Godot: Godot 3.0 not working with Mono 5.8

[Moghedien]

Godot version:
3.0

OS/device including version:
Windows 7

Issue description:
Using Mono 5.8.0.108 leads to following error:

Your mono runtime and class libraries are out of sync.
The out of sync library is: C:\Program Files\Mono\lib\/mono/4.5/mscorlib.dll

When you update one from git you need to update, compile and install
the other too.
Do not report this as a bug unless you're sure you have updated correctly:
you probably have a broken mono install.
If you see other errors or faults after this message they are probably related
and you need to fix your mono install first.
ERROR: The build method threw an exception.
System.MissingMethodException: Attempted to access a missing method.
At: modules\mono\editor\godotsharp_builds.cpp:488

Using Mono 5.4.1.7 just works fine

Steps to reproduce:
Install Mono 5.8.0.108 and try to start a project

[bruvzg]

Try replacing mono-2.0-sgen.dll in Godot folder with one from 5.8 SDK, if it won't help rebuild Godot with new Mono version.

[Calinou]

I can compile Godot with Mono 5.8 enabled, but I get a segmentation fault when creating a C# solution from the editor:

https://gist.github.com/Calinou/139974a40a9e5da4b60123b1be820f72

[bruvzg]

cbdd410 with Mono 5.8.0.108 builds and works on macOS 10.13.3: clang 900.0.39.2 (x86-64) and Debian buster/sid: clang 4.0.1-8 (x86-64 and armv7).

Tested: new project, creating C# solution, "Hello world" C# script, building and running project.

[maikramer]

Ubuntu 18.04 custom build with mono 5.8, no problems here

[JamesHinshelwood]

Same issue on Ubuntu 16.04. Fixed by downgrading mono to 5.4

[bruvzg]

cbdd410 with Mono 5.8.0 on Windows 10: mingw-w64 5.0.3 / gcc 7.2.0 cross build (x86-64 and x86) and MSVC VS2017 15.5.3 build (x86-64 and x86), 64-bit versions works OK, 32-bit editor works but project crashes on start in mono_class_get_methods.

Make sure to manually remove GodotSharpTools.dll and mono sgen lib from bin folder before rebuilding, scons is not detecting mono runtime change and keep old libs.

Update:

| OS | Compiler | Arch | Result |
| ---------------------- | ------------------------ | ------- | ---------------------- |
| macOS 10.13.3 (17D47) | Xcode clang 900.0.39.2 | x86-64 | OK |
| OSX 10.9.5 (13F1911) | clang 5.0.1 | x86-64 | OK |
| Windows 10 | mingw-w64 gcc 7.2.0 | x86-64 | OK |
| Windows 10 | mingw-w64 gcc 7.2.0 | x86 | Crash on project start |
| Windows 10 | VS 2017 15.5.3 | x86-64 | OK |
| Windows 10 | VS 2017 15.5.3 | x86 | Crash on project start |
| Debian buster/sid | clang 4.0.1 | x86-64 | OK |
| Debian buster/sid | clang 4.0.1 | x86 | OK |
| Debian buster/sid | clang 4.0.1 | armv7l | OK |
| Debian buster/sid | gcc 7.3.0 | x86-64 | OK |
| Debian buster/sid | gcc 7.3.0 | x86 | OK |

[LaurentOngaro]

Try replacing mono-2.0-sgen.dll in Godot folder with one from 5.8 SDK, if it won't help rebuild Godot with new Mono version.

To avoid duplicate Dll in windows, I've deleted the mono-2.0-sgen.dll in the Godot folder and I've made a junction from the mono-2.0-sgen.dll file of the mono SDK (5.8) to the Godot Folder. It works like a charm.

[PeterPansen]

Hey,

Similar problem on OSX.

Having more recent Mono (5.8) will cause the application to crash immediately after starting.

Installing Mono 5.4.1 fixed the issue for me.

[neikeq]

This was fixed by #15641. Now Godot ships with mscorlib.