Index: libcxx/trunk/CMakeLists.txt
===================================================================
--- libcxx/trunk/CMakeLists.txt
+++ libcxx/trunk/CMakeLists.txt
@@ -97,7 +97,12 @@
 cmake_dependent_option(LIBCXX_INSTALL_EXPERIMENTAL_LIBRARY
         "Install libc++experimental.a" ON
         "LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY;LIBCXX_INSTALL_LIBRARY" OFF)
-set(LIBCXX_ABI_VERSION 1 CACHE STRING "ABI version of libc++.")
+if (FUCHSIA)
+  set(DEFAULT_ABI_VERSION 2)
+else()
+  set(DEFAULT_ABI_VERSION 1)
+endif()
+set(LIBCXX_ABI_VERSION ${DEFAULT_ABI_VERSION} CACHE STRING "ABI version of libc++.")
 option(LIBCXX_ABI_UNSTABLE "Unstable ABI of libc++." OFF)
 option(LIBCXX_ABI_FORCE_ITANIUM "Ignore auto-detection and force use of the Itanium ABI.")
 option(LIBCXX_ABI_FORCE_MICROSOFT "Ignore auto-detection and force use of the Microsoft ABI.")
@@ -619,7 +624,7 @@
 endif()
 
 # Configuration file flags =====================================================
-if (NOT LIBCXX_ABI_VERSION EQUAL "1")
+if (NOT LIBCXX_ABI_VERSION EQUAL DEFAULT_ABI_VERSION)
   config_define(${LIBCXX_ABI_VERSION} _LIBCPP_ABI_VERSION)
 endif()
 config_define_if(LIBCXX_ABI_UNSTABLE _LIBCPP_ABI_UNSTABLE)