[libc++] Add site config option for ABI macros

Some ABI macros affect headers, so it's nice to have a site config
option for them. Add a LIBCXX_ABI_DEFINES cmake macro to allow
specifying a list of ABI macros to define in the site config.

The primary design constraint (as discussed with Eric on IRC a while
back) was to not have to repeat the ABI macro names in cmake, which only
leaves a free-form cmake list as an option. A somewhat unfortunate
consequence is that we can't verify that the ABI macros being defined
actually exist, though we can at least perform some basic sanity
checking, since all the ABI macros begin with _LIBCPP_ABI_.

Differential Revision: https://reviews.llvm.org/D36719

llvm-svn: 314946

libcxx/CMakeLists.txt

@@ -607,6 +607,19 @@ config_define_if(LIBCXX_HAS_EXTERNAL_THREAD_API _LIBCPP_HAS_THREAD_API_EXTERNAL)
 config_define_if(LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY _LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL)
 config_define_if(LIBCXX_HAS_MUSL_LIBC _LIBCPP_HAS_MUSL_LIBC)
 
+set(LIBCXX_ABI_DEFINES "" CACHE STRING "A semicolon separated list of ABI macros to define in the site config header")
+if (LIBCXX_ABI_DEFINES)
+  set(abi_defines)
+  foreach (abi_define ${LIBCXX_ABI_DEFINES})
+    if (NOT abi_define MATCHES "^_LIBCPP_ABI_")
+      message(SEND_ERROR "Invalid ABI macro ${abi_define} in LIBCXX_ABI_DEFINES")
+    endif()
+    list(APPEND abi_defines "#define ${abi_define}")
+  endforeach()
+  string(REPLACE ";" "\n" abi_defines "${abi_defines}")
+  config_define(${abi_defines} _LIBCPP_ABI_DEFINES)
+endif()
+
 # By default libc++ on Windows expects to use a shared library, which requires
 # the headers to use DLL import/export semantics. However when building a
 # static library only we modify the headers to disable DLL import/export.

libcxx/docs/BuildingLibcxx.rst

@@ -347,6 +347,13 @@ The following options allow building libc++ for a different ABI version.
   Build the "unstable" ABI version of libc++. Includes all ABI changing features
   on top of the current stable version.
 
+.. option:: LIBCXX_ABI_DEFINES:STRING
+
+  **Default**: ``""``
+
+  A semicolon-separated list of ABI macros to persist in the site config header.
+  See ``include/__config`` for the list of ABI macros.
+
 .. _LLVM-specific variables:
 
 LLVM-specific options

libcxx/include/__config_site.in

@@ -24,4 +24,6 @@
 #cmakedefine _LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL
 #cmakedefine _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
 
+@_LIBCPP_ABI_DEFINES@
+
 #endif // _LIBCPP_CONFIG_SITE

libcxx/utils/libcxx/test/config.py

@@ -668,7 +668,7 @@ def parse_config_site_and_add_features(self, header):
                 self.config.available_features.add('libcpp-abi-version-v%s'
                     % feature_macros[m])
                 continue
-            assert m.startswith('_LIBCPP_HAS_') or m == '_LIBCPP_ABI_UNSTABLE'
+            assert m.startswith('_LIBCPP_HAS_') or m.startswith('_LIBCPP_ABI_')
             m = m.lower()[1:].replace('_', '-')
             self.config.available_features.add(m)
         return feature_macros