library binary, and 755 include all the required locale facets, as well as things like 756 std::basic_streambuf, et al. 757</para></listitem> 758 759<listitem><para> Adding an explicit copy constructor or destructor to a 760class that would otherwise have implicit versions. This will change 761the way the compiler deals with this class in by-value return 762statements or parameters: instead of passing instances of this 763class in registers, the compiler will be forced to use memory. See the 764section on <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://itanium-cxx-abi.github.io/cxx-abi/abi.html#calls">Function 765Calling Conventions and APIs</link> 766 of the C++ ABI documentation for further details. 767</para></listitem> 768 769</orderedlist> 770 771</section> 772 773 774 775<section xml:id="abi.impl"><info><title>Implementation</title></info> 776 777 778<orderedlist> 779 <listitem> 780 <para> 781 Separation of interface and implementation 782 </para> 783 <para> 784 This is accomplished by two techniques that separate the API from 785 the ABI: forcing undefined references to link against a library 786 binary for definitions. 787 </para> 788 789<variablelist> 790 <varlistentry> 791 <term>Include files have declarations, source files have defines</term> 792 793 <listitem> 794 <para> 795 For non-templatized types, such as much of <code>class 796 locale</code>, the appropriate standard C++ include, say 797 <code>locale</code>, can contain full declarations, while 798 various source files (say <code> locale.cc, locale_init.cc, 799 localename.cc</code>) contain definitions. 800 </para> 801 </listitem> 802 </varlistentry> 803 804 <varlistentry> 805 <term>Extern template on required types</term> 806 807 <listitem> 808 <para> 809 For parts of the standard that have an explicit list of 810 required instantiations, the GNU extension syntax <code> extern 811 template </code> can be used to control where template 812 definitions reside. By marking required instantiations as 813 <code> extern template </code> in include files, and providing 814 explicit instantiations in the appropriate instantiation files, 815 non-inlined template functions can be versioned. This technique 816 is mostly used on parts of the standard that require <code> 817 char</code> and <code> wchar_t</code> instantiations, and 818 includes <code> basic_string</code>, the locale facets, and the 819 types in <code> iostreams</code>. 820 </para> 821 </listitem> 822 </varlistentry> 823 824 </variablelist> 825 826 <para> 827 In addition, these techniques have the additional benefit that they 828 reduce binary size, which can increase runtime performance. 829 </para> 830 </listitem> 831 832 <listitem> 833 <para> 834 Namespaces linking symbol definitions to export mapfiles 835 </para> 836 <para> 837 All symbols in the shared library binary are processed by a 838 linker script at build time that either allows or disallows 839 external linkage. Because of this, some symbols, regardless of 840 normal C/C++ linkage, are not visible. Symbols that are internal 841 have several appealing characteristics: by not exporting the 842 symbols, there are no relocations when the shared library is 843 started and thus this makes for faster runtime loading 844 performance by the underlying dynamic loading mechanism. In 845 addition, they have the possibility of changing without impacting 846 ABI compatibility. 847 </para> 848 849<para>The following namespaces are transformed by the mapfile:</para> 850 851<variablelist> 852 853 <varlistentry> 854<term><code>namespace std</code></term> 855<listitem><para> Defaults to exporting all symbols in label 856<code>GLIBCXX</code> that do not begin with an underscore, i.e., 857<code>__test_func</code> would not be exported by default. Select 858exceptional symbols are allowed to be visible.</para></listitem> 859 </varlistentry> 860 861 <varlistentry> 862<term><code>namespace __gnu_cxx</code></term> 863<listitem><para> Defaults to not exporting any symbols in label 864<code>GLIBCXX</code>, select items are allowed to be visible.</para></listitem> 865 </varlistentry> 866 867 <varlistentry> 868<term><code>namespace __gnu_internal</code></term> 869<listitem><para> Defaults to not exported, no items are allowed to be visible.</para></listitem> 870 </varlistentry> 871 872 <varlistentry> 873<term><code>namespace __cxxabiv1</code>, aliased to <code> namespace abi</code></term> 874<listitem><para> Defaults to not exporting any symbols in label 875<code>CXXABI</code>, select items are allowed to be visible.</para></listitem> 876 </varlistentry> 877 878</variablelist> 879<para> 880</para> 881</listitem> 882 883 <listitem><para>Freezing the API</para> 884 <para>Disallowed changes, as above, are not made on a stable release 885branch. Enforcement tends to be less strict with GNU extensions that 886standard includes.</para> 887</listitem> 888</orderedlist> 889 890</section> 891 892<section xml:id="abi.testing"><info><title>Testing</title></info> 893 894 895 <section xml:id="abi.testing.single"><info><title>Single ABI Testing</title></info> 896 897 898 <para> 899 Testing for GNU C++ ABI changes is composed of two distinct 900 areas: testing the C++ compiler (g++) for compiler changes, and 901 testing the C++ library (libstdc++) for library changes. 902 </para> 903 904 <para> 905 Testing the C++ compiler ABI can be done various ways. 906 </para> 907 908 <para> 909 One. Intel ABI checker. 910 </para> 911 912<para> 913Two. 914The second is yet unreleased, but has been announced on the gcc 915mailing list. It is yet unspecified if these tools will be freely 916available, and able to be included in a GNU project. Please contact 917Mark Mitchell (mark@codesourcery.com) for more details, and current 918status. 919</para> 920 921<para> 922Three. 923Involves using the vlad.consistency test framework. This has also been 924discussed on the gcc mailing lists. 925</para> 926 927<para> 928Testing the C++ library ABI can also be done various ways. 929</para> 930 931<para> 932One. 933(Brendan Kehoe, Jeff Law suggestion to run 'make check-c++' two ways, 934one with a new compiler and an old library, and the other with an old 935compiler and a new library, and look for testsuite regressions) 936</para> 937 938<para> 939Details on how to set this kind of test up can be found here: 940http://gcc.gnu.org/ml/gcc/2002-08/msg00142.html 941</para> 942 943<para> 944Two. 945Use the 'make check-abi' rule in the libstdc++ Makefile. 946</para> 947 948<para> 949This is a proactive check of the library ABI. Currently, exported symbol 950names that are either weak or defined are checked against a last known 951good baseline. Currently, this baseline is keyed off of 3.4.0 952binaries, as this was the last time the .so number was incremented. In 953addition, all exported names are demangled, and the exported objects 954are checked to make sure they are the same size as the same object in 955the baseline. 956 957Notice that each baseline is relative to a <emphasis>default</emphasis> 958configured library and compiler: in particular, if options such as 959--enable-clocale, or --with-cpu, in case of multilibs, are used at 960configure time, the check may fail, either because of substantive 961differences or because of limitations of the current checking 962machinery. 963</para> 964 965<para> 966This dataset is insufficient, yet a start. Also needed is a 967comprehensive check for all user-visible types part of the standard 968library for sizeof() and alignof() changes. 969</para> 970 971<para> 972Verifying compatible layouts of objects is not even attempted. It 973should be possible to use sizeof, alignof, and offsetof to compute 974offsets for each structure and type in the standard library, saving to 975another datafile. Then, compute this in a similar way for new 976binaries, and look for differences. 977</para> 978 979<para> 980Another approach might be to use the -fdump-class-hierarchy flag to 981get information. However, currently this approach gives insufficient 982data for use in library testing, as class data members, their offsets, 983and other detailed data is not displayed with this flag. 984(See PR g++/7470 on how this was used to find bugs.) 985</para> 986 987<para> 988Perhaps there are other C++ ABI checkers. If so, please notify 989us. We'd like to know about them! 990</para> 991 992 </section> 993 <section xml:id="abi.testing.multi"><info><title>Multiple ABI Testing</title></info> 994 995<para> 996A "C" application, dynamically linked to two shared libraries, liba, 997libb. The dependent library liba is a C++ shared library compiled with 998GCC 3.3, and uses io, exceptions, locale, etc. The dependent library 999libb is a C++ shared library compiled with GCC 3.4, and also uses io, 1000exceptions, locale, etc. 1001</para> 1002 1003<para> As above, libone is constructed as follows: </para> 1004<programlisting> 1005%$bld/H-x86-gcc-3.4.0/bin/g++ -fPIC -DPIC -c a.cc 1006 1007%$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 1008 1009%ln -s libone.so.1.0.0 libone.so 1010 1011%$bld/H-x86-gcc-3.4.0/bin/g++ -c a.cc 1012 1013%ar cru libone.a a.o 1014</programlisting> 1015 1016<para> And, libtwo is constructed as follows: </para> 1017 1018<programlisting> 1019%$bld/H-x86-gcc-3.3.3/bin/g++ -fPIC -DPIC -c b.cc 1020 1021%$bld/H-x86-gcc-3.3.3/bin/g++ -shared -Wl,-soname -Wl,libtwo.so.1 -Wl,-O1 -Wl,-z,defs b.o -o libtwo.so.1.0.0 1022 1023%ln -s libtwo.so.1.0.0 libtwo.so 1024 1025%$bld/H-x86-gcc-3.3.3/bin/g++ -c b.cc 1026 1027%ar cru libtwo.a b.o 1028</programlisting> 1029 1030<para> ...with the resulting libraries looking like </para> 1031 1032<screen> 1033<computeroutput> 1034%ldd libone.so.1.0.0 1035 libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x40016000) 1036 libm.so.6 => /lib/tls/libm.so.6 (0x400fa000) 1037 libgcc_s.so.1 => /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x4011c000) 1038 libc.so.6 => /lib/tls/libc.so.6 (0x40125000) 1039 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x00355000) 1040 1041%ldd libtwo.so.1.0.0 1042 libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0x40027000) 1043 libm.so.6 => /lib/tls/libm.so.6 (0x400e1000) 1044 libgcc_s.so.1 => /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x40103000) 1045 libc.so.6 => /lib/tls/libc.so.6 (0x4010c000) 1046 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x00355000) 1047</computeroutput> 1048</screen> 1049 1050<para> 1051 Then, the "C" compiler is used to compile a source file that uses 1052 functions from each library. 1053</para> 1054<programlisting> 1055gcc test.c -g -O2 -L. -lone -ltwo /usr/lib/libstdc++.so.5 /usr/lib/libstdc++.so.6 1056</programlisting> 1057 1058<para> 1059 Which gives the expected: 1060</para> 1061 1062<screen> 1063<computeroutput> 1064%ldd a.out 1065 libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0x00764000) 1066 libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x40015000) 1067 libc.so.6 => /lib/tls/libc.so.6 (0x0036d000) 1068 libm.so.6 => /lib/tls/libm.so.6 (0x004a8000) 1069 libgcc_s.so.1 => /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x400e5000) 1070 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x00355000) 1071</computeroutput> 1072</screen> 1073 1074<para> 1075 This resulting binary, when executed, will be able to safely use 1076 code from both liba, and the dependent libstdc++.so.6, and libb, 1077 with the dependent libstdc++.so.5. 1078</para> 1079 </section> 1080</section> 1081 1082<section xml:id="abi.issues"><info><title>Outstanding Issues</title></info> 1083 1084 1085<para> 1086 Some features in the C++ language make versioning especially 1087 difficult. In particular, compiler generated constructs such as 1088 implicit instantiations for templates, typeinfo information, and 1089 virtual tables all may cause ABI leakage across shared library 1090 boundaries. Because of this, mixing C++ ABIs is not recommended at 1091 this time. 1092</para> 1093 1094<para> 1095 For more background on this issue, see these bugzilla entries: 1096</para> 1097 1098<para> 1099<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://gcc.gnu.org/PR24660">24660: versioning weak symbols in libstdc++</link> 1100</para> 1101 1102<para> 1103<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://gcc.gnu.org/PR19664">19664: libstdc++ headers should have pop/push of the visibility around the declarations</link> 1104</para> 1105 1106</section> 1107 1108<bibliography xml:id="abi.biblio"><info><title>Bibliography</title></info> 1109 1110 <biblioentry xml:id="biblio.abicheck"> 1111 <title> 1112 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1113 xlink:href="http://abicheck.sourceforge.net"> 1114 ABIcheck 1115 </link> 1116 </title> 1117 </biblioentry> 1118 1119 <biblioentry xml:id="biblio.cxxabi"> 1120 <title> 1121 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1122 xlink:href="https://itanium-cxx-abi.github.io/cxx-abi/"> 1123 Itanium C++ ABI 1124 </link> 1125 </title> 1126 </biblioentry> 1127 1128 1129 <biblioentry> 1130 <title> 1131 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1132 xlink:href="https://software.intel.com/en-us/articles/intel-compilers-for-linux-compatibility-with-gnu-compilers"> 1133 Intel Compilers for Linux: Compatibility with GNU Compilers 1134 </link> 1135 </title> 1136 </biblioentry> 1137 1138 <biblioentry> 1139 <title> 1140 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1141 xlink:href="http://docs.oracle.com/cd/E23824_01/html/819-0690/index.html"> 1142 Linker and Libraries Guide (document 819-0690) 1143 </link> 1144 </title> 1145 </biblioentry> 1146 1147 1148 <biblioentry> 1149 <title> 1150 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1151 xlink:href="http://docs.oracle.com/cd/E19422-01/819-3689/"> 1152 Sun Studio 11: C++ Migration Guide (document 819-3689) 1153 </link> 1154 </title> 1155 </biblioentry> 1156 1157 <biblioentry> 1158 <title> 1159 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1160 xlink:href="https://www.akkadia.org/drepper/dsohowto.pdf"> 1161 How to Write Shared Libraries 1162 </link> 1163 </title> 1164 1165 <author> 1166 <personname> 1167 <firstname>Ulrich</firstname><surname>Drepper</surname> 1168 </personname> 1169 </author> 1170 </biblioentry> 1171 1172 <biblioentry> 1173 <title> 1174 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1175 xlink:href="http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ihi0036b/index.html"> 1176 C++ ABI for the ARM Architecture 1177 </link> 1178 </title> 1179 </biblioentry> 1180 1181 <biblioentry> 1182 <title> 1183 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1184 xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1976.html"> 1185 Dynamic Shared Objects: Survey and Issues 1186 </link> 1187 </title> 1188 1189 <subtitle> 1190 ISO C++ J16/06-0046 1191 </subtitle> 1192 <author><personname><firstname>Benjamin</firstname><surname>Kosnik</surname></personname></author> 1193 </biblioentry> 1194 1195 <biblioentry> 1196 <title> 1197 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1198 xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2013.html"> 1199 Versioning With Namespaces 1200 </link> 1201 </title> 1202 <subtitle> 1203 ISO C++ J16/06-0083 1204 </subtitle> 1205 <author><personname><firstname>Benjamin</firstname><surname>Kosnik</surname></personname></author> 1206 </biblioentry> 1207 1208 <biblioentry> 1209 <title> 1210 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1211 xlink:href="http://syrcose.ispras.ru/2009/files/02_paper.pdf"> 1212 Binary Compatibility of Shared Libraries Implemented in C++ 1213 on GNU/Linux Systems 1214 </link> 1215 </title> 1216 1217 <subtitle> 1218 SYRCoSE 2009 1219 </subtitle> 1220 <author><personname><firstname>Pavel</firstname><surname>Shved</surname></personname></author> 1221 <author><personname><firstname>Denis</firstname><surname>Silakov</surname></personname></author> 1222 </biblioentry> 1223</bibliography> 1224 1225</section> 1226