export the weakly-linked symbols (#981)

Summary:
Pull Request resolved: #981

title

Reviewed By: jacobkahn

Differential Revision: D30003295

fbshipit-source-id: 129e41ab3785431bd0676400212c8027612074a5

Author: Tatiana Likhomanenko

CMakeLists.txt

@@ -15,4 +15,18 @@ if (NOT TARGET flashlight::flashlight-app-asr)
   message(FATAL_ERROR "flashlight must be build with app/asr for wav2letter++")
 endif ()
 
+include(CheckCXXCompilerFlag)
+# All libraries should have their symbols exported so plugins can lazily
+# symbols from any of them
+check_cxx_compiler_flag("-rdynamic" COMPILER_SUPPORTS_RDYNAMIC)
+if(${COMPILER_SUPPORTS_RDYNAMIC})
+  message(STATUS "-rdynamic supported.")
+  set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -rdynamic")
+  set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -rdynamic")
+else()
+  message(WARNING
+    "This compiler doesn't support dynamic symbol exports. "
+    "Plugin functionality likely won't work.")
+endif()
+
 add_subdirectory(${PROJECT_SOURCE_DIR}/recipes)