====== Symbol Versioning ======

Starting with %%FreeBSD%% 7.0, several libraries (including ''%%libc%%'' and the thread libraries) use symbol versioning.

This means that each exported symbol has a version tag attached to it, and that when a program is compiled and linked, the linker resolves symbols against the newest available version tag.

When the API changes—for instance, the argument list or return type of a function changes—the old version of the function is replaced with a compatibility stub.  Symbol versioning ensures that old programs will use the compatibility stub, while new ones will use the new version.

Currently defined version tags are:

^ Tag ^ Version ^
| FBSD_1.0 | %%FreeBSD%% 7 |
| FBSD_1.1 | %%FreeBSD%% 8 |
| FBSD_1.2 | %%FreeBSD%% 9 |
| FBSD_1.3 | %%FreeBSD%% 10 |
| FBSD_1.4 | %%FreeBSD%% 11 |
| FBSD_1.5 | %%FreeBSD%% 12 |
| FBSD_1.6 | %%FreeBSD%% 13 |
| FBSD_1.7 | %%FreeBSD%% 14 |

===== Further reading =====

  * BinaryCompatibility
  * http://people.freebsd.org/~deischen/symver/library_versioning.txt
  * http://comments.gmane.org/gmane.os.freebsd.devel.threading/4092