Require OpenSSL by default and add list it as a dependency for Conan

OpenSSL support remains optional, but instead of including it or not solely depending on whether cmake manages to find it, there is now a DDSC_ENABLE_OPENSSL option that defaults to "ON". Setting to OFF removes the dependency. The Conan configuration has been updated to automatically provide openssl 1.1.1a.

Signed-off-by: Erik Boasson <eb@ilities.com>

conanfile.txt

@@ -1,5 +1,6 @@
 [requires]
 cunit/2.1-3@bincrafters/stable
+OpenSSL/1.1.1a@conan/stable
 
 [generators]
 cmake

src/cmake/modules/FindOpenSSL.cmake

@@ -10,8 +10,8 @@
 # SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 #
 if(TARGET CONAN_PKG::OpenSSL)
-  add_library(OpenSSL INTERFACE IMPORTED) #ALIAS CONAN_PKG::OpenSSL)
-  target_link_libraries(OpenSSL INTERFACE CONAN_PKG::OpenSSL)
+  add_library(OpenSSL::SSL INTERFACE IMPORTED)
+  target_link_libraries(OpenSSL::SSL INTERFACE CONAN_PKG::OpenSSL)
   set(OPENSSL_FOUND TRUE)
 else()
   # Loop over a list of possible module paths (without the current directory).

src/core/CMakeLists.txt

@@ -33,10 +33,18 @@ endif()
 
 add_definitions(-DDDSI_INCLUDE_NETWORK_PARTITIONS -DDDSI_INCLUDE_SSM)
 
+option(DDSC_ENABLE_OPENSSL "Enable openssl support" ON)
+if(DDSC_ENABLE_OPENSSL)
   find_package(OpenSSL)
   if(OPENSSL_FOUND)
     add_definitions(-DDDSI_INCLUDE_SSL)
-  target_link_libraries(ddsc PRIVATE OpenSSL)
+    target_link_libraries(ddsc PRIVATE OpenSSL::SSL)
+    if(CMAKE_GENERATOR MATCHES "Visual Studio")
+      set_target_properties(ddsc PROPERTIES LINK_FLAGS "/ignore:4099")
+    endif()
+  else()
+    message(FATAL_ERROR "To build without openssl support, set DDSC_ENABLE_OPENSSL to OFF")
+  endif()
 endif()
 
 include(ddsi/CMakeLists.txt)