Stream: beginners

Topic: ✔ failed to open file "app/../platform/dynhost"

Jared Cone (Sep 27 2024 at 06:37):

I'm attempting to make a barebones platform to help me better understand the roc building and linking process. I used basic-cli as a starting point (removing all platform functions). I can think of two key differences that I'm trying to do different from basic-cli:

• The host bin and lib are produced from a single crate (single toml file?)
• I'm using a shell script to build instead of build.roc. The script was made by studying build.roc.

Link to the project: https://github.com/jared-cone/roctris2

I'm running build-app.sh

Here's the output:

jared@jared-laptop:~/Home/roctris2$ ./build-app.sh
0 errors and 0 warnings found in 183 ms
 while successfully building:

    platform/libapp.so
   Compiling libc v0.2.155
   Compiling backtrace v0.3.69
   Compiling host v0.0.1 (/home/jared/Home/roctris2/platform/crates/host)
    Finished `release` profile [optimized] target(s) in 2.21s
🔨 Rebuilding platform...
An internal compiler expectation was broken.
This is definitely a compiler bug.
Please file an issue here: <https://github.com/roc-lang/roc/issues/new/choose>
failed to open file "app/../platform/dynhost": No such file or directory (os error 2)
Location: crates/linker/src/lib.rs:552:29

and if I try the legacy linker:

jared@jared-laptop:~/Home/roctris2$ roc build --linker=legacy app/test.roc
🔨 Rebuilding platform...
ld: /usr/lib/x86_64-linux-gnu/Scrt1.o: in function `_start':
(.text+0x1b): undefined reference to `main'
thread 'main' panicked at crates/compiler/build/src/program.rs:1031:17:
not yet implemented: gracefully handle `ld` (or `zig` in the case of wasm with --optimize) returning exit code Some(1)
stack backtrace:
   0: rust_begin_unwind
   1: core::panicking::panic_fmt
   2: roc_build::program::build_loaded_file
   3: roc_build::program::build_file
   4: roc_cli::build
   5: roc::main

so where did I mess up? :)

Luke Boswell (Sep 27 2024 at 07:16):

This is complicated to answer I think. Anton and I spent a lot of time finding the right incantation to get the rust compiler to play nicely.

I think if you remove the bin and just have a lib you will have a much nicer time getting this to work, but then you will be limited to the legacy linker (this may be ok for your purposes).

Jared Cone (Sep 27 2024 at 07:18):

Yep I'm fine with legacy linker. Currently when I build it produces a bin and a lib. I don't know rust: is that lib the same that would be produced as a lib that's in its own crate?

Luke Boswell (Sep 27 2024 at 07:18):

I think the issues stem from the way we do linking currently and unique things with the rust compiler. I've seen it work this way though, if you checkout the examples/platform-switching/rust-platform in the repo, there is an example. Though this uses a host.c to do something intermediate.

Luke Boswell (Sep 27 2024 at 07:19):

Jared Cone said:

Yep I'm fine with legacy linker. Currently when I build it produces a bin and a lib. I don't know rust: is that lin the same that would be produced as a lib that's in its own crate?

If you're fine with just the legacy linker, it get's much easier.

Luke Boswell (Sep 27 2024 at 07:24):

Also, https://github.com/lukewilliamboswell/basic-ssg is another Rust platform that is much simpler and supports cross-compilation to build for all the supported roc targets.

Jared Cone (Sep 27 2024 at 14:31):

Thanks Luke! We got it sorted using the legacy linker.

Notification Bot (Sep 28 2024 at 02:48):

Jared Cone has marked this topic as resolved.

Last updated: Jul 26 2025 at 12:14 UTC