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raylib-fortran-wasm

Toolchain & template repository for projects developed in Fortran with Raylib targetting the web.

References that helped me put this together

Getting Started

Dependencies

The aforementioned StarGate01/Full-Stack-Fortran repository has a really nice Docker container containing all of the required dependencies, which I would highly recommend you use! ./dbuild.sh pulls that container to run the Makefile.

Otherwise, the version numbers for these dependencies are very important. As explained at https://dragonegg.llvm.org/, only GCC 4.6 was fully supported as of the last version released before LLVM marked DragonEgg as obsolete. As far as emscripten goes, StarGate01/Full-Stack-Fortran#10 explains the incompatibility of LLVM 3.3 IR with versions of Emscripten past 3.1.3.

  • DragonEgg LLVM 3.3
  • Emscripten 3.1.3
  • GFortran 4.6.4

For running my shim script, Node.js will have to be installed as well. The version of node I have didn't support .matchAll, so I added a polyfill for it.

How It Works

Patching Interkosmos's Bindings

Run: ./init.sh

Fetches both Raylib 5.0 WASM distribution zip as well as the latest source tree from interkosmos/fortran-raylib.

Interkosmos's bindings nearly work, but we need to patch them to compile with this ancient GCC 4.6 + DragonEgg setup. It might be a compiler flag somewhere that would fix this more easily (It feels like some sort of premature/incorrect optimization happening), but I couldn't figure it out - so let's patch and shim the bindings!

Things that we can shim:

  • GFortran 4.6 inserts an int as argument on functions that take no arguments
  • GFortran 4.6 splits Vector3 as argument into three floats as arguments
  • GFortran 4.6 can't understand implicit none (type, external)

How we fix this:

  • Scan header file for Vector3 and (void)
  • For all instances of those, prepend the c bind names in Interkosmos's bindings with something (We'll use shim_).
  • Create a shim.c file which implements the incorrect function signature (as shim_%) and remaps it to the correct signature.
  • Cut out the (type, external part from the implicit none lines.

Building Your App

Edit the Makefile, then run ./dbuild.sh.

One important thing to note is that wasm raylib builds are expected to use emscripten_set_main_loop rather than a while loop in main.