melonDS - now also for macOS!
Hi everyone, I’m WaluigiWare64. Some of you may know me already from around here.
melonDS now also supports macOS!

If you want to test it, scroll down to the bottom of the post. I’ll be explaining about what needed to be changed for it to work.

This originally started as a little challenge. "It shouldn't be that hard," I thought. However, it wasn't as easy as I would have hoped, but I got there in the end.

- The JIT recompiler

Thanks Generic (aka RSDuck) for helping me out a lot here and guiding me!


It mapped memory using "memfd_create()" on Linux, which didn't exist on macOS. Instead, on macOS shm_open is used to create the fastmem memory.
macOS also didn't have "->gregs" in "uc_mcontext" and no "REG_RIP" either. This has to be changed to "->__ss.__rip" instead.
Then, it would crash with a "bus error" on attempting to load. This was caused because macOS returned "bus error" instead of "segmentation fault", so the signal handler couldn't handle it.
Note: fastmem was disabled because it caused all sorts of errors while trying to boot firmware or run games. If anyone manages to fix it, send a pull request!

The JIT itself

The JIT would build, but at link time it would complain about "ARM_Dispatch" and "ARM_Ret" being undefined. Apparently in the Mach-O format (used in macOS) global function names defined in assembly are required to be prepended by an underscore.
Then it would crash upon booting firmware or trying to load a game. This was caused by the line here which tried to reprotect some memory to make it executable. On macOS, new memory is now mmap'ed instead.

- The OpenGL renderer

macOS complained about not being able to find "GL/gl.h" and "GL/glext.h". These includes had to be changed to "OpenGL/gl3.h" and "OpenGL/gl3ext.h" on macOS and the OpenGL framework was linked.
Also the functions defined by the OpenGL macronator already existed on macOS, which caused "ambiguous reference" errors. The macronator was ifndef'd out.

- Direct Mode

Direct Mode used "AF_PACKET" to get the MAC address, which doesn't exist on macOS. "AF_LINK" was used instead.
The library names of libpcap had to be changed to "libpcap.A.dylib" and "libpcap.dylib" on macOS.

- Binding Keys

This was a simple fix. For some reason, macOS didn't give focus to the buttons in the key binding menu when they were pressed, which meant that they couldn't detect keys. I had to set the focus policy to Qt::StrongFocus to get them to accept focus.

- App Bundle

Now it built fine and it worked, but it came as a Unix executable, not a macOS app bundle. I had to add some lines in CMakeLists.txt to make it build an app bundle.
I also generated a macOS ".icns" icon file for melonDS, so now the icon showed up on the app bundle.

- No libslirp available in Homebrew

Homebrew (the package manager) didn't have libslirp in their repositories, so I created a pull request here which was merged.

Here are the downloads. If you find any issues, make sure you comment here and tell me so I can fix it!
You will have to install the appropriate libraries beforehand with the Homebrew Package Manager.
In Terminal paste the following command to install the required libraries.
brew install qt5 sdl2 libslirp

melonDS 0.9 beta for macOS x86_64
To unzip the above download, you may need to use a program like The Unarchiver.
reglo says:
Jan 22nd 2021
The top screen of the nds isn't working. Sometimes the bottom screen doesn't work.
Justin says:
Jan 26th 2021
hey, why does it say every time I open it it reads: "MelonDS cannot be opened because the developer cannot be verified"? I just need to run regular DS games with it, and I don't need homebrew either. Im running this on a 2015 MacBook Pro, so it should run fine. What has to be one to stop this message from appearing and the program to be loaded? It can't open it without the program saying that it cant verify that its free from malware.
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