Trying to come up with a flexible way to include applink

.github/workflows/test.yml

@@ -26,18 +26,13 @@ jobs:
       - name: Set PATH to find vcpkg dependencies
         run: |
           echo "PATH=${{ env.PATH }};${{ env.LIBUV_BIN_DIR }};${{ env.KERBEROS_BIN_DIR }};${{ env.OPENSSL_BIN_DIR }}" >> $env:GITHUB_ENV
-      - name: Link OpenSSL applink.c into src
-        run: |
-          echo "OPENSSL_INCLUDE_DIR contents:"
-          ls ${{ env.OPENSSL_INCLUDE_DIR }}\openssl
-          ln -s ${{ env.OPENSSL_INCLUDE_DIR }}\openssl\applink.c .\src\applink.c
       - name: Fix name of static zlib dir
         run: ln -s ${{ env.ZLIB_LIB_DIR }}\zlib.lib ${{ env.ZLIB_LIB_DIR }}\zlibstatic.lib
       - name: Build and run tests
         run: |
           mkdir build
           cd build
-          cmake -G "NMake Makefiles" -DCASS_BUILD_UNIT_TESTS=On ..
+          cmake -G "NMake Makefiles" -DCASS_BUILD_UNIT_TESTS=On -DCASS_OPENSSL_APPLINK=${{ env.OPENSSL_INCLUDE_DIR }}\openssl\applink.c ..
           nmake
           ls .
           ldd ./cassandra-unit-tests.exe

CMakeLists.txt

@@ -5,6 +5,10 @@ set(CASS_ROOT_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 set(CASS_SRC_DIR "${CASS_ROOT_DIR}/src")
 set(CASS_INCLUDE_DIR "${CASS_ROOT_DIR}/include")
 
+# Allow user to specify the location of applink.c.  Some Windows builds require this as an
+# interface into OpenSSL BIO ops.  See https://docs.openssl.org/1.1.1/man3/OPENSSL_Applink/#synopsis
+set(CASS_OPENSSL_APPLINK "")
+
 # Ensure functions/modules are available
 list(APPEND CMAKE_MODULE_PATH ${CASS_ROOT_DIR}/cmake)
 

src/CMakeLists.txt

@@ -13,6 +13,9 @@ endif()
 
 if(CASS_USE_OPENSSL)
   list(APPEND SOURCES ssl/ssl_openssl_impl.cpp ssl/ring_buffer_bio.cpp)
+  if(WIN32 AND (NOT CASS_OPENSSL_APPLINK STREQUAL ""))
+    list(APPEND SOURCES ${CASS_OPENSSL_APPLINK})
+  endif()
 else()
   list(APPEND SOURCES ssl/ssl_no_impl.cpp)
 endif()