Combining native-windows-gui and tokio

Hi there,

I'm trying to do some native windows rust programming. I'm using native-windows-gui and native-windows-derive to do it, but if I try to mix that with tokio, I get the following:

No entry point found error for GetWindowSubclass. On console, I get:

error: process didn't exit successfully: `C:\source\myprojectanem\target\debug\myprojectname.exe` (exit code: 0xc0000139, STATUS_ENTRYPOINT_NOT_FOUND)

If I change

#[tokio::main]
async fn main() {

to:

fn main() {

The problem goes away, but obviously I can't use tokio then.

Any clue what the problem is and how to fix it?

View original on lemmy.ml

Comments5

modulus

lemmy.ml

Apparently the problem is due to an incompatibility between the use of certain libraries (winapi and windows-sys) which use different versions of COM. At least so I deduce from the documentation I've read.

There's a workaaround:

On Cargo.toml, use.

[build-dependencies]
embed-manifest = "1.3.1"

And on the root of the project (not the src dir) create a build.rs file with the following content:

use embed_manifest::{embed_manifest, new_manifest};

fn main() {
    if std::env::var_os("CARGO_CFG_WINDOWS").is_some() {
        embed_manifest(new_manifest("Contoso.Sample")).expect("unable to embed manifest file");
    }
    println!("cargo:rerun-if-changed=build.rs");
}

This embeds a manifest together with the executable, solving the issue.

snaggen reply

programming.dev

wouldn't it be better to use #[cfg(target_os = "windows")] instead of checking an env variable?

Reference: https://doc.rust-lang.org/rust-by-example/attribute/cfg.html

modulus reply

lemmy.ml

Possibly yes. I'll check if the results are equivalent.

cbarrick

lemmy.world

You can manually convert a tokio::main to a regular main by constructing a tokio runtime and telling it to block on a top-level future (e.g. an async block).

https://tokio.rs/tokio/tutorial/hello-tokio

That will at least help you break down the problem to locate the issue.

I don't know anything about Windows though. Maybe there's some per-thread setup that needs to be done in tokio's thread pool?

modulus reply

lemmy.ml

Same erro by using this approach.

Tokio works fine, by itself. windows-native-gui works fine, by itself. It is the combination that causes this issue.