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
diff --git a/libcxx/include/__config b/libcxx/include/__config
index 9f90a5b..b0a3091 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -519,20 +519,20 @@
#ifdef _WIN32
-// only really useful for a DLL. _LIBCPP_DLL should be a compiler builtin define ideally...
-#if defined(_LIBCPP_DLL) && defined(cxx_EXPORTS)
-# define _LIBCPP_DLL_VIS __declspec(dllexport)
-# define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS
-# define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS _LIBCPP_DLL_VIS
-#elif defined(_LIBCPP_DLL)
-# define _LIBCPP_DLL_VIS __declspec(dllimport)
-# define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS _LIBCPP_DLL_VIS
-# define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
-#else
+#if defined(_LIBCPP_DISABLE_DLL_IMPORT_EXPORT)
# define _LIBCPP_DLL_VIS
# define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS
# define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
+#elif defined(_LIBCPP_BUILDING_LIBRARY)
+# define _LIBCPP_DLL_VIS __declspec(dllexport)
+# define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS
+# define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS _LIBCPP_DLL_VIS
+#else
+# define _LIBCPP_DLL_VIS __declspec(dllimport)
+# define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS _LIBCPP_DLL_VIS
+# define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
#endif
+
#define _LIBCPP_TYPE_VIS _LIBCPP_DLL_VIS
#define _LIBCPP_FUNC_VIS _LIBCPP_DLL_VIS
#define _LIBCPP_EXCEPTION_ABI _LIBCPP_DLL_VIS
diff --git a/libcxx/include/__config_site.in b/libcxx/include/__config_site.in
index dce30bc..ba0e8be 100644
--- a/libcxx/include/__config_site.in
+++ b/libcxx/include/__config_site.in
@@ -21,5 +21,6 @@
#cmakedefine _LIBCPP_HAS_MUSL_LIBC
#cmakedefine _LIBCPP_HAS_THREAD_API_PTHREAD
#cmakedefine _LIBCPP_HAS_THREAD_API_EXTERNAL
+#cmakedefine _LIBCPP_DISABLE_DLL_IMPORT_EXPORT
#endif // _LIBCPP_CONFIG_SITE
