Platforms without any exceptions support

[glebm]

I'm trying to port DevilutionX to the original XBox NXDK

This platform does not support exceptions at all, which results in:

lld: error: undefined symbol: ___std_terminate
>>> referenced by libSDL_audiolib.lib(SdlMutex.cpp.obj):(int `public: __thiscall std::exception::exception(class exception::dtor$2 const &)'::`1'::dtor$2)

Not sure what the best way to resolve this is.

[realnc]

There's no std::terminate()? That's weird. So if you call that directly, you get the same error?

[glebm]

Yeah, there is no exceptions support at all and it looks like std::terminate is part of the exceptions support.

We'd need to call std::exit or std::abort instead.

[realnc]

Does the obvious workaround of simply providing an implementation of std::terminate work?

[glebm]

Defining anything in the std namespace is UB IIRC.
It would probably need to be compiler-specific (___std_terminate) and while it may work, it doesn't seem like a good workaround.

I think the solution in #33 is a better option here.
I can imagine in many cases sound is the only thing threads are used for (e.g. this is the case for DevilutionX single player), so failing to create a mutex is not necessarily a fatal error.

Alternatively, there could be a CMake option to replace that one throw with std::exit.

[realnc]

Defining anything in the std namespace is UB IIRC. It would probably need to be compiler-specific (___std_terminate) and while it may work, it doesn't seem like a good workaround.

It seems like an excellent workaround, until fixed in the SDK itself, at which point you should get a link error and can then remove it again. I looked at https://github.com/XboxDev/nxdk/issues and nobody has reported the issue yet though.

Defining things in std may be UB, but at this point you're implementing your own std missing function that should be there to begin with.

[glebm]

I tried the workaround but it doesn't work because there are some other undefined symbols as well:

lld: error: undefined symbol: __CxxThrowException@8
>>> referenced by libSDL_audiolib.lib(SdlMutex.cpp.obj):(public: __thiscall SdlMutex::SdlMutex(void))

lld: error: undefined symbol: ___std_terminate
>>> referenced by libSDL_audiolib.lib(SdlMutex.cpp.obj):(int `public: __thiscall std::exception::exception(class exception::dtor$2 const &)'::`1'::dtor$2)

lld: error: undefined symbol: ___CxxFrameHandler3
>>> referenced by libSDL_audiolib.lib(SdlMutex.cpp.obj):(___ehhandler$??0exception@std@@QAE@ABV01@@Z)

Defining std::terminate leads to duplicate symbol definition.

I looked at XboxDev/nxdk/issues and nobody has reported the issue yet though.

There is this issue XboxDev/nxdk#463

[glebm]

Putting aside the lack of a workaround, does this really need to be an exception?

You said in #33 (comment):

Locking is not optional. If a lock cannot be acquired, the application should shut down since something is seriously broken. The exception that is thrown simply gives applications the opportunity to do a more graceful shutdown. It's not a condition that can just be logged and then have execution resumed.

However, multi-threading is not a critical feature for a lot of the applications.

DevilutionX can run perfectly well on a single thread in single player (just without audio).

I don't think SDL_audiolib should be deciding that for the application.

Can you please reconsider merging #33 instead?

[realnc]

Does the improve-exceptions branch work? 8d11c63 is the relevant commit.

[glebm]

Hmm, it doesn't work with that branch

-- Performing Test HAVE_EXCEPTIONS - Failed

lld: error: undefined symbol: ___std_terminate
>>> referenced by libSDL_audiolib.lib(SdlMutex.cpp.obj)

lld: error: undefined symbol: ___CxxFrameHandler3
>>> referenced by libSDL_audiolib.lib(SdlMutex.cpp.obj):(___ehhandler$??0SdlMutex@@QAE@XZ)
>>> referenced by libSDL_audiolib.lib(SdlMutex.cpp.obj):(___ehhandler$?lock@SdlMutex@@QAEXXZ)
>>> referenced by libSDL_audiolib.lib(SdlMutex.cpp.obj):(___ehhandler$?unlock@SdlMutex@@QAEXXZ)

Perhaps set_source_files_properties should not be called if the exceptions test fails.

[glebm]

With #37 it links!