Temporary workaround for ZynAddSubFx name clashes

[Wallacoloo]

Once Zyn 2.5 is ready to be merged, that should solve all the issues we've been having with the conflicting LMMS Engine and Zyn Engine classnames. Until then, this is the small patch that I've been using on my system in order to work around the issue (#2049, #2053, etc). It just renames Engine as LmmsCore, so that the two classes now have different symbol names, but then it typedefs it back to Engine so that the rest of LMMS doesn't need to be modified (for the most part).

I'm sharing this in case anyone else would find such a patch useful, and to see if there's demand for something like this to be merged while we work on readying Zyn 2.5. I must emphasize that this is meant to be temporary - I would not like to see this reside in the LMMS codebase for very long, if at all. Luckily, if people think this is worth merging, it's easy to revert once @curlymorphic's Zyn branch is merged.

[curlymorphic]

I feel It may be a good idea to merge this, as lmms appears to be lacking Devs that know about windows, meaning the zasf upgrade could be a long way off.

An alternative could be to patch our zasf 2.4, although Im not sure that is any less of a hack

[Wallacoloo]

@tresf I saw you mention this PR over in #2269. I tried rebasing this today, and for whatever reason it worked when running it from /home/colin/, but it fails inside a call to SDL_Init when I install it & run it from /usr/local/bin with the message:

Inconsistency detected by ld.so: dl-close.c: 811: _dl_close: Assertion `map->l_init_called' failed!

and the program exited with error code 127.

I'm not sure what the issue is (I made clean & tried again. Also reinstalled SDL. Master branch doesn't have the issue). I pushed the rebased version to engine-rename-min2 though.

[tresf]

@Wallacoloo I'm not an expert on the name clash stuff, but AFAIK, it was the remote processes that caused the hangup, so perhaps SDL uses something like that?

I assume you've tried the obvious... changing AudioSdl.cpp#L129 to use the new name (although I don't know why it would matter since AFAIK its statically linked).

[Wallacoloo]

@tresf turns out that remnants of the old build were still sitting around even after running make clean. I removed my build directory, re-ran cmake & then make && make install and I am no longer having the SDL issue I reported earlier.

I pushed the results of the rebase to this branch, so it should merge fine if there's a concensus for this over @shimpe's #2494.

[tresf]

Thanks. Merging to get 1.2 back on track. Easy enough to revert if needed.

[tresf]

@Wallacoloo one last thing... should we include a comment about why the name differs from the header? I feel someone may change this back later in a cleanup effort if we don't explain why the discrepancy occurs.

[Wallacoloo]

@tresf I added this blurb to the top & moved the typedef further up near that documentation:

// Note: This class is called 'LmmsCore' instead of 'Engine' because of naming
// conflicts caused by ZynAddSubFX. See https://github.com/LMMS/lmms/issues/2269
// and https://github.com/LMMS/lmms/pull/2118 for more details.
//
// The workaround was to rename Lmms' Engine so that it has a different symbol
// name in the object files, but typedef it back to 'Engine' and keep it inside
// of Engine.h so that the rest of the codebase can be oblivious to this issue
// (and it could be fixed without changing every single file).

[tresf]

@Wallacoloo 👍

Squash before merging?

Edit: Zyn launches on Ubuntu 12.04 x64 + engine-rename-min branch....

However, the console does show some strange signs.

RemotePluginClient::shmget: No such file or directory
Starting Audio: NULL
Audio Started
Starting MIDI: NULL
MIDI Started
RemotePlugin::DebugMessage: failed getting shared memory

[tmerr]

Works for me on Arch. The console output is the same as @tresf's but lacks the shared memory error.

[Wallacoloo]

@tresf Squashed. I'm not getting the shared memory error either, but I am also using Arch.

[tresf]

@Wallacoloo merging. Let's see how this goes. 👍 :)

[klopsi]

My entire desktop used to crash when clicking zyn's 'Show Gui'. Both in 1.1.3 branch and master (built from source).

Today, Jan 5, I did a git clone https://github.com/LMMS/lmms.git
git log shows "Temporary workaround for ZynAddSubFx name clashes"

No problems building lmms.

When I run build/lmms and click zyn's Show Gui, my Desktop (Xserver?) still crashes.

Running linux Mint 17.3 (xfce)
Graphics: Card-1: Intel 3rd Gen Core processor Graphics Controller
Display Server: X.Org 1.17.1 drivers: intel (unloaded: fbdev,vesa)

:(
EDIT: Started LMMS in a nested xserver (xserver-xephyr) and Show Gui does not crash anything there.

[tresf]

@klopsi please see #2100. If it is the same thing, this isn't our bug.

[shimpe]

@klopsi at the risk of stating the obvious, also make sure you don't have previous versions of lmms lingering about your system

[tresf]

@shimpe the X-server crashing most likely isn't our bug. http://www.kvraudio.com/forum/viewtopic.php?f=47&t=440054&sid=331c5810b2f0c35f74814223e45ea91a

[shimpe]

@tresf Well.. it used to log me out of KDE before it was fixed.

[klopsi]

Thanks for your comments! The bug was in Xorg! Upgrading xorg using the ubuntu xorg-edgers ppa solved the problem. https://launchpad.net/~xorg-edgers/+archive/ubuntu/ppa