Stream: beginners

Topic: Platform from src debug

Luke Boswell (Jun 19 2023 at 22:00):

Is there a way to instruct roc cli to build a rust platform and use debug instead of release? I am trying to debug some things using dbg! macros and not sure how to do this when using roc dev myapp.roc which rebuilds the platform.

Brendan Hansknecht (Jun 19 2023 at 22:02):

If you don't pass --optimize it should build a rust platform in debug mode.

Brendan Hansknecht (Jun 19 2023 at 22:02):

As long as you have a local platform of course that is getting built from source

Luke Boswell (Jun 19 2023 at 22:03):

So, packages { pf: "../src/main.roc" } should be building and running in debug then?

Luke Boswell (Jun 19 2023 at 22:05):

hmm, I think there is something else going on here. Thanks @Brendan Hansknecht

Brendan Hansknecht (Jun 19 2023 at 22:05):

yeah, should be. You should see roc saying rebuilding host.

Brendan Hansknecht (Jun 19 2023 at 22:06):

also, you should be able to delete target/release and it should still run without recompile. Cause it will use the rust debug build

Luke Boswell (Jun 19 2023 at 22:07):

It looks like bdg is working. I think the issue is something about my "glue" types and passing values between Roc and rust

Luke Boswell (Jun 19 2023 at 22:07):

dbg*

Luke Boswell (Jun 19 2023 at 22:18):

@Brendan Hansknecht can you please have a look at this? Am I missing something obvious here? I feel like maybe I can't just pass a command_glue::Command straight into the roc_fx_commandStatus?

# Effect.roc
commandStatus : InternalCommand.Command -> Effect U8

# InternalCommand.roc
Command : {
    program : Str,
    args : List Str, # [arg0, arg1, arg2, arg3, ...]
    envs : List Str, # [key0, value0, key1, value1, key2, value2, ...]
}

// command_glue.rs
#[derive(Clone, Default, Debug, PartialEq, PartialOrd, Eq, Ord, Hash, )]
#[repr(C)]
pub struct Command {
    pub args: roc_std::RocList<roc_std::RocStr>,
    pub envs: roc_std::RocList<roc_std::RocStr>,
    pub program: roc_std::RocStr,
}

# lib.rs
pub extern "C" fn roc_fx_commandStatus(cmd: &command_glue::Command) -> u8

Brendan Hansknecht (Jun 19 2023 at 22:21):

That looks like it should be correct to me

Luke Boswell (Jun 19 2023 at 22:21):

I had it working fine just passing in a RocStr but recently changed it to the struct Command

Brendan Hansknecht (Jun 19 2023 at 22:22):

One guess, maybe it explicitly needs to be a pointer instead of &

Brendan Hansknecht (Jun 19 2023 at 22:22):

Does it work if you remove one of the fields?

Luke Boswell (Jun 19 2023 at 22:24):

I've just pushed my WIP to #55

Luke Boswell (Jun 19 2023 at 22:24):

I'll try removing all the fields except the RocStr

Luke Boswell (Jun 19 2023 at 22:26):

Yeah, it works ok removing the args and envs fields from command_glue::Command

Brendan Hansknecht (Jun 19 2023 at 22:26):

My current guess is that is is related to #5544 and since the size is 72 bytes (which is over 64 bytes) it becomes a pointer.

Brendan Hansknecht (Jun 19 2023 at 22:26):

So it should work with 2 fields, but fail with 3

Brendan Hansknecht (Jun 19 2023 at 22:27):

With 3 probably just need to change the input type to a pointer.

Brendan Hansknecht (Jun 19 2023 at 22:27):

but maybe something more complex is needed

Luke Boswell (Jun 19 2023 at 22:28):

Ok, thanks. It doesn't work with two or three fields.

Luke Boswell (Jun 19 2023 at 22:28):

To change to a pointer, I need to use a Box type right?

Brendan Hansknecht (Jun 19 2023 at 22:31):

Hmm. breaks with 2. Maybe it is something else, not sure. Anyway, I would test with a *const command_glue::Command

Luke Boswell (Jun 19 2023 at 22:32):

Works!! :tada:

Luke Boswell (Jun 19 2023 at 22:33):

Thank you

Luke Boswell (Jun 19 2023 at 22:35):

Pushed to this commit in case anyone finds this thread in future and wants to know how to use Box as a workaround here.

Brendan Hansknecht (Jun 19 2023 at 22:37):

Hmm. that isn't what I meant, but is a patch I guess. Pretty wasteful to just box for that. Though it is always a workaround to any glue issues.

My suggestion would not use box on the roc side at all. It would just use the pointer on the rust side.

Brendan Hansknecht (Jun 19 2023 at 22:38):

Not saying my suggestion would work, but this api definitely should work without any box on the roc side.

Brendan Hansknecht (Jun 19 2023 at 22:49):

Hmm. I just tested your code on my m1 mac and I think your original code works just fine. Like without any changes....hmm

Last updated: Jul 26 2025 at 12:14 UTC