| |
| ==================== |
| Libc++ ABI stability |
| ==================== |
| |
| Libc++ aims to preserve stable ABI to avoid subtle bugs when code built to the old ABI |
| is linked with the code build to the new ABI. At the same time, libc++ allows ABI-breaking |
| improvements and bugfixes for the scenarios when ABI change is not a issue. |
| |
| To support both cases, libc++ allows specifying the ABI version at the |
| build time. The version is defined with a cmake option |
| LIBCXX_ABI_VERSION. Another option LIBCXX_ABI_UNSTABLE can be used to |
| include all present ABI breaking features. These options translate |
| into C++ macro definitions _LIBCPP_ABI_VERSION, _LIBCPP_ABI_UNSTABLE. |
| |
| Any ABI-changing feature is placed under it's own macro, _LIBCPP_ABI_XXX, which is enabled |
| based on the value of _LIBCPP_ABI_VERSION. _LIBCPP_ABI_UNSTABLE, if set, enables all features at once. |