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