Wasm text file preprocessor

[vouillon]

For a start, it is only used to manage runtime differences between OCaml versions, and to provide some syntactic sugar for strings. But I plan to use it for a WASI version of the runtime and to implement the use-js-string flag.

[hhugo]

Have you considered using this to add sugars to help write control flows (e.g having a switch instruction ) ?

[vouillon]

Have you considered using this to add sugars to help write control flows (e.g having a switch instruction ) ?

That seems a good idea, indeed!

[hhugo]

Have you consider having subcommands inside wasm_of_ocaml instead ?

[vouillon]

We have the issue that wasmoo_util link is used to build the runtime which is then included in wasm_of_ocaml.
But maybe I can have an internal binary to do that and also expose the same functionality as a wasm_of_ocaml subcommand.

[hhugo]

Shouldn't the runtime be linked later ? If we want to have it conditional on flags such as use-js-strings ?

[vouillon]

My current plan is to have a set of precompiled runtimes for the most common options, and to compile runtimes on the fly otherwise.
It's a bit slow to compile and link the runtime. That's especially noticeable when we have a large number of executables, like with the Js_of_ocaml test suite.
But maybe we could share the runtimes produced by wasm_of_ocaml build-runtime between executables, using a similar trick in dune as for ppxs?

[vouillon]

But maybe I can have an internal binary to do that and also expose the same functionality as a wasm_of_ocaml subcommand.

I have implemented this. Does this look good to you?