Urho3D + OpenSSL "UI" Conflict

I need my application to work where Urho3D networking does not (the web). I built a websocket client and when I try to include both Urho3D and OpenSSL I get:

In file included from /usr/include/openssl/engine.h:24,
from …/include/boost/asio/ssl/detail/openssl_types.hpp:26,
from …/include/boost/asio/ssl/context_base.hpp:19,
from …/include/boost/asio/ssl/context.hpp:23,
from …/include/boost/asio/ssl/stream.hpp:26,
from …/include/boost/beast/websocket/ssl.hpp:16,
from …/include/boost/beast/ssl/ssl_stream.hpp:16,
from …/include/boost/beast/ssl.hpp:15,
from include/websocket.hpp:111,
from login.hpp:10,
from main.cpp:1:
/usr/include/openssl/ui.h:42:1: error: reference to ‘UI’ is ambiguous
42 | UI *UI_new(void);
/usr/local/include/Urho3D/UI/UI.h:60:18: note: candidates are: ‘class Urho3D::UI’
60 | class URHO3D_API UI : public Object
In file included from /usr/include/openssl/crypto.h:25,
from /usr/include/openssl/bio.h:20,
from /usr/include/openssl/conf.h:13,
from …/include/boost/asio/ssl/detail/openssl_types.hpp:23,
from …/include/boost/asio/ssl/context_base.hpp:19,
from …/include/boost/asio/ssl/context.hpp:23,
from …/include/boost/asio/ssl/stream.hpp:26,
from …/include/boost/beast/websocket/ssl.hpp:16,
from …/include/boost/beast/ssl/ssl_stream.hpp:16,
from …/include/boost/beast/ssl.hpp:15,
from include/websocket.hpp:111,
from login.hpp:10,
from main.cpp:1:
/usr/include/openssl/ossl_typ.h:144:22: note: ‘typedef struct ui_st UI’
144 | typedef struct ui_st UI;
In file included from /usr/include/openssl/engine.h:24,
from …/include/boost/asio/ssl/detail/openssl_types.hpp:26,
from …/include/boost/asio/ssl/context_base.hpp:19,
from …/include/boost/asio/ssl/context.hpp:23,
from …/include/boost/asio/ssl/stream.hpp:26,
from …/include/boost/beast/websocket/ssl.hpp:16,
from …/include/boost/beast/ssl/ssl_stream.hpp:16,
from …/include/boost/beast/ssl.hpp:15,
from include/websocket.hpp:111,
from login.hpp:10,
from main.cpp:1:

Note reference to ‘UI’ is ambiguous and the two suggested candidates in the above (one from Urho3D, and other from OpenSSL). I have bolded the relevant lines to make it slightly easier to read.

I am not polluting namespaces (not using using anywhere).

Is this something we were already aware of? How do I get around it if both Urho3D and OpenSSL want UI in the public namespace?

I am running G++ v9.3.0 from the Ubuntu 20.04 repos.

I have never used this, but maybe this is what you need? Urho3D/HttpRequestDemo.cpp at master · urho3d/Urho3D · GitHub

1 Like

I don’t really understand why the UI inside the Urho3D namespace is conflicting with UI from a C(ish) global scope.

As long as the header which contains typedef struct ui_st UI was included outside of Urho3D namespace. Both of them should be accessible without conflict based on current scope.

I.e. if you’re inside Urho3D namespace then you access Urho3D::UI simply as UI and the one from OpenSSL as ::UI. Note the :: which implies you want the one from the global scope.

And if you are in the global scope then you access UI from Urho3D namespace as Urho3D::UI and UI from OpenSSL simply as UI.

The only time this becomes an issue is when a macro is used that doesn’t take that into consideration. In which case the macro must be adjusted to account for the possible conflict.

First make sure the OpenSSL headers were not included inside the Urho3D namespace. Like:

namespace Urho3D {
#include <someheader.h>
}

Second. Make sure you are not importing the Urho3D namespace into your global scope. Like:

namespace Urho3D {
}
using namespace Urho3D;

Rather, import what you need:

namespace Urho3D {
}
using Urho3D::TypeYouNeed;
using Urho3D::FunctionYouNeed;

Once you make sure those identifiers don’t exist in the same scope at the same time. You should have no issues addressing one or the other.

Anyway, I haven’t really tried to use OpenSSL with Urho at the same time. So I have no clue about your current situation.

This is the strange part.

I am not using using namespace Urho3D; (grep’ed to be extra sure). Nor is my code using any namespaces at all yet (this is still the start of the project so I have not gotten that far yet).

They just conflict. I am not really sure how to further investigate this.

Update.

By changing the order in which the headers were included (Urho3D last) fixed the issue.

No idea what that is about.

Did you include DebugNew.h?

Not really sure what that is besides what I can take away from the name. I will look into it.

Thanks.

Edit
That seems to be for MSVC only. I am on Linux using GCC. I appreciate the help, though.