DioxusLabs/dioxus · error

Failed to write rustc args to file

Error message

Failed to write rustc args to file

What it means

Final step of the rustc wrapper's arg capture: writing the serialized args to {crate_name}.{lib|bin}.json fails at the fs::write level after the directory already exists - disk full, permission denied on the file, or an OS-level path problem.

Source

Thrown at packages/cli/src/rustcwrapper.rs:135

                .map(|s| s.as_str());

            let serialized_args =
                serde_json::to_string(rustc_args).expect("Failed to serialize rustc args");

            // Write args with an explicit target suffix: {crate_name}.lib.json or
            // {crate_name}.bin.json. This avoids the ambiguity of a bare {crate_name}.json
            // and ensures lib+bin crates don't overwrite each other.
            let suffix = match crate_type {
                Some("lib" | "rlib") => "lib",
                Some("bin") => "bin",
                _ => "bin", // proc-macro, cdylib, etc. — treat as bin
            };

            std::fs::write(
                args_dir.join(format!("{crate_name}.{suffix}.json")),
                &serialized_args,
            )
            .expect("Failed to write rustc args to file");
        }
    }
}

/// Check if the arguments indicate a linking step, including those in command files.
fn has_linking_args() -> bool {
    for arg in std::env::args() {
        // Direct check for linker-like arguments
        if arg.ends_with(".o") || arg == "-flavor" {
            return true;
        }

        // Check inside command files
        if let Some(path_str) = arg.strip_prefix('@') {
            if let Ok(file_binary) = std::fs::read(path_str) {
                // Handle both UTF-8 and UTF-16LE encodings for response files.
                let content = String::from_utf8(file_binary.clone()).unwrap_or_else(|_| {
                    let binary_u16le: Vec<u16> = file_binary

View on GitHub (pinned to 393d190a80)

Solutions

1. Free disk space or raise the quota, then rebuild
2. Delete the dioxus rustc-args directory under target and retry so files are recreated cleanly
3. Set CARGO_TARGET_DIR to a short path (e.g. C:\\dx\\target) to dodge Windows path-length limits
4. Don't share one target dir between dx instances running as different users

When it happens

Trigger: ENOSPC/quota exhaustion during a dx build; a same-named args file owned by another user from a concurrent build; path-length limits on Windows with deep target dirs and long crate names.

Common situations: CI runners with small ephemeral disks; two dx builds sharing one target dir under different users; very deep project paths on Windows.

Related errors

• Failed to create args directory for rustc wrapper
• failed to read input file
• failed to write js module
• esbuild failed: {stderr}
• Failed to run linker

AI-assisted analysis of DioxusLabs/dioxus@393d190a80 (2026-08-16). Data as JSON: /api/errors/665b011910203da4. Report an issue: GitHub.