Expect DLL builds on Windows by default and require a custom __config for static
builds.
On Windows the __declspec(dllimport) and __declspec(dllexport) attributes
require linking to a DLL, not a static library. Previously these annotations
were disabled by default unless _LIBCPP_DLL was defined. However the DLL
configuration is probably the more common one, so it should be supported by
default.
This patch enables import/export attributes by default and adds a
_LIBCPP_DISABLE_DLL_IMPORT_EXPORT macro which can be used to disable this
behavior. If libc++ is built as a static library on Windows then a custom __config
header will be generated that predefines this macro.
This patch is based off work by Shoaib Meenai.
llvm-svn: 282449
diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index a80349a..5904c06 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -330,6 +330,8 @@
# headers
add_compile_flags_if_supported(-nostdinc++)
+# Let the library headers know they are currently being used to build the
+# library.
add_definitions(-D_LIBCPP_BUILDING_LIBRARY)
# Warning flags ===============================================================
@@ -455,6 +457,14 @@
config_define_if(LIBCXX_HAS_EXTERNAL_THREAD_API _LIBCPP_HAS_THREAD_API_EXTERNAL)
config_define_if(LIBCXX_HAS_MUSL_LIBC _LIBCPP_HAS_MUSL_LIBC)
+# 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.
+if (DEFINED WIN32 AND LIBCXX_ENABLE_STATIC AND NOT LIBCXX_ENABLE_SHARED)
+ message(STATUS "Generating custom __config for non-DLL Windows build")
+ config_define(ON _LIBCPP_DISABLE_DLL_IMPORT_EXPORT)
+endif()
+
if (LIBCXX_NEEDS_SITE_CONFIG)
configure_file(
include/__config_site.in
