export all symbols for Windows DLLs

CMakeLists.txt

-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.4)
 
 project(olm VERSION 3.1.0 LANGUAGES CXX C)
 
@@ -15,6 +15,7 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_STANDARD_REQUIRED ON)
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
+set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON)
 
 if(NOT CMAKE_BUILD_TYPE)
     set(CMAKE_BUILD_TYPE Release)