abi.xml revision 1.10
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 <listitem><para>GCC 8.0.0: libstdc++.so.6.0.25</para></listitem> 271 </itemizedlist> 272 <para> 273 Note 1: Error should be libstdc++.so.3.0.3. 274 </para> 275 <para> 276 Note 2: Not strictly required. 277 </para> 278 <para> 279 Note 3: This release (but not previous or subsequent) has one 280 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> 281 in the GCC bug database. 282 </para> 283 </listitem> 284 285 <listitem><para>Symbol versioning on the libstdc++.so binary.</para> 286 287 <para>mapfile: libstdc++-v3/config/abi/pre/gnu.ver</para> 288 <para>It is versioned with the following labels and version 289 definitions, where the version definition is the maximum for a 290 particular release. Note, only symbols which are newly introduced 291 will use the maximum version definition. Thus, for release series 292 with the same label, but incremented version definitions, the later 293 release has both versions. (An example of this would be the 294 GCC 3.2.1 release, which has GLIBCPP_3.2.1 for new symbols and 295 GLIBCPP_3.2 for symbols that were introduced in the GCC 3.2.0 296 release.) If a particular release is not listed, it has the same 297 version labels as the preceding release. 298 </para> 299 <itemizedlist> 300 <listitem><para>GCC 3.0.0: (Error, not versioned)</para></listitem> 301 <listitem><para>GCC 3.0.1: (Error, not versioned)</para></listitem> 302 <listitem><para>GCC 3.0.2: (Error, not versioned)</para></listitem> 303 <listitem><para>GCC 3.0.3: (Error, not versioned)</para></listitem> 304 <listitem><para>GCC 3.0.4: (Error, not versioned)</para></listitem> 305 <listitem><para>GCC 3.1.0: GLIBCPP_3.1, CXXABI_1</para></listitem> 306 <listitem><para>GCC 3.1.1: GLIBCPP_3.1, CXXABI_1</para></listitem> 307 <listitem><para>GCC 3.2.0: GLIBCPP_3.2, CXXABI_1.2</para></listitem> 308 <listitem><para>GCC 3.2.1: GLIBCPP_3.2.1, CXXABI_1.2</para></listitem> 309 <listitem><para>GCC 3.2.2: GLIBCPP_3.2.2, CXXABI_1.2</para></listitem> 310 <listitem><para>GCC 3.2.3: GLIBCPP_3.2.2, CXXABI_1.2</para></listitem> 311 <listitem><para>GCC 3.3.0: GLIBCPP_3.2.2, CXXABI_1.2.1</para></listitem> 312 <listitem><para>GCC 3.3.1: GLIBCPP_3.2.3, CXXABI_1.2.1</para></listitem> 313 <listitem><para>GCC 3.3.2: GLIBCPP_3.2.3, CXXABI_1.2.1</para></listitem> 314 <listitem><para>GCC 3.3.3: GLIBCPP_3.2.3, CXXABI_1.2.1</para></listitem> 315 <listitem><para>GCC 3.4.0: GLIBCXX_3.4, CXXABI_1.3</para></listitem> 316 <listitem><para>GCC 3.4.1: GLIBCXX_3.4.1, CXXABI_1.3</para></listitem> 317 <listitem><para>GCC 3.4.2: GLIBCXX_3.4.2</para></listitem> 318 <listitem><para>GCC 3.4.3: GLIBCXX_3.4.3</para></listitem> 319 <listitem><para>GCC 4.0.0: GLIBCXX_3.4.4, CXXABI_1.3.1</para></listitem> 320 <listitem><para>GCC 4.0.1: GLIBCXX_3.4.5</para></listitem> 321 <listitem><para>GCC 4.0.2: GLIBCXX_3.4.6</para></listitem> 322 <listitem><para>GCC 4.0.3: GLIBCXX_3.4.7</para></listitem> 323 <listitem><para>GCC 4.1.1: GLIBCXX_3.4.8</para></listitem> 324 <listitem><para>GCC 4.2.0: GLIBCXX_3.4.9</para></listitem> 325 <listitem><para>GCC 4.3.0: GLIBCXX_3.4.10, CXXABI_1.3.2</para></listitem> 326 <listitem><para>GCC 4.4.0: GLIBCXX_3.4.11, CXXABI_1.3.3</para></listitem> 327 <listitem><para>GCC 4.4.1: GLIBCXX_3.4.12, CXXABI_1.3.3</para></listitem> 328 <listitem><para>GCC 4.4.2: GLIBCXX_3.4.13, CXXABI_1.3.3</para></listitem> 329 <listitem><para>GCC 4.5.0: GLIBCXX_3.4.14, CXXABI_1.3.4</para></listitem> 330 <listitem><para>GCC 4.6.0: GLIBCXX_3.4.15, CXXABI_1.3.5</para></listitem> 331 <listitem><para>GCC 4.6.1: GLIBCXX_3.4.16, CXXABI_1.3.5</para></listitem> 332 <listitem><para>GCC 4.7.0: GLIBCXX_3.4.17, CXXABI_1.3.6</para></listitem> 333 <listitem><para>GCC 4.8.0: GLIBCXX_3.4.18, CXXABI_1.3.7</para></listitem> 334 <listitem><para>GCC 4.8.3: GLIBCXX_3.4.19, CXXABI_1.3.7</para></listitem> 335 <listitem><para>GCC 4.9.0: GLIBCXX_3.4.20, CXXABI_1.3.8</para></listitem> 336 <listitem><para>GCC 5.1.0: GLIBCXX_3.4.21, CXXABI_1.3.9</para></listitem> 337 <listitem><para>GCC 6.1.0: GLIBCXX_3.4.22, CXXABI_1.3.10</para></listitem> 338 <listitem><para>GCC 7.1.0: GLIBCXX_3.4.23, CXXABI_1.3.11</para></listitem> 339 <listitem><para>GCC 7.2.0: GLIBCXX_3.4.24, CXXABI_1.3.11</para></listitem> 340 <listitem><para>GCC 8.0.0: GLIBCXX_3.4.25, CXXABI_1.3.11</para></listitem> 341 </itemizedlist> 342 </listitem> 343 344 <listitem> 345 <para>Incremental bumping of a compiler pre-defined macro, 346 __GXX_ABI_VERSION. This macro is defined as the version of the 347 compiler v3 ABI, with g++ 3.0 being version 100. This macro will 348 be automatically defined whenever g++ is used (the curious can 349 test this by invoking g++ with the '-v' flag.) 350 </para> 351 352 <para> 353 This macro was defined in the file "lang-specs.h" in the gcc/cp directory. 354 Later versions defined it in "c-common.c" in the gcc directory, and from 355 G++ 3.4 it is defined in c-cppbuiltin.c and its value determined by the 356 '-fabi-version' command line option. 357 </para> 358 359 <para> 360 It is versioned as follows, where 'n' is given by '-fabi-version=n': 361 </para> 362 <itemizedlist> 363 <listitem><para>GCC 3.0: 100</para></listitem> 364 <listitem><para>GCC 3.1: 100 (Error, should be 101)</para></listitem> 365 <listitem><para>GCC 3.2: 102</para></listitem> 366 <listitem><para>GCC 3.3: 102</para></listitem> 367 <listitem><para>GCC 3.4, GCC 4.x: 102 (when n=1)</para></listitem> 368 <listitem><para>GCC 3.4, GCC 4.x: 1000 + n (when n>1) </para></listitem> 369 <listitem><para>GCC 3.4, GCC 4.x: 999999 (when n=0)</para></listitem> 370 </itemizedlist> 371 <para/> 372 </listitem> 373 374 <listitem> 375 <para>Changes to the default compiler option for 376 <code>-fabi-version</code>. 377 </para> 378 <para> 379 It is versioned as follows: 380 </para> 381 <itemizedlist> 382 <listitem><para>GCC 3.0: (Error, not versioned) </para></listitem> 383 <listitem><para>GCC 3.1: (Error, not versioned) </para></listitem> 384 <listitem><para>GCC 3.2: <code>-fabi-version=1</code></para></listitem> 385 <listitem><para>GCC 3.3: <code>-fabi-version=1</code></para></listitem> 386 <listitem><para>GCC 3.4, GCC 4.x: <code>-fabi-version=2</code> <emphasis>(Incompatible with previous)</emphasis></para></listitem> 387 <listitem><para>GCC 5 and higher: <code>-fabi-version=0</code> <emphasis>(See GCC manual for meaning)</emphasis></para></listitem> 388 </itemizedlist> 389 <para/> 390 </listitem> 391 392 <listitem xml:id="abi.versioning.__GLIBCXX__"> 393 <para>Incremental bumping of a library pre-defined macro. For releases 394 before 3.4.0, the macro is <symbol>__GLIBCPP__</symbol>. For later 395 releases, it's <symbol>__GLIBCXX__</symbol>. (The libstdc++ project 396 generously changed from CPP to CXX throughout its source to allow the 397 "C" pre-processor the CPP macro namespace.) These macros are defined 398 as the date the library was released, in compressed ISO date format, 399 as an integer constant. 400 </para> 401 402 <para> 403 This macro is defined in the file 404 <filename class="headerfile">c++config</filename> in the 405 <filename class="directory">libstdc++-v3/include/bits</filename> 406 directory. Up to GCC 4.1.0, it was 407 changed every night by an automated script. Since GCC 4.1.0 it is set 408 during configuration to the same value as 409 <filename>gcc/DATESTAMP</filename>, so for an official release its value 410 is the same as the date of the release, which is given in the <link 411 xmlns:xlink="http://www.w3.org/1999/xlink" 412 xlink:href="https://gcc.gnu.org/develop.html#timeline">GCC Release 413 Timeline</link>. 414 </para> 415 416 <para> 417 This macro can be used in code to detect whether the C++ Standard Library 418 implementation in use is libstdc++, but is not useful for detecting the 419 libstdc++ version, nor whether particular features are supported. 420 The macro value might be a date after a feature was added to the 421 development trunk, but the release could be from an older branch without 422 the feature. For example, in the 5.4.0 release the macro has the value 423 <literal>20160603</literal> which is greater than the 424 <literal>20160427</literal> value of the macro in the 6.1.0 release, 425 but there are features supported in the 6.1.0 release that are not 426 supported in 5.4.0 release. 427 You also can't test for the exact values listed below to try and 428 identify a release, because a snapshot taken from the gcc-5-branch on 429 2016-04-27 would have the same value for the macro as the 6.1.0 release 430 despite being a different version. 431 Many GNU/Linux distributions build their GCC packages from snapshots, so 432 the macro can have dates that don't correspond to official releases. 433 </para> 434 435 <para> 436 It is versioned as follows: 437 </para> 438 <itemizedlist> 439 <listitem><para>GCC 3.0.0: <literal>20010615</literal></para></listitem> 440 <listitem><para>GCC 3.0.1: <literal>20010819</literal></para></listitem> 441 <listitem><para>GCC 3.0.2: <literal>20011023</literal></para></listitem> 442 <listitem><para>GCC 3.0.3: <literal>20011220</literal></para></listitem> 443 <listitem><para>GCC 3.0.4: <literal>20020220</literal></para></listitem> 444 <listitem><para>GCC 3.1.0: <literal>20020514</literal></para></listitem> 445 <listitem><para>GCC 3.1.1: <literal>20020725</literal></para></listitem> 446 <listitem><para>GCC 3.2.0: <literal>20020814</literal></para></listitem> 447 <listitem><para>GCC 3.2.1: <literal>20021119</literal></para></listitem> 448 <listitem><para>GCC 3.2.2: <literal>20030205</literal></para></listitem> 449 <listitem><para>GCC 3.2.3: <literal>20030422</literal></para></listitem> 450 <listitem><para>GCC 3.3.0: <literal>20030513</literal></para></listitem> 451 <listitem><para>GCC 3.3.1: <literal>20030804</literal></para></listitem> 452 <listitem><para>GCC 3.3.2: <literal>20031016</literal></para></listitem> 453 <listitem><para>GCC 3.3.3: <literal>20040214</literal></para></listitem> 454 <listitem><para>GCC 3.4.0: <literal>20040419</literal></para></listitem> 455 <listitem><para>GCC 3.4.1: <literal>20040701</literal></para></listitem> 456 <listitem><para>GCC 3.4.2: <literal>20040906</literal></para></listitem> 457 <listitem><para>GCC 3.4.3: <literal>20041105</literal></para></listitem> 458 <listitem><para>GCC 3.4.4: <literal>20050519</literal></para></listitem> 459 <listitem><para>GCC 3.4.5: <literal>20051201</literal></para></listitem> 460 <listitem><para>GCC 3.4.6: <literal>20060306</literal></para></listitem> 461 <listitem><para>GCC 4.0.0: <literal>20050421</literal></para></listitem> 462 <listitem><para>GCC 4.0.1: <literal>20050707</literal></para></listitem> 463 <listitem><para>GCC 4.0.2: <literal>20050921</literal></para></listitem> 464 <listitem><para>GCC 4.0.3: <literal>20060309</literal></para></listitem> 465 <listitem><para> 466 GCC 4.1.0 and later: the GCC release date, as shown in the 467 <link xmlns:xlink="http://www.w3.org/1999/xlink" 468 xlink:href="https://gcc.gnu.org/develop.html#timeline">GCC 469 Release Timeline</link> 470 </para></listitem> 471 </itemizedlist> 472 <para/> 473 </listitem> 474 475 <listitem> 476 <para> 477 Since GCC 7, incremental bumping of a library pre-defined macro, 478 <symbol>_GLIBCXX_RELEASE</symbol>. This macro is defined to the GCC 479 major version that the libstdc++ headers belong to, as an integer constant. 480 When compiling with GCC it has the same value as GCC's pre-defined 481 macro <symbol>__GNUC__</symbol>. 482 This macro can be used when libstdc++ is used with a non-GNU 483 compiler where <symbol>__GNUC__</symbol> is not defined, or has a 484 different value that doesn't correspond to the libstdc++ version. 485 </para> 486 487 <para> 488 This macro is defined in the file 489 <filename class="headerfile">c++config</filename> in the 490 <filename class="directory">libstdc++-v3/include/bits</filename> 491 directory and is generated automatically by autoconf as part of the 492 configure-time generation of 493 <filename class="headerfile">config.h</filename> and subsequently 494 <filename class="headerfile"><bits/c++config.h></filename>. 495 </para> 496 </listitem> 497 498 <listitem> 499 <para> 500 Historically, incremental bumping of a library pre-defined macro, 501 <symbol>_GLIBCPP_VERSION</symbol>. This macro was defined as the 502 released version of the library, as a string literal. This was only 503 implemented in GCC 3.1.0 releases and higher, and was deprecated in 504 3.4.x (where it was called <symbol>_GLIBCXX_VERSION</symbol>), 505 and is not defined in 4.0.0 and higher. 506 </para> 507 508 <para> 509 This macro is defined in the same file as 510 <symbol>_GLIBCXX_RELEASE</symbol>, described above. 511 </para> 512 513 <para> 514 It is versioned as follows: 515 </para> 516 <itemizedlist> 517 <listitem><para>GCC 3.0.0: <literal>"3.0.0"</literal></para></listitem> 518 <listitem><para>GCC 3.0.1: <literal>"3.0.0"</literal> (Error, should be <literal>"3.0.1"</literal>)</para></listitem> 519 <listitem><para>GCC 3.0.2: <literal>"3.0.0"</literal> (Error, should be <literal>"3.0.2"</literal>)</para></listitem> 520 <listitem><para>GCC 3.0.3: <literal>"3.0.0"</literal> (Error, should be <literal>"3.0.3"</literal>)</para></listitem> 521 <listitem><para>GCC 3.0.4: <literal>"3.0.0"</literal> (Error, should be <literal>"3.0.4"</literal>)</para></listitem> 522 <listitem><para>GCC 3.1.0: <literal>"3.1.0"</literal></para></listitem> 523 <listitem><para>GCC 3.1.1: <literal>"3.1.1"</literal></para></listitem> 524 <listitem><para>GCC 3.2.0: <literal>"3.2"</literal></para></listitem> 525 <listitem><para>GCC 3.2.1: <literal>"3.2.1"</literal></para></listitem> 526 <listitem><para>GCC 3.2.2: <literal>"3.2.2"</literal></para></listitem> 527 <listitem><para>GCC 3.2.3: <literal>"3.2.3"</literal></para></listitem> 528 <listitem><para>GCC 3.3.0: <literal>"3.3"</literal></para></listitem> 529 <listitem><para>GCC 3.3.1: <literal>"3.3.1"</literal></para></listitem> 530 <listitem><para>GCC 3.3.2: <literal>"3.3.2"</literal></para></listitem> 531 <listitem><para>GCC 3.3.3: <literal>"3.3.3"</literal></para></listitem> 532 <listitem><para>GCC 3.4: <literal>"version-unused"</literal></para></listitem> 533 <listitem><para>GCC 4 and later: not defined</para></listitem> 534 </itemizedlist> 535 <para/> 536 </listitem> 537 538 <listitem> 539 <para> 540 Matching each specific C++ compiler release to a specific set of 541 C++ include files. This is only implemented in GCC 3.1.1 releases 542 and higher. 543 </para> 544 <para> 545 All C++ includes are installed in 546 <filename class="directory">include/c++</filename>, then nested in a 547 directory hierarchy corresponding to the C++ compiler's released 548 version. This version corresponds to the variable "gcc_version" in 549 "libstdc++-v3/acinclude.m4," and more details can be found in that 550 file's macro GLIBCXX_CONFIGURE (GLIBCPP_CONFIGURE before GCC 3.4.0). 551 </para> 552 <para> 553 C++ includes are versioned as follows: 554 </para> 555 <itemizedlist> 556 <listitem><para>GCC 3.0.0: include/g++-v3</para></listitem> 557 <listitem><para>GCC 3.0.1: include/g++-v3</para></listitem> 558 <listitem><para>GCC 3.0.2: include/g++-v3</para></listitem> 559 <listitem><para>GCC 3.0.3: include/g++-v3</para></listitem> 560 <listitem><para>GCC 3.0.4: include/g++-v3</para></listitem> 561 <listitem><para>GCC 3.1.0: include/g++-v3</para></listitem> 562 <listitem><para>GCC 3.1.1: include/c++/3.1.1</para></listitem> 563 <listitem><para>GCC 3.2.0: include/c++/3.2</para></listitem> 564 <listitem><para>GCC 3.2.1: include/c++/3.2.1</para></listitem> 565 <listitem><para>GCC 3.2.2: include/c++/3.2.2</para></listitem> 566 <listitem><para>GCC 3.2.3: include/c++/3.2.3</para></listitem> 567 <listitem><para>GCC 3.3.0: include/c++/3.3</para></listitem> 568 <listitem><para>GCC 3.3.1: include/c++/3.3.1</para></listitem> 569 <listitem><para>GCC 3.3.2: include/c++/3.3.2</para></listitem> 570 <listitem><para>GCC 3.3.3: include/c++/3.3.3</para></listitem> 571 <listitem><para>GCC 3.4.x: include/c++/3.4.x</para></listitem> 572 <listitem><para>GCC 4.x.y: include/c++/4.x.y</para></listitem> 573 <listitem><para>GCC 5.x.0: include/c++/5.x.0</para></listitem> 574 <listitem><para>GCC 6.x.0: include/c++/6.x.0</para></listitem> 575 <listitem><para>GCC 7.x.0: include/c++/7.x.0</para></listitem> 576 <listitem><para>GCC 8.x.0: include/c++/8.x.0</para></listitem> 577 </itemizedlist> 578 <para/> 579 </listitem> 580 </orderedlist> 581 582<para> 583 Taken together, these techniques can accurately specify interface 584 and implementation changes in the GNU C++ tools themselves. Used 585 properly, they allow both the GNU C++ tools implementation, and 586 programs using them, an evolving yet controlled development that 587 maintains backward compatibility. 588</para> 589 590 591 </section> 592 593 <section xml:id="abi.versioning.prereq"><info><title>Prerequisites</title></info> 594 595 <para> 596 Minimum environment that supports a versioned ABI: A supported 597 dynamic linker, a GNU linker of sufficient vintage to understand 598 demangled C++ name globbing (ld) or the Sun linker, a shared 599 executable compiled 600 with g++, and shared libraries (libgcc_s, libstdc++) compiled by 601 a compiler (g++) with a compatible ABI. Phew. 602 </para> 603 604 <para> 605 On top of all that, an additional constraint: libstdc++ did not 606 attempt to version symbols (or age gracefully, really) until 607 version 3.1.0. 608 </para> 609 610 <para> 611 Most modern GNU/Linux and BSD versions, particularly ones using 612 GCC 3.1 and later, will meet the 613 requirements above, as does Solaris 2.5 and up. 614 </para> 615 </section> 616 617 <section xml:id="abi.versioning.config"><info><title>Configuring</title></info> 618 619 620 <para> 621 It turns out that most of the configure options that change 622 default behavior will impact the mangled names of exported 623 symbols, and thus impact versioning and compatibility. 624 </para> 625 626 <para> 627 For more information on configure options, including ABI 628 impacts, see: 629 <link linkend="manual.intro.setup.configure">here</link> 630 </para> 631 632 <para> 633 There is one flag that explicitly deals with symbol versioning: 634 --enable-symvers. 635 </para> 636 637 <para> 638 In particular, libstdc++-v3/acinclude.m4 has a macro called 639 GLIBCXX_ENABLE_SYMVERS that defaults to yes (or the argument 640 passed in via --enable-symvers=foo). At that point, the macro 641 attempts to make sure that all the requirement for symbol 642 versioning are in place. For more information, please consult 643 acinclude.m4. 644 </para> 645 </section> 646 647 <section xml:id="abi.versioning.active"><info><title>Checking Active</title></info> 648 649 650 <para> 651 When the GNU C++ library is being built with symbol versioning 652 on, you should see the following at configure time for 653 libstdc++ (showing either 'gnu' or another of the supported styles): 654 </para> 655 656<screen> 657<computeroutput> 658 checking versioning on shared library symbols... gnu 659</computeroutput> 660</screen> 661 662<para> 663 If you don't see this line in the configure output, or if this line 664 appears but the last word is 'no', then you are out of luck. 665</para> 666 667<para> 668 If the compiler is pre-installed, a quick way to test is to compile 669 the following (or any) simple C++ file and link it to the shared 670 libstdc++ library: 671</para> 672 673<programlisting> 674#include <iostream> 675 676int main() 677{ std::cout << "hello" << std::endl; return 0; } 678 679%g++ hello.cc -o hello.out 680 681%ldd hello.out 682 libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0x00764000) 683 libm.so.6 => /lib/tls/libm.so.6 (0x004a8000) 684 libgcc_s.so.1 => /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x40016000) 685 libc.so.6 => /lib/tls/libc.so.6 (0x0036d000) 686 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x00355000) 687 688%nm hello.out 689</programlisting> 690 691<para> 692If you see symbols in the resulting output with "GLIBCXX_3" as part 693of the name, then the executable is versioned. Here's an example: 694</para> 695 696<para> 697 <code>U _ZNSt8ios_base4InitC1Ev@@GLIBCXX_3.4</code> 698</para> 699 700<para> 701On Solaris 2, you can use <code>pvs -r</code> instead: 702</para> 703 704<programlisting> 705%g++ hello.cc -o hello.out 706 707%pvs -r hello.out 708 libstdc++.so.6 (GLIBCXX_3.4, GLIBCXX_3.4.12); 709 libgcc_s.so.1 (GCC_3.0); 710 libc.so.1 (SUNWprivate_1.1, SYSVABI_1.3); 711</programlisting> 712 713<para> 714<code>ldd -v</code> works too, but is very verbose. 715</para> 716 717 </section> 718</section> 719 720<section xml:id="abi.changes_allowed"><info><title>Allowed Changes</title></info> 721 722 723<para> 724The following will cause the library minor version number to 725increase, say from "libstdc++.so.3.0.4" to "libstdc++.so.3.0.5". 726</para> 727<orderedlist> 728 <listitem><para>Adding an exported global or static data member</para></listitem> 729 <listitem><para>Adding an exported function, static or non-virtual member function</para></listitem> 730 <listitem><para>Adding an exported symbol or symbols by additional instantiations</para></listitem> 731</orderedlist> 732<para> 733Other allowed changes are possible. 734</para> 735 736</section> 737 738<section xml:id="abi.changes_no"><info><title>Prohibited Changes</title></info> 739 740 741<para> 742The following non-exhaustive list will cause the library major version 743number to increase, say from "libstdc++.so.3.0.4" to 744"libstdc++.so.4.0.0". 745</para> 746 747<orderedlist> 748 <listitem><para>Changes in the gcc/g++ compiler ABI</para></listitem> 749<listitem><para>Changing size of an exported symbol</para></listitem> 750<listitem><para>Changing alignment of an exported symbol</para></listitem> 751<listitem><para>Changing the layout of an exported symbol</para></listitem> 752<listitem><para>Changing mangling on an exported symbol</para></listitem> 753<listitem><para>Deleting an exported symbol</para></listitem> 754<listitem><para>Changing the inheritance properties of a type by adding or removing 755 base classes</para></listitem> 756<listitem><para> 757 Changing the size, alignment, or layout of types 758 specified in the C++ standard. These may not necessarily be 759 instantiated or otherwise exported in the library binary, and 760 include all the required locale facets, as well as things like 761 std::basic_streambuf, et al. 762</para></listitem> 763 764<listitem><para> Adding an explicit copy constructor or destructor to a 765class that would otherwise have implicit versions. This will change 766the way the compiler deals with this class in by-value return 767statements or parameters: instead of passing instances of this 768class in registers, the compiler will be forced to use memory. See the 769section on <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://itanium-cxx-abi.github.io/cxx-abi/abi.html#calls">Function 770Calling Conventions and APIs</link> 771 of the C++ ABI documentation for further details. 772</para></listitem> 773 774</orderedlist> 775 776</section> 777 778 779 780<section xml:id="abi.impl"><info><title>Implementation</title></info> 781 782 783<orderedlist> 784 <listitem> 785 <para> 786 Separation of interface and implementation 787 </para> 788 <para> 789 This is accomplished by two techniques that separate the API from 790 the ABI: forcing undefined references to link against a library 791 binary for definitions. 792 </para> 793 794<variablelist> 795 <varlistentry> 796 <term>Include files have declarations, source files have defines</term> 797 798 <listitem> 799 <para> 800 For non-templatized types, such as much of <code>class 801 locale</code>, the appropriate standard C++ include, say 802 <code>locale</code>, can contain full declarations, while 803 various source files (say <code> locale.cc, locale_init.cc, 804 localename.cc</code>) contain definitions. 805 </para> 806 </listitem> 807 </varlistentry> 808 809 <varlistentry> 810 <term>Extern template on required types</term> 811 812 <listitem> 813 <para> 814 For parts of the standard that have an explicit list of 815 required instantiations, the GNU extension syntax <code> extern 816 template </code> can be used to control where template 817 definitions reside. By marking required instantiations as 818 <code> extern template </code> in include files, and providing 819 explicit instantiations in the appropriate instantiation files, 820 non-inlined template functions can be versioned. This technique 821 is mostly used on parts of the standard that require <code> 822 char</code> and <code> wchar_t</code> instantiations, and 823 includes <code> basic_string</code>, the locale facets, and the 824 types in <code> iostreams</code>. 825 </para> 826 </listitem> 827 </varlistentry> 828 829 </variablelist> 830 831 <para> 832 In addition, these techniques have the additional benefit that they 833 reduce binary size, which can increase runtime performance. 834 </para> 835 </listitem> 836 837 <listitem> 838 <para> 839 Namespaces linking symbol definitions to export mapfiles 840 </para> 841 <para> 842 All symbols in the shared library binary are processed by a 843 linker script at build time that either allows or disallows 844 external linkage. Because of this, some symbols, regardless of 845 normal C/C++ linkage, are not visible. Symbols that are internal 846 have several appealing characteristics: by not exporting the 847 symbols, there are no relocations when the shared library is 848 started and thus this makes for faster runtime loading 849 performance by the underlying dynamic loading mechanism. In 850 addition, they have the possibility of changing without impacting 851 ABI compatibility. 852 </para> 853 854<para>The following namespaces are transformed by the mapfile:</para> 855 856<variablelist> 857 858 <varlistentry> 859<term><code>namespace std</code></term> 860<listitem><para> Defaults to exporting all symbols in label 861<code>GLIBCXX</code> that do not begin with an underscore, i.e., 862<code>__test_func</code> would not be exported by default. Select 863exceptional symbols are allowed to be visible.</para></listitem> 864 </varlistentry> 865 866 <varlistentry> 867<term><code>namespace __gnu_cxx</code></term> 868<listitem><para> Defaults to not exporting any symbols in label 869<code>GLIBCXX</code>, select items are allowed to be visible.</para></listitem> 870 </varlistentry> 871 872 <varlistentry> 873<term><code>namespace __gnu_internal</code></term> 874<listitem><para> Defaults to not exported, no items are allowed to be visible.</para></listitem> 875 </varlistentry> 876 877 <varlistentry> 878<term><code>namespace __cxxabiv1</code>, aliased to <code> namespace abi</code></term> 879<listitem><para> Defaults to not exporting any symbols in label 880<code>CXXABI</code>, select items are allowed to be visible.</para></listitem> 881 </varlistentry> 882 883</variablelist> 884<para> 885</para> 886</listitem> 887 888 <listitem><para>Freezing the API</para> 889 <para>Disallowed changes, as above, are not made on a stable release 890branch. Enforcement tends to be less strict with GNU extensions that 891standard includes.</para> 892</listitem> 893</orderedlist> 894 895</section> 896 897<section xml:id="abi.testing"><info><title>Testing</title></info> 898 899 900 <section xml:id="abi.testing.single"><info><title>Single ABI Testing</title></info> 901 902 903 <para> 904 Testing for GNU C++ ABI changes is composed of two distinct 905 areas: testing the C++ compiler (g++) for compiler changes, and 906 testing the C++ library (libstdc++) for library changes. 907 </para> 908 909 <para> 910 Testing the C++ compiler ABI can be done various ways. 911 </para> 912 913 <para> 914 One. Intel ABI checker. 915 </para> 916 917<para> 918Two. 919The second is yet unreleased, but has been announced on the gcc 920mailing list. It is yet unspecified if these tools will be freely 921available, and able to be included in a GNU project. Please contact 922Mark Mitchell (mark@codesourcery.com) for more details, and current 923status. 924</para> 925 926<para> 927Three. 928Involves using the vlad.consistency test framework. This has also been 929discussed on the gcc mailing lists. 930</para> 931 932<para> 933Testing the C++ library ABI can also be done various ways. 934</para> 935 936<para> 937One. 938(Brendan Kehoe, Jeff Law suggestion to run 'make check-c++' two ways, 939one with a new compiler and an old library, and the other with an old 940compiler and a new library, and look for testsuite regressions) 941</para> 942 943<para> 944Details on how to set this kind of test up can be found here: 945http://gcc.gnu.org/ml/gcc/2002-08/msg00142.html 946</para> 947 948<para> 949Two. 950Use the 'make check-abi' rule in the libstdc++ Makefile. 951</para> 952 953<para> 954This is a proactive check of the library ABI. Currently, exported symbol 955names that are either weak or defined are checked against a last known 956good baseline. Currently, this baseline is keyed off of 3.4.0 957binaries, as this was the last time the .so number was incremented. In 958addition, all exported names are demangled, and the exported objects 959are checked to make sure they are the same size as the same object in 960the baseline. 961 962Notice that each baseline is relative to a <emphasis>default</emphasis> 963configured library and compiler: in particular, if options such as 964--enable-clocale, or --with-cpu, in case of multilibs, are used at 965configure time, the check may fail, either because of substantive 966differences or because of limitations of the current checking 967machinery. 968</para> 969 970<para> 971This dataset is insufficient, yet a start. Also needed is a 972comprehensive check for all user-visible types part of the standard 973library for sizeof() and alignof() changes. 974</para> 975 976<para> 977Verifying compatible layouts of objects is not even attempted. It 978should be possible to use sizeof, alignof, and offsetof to compute 979offsets for each structure and type in the standard library, saving to 980another datafile. Then, compute this in a similar way for new 981binaries, and look for differences. 982</para> 983 984<para> 985Another approach might be to use the -fdump-class-hierarchy flag to 986get information. However, currently this approach gives insufficient 987data for use in library testing, as class data members, their offsets, 988and other detailed data is not displayed with this flag. 989(See PR g++/7470 on how this was used to find bugs.) 990</para> 991 992<para> 993Perhaps there are other C++ ABI checkers. If so, please notify 994us. We'd like to know about them! 995</para> 996 997 </section> 998 <section xml:id="abi.testing.multi"><info><title>Multiple ABI Testing</title></info> 999 1000<para> 1001A "C" application, dynamically linked to two shared libraries, liba, 1002libb. The dependent library liba is a C++ shared library compiled with 1003GCC 3.3, and uses io, exceptions, locale, etc. The dependent library 1004libb is a C++ shared library compiled with GCC 3.4, and also uses io, 1005exceptions, locale, etc. 1006</para> 1007 1008<para> As above, libone is constructed as follows: </para> 1009<programlisting> 1010%$bld/H-x86-gcc-3.4.0/bin/g++ -fPIC -DPIC -c a.cc 1011 1012%$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 1013 1014%ln -s libone.so.1.0.0 libone.so 1015 1016%$bld/H-x86-gcc-3.4.0/bin/g++ -c a.cc 1017 1018%ar cru libone.a a.o 1019</programlisting> 1020 1021<para> And, libtwo is constructed as follows: </para> 1022 1023<programlisting> 1024%$bld/H-x86-gcc-3.3.3/bin/g++ -fPIC -DPIC -c b.cc 1025 1026%$bld/H-x86-gcc-3.3.3/bin/g++ -shared -Wl,-soname -Wl,libtwo.so.1 -Wl,-O1 -Wl,-z,defs b.o -o libtwo.so.1.0.0 1027 1028%ln -s libtwo.so.1.0.0 libtwo.so 1029 1030%$bld/H-x86-gcc-3.3.3/bin/g++ -c b.cc 1031 1032%ar cru libtwo.a b.o 1033</programlisting> 1034 1035<para> ...with the resulting libraries looking like </para> 1036 1037<screen> 1038<computeroutput> 1039%ldd libone.so.1.0.0 1040 libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x40016000) 1041 libm.so.6 => /lib/tls/libm.so.6 (0x400fa000) 1042 libgcc_s.so.1 => /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x4011c000) 1043 libc.so.6 => /lib/tls/libc.so.6 (0x40125000) 1044 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x00355000) 1045 1046%ldd libtwo.so.1.0.0 1047 libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0x40027000) 1048 libm.so.6 => /lib/tls/libm.so.6 (0x400e1000) 1049 libgcc_s.so.1 => /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x40103000) 1050 libc.so.6 => /lib/tls/libc.so.6 (0x4010c000) 1051 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x00355000) 1052</computeroutput> 1053</screen> 1054 1055<para> 1056 Then, the "C" compiler is used to compile a source file that uses 1057 functions from each library. 1058</para> 1059<programlisting> 1060gcc test.c -g -O2 -L. -lone -ltwo /usr/lib/libstdc++.so.5 /usr/lib/libstdc++.so.6 1061</programlisting> 1062 1063<para> 1064 Which gives the expected: 1065</para> 1066 1067<screen> 1068<computeroutput> 1069%ldd a.out 1070 libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0x00764000) 1071 libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x40015000) 1072 libc.so.6 => /lib/tls/libc.so.6 (0x0036d000) 1073 libm.so.6 => /lib/tls/libm.so.6 (0x004a8000) 1074 libgcc_s.so.1 => /mnt/hd/bld/gcc/gcc/libgcc_s.so.1 (0x400e5000) 1075 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x00355000) 1076</computeroutput> 1077</screen> 1078 1079<para> 1080 This resulting binary, when executed, will be able to safely use 1081 code from both liba, and the dependent libstdc++.so.6, and libb, 1082 with the dependent libstdc++.so.5. 1083</para> 1084 </section> 1085</section> 1086 1087<section xml:id="abi.issues"><info><title>Outstanding Issues</title></info> 1088 1089 1090<para> 1091 Some features in the C++ language make versioning especially 1092 difficult. In particular, compiler generated constructs such as 1093 implicit instantiations for templates, typeinfo information, and 1094 virtual tables all may cause ABI leakage across shared library 1095 boundaries. Because of this, mixing C++ ABIs is not recommended at 1096 this time. 1097</para> 1098 1099<para> 1100 For more background on this issue, see these bugzilla entries: 1101</para> 1102 1103<para> 1104<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://gcc.gnu.org/PR24660">24660: versioning weak symbols in libstdc++</link> 1105</para> 1106 1107<para> 1108<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> 1109</para> 1110 1111</section> 1112 1113<bibliography xml:id="abi.biblio"><info><title>Bibliography</title></info> 1114 1115 <biblioentry xml:id="biblio.abicheck"> 1116 <title> 1117 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1118 xlink:href="http://abicheck.sourceforge.net"> 1119 ABIcheck 1120 </link> 1121 </title> 1122 </biblioentry> 1123 1124 <biblioentry xml:id="biblio.cxxabi"> 1125 <title> 1126 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1127 xlink:href="https://itanium-cxx-abi.github.io/cxx-abi/"> 1128 Itanium C++ ABI 1129 </link> 1130 </title> 1131 </biblioentry> 1132 1133 1134 <biblioentry> 1135 <title> 1136 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1137 xlink:href="https://software.intel.com/en-us/articles/intel-compilers-for-linux-compatibility-with-gnu-compilers"> 1138 Intel Compilers for Linux: Compatibility with GNU Compilers 1139 </link> 1140 </title> 1141 </biblioentry> 1142 1143 <biblioentry> 1144 <title> 1145 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1146 xlink:href="https://docs.oracle.com/cd/E23824_01/html/819-0690/index.html"> 1147 Linker and Libraries Guide (document 819-0690) 1148 </link> 1149 </title> 1150 </biblioentry> 1151 1152 1153 <biblioentry> 1154 <title> 1155 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1156 xlink:href="https://docs.oracle.com/cd/E19422-01/819-3689/"> 1157 Sun Studio 11: C++ Migration Guide (document 819-3689) 1158 </link> 1159 </title> 1160 </biblioentry> 1161 1162 <biblioentry> 1163 <title> 1164 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1165 xlink:href="https://www.akkadia.org/drepper/dsohowto.pdf"> 1166 How to Write Shared Libraries 1167 </link> 1168 </title> 1169 1170 <author> 1171 <personname> 1172 <firstname>Ulrich</firstname><surname>Drepper</surname> 1173 </personname> 1174 </author> 1175 </biblioentry> 1176 1177 <biblioentry> 1178 <title> 1179 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1180 xlink:href="http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ihi0036b/index.html"> 1181 C++ ABI for the ARM Architecture 1182 </link> 1183 </title> 1184 </biblioentry> 1185 1186 <biblioentry> 1187 <title> 1188 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1189 xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1976.html"> 1190 Dynamic Shared Objects: Survey and Issues 1191 </link> 1192 </title> 1193 1194 <subtitle> 1195 ISO C++ J16/06-0046 1196 </subtitle> 1197 <author><personname><firstname>Benjamin</firstname><surname>Kosnik</surname></personname></author> 1198 </biblioentry> 1199 1200 <biblioentry> 1201 <title> 1202 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1203 xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2013.html"> 1204 Versioning With Namespaces 1205 </link> 1206 </title> 1207 <subtitle> 1208 ISO C++ J16/06-0083 1209 </subtitle> 1210 <author><personname><firstname>Benjamin</firstname><surname>Kosnik</surname></personname></author> 1211 </biblioentry> 1212 1213 <biblioentry> 1214 <title> 1215 <link xmlns:xlink="http://www.w3.org/1999/xlink" 1216 xlink:href="http://syrcose.ispras.ru/2009/files/02_paper.pdf"> 1217 Binary Compatibility of Shared Libraries Implemented in C++ 1218 on GNU/Linux Systems 1219 </link> 1220 </title> 1221 1222 <subtitle> 1223 SYRCoSE 2009 1224 </subtitle> 1225 <author><personname><firstname>Pavel</firstname><surname>Shved</surname></personname></author> 1226 <author><personname><firstname>Denis</firstname><surname>Silakov</surname></personname></author> 1227 </biblioentry> 1228</bibliography> 1229 1230</section> 1231