Karakatiza (Dec 17 2023 at 21:00): Karakatiza (Dec 17 2023 at 21:00):Does legacy linker not support cli arguments, e.g. with roc dev --linker=legacy -- http://localhost:8080 Arg.list returns an empty list?
Luke Boswell (Dec 17 2023 at 21:51):It should do. Also Arg.list should at least return the name of the executable I think.
Karakatiza (Dec 17 2023 at 22:03):It does return the name, but with either roc dev or standalone executable args don't seem to get passed.
Brendan Hansknecht (Dec 17 2023 at 22:05):Legacy linker should have nothing to do with the args
Brendan Hansknecht (Dec 17 2023 at 22:06):Not sure what is eating the args in this case
Brendan Hansknecht (Dec 17 2023 at 22:06):I have definitely gotten all args from Args.list maybe an issue specific to OS?
Karakatiza (Dec 17 2023 at 22:07):Weird. I'm on non-WSL Ubuntu ~20. I'll do some more testing tomorrow
Brendan Hansknecht (Dec 17 2023 at 22:08):Hmm....actually one idea. How does rust initialize args? I have never dug into that. Calling rust from c may not initialize the args. So could be a legacy linker issue due to that.
Brendan Hansknecht (Dec 17 2023 at 22:25):Could be an issue with this?
On glibc Linux systems, arguments are retrieved by placing a function in .init_array. glibc passes argc, argv, and envp to functions in .init_array, as a non-standard extension. This allows std::env::args to work even in a cdylib or staticlib, as it does on macOS and Windows.
Brendan Hansknecht (Dec 17 2023 at 22:25):From the rust docs: https://doc.rust-lang.org/std/env/fn.args.html
Karakatiza (Mar 21 2024 at 06:54):Coming back to this as the issue persists; I needed to create a CLI program that both utilizes Arg.list and roc-json library, and it looks like either way one of them gets broken whether or not you use --linker=legacy :smiling_face_with_tear:
Luke Boswell (Mar 21 2024 at 07:55):What if you build the program first?
roc build --linker=legacy abc.roc
And then run it passing some args...
abc http://localhost:8080
Luke Boswell (Mar 21 2024 at 07:57):Karakatiza said:
It does return the name, but with either roc dev or standalone executable args don't seem to get passed.
I see you've tried that... strange
Karakatiza (Mar 28 2024 at 00:57):@Luke Boswell does it make sense to work on my own implementation for JSON in Roc just to get things done? Or is there a specific syntax in roc-json code that could be refactored in a fork to avoid the bug it is blocked by without legacy linker?
Luke Boswell (Mar 28 2024 at 01:06):Do you have an example you can share or are working on?
Luke Boswell (Mar 28 2024 at 01:06):I wouldn't suggest writing a new implementation
Luke Boswell (Mar 28 2024 at 01:11):I can try and re-produce on my linux machine later today, I'll have a look now on my mac
Karakatiza (Mar 28 2024 at 01:14):Don't have a share-able piece of code, but I simply would like to write a program that uses Arg.list and roc-json library at the same time
Luke Boswell (Mar 28 2024 at 01:19):I'm working on an example now
Luke Boswell (Mar 28 2024 at 01:25):Curiously,
This works
main =
args <- Arg.list |> Task.await
Stdout.line "Foo, first: $(Inspect.toStr args)"
But this crashes with panicked at 'called Option::unwrap() on a None value', crates/compiler/mono/src/ir.rs:6143:56
main = run |> Task.onErr \err -> Stdout.line "ERROR: $(Inspect.toStr err)"
run =
args <- Arg.list |> Task.await
Stdout.line "Foo, first: $(Inspect.toStr args)"
Does the first program work with --linker=legacy for you?
Luke Boswell (Mar 28 2024 at 01:27):Yes,
$ roc run --linker=legacy test-arg-json.roc -- blah
Foo, first: ["/var/folders/48/39th9k0n0wdcj18k3yhm_g5c0000gn/T/.tmpfcsKBR/roc_app_binary", "blah"]
So I suspect there is a bug or something strange in the platform
Luke Boswell (Mar 28 2024 at 01:28):Specifically with Arg
Luke Boswell (Mar 28 2024 at 01:32):Found the issue
Luke Boswell (Mar 28 2024 at 01:33):Have a workaround, just making an example with json for you
Karakatiza (Mar 28 2024 at 01:33):Oh well, it doesn't work on Ubuntu 22.04.4 LTS with --linker=legacy for me.
Karakatiza (Mar 28 2024 at 01:33):The output without --linker=legacy is as expected, Foo, first: ["/proc/self/fd/3", "blah"]
Karakatiza (Mar 28 2024 at 01:34):With - Foo, first: []
Karakatiza (Mar 28 2024 at 01:34):base-cli 0.8.1
Luke Boswell (Mar 28 2024 at 01:43):So what I had to do was modify basic-cli and use a local copy. I changed the err type on the Arg.list in the platform as follows.
## Gives a list of the program's command-line arguments.
# list : Task (List Str) * <-- err type BROKEN
# list : Task (List Str) a <-- err type BROKEN
# list : Task (List Str) _ <-- err type BROKEN
list : Task (List Str) []
list =
Effect.args
|> Effect.map Ok
|> InternalTask.fromEffect
The I used the following program with something like $ roc dev test-arg-json.roc -- "{"field":"value"}"
app "json"
packages {
cli: "../basic-cli/platform/main.roc",
# cli: "https://github.com/roc-lang/basic-cli/releases/download/0.8.1/x8URkvfyi9I0QhmVG98roKBUs_AZRkLFwFJVJ3942YA.tar.br",
json: "https://github.com/lukewilliamboswell/roc-json/releases/download/0.6.3/_2Dh4Eju2v_tFtZeMq8aZ9qw2outG04NbkmKpFhXS_4.tar.br",
}
imports [
cli.Stdout,
cli.Task.{ Task },
cli.Arg,
json.Core.{json},
]
provides [main] to cli
main = run |> Task.onErr \err -> Stdout.line "ERROR: $(Inspect.toStr err)"
run =
firstArgStr <- getArgs |> Task.await
result = parseJson firstArgStr
result
|> Inspect.toStr
|> Stdout.line
getArgs : Task Str _
getArgs =
args <-
Arg.list
|> Task.mapErr UnableToGetArgs
|> Task.await
when args is
[_, first, ..] -> Task.ok first
_ -> Task.err UnableToParseArgs
parseJson : Str -> Result { field: Str } _
parseJson = \str ->
Decode.fromBytes (Str.toUtf8 str) json
|> Result.mapErr \err ->
when err is
Leftover bytes -> Leftover (Str.fromUtf8 bytes)
_ -> JsonErr err
This doesn't parse the json correctly, I'm forgetting how to use roc-json, but it runs and gives an nice error (Err (Leftover (Ok "{field:value}")))
Luke Boswell (Mar 28 2024 at 01:45):Are you able to test this please?
Karakatiza (Mar 28 2024 at 01:45):Could you reproduce my issue, though?
Luke Boswell (Mar 28 2024 at 01:46):I don't see any difference with using --linker=legacy, but I'm on my mac
Karakatiza (Mar 28 2024 at 02:02):Will have to test your example tomorrow
It seems my issue is a different one, and I do not have the expertise or capacity to debug the Rust implementation you mentioned a while ago in this thread
Luke Boswell (Mar 28 2024 at 02:05):In case it helps here is the current implementation of Args.list effect in the platform.
#[no_mangle]
pub extern "C" fn roc_fx_args() -> RocList<RocStr> {
// TODO: can we be more efficient about reusing the String's memory for RocStr?
std::env::args_os()
.map(|os_str| RocStr::from(os_str.to_string_lossy().borrow()))
.collect()
}
I would recommend writing a simple rust program and seeing what the behaviour is just using std::env::args_os() to see if it is a roc issue or something else.
Brendan Hansknecht (Mar 28 2024 at 02:30):Mac is always legacy linker
Brendan Hansknecht (Mar 28 2024 at 02:30):So wouldn't be able to repro linking bugs seen on linux
Karakatiza (Mar 28 2024 at 02:32):In my case the bug is reproduced with legacy linker, so that would mean the mac and linux legacy linker behavior is different
Brendan Hansknecht (Mar 28 2024 at 02:40):Ah, I missed that. Intriguing
Karakatiza (Mar 29 2024 at 00:31):I haven't yet tested the above patch to base-cli or a simple Rust program, but it seems like roc-json works as expected without --linker=legacy despite the warning in the docs. I will come back to this thread if I hit a wall
Last updated: Jul 26 2025 at 12:14 UTC