1 1.1 joerg 2 1.1 joerg ==================== 3 1.1 joerg Libc++ ABI stability 4 1.1 joerg ==================== 5 1.1 joerg 6 1.1 joerg Libc++ aims to preserve stable ABI to avoid subtle bugs when code built to the old ABI 7 1.1 joerg is linked with the code build to the new ABI. At the same time, libc++ allows ABI-breaking 8 1.1 joerg improvements and bugfixes for the scenarios when ABI change is not a issue. 9 1.1 joerg 10 1.1 joerg To support both cases, libc++ allows specifying the ABI version at the 11 1.1 joerg build time. The version is defined with a cmake option 12 1.1 joerg LIBCXX_ABI_VERSION. Another option LIBCXX_ABI_UNSTABLE can be used to 13 1.1 joerg include all present ABI breaking features. These options translate 14 1.1 joerg into C++ macro definitions _LIBCPP_ABI_VERSION, _LIBCPP_ABI_UNSTABLE. 15 1.1 joerg 16 1.1 joerg Any ABI-changing feature is placed under it's own macro, _LIBCPP_ABI_XXX, which is enabled 17 1.1 joerg based on the value of _LIBCPP_ABI_VERSION. _LIBCPP_ABI_UNSTABLE, if set, enables all features at once. 18