Oskar Hahn (Jan 20 2025 at 21:28): Oskar Hahn (Jan 20 2025 at 21:28):What is the current way to create a wasm platform?
For a "normal" platform, I know what to do to create the files for the surgical or the legacy linker. But what is needed for was wasm-platform?
When I create an app and try to build it, as if the platform was there, I get the error message: No host.zig file found at examples/../platform/host.zig when building wasm32 target.. Is host.zig hardcoded?
If I create the file, I get the error error: wasm-ld: entry symbol not defined (pass --no-entry to suppress): _start. Is the zig-command hard coded? Is there any way I could use a build.zig? If I just create an _start function, an .wasm file is created, but it imports functions like wasi_snapshot_preview1. So its not a normal .wasm file, but a wasi file.
Brendan Hansknecht (Jan 20 2025 at 21:29):I think wasm is very hardcode currently
Brendan Hansknecht (Jan 20 2025 at 21:29):The current state is to copy an example and use zig or to use --no-link and the directly interact with the generated wasm
Brendan Hansknecht (Jan 20 2025 at 21:30):That is at least my current understanding from when I last used it.
Brendan Hansknecht (Jan 20 2025 at 21:30):And yeah, I think the exact build command is hard coded as well.
Brendan Hansknecht (Jan 20 2025 at 21:30):I would assume using --no-link and then having build.zig control all the linking would be the easiest way today
Brendan Hansknecht (Jan 20 2025 at 21:31):I think that is what roc-wasm4 does
Oskar Hahn (Jan 20 2025 at 21:33):But this means, there is no way to create a precompiled platform. You need to create some sort of app.o file and link it with the host.o-file to a .wasmfile?
Brendan Hansknecht (Jan 20 2025 at 21:44):I would need to mess around with the tool chain, but I don't think we have ever had working recompiled hosts for wasm
Brendan Hansknecht (Jan 20 2025 at 21:45):It has always been more adhoc and could use help
Oskar Hahn (Jan 20 2025 at 21:47):If I understand wasm4 correctly, it has a build.zig and a build_roc.zig. To build a wasm file, you call build.zig which calls build_roc.zig. build_roc.zig calls the roc compiler with --no-link. It creates an app.o that is used by build.zig to create the final wasm-file.
Oskar Hahn (Jan 20 2025 at 21:49):If there where support for a recompiled host, it would probably work like the legacy linker. Is this correct? The platform would provide some sort of host.o file, that roc can use to link it with the app.
Luke Boswell (Jan 20 2025 at 22:05):This is an area that needs some love in the roc build pipeline.
Here's how I do it in the wasm template https://github.com/lukewilliamboswell/roc-platform-template-wasi/blob/main/build.sh
Luke Boswell (Jan 20 2025 at 22:06):I think steps 2&3 are not currently done by roc build, but I think they should.
At least this is what I remember from when I was last looking at it.
Luke Boswell (Jan 20 2025 at 22:07):After syntax season... I'm keen to loop back and clean up all these templates.
Luke Boswell (Jan 20 2025 at 22:08):I'm definitely keen to pickup the WASM platform stuff again. I'd still like to build a playground in the browser.
Luke Boswell (Jan 20 2025 at 22:16):Also for reference, another (slightly more modern) example I have is the js-dom experiment https://github.com/lukewilliamboswell/roc-experiment-js-dom
This uses Rust and builds both a WASI cli, and also a WASM module for the browser using wasm-pack.
Using rust for WASM platforms is also a good option right now -- though it's the same limitation, there isn't a good way to pre-build the host.
Richard Feldman (Jan 20 2025 at 22:23):Luke Boswell said:
I'm definitely keen to pickup the WASM platform stuff again. I'd still like to build a playground in the browser.
it would be super rad to have this before redoing all the tutorials for static dispatch and everything, so they could be built around being interactive! :smiley:
Last updated: Jul 26 2025 at 12:14 UTC